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Part a
The main conclusion made in the film An Inconvenient Truth was that the global warming is caused by the increasing level of carbon dioxide. The release of carbon dioxide in the atmosphere along with other greenhouse gases is primarily responsible for the general rise in temperature of the world. Not only the change in climate, but also increasing number of storms, natural disasters and extinction of animal species are being caused by the changes in carbon emissions. If some actions if not taken by the governments and the policies of states are not changed, then there will be grave consequences in the future.

Part b
There were a number of evidences that were presented by the narrator in the film. The first prove was that a person studied the changes in the daily temperatures with the changes in carbon dioxide and found the temperature rise to be directly related to the change in carbon emissions.
The film reported that the scientists have studied the ice from the glaciers and they were able to find out the history from that ice. There were bubbles in the ice when it was brought to the surface and from these bubbles the scientists were able to find the amount of carbon dioxide and the temperature in the atmosphere when the ice was formed. It was evident from the research that the temperature raised as the carbon levels were increasing and vice versa. Gore presented this in form of a graph which included past comparison of 650,000 years. It was also shown that recently the levels of carbon dioxide have risen to the amounts like never before. With that temperature has also risen.

It was also shown by Gore that the top ten hottest years have been recorded in the past twenty years, 2005 being the hottest year ever. The melting ice caps are another evidence of the direct relation of global warming with carbon emissions. Most of the glaciers of in the world have melted and is causing the level of sea to be increased. The animals living in the Polar Regions are getting affected the most. This is evident as the scientists have never found polar bears drowned in the seas before but now they have. This is because of the reduced amounts of glaciers, the animals are not able to find glaciers where they can rest or live.

Question 2
Oil
Pros
    -     Releases a lot of energy when burnt
    -    Many forms of oil can be extracted when heated
Cons
- If spilled in an ocean, can cause grave harm to the marine life under the ocean
-  It is running out because of the extreme use in industries and home

Coal
Pros
    -     Present in bulk under the surface of the earth
    -    Inexpensive because of the large volume present in the earth surface
Cons
 Very difficult to extract from the earth
-  Dangerous emission are made when burnt such as Sulfur dioxide and Nitrogen dioxide

Solar
Pros
    -     Renewable form of energy
    -    Does not have any side effects on the environments

Cons
 Cannot provide a continuous supply of energy, i.e. at night or a cloudy day
-  Expensive equipment to convert into electricity

Nuclear
Pros
    -     Lot of energy can be generated from a little amount of raw material
    -    Generates less amount of pollution as compared to burning of fossil fuels

Cons
- The disposal of waste is a dilemma
-  Extreme safety is required to handle toxic material

Hydroelectric
Pros
    -     Generates no pollution
    -    This is a renewable energy source
Cons
 Dams are very expensive to construct
-  Dams suffer from problems of siltation which cause the dam to be blocked after some time

Wind
Pros
 -     A renewable source of energy
 -    Can be generated cheaply
Cons
 The turbines can be easily damaged by natural disasters
-  Cannot provide a continuous supply of energy as the generation is dependent upon wind speed

Question 3
The six indicators that the geologist could use to determine climate change in the geologic past are as follows
The melting of the ice caps is the most visible and prominent indicator of the climate change. Since the past hundreds of years, the north pole and the south pole has frozen glaciers which are now collapsing and melting into the oceans
Increasing occurrences of natural disasters such as hurricanes, earthquakes and volcanic eruptions are because of changes in seasonal variations
Many animals which reside in the polar regions of the world like polar bears, penguins and walruses are finding it difficult to survive because of the melting ice caps which were their homes
The increasing amounts of floods in some parts of the world such as China, India and United States and the droughts in some parts of the world like Nigeria and Ethiopia are showing climate change
The early migration of birds to the north for breeding implies the changes in climate as these birds only migrate when spring arrives in the north. This early migration is sound proof of the early arrival of spring in north.

The timings of the yearly natural events continue to change such as the Monsoon Season in India, Pakistan and Bangladesh. Monsoon Season used to start roughly in the end of June and would continue for two months, but now it starts in the end of July and start of August

Question 4
Some countries include the naturally occurring gases and liquids both in the definition of petroleum reserves. These petroleum reserves consist of hydrocarbon compounds. However, other countries might only include the liquid component of hydrocarbon compounds. This difference in the definition causes the problem. Countries should only include the quantity of petroleum that is economically and physically available for production.

The biggest problem here is that the aggregate amount of petroleum reserves available for the world to use is miscalculated. This does not only results in wrong prices for the petroleum products but also results in miscalculation by the scientists for the time till petroleum will last.

Geological Features

The Sahara Desert, covering most of North Africa, is the largest desert in the world. From north to south, the Sahara is between 800 and 1,200 miles and is at least 3,000 miles (4,800 km) from east to west. Due to the massive size of the Sahara, Africa is split into two regions that which lies above or forms part of the Sahara and the rest of Africa, south of the Sahara (ThinkQuest Team, 1998). Some of the Sahara deserts geological features would include butte, blowout, and loess, as illustrated above.

Butte
It is a narrow, flat-topped hill of resistant rock with very steep sides and probably a former mesa (Katz, 2010). This landform is most often composed of sedimentary rock, formed by the accumulation and compression of sediment. The top layer is a hardened layer of rock that is resistant to erosion, which is the gradual wearing away of Earth surfaces through the action of wind and water. Sometimes this top layer, called the cap rock, is not sedimentary rock but is cooled and hardened lava that had spread out across the landscape in repeated flows from fissures or cracks in the ground (Mesa, 2010).

Going to the Sun Road, Glacier National Park
Source
Above is a picture of mountain ranges in Glacier National Park. It is a photo taken by a person going to the Sun Road.

Horns
When three or more corries erode backwards and meet, they cannot form an arete it has steep sides but does not have the length to make a ridge. Imagine three corries at the corners of a triangle, eventually all eroding back and meeting in the middle. A sharp pointed pyramid shape is created. This is called a pyramidal peak, or horn, and is a common shape for mountain tops in well-glaciated areas (Aretes, 2006).

Arete
It is a steep-sided, sharp-edged bedrock ridge formed by two glaciers eroding away on opposite sides of the ridge (Lemke, 1998). When a corrie is formed, its back and side walls tend to be steep and jagged, perhaps almost vertical. When two corries form next to each other, and their adjacent walls are eroded backwards until they meet, a narrow and pointed rock ridge is formed. This is often likened to a knife edge, with near vertical sides and a sharp top edge. This feature is called an arete (Aretes, 2006).

U-shaped valley
U-shaped valleys often start as river valleys that existed before glaciation occurred. The glaciers then followed the existing V-shaped valleys, eroding and deepening them as the ice moved. Over time the valleys become straightened, widened and deepened, keeping the steep sides and acquiring a flat base. U-shaped valleys are also known as glacial troughs (U-shaped, 2006).

Source
The central part of Panum Crater is a rhyolite dome, formed around 650 years ago by slow rising of viscous, relatively cool magma, rich in silica, hence the high obsidian content of the resulting rocks. Surrounding the dome is a tufa ring, slightly lower in height, composed of ash and pumice ejected from the vent in an earlier, more violent stage of the eruption. The narrow spires seen today on top of the dome were created when the main mass had cooled and hardened, but the residual lava below still had enough force to split the surface and extrude into pinnacles (Crossley).

Crater
A volcanic crater is a circular-lowered ground caused by volcanic activity at the top of the volcano, the opening of the volcano. It is a circular basin in which magma erupts as gases, lava and ejecta. It can be in various sizes and various depths. In majority, craters occur from volcanic deposits such as lava flows and tephra.

Dome  
A lava dome occurs when the volcano rebuilds itself. Domes are roughly circular-shaped protrusion resulting from the slow extrusion during the eruption of the volcano. It forms mostly within the crater. The dome shape occurs because of the high viscosity that prevents the lava to flow very far. Domes may reach heights of several hundred meters, and can grow slowly and steadily for months.
Tephra (Ejecta) Ring The ejecta ring is made up of small bits of pumice, ash, obsidian fragments, and well-rounded granitic pebbles (which are part of the surrounding rock and not formed during the eruption) that are ejected during the final explosive stage of the eruption.

Cost and Benefits of Solar Energy

The world is witnessing unpredictable climate changes due to global warming. Over the past century the world forest cover has declined by over half as mines for fossil fuels are risking exhaustion. All these are despite the fact that solar energy can be used for supplying almost all energy needs of the community. Over the past few decades, the solar energy field had not received much research and engineering concerns. However, in the current society, there are varieties of solar equipment which can aid in converting solar radiations into other forms of power for man. The common uses include cooking, lighting, heating, and water treatment. The engineering field of solar vehicles is currently receiving extensive attention after it had previously shown remarkable development. This has the implication that solar energy is increasingly becoming the best solution to the problems of environmental pollution and depletion of resources. Therefore, there is need to create awareness to the general public on the importance of adopting solar energy for use in the community. The manufacturers and the government should engage in talks to consider lowering the cost of the solar equipment to enable more people to start enjoying the long term benefits of solar energy.

Cost and Benefits of Solar Energy
Solar energy is one of the oldest natural power sources in the world. This form of energy can be used directing for heating or lighting purposes. However, with increased technological advancements in the modern human community, solar energy can be tapped and converted into electrical energy, thus making it useful for running other home appliances (Swanson, 2008). There are many benefits associated with solar energy. Being a natural form of energy, solar energy is useful both to the community and the environment. This is because it can help in reducing the effects of global warming as well as saving our natural resources. This is very important for the sustainable future existence of the community.
   
Still, solar energy is praised to have the advantage of reducing the operating costs of energy utilities (Ghassemi 9). Just to be appreciated here is the fact that solar energy greatly reduces the maintenance costs. This is because once installed, solar power system call for limited maintenance. However, solar energy has a number of associated costs (Swanson, 2008). Since this form of energy is dependent on radiation from the sun, its reliability is varied. This is due to the fact that there are constant variations in the amount of sun radiations reaching the earth surface from time to time.
   
Another commonly cited cost of solar energy is that with the modern developments, the amount of energy that can be harnessed from the solar energy is limited only to low power consuming appliances (Gordon 36). However, despite these costs, the benefits of solar energy can never be underestimated. This paper is written as a discussion on solar energy. The author will in particular give a discussion on the costs and benefits of solar energy.

Definition and Common Applications of Solar Energy
Solar energy can be defined as a natural form of energy founded from the light and heat radiation from the sun (Kalogirou 19). In a more general way, solar energy is responsible for almost all forms of renewable sources of energy in the community. This is because through the influence of radiation from the sun - wind, waves and biomass are developed. According to available scientific evidence, the amount of energy radiated from the sun is capable of sustaining the energy requirements of the world population.
   
This is nevertheless limited by the ability of mankind to design and implement highly efficient solar energy harnessing mechanisms (Kalogirou 23). It is also to be appreciated that the amount of solar radiation felt on the earth surface various from region to region. The regions near the equator for instance are marked with high levels of solar energy. It is due to this reason that the tropical climate regions should invest much of their resources in utilizing the benefits of solar powered energy sources.

Over the years man has used solar energy for heating and lighting purposes. However, following the effects of modern technological developments, solar energy can be converted into electricity for use in running other appliances (DeGunther 18). The most commonly used appliances are house lighting bulbs, entertainments sets and cooking appliances among others. Security systems can also be powered by solar energy. This development employs the use of photovoltaic cell for collecting the solar energy.

In the agricultural sector, solar energy is increasingly becoming useful in determining both the growth rate and quality of horticultural crops through greenhouse farming practices (Parrot, 2007). The past few decades have witnessed an increase in the use of solar thermal energy in the community. According to research findings, most of the domestic water heating systems in the United States are powered by solar energy. Still, the reports indicate that an estimated 50 percent of residential home heating, cooling, and ventilating systems are powered by solar energy.

Other applications for solar energy could include water treatment and cooking. With the use of solar bowls, it is possible to generate steams for cooking (Kalogirou 24). It is worth noting here that solar energy is currently employed in heating process. These processes are realized by using parabolic dishes, solar trough reflectors and are commonly used in cloth manufacturing factories. Based on all these, solar energy can be effectively employed to serve in providing for most of the energy needs in the community.   

Benefits of Solar Energy
    There are various benefits which can be realized from the use of solar energy in the society (Parrot, 2007). First, solar energy is a renewable source of energy. The sustainable future of any economy is highly dependent on the long term availability of its natural resources. Most of the modern supply of energy in the human society is from biomass and fossil fuels. Although biomass is regarded to as a renewable source of energy, the ever increasing dependence on such sources of energy has evidently compromised the amount of forest cover in the world (Ghassemi 12). This threatens the sustainable preservation of our ecosystem.
   
On the other side, fossil fuels are non-renewable natural resources. Nevertheless, sun radiations are natural and renewable through the natural solar system cycles. This has the implication that solar energy can serve the energy needs of a community over the long run. According to available information on solar energy, it is claimed that the amount of energy from sun radiation can reliably serve the energy needs of the global community. Therefore, solar energy is a real solution to the problem of exhaustion of our natural resources (Parrot, 2007).
   
Another benefit of using solar energy is that they are friendly to both the community and the environment (Kalogirou 23). The global community is eminently facing the problem of global warming. Indeed, this problem has been blamed for the frequent changes in climatic which have the direct result of increased natural disasters in the community (Gordon 56). Such have also compromised the reliability of agricultural practices in the community, a factor that leads to the problem of food insecurity. According to reliable scientific evidence, the problem of global warming is mainly caused by mankind activities.
Cutting down of trees and increased production of greenhouse gases in the production industries. Nevertheless, the sun is evidently termed as one of the natural sources of green energy. Just to be assessed the fact that the leading producer of greenhouse gases is the fossil fuel that used in the production of the electricity. Also to be noted, the cutting down of trees in the community is driven by human need for energy. Therefore, engaging the community in using solar energy could sufficiently resolve environmental problems that community faces.
   
Solar generated energy is of low cost compared to other common forms of energy (Gordon 67). Solar energy is freely gotten from the sun. This means that the only cost to be incurred by the investor of that of purchasing and installing the sun radiation absorbing and converting equipment. However, other forms of energy are supplied at a cost for the long term profitability of the supplying company or individual. Still, it is worth to be noted here that such expenses are constantly varying with time depending on the prevailing demand and supply conditions (Kalogirou 23). Based on this argument therefore solar generated energy will always remain the best option for the long term economic gain of members in the community.
  
 Solar power systems dictate for little or no maintenance costs after installation (Ghassemi 14). Another economical benefit of solar generated energy is that is does not require constant maintenance as compared to other forms of energy generating equipment. According to available statistical evidence on the durability of solar energy equipment, it is evident that a single installation can last for over ten years without any need for repair or replacement (Swanson, 2008). This advantage has been closely attributed to the fact that a factory that makes them, its production have minimal or no tear and wear problems. This has the ultimate advantage of making their operational costs lower compared to other forms of energies in the society.
   
Still, solar power is marked with tax breaks provided for as incentives by the American government. The problem of global warming has been given some substantial attention by the government of the United States of America. This can be reflected on its green energy policy. Such have prompted the government to provide subsidies on solar energy generating equipment sold to the citizens (DeGunther 31). Due to this reason, the American citizens should engage in installing solar energy generators not only to benefit from the government incentives but also to enjoy the long term benefits of solar energy.
   
There is also the benefit of choice based on variety of equipments and applications. Solar energy can be used for executing as many activities as other forms of energy like electricity do. Nevertheless, solar equipment is available in variety. Such include cooking equipment, heating, and lighting installation among other or even a combination of all (Parrot, 2007). Still to be appreciated is the fact that these solar equipment are of different ratings and prices. However, for energy forms like electricity, the supply is mostly constant, a factor which can lead to misuse. Therefore, solar energy gives the individual the benefit of flexibility depending on the desired purpose and the cost.
   
Solar energy has the ultimate potential of supplying residential and manufacturing industries with electricity. According to available information, a 14MW solar power station was completed in 2007 in the Nevada state of America (DeGunther 51). Although this power station and other around the world are not reliable in supply due to solar fluctuations, research works are underway which seek to develop a renewable sources combined power plant to produce constant power throughout the day. This has the direct implication that with increased research activities on renewable energy solar energy will be modified to suit into the day-to-day power needs of the community.
  
 Since mid 1970s, there have been many attempts by engineers and scientists to develop solar power vehicles. In the modern time, the world can boast of succeeding in the designing of a solar powered car which can run up to a maximum speed of almost 100kmh (Ghassemi 15). In addition to this achievement, this solar vehicle field remains open to accelerated developments. This is closely attributed to the various solar car challenges, which are being initiated. Such include the World Solar Challenge, the North American Solar Challenge, and the planned South African Solar Challenge. There are boats powered by solar energy which are operating across the Pacific Ocean and the Atlantic Ocean. Developments have been witnessed in the designing of a solar powered aircraft.

In 2007, the BAE Systems designed a solar aircraft that could fly above 29,524 meters with 54 hours as its total flight capability (Gordon 41). More engineering research is still going on in a move to design solar vehicles with high efficiencies. Based on all these examples, it is quite clear that solar energy is eventually being modeled to match the needs of mankind. With vehicles capable of being powered by solar power, the world will no doubt preserve its natural resources for the sustainable future of the ecosystem.

Cost of solar energy    
Despite the many advantages associated with solar energy in the community, there are a number of costs which compromise the appreciation of the energy in the society (Swanson, 2008). First, solar energy is unpredictable. The efficiency and reliability of solar energy is solely dependent on the availability of solar radiations. It is common sense that such a form of energy cannot be generated during the night. Although this problem is resolved by using energy storage equipment like batteries, the capacity of such might be way below the requirements of the residents (Swanson, 2008). Still, cooking or process heating equipments can only be operated during the day.
  
 Also on the problem of unpredictability of solar energy, the amount of solar radiation received on the earth surface varies from time to time (Kalogirou 26). This claim is based on the fact that such radiation can be significantly blocked by clouds or their heating effect compromised by other factors like cold weather seasons. This has the simple implication that the amount of solar energy that the equipment can supply remains unreliable. Therefore, such a form of energy can be a negation to the high profile lifestyles upheld by some members of the community. Such conditions could dictate for additional energy supply requirements, a factor which contradicts the essence of the solar energy.
   
Available scientific information clearly indicates that the amount of solar radiation reaching the earth surface increases as one move to the equator. This means that the people living along or near the equatorial line have higher advantage of enjoying the sustainable benefits of solar energy. This is a cost of solar energy as those living far away from the line of equator have no chances of enjoying such benefits.
   
Another commonly cited cost of solar energy is that the equipments seem to be quite expensive for the common man to afford. According to the current market price, the cheapest solar panel is costing an estimated 2,000 with more reliable ones costing an approximated over 12,000. It is worth noting here that most poor people in the United States can rarely afford to sacrifice such a huge amount of money (DeGunther 56). Therefore, the high costs of such solar equipments are posing a limiting factor on the widespread use of solar energy in the community.
   
Opponents of solar energy have claimed that most of the modern technological developments in this field are limited for appliances which require low power (Ghassemi 9). It is sufficiently evident that solar energy can be used for powering the operation of heavy factory machines as used in the process heating configurations. Nevertheless, such setups are not only expensive but require a big space, something that lacks in many families. Just to be underscored, the fact that even the most efficient and size effective solar equipment are is marked with high prices which compromises their market.   

Recommendations
    Solar energy is a free and renewable form of energy that does not have negative effects on the environment. Still asserted is the fact that this type of energy is estimated to have a potential far high above the requirements of the world population. It is only the efficiency of the solar equipment designed by man that can limit the enjoyable benefits of using solar energy in the community.
   
Many have claimed of the ineffectiveness of solar energy in supplying a constant energy. Solar energy can be stored in different forms using different storage methods. Such could include thermal mass, phase change storage materials, thermal energy storage, and the grid energy storage techniques. This clearly indicates that every application of solar energy has its suitable storage method. Therefore, engaging in the full installation of the solar energy setup and its storage could sufficiently resolve the concern by many people that solar energy cannot supply constant energy.
   
In a capitalistic society, nothing goes for free. Therefore, solar equipment designers have to make money from their sweat while those who sacrifice to buy enjoy the long term benefits of their sacrifice (Kalogirou 35). However, given the importance of solar energy particularly as a remedy to environmental destruction and global warming, the government should increase its subsidies for solar equipment. Such will bring the advantage of increased installation, thus reduced use of biomass and fossil fuel, thus preserving both the environment and its natural resources for the future.
   
On the problem of solar radiation varying from region to region, people should select the best type of solar equipment that suits their region of stay. According to available statistics, it is evidently clear that in most regions where radiations from the sun are not strong enough, solar energy is mainly employed for warming swimming pools (Gordon 17). This is because water heating systems generally require low solar energy than a rechargeable battery. In regions where solar radiation is not consistent, a backup supply could be installed for use when solar power is very low. Such could no doubt save the owner some energy costs compared to the cost of full scale external energy supply.
   
Given the much which has been developed in the solar energy technology, the use of solar power in the community should be encouraged. Necessity is the mother of invention. This means that unless members of the community are encouraged to use the technology, the inefficiencies will never be noted and thus will never be solved. Scientists on the other side should engage in resolving questions of high costs for quality solar equipment. Such could be easily achieved through engaging in mass production, thus reduced costs for the items. This is very vital in creating a sustainable market for the products.
   
It is established that solar energy has a potential for replacing non-renewable sources of energy which are commonly used in the modern community (Ghassemi 9). This could serve the crucial role of ensuring effective preservation of the environment. Another advantage of solar energy is that it is a viable solution to the problem of global warming that is threatening the sustainable social and economic development of the human community (Swanson, 2008). It is still evident that many pilot research works on the potential utilization of solar energy in almost all aspects of life have been going on with increasing signs of success. This has the implication that although solar energy is currently underutilized, ongoing technological advancement together with the need to resolve the problem of global warming will dictate for use of solar power in the community.

Plate Tectonics

Large earthquakes are thought to occur more or less regularly in space along major fault systems and, in time, as a result of gradual stress buildup and sudden release by failure. This repetitive cycle of strain accumulation and release, termed the seismic or earthquake cycle, is driven by plate tectonics along the worlds major plate boundaries and fault systems.
(National Research Council, 55)

California has had at least eighty magnitude 6.0 or larger earthquakes in the past two hundred years or so, since the first European settlements on the land. A number of these earthquakes, including the 8.3 magnitude 1906 San Francisco disaster, have occurred along the San Andreas fault, a tectonic plate boundary that is an earthquake threat for both Los Angeles and San Francisco. The San Andreas Fault runs through central and southern California, spanning hundreds of kilometers (Fradkin 4). We can better understand what the San Andreas fault is and why areas flanking this fault line are forever prone to earthquakes by exploring the fundamental geological dynamics of earthquakes, i.e., plate tectonics. The study of plate tectonics helps us have a better notion of how the San Andreas Fault could cause such a huge disaster in the past and can very likely cause an even bigger one in the near future,

Plate tectonics is the study of subterranean movements of the planet. The interior of the Earth is divided into four distinct layers. In the center of Earth is the spherical core, which is made of solid nickel and iron. This is surrounded by outer core, a layer of molten nickel and iron. Thickly wrapped around the Earths liquid and solid cores is the mantle, which is made of molten rock. The top layers of the mantle are called the asthenosphere and lithosphere, which are chiefly responsible for creating earthquakes.
(Source Klous, 24)

Above these layers is the Earths periphery called crust, which is made of solid rock, and rests on top of the uppermost mantle. The part of the crust that makes the continents is 35 to 70 km thick. The part under the oceans, the ocean crust, is much thinner and is only about 5 to 10 km thick. The huge pressure form the crust stops the incredibly hot rock in the mantle from turning into liquid. The solid-rock crust is only the thin outer layer of the Earth, with the mantle taking up nearly of half the earths radius and the outer and inner cores taking up about another half. (Geology.com).
You can think of Earth as something like at giant piece of fruit. Its inner core is like the pit of a cherry or peach. The mantle is like the layer of juicy pulp in the middle of the fruit. The crust is lie the outer skin of the fruit. Compared to the size of the whole earth, the crust is a rather thin skin. (Silverstein et al., 9)

4.5 billion years ago, the Earth was formed out of hot gases. As the Earth cooled, the lithosphere cracked and split into seven large and twelve small floating pieces of a jigsaw puzzle, with uneven and ragged edges. These huge pieces of crust and the upper part of the lithosphere are called tectonic plates, and continuously move over the viscous mantle rubbing and pushing against each other. These plates move at somewhat the same speed as human fingernails grow, ranging from 10 to 130 millimeters per year. The tectonic plates have to move because of the slow swirling movements of semi-molten rock deep in the mantle.

Plate tectonics studies the crunching, grinding and jostling and other dynamics of friction between the giant rocky plates under the Earths surface, on which are situated continents and oceans.  The boundaries between two such massive, constantly moving tectonic plates are called faults. When the Earths plates move against each other, the lithosphere absorbs much stress. However, when this stress accumulates up to a breaking point, the lithosphere breaks or shifts (Glasscoe).

An earthquake is caused by a sudden, violent shifting of the tectonic plates which releases stress that accumulates along geologic faults. The areas lying in vicinity of the fault line are especially susceptible to earthquakes (although significant tremors can occur in relatively stable interior of continents). The San Andreas Fault is a fracture appearing where the North American and the Pacific plates slide past each other. Passing through south California, it is perhaps the most well-known of faults, infamous for causing severe earthquakes.    

The theory of plate tectonics came into its own by 1970s, developing from the continental drift theory which was originally proposed by Alfred Wegner in 1912 and being further bolstered by the Sea Floor Spreading Theory that emerged in the 1960s. Plate tectonics is the science of earthquakes, it also explains the sweeping geological transformation of the planetary landscape over hundreds of millions of years. The theory of plate tectonics has revolutionized the thought paradigm in earth sciences during the past couple of decades. Most of the geological action such as the formation of mountains, volcanoes, rift valleys, is caused by the complex interactions happening at plate boundaries.

Although a knowledge of the planets past and future geological evolution is crucial for understanding our biological evolution as well as for a better understanding of our world in general, the study of plate tectonics is much more relevant and urgent because it explains why earthquakes occur, and why they do not occur randomly, with a majority of them being distributed across relatively narrow and clearly demarcated areas of earths surface called seismic zones. 

The narrow belts of seismic zones happen to be along the boundaries of plates or fault lines, with the interior of these plates being relatively safe and free from earthquakes. Anomalous earthquakes that occur in the interior region of a tectonic plate, despite constituting less than one percent of worlds total number of earthquakes, can still pose significant threat in terms of damage they cause. 

The planet Earth has seven major crustal plates, which are subdivided into many smaller plates. The pattern of their movement is highly complex and shows very little symmetry. The complexity involved is of such a degree that the more we learn about the structure and behavior of the major plates, the more complicated and intricate the motions and maneuvers of these plates have become.

The forbidding complexity of the movement of earths tectonic plates is sadly disappointing because it severely limits our abilities to predict earthquakes in the near future. Although it is easy to point out the general regions on the Earths surface where large-scale earthquakes can be expected, it is still nearly impossible to predict when and where exactly a large earthquake would occur, with any significant degree of accuracy. This is because the general time frame for notable changes happening in plate tectonics is very large, spanning millions of years. Over the span of merely a year or a decade, the minute motions of the plates amount to only several centimeters. Therefore it would be difficult to estimate where exactly an earthquake-prone area such as San Francisco or Los Angeles is positioned in the gradual worldwide processes of strain buildup and strain release.

Close monitoring of movements of stress and strain in local areas can considerably increase our chances of predicting the onset of renewed activity at a fault line, but accuracy still remains an elusive goal. Plate tectonics can lead us to develop more sophisticated techniques for earthquake prediction, and there is still vast scope of improvement in the earthquake predicting technologies we currently have. By the late twentieth century, earthquake predicting technologies were considered to be still in their infancy. Although there have been significant developments in the past decade in this direction, they have not yet led to a dramatic breakthrough, or do not even promise one yet.    

Geological technology developed from our knowledge of plate tectonics may reach a point within the foreseeable future at which scientifically credible earthquake predictions can be made. Some scientists such as Robert J.Geller, a US geologist at the University of Tokyo, however, suggest that earthquake prediction may be inherently impossible. While it remains to be seen how far we can improve our capacity of earthquake prediction in the next several years, the potential havoc that earthquakes can wreak is rapidly increasing, as the tension keeps building up under major metropolitan areas such as Los Angeles and San Francisco. If a major earthquake were to occur in heavily populated areas lying in the vicinity of the San Andreas in the near future  and major earthquakes are already overdue in many parts of California overlying the fault zone  it could lead to a tragedy that may dwarf the great 1906 San Francisco earthquake in comparison. As scientists keep trying to render the predictive methods more effective, the stakes in terms of lives and property that could be saved are increasing at an alarming pace.  

Ocean and Atmosphere Interaction in India

The interactions of the earth and atmosphere occur through advection of materials from one region or part to another. Generally, oceans are embedded on the earths surface, and the air which is the main atmospheric medium usually circulates to the oceanic medium in form of wind. As the winds blow over the ocean surfaces, it interacts with the oceanic medium (water), which either increases or reduces its velocity. Winds blowing on the ocean water surface cause the development of coupling frictional force, known as frictional drag. The developed frictional drag imparts a push force on the water, which sometimes lead to pilling up of oceanic water to form ocean tides. Overtly, the movement of the media in both parts, which is the oceanic waters and the atmospheric air, occur as result of temperature and pressure changes among other factors.
These in turn affects the weather changes of a place or region (Xie, 1994).

The amount of rainfall that is received in any given region is determined by the amount of water vapor available in the atmosphere for precipitation. The variation realized in the quantity of the atmospheric water vapor is largely as a result of the temperature fluctuation within the ocean.  A decrease in oceanic temperatures leads to decrease in the evaporation rate of the water in the ocean surface. The subsequent effect is a decrease in the amount of atmospheric water vapor. Conversely, an increase in the oceanic temperature augments the water evaporation rate, and consequently an increase in the atmospheric water vapor is realized. India is depicted as one of the most affected states by unpredictable weather changes, thus, this has triggered our interest of understanding how temperature and winds, being two of the most important determining factors of the weather affects this region at different periods of the year (Glantz, 1991).

Figure 2 Sea Surface Temperature  Monsoon Winds of January and August
Discussion of the Data
India is a very large region with a wide variation in the monthly weather conditions. The largeness of the study region has dictated the use contrast scale methods, in which different color shades was employed in the collection and representation of the various changes of weather factors of temperature and rainfall in the region. Applying this mode, it was assumed that the higher the concentration and the brightness of the color shade, the greater the intensity and amount of the measured factor. Using the color scale shades to indicate rainfall range of the different parts of the region, its vivid that the region experience two extremes of precipitations. According to the revealed information, India receives a monthly rainfall ranging between zero and 40 mm in the month of January. Most of the high amounts of rainfall are received in the pole parts of the region, while the largest central region experiences the least amount of rainfall, as illustrated in the figure (1), with the blue and light blue shades respectively. Undoubtedly, the extreme parts to the Southern East and the
Northern East had highest rainfall precipitation of all other parts (Glantz, 1991).

During the month of August, the amount of rainfall received in the entire Indian region is generally higher compared to amount received in January. In this month, there is a gradual change in the amount of precipitation received in the region. The North Eastern and the South western Purple shaded are the parts of the region that had a highest amount of rainfall precipitation. The precipitation of rainfall decreased as one moved to the South Eastern and North western parts of the region, as demonstrated by the changing of the color shades from purple, light purple, dark red, red, light red, brown, yellow, dark green, green and  light green respectively. During the month of August, inhabitants in the places along the ocean coastal strip are struck by the South Western and the North Eastern monsoons, which are warm, humid winds that blow along the Indian coast. The low temperature offshore winds blows from the regions of high pressure at the ocean centers to the coastal strips, a region of low pressure. 

The moderately hot offshore winds collect the suspended water vapor over the ocean water surfaces until it becomes saturated. As the temperature in the ocean increase, more water vapor is formed through evaporation process therefore, in order to accommodate and collect maximum amount of the ever increasing amounts of water vapor, the wind expands elastically allowing absorption to take place. As the warm south western and the North eastern monsoons approach the cold region of the Indias Coastal strip, excess heat is conventionally lost to the surrounding cool air, bringing about a decrease in temperature. The winds transverses across the cooler coastal parts, where a large proportion of the water vapor content is condensed, forming clouds that falls as heavy precipitates along the opposite coastal strips. When north eastern and south western wind fronts meet, there is diversion and deviation of the wind direction. This causes the spreading of the unsaturated moist winds to all other parts of the region. 

FUTURE EARTH- CLIMATE OF EARTH (AROUND THE EQUATOR) 250 MILLION YEARS LATER

The story about the climate at the equator 250 million years ago is both interesting and frightening. Interesting, because it puts all the things we concern ourselves with right now in perspective, and they seem very insignificant, and frightening, because of what it suggests is in store for us. It is believed that 250 million years from now, by a process of subduction, a giant continent called Pangea Ultima will be formed, which will consist of North America and Africa married to one another with South America rounding off the bottom of the supercontinent. A miniscule ocean basin will remain at the bottom of the two continents.

This marriage and other changes will cause a big effect on temperature. The huge landmass will mean that winds reaching the land will be denuded of their moisture. Much of what is now southern North America will fall on the Equator. Because it will be robbed of any moisture bearing winds, it will probably become barren, and may even form into a desert. The beaches of Miami will probably be replaced by an Arizona like landscape. In addition to the geosphere, the water bodies (the hydrosphere) will also make a big impact on the temperature and climate around the equator. What is today the Indian Ocean will be trapped, creating a giant lake like body the size of modern Australia.  Being trapped like a lake, the Indian Ocean will not be able to circulate air currents and therefore affect temperature. Parts of the Indian subcontinent that will then (and even today to) fall on the equator will likely not benefit from the South Western and North Eastern monsoons that bring rain and influence temperature.

The atmosphere will not be left behind in this giant drama. The atmosphere acts a conduit in the transfer of heat and water from the oceans and seas to the land. The formation of a new giant ocean and a supercontinent will make the transmission of this heat energy from the sea to the land and water vapour (which is deposited on land as rain) more difficult. Instead of carrying moisture laden winds, large parts of the giant landmasses, particularly around the equator will be affected by hot, dry winds, which will increase temperature on the surface as well. In the same vein, the atmosphere may serve to radiate hot air outwards from the centre of these giant continents to the peripheries, which could increase the temperature in other regions, and also affect the surface temperature. As a consequence, the temperature overall might rise, exacerbating the effect of climate change induced by human factors.

The outlook is not all grim however. Higher temperatures, coupled with a giant lake like Indian Ocean (providing an abundant supply of water) could result in the proliferation of plant life in much of equatorial Africa, South America and Asia. The proliferation of plant life would bring down temperatures and reduce levels of carbon dioxide in the atmosphere, countering the effects of global warming. The contortion of the landmass of Eurasia will bring the eastern parts of Russia, such as the port city of Vladivostok along the equator. The climate pattern in Russia in particular will therefore completely change, becoming much less severe and a lot more temperate and even equatorial. Finally, California and large parts of then equatorial North America will have very heavy, even torrential rainfall. Them being the first landmasses after several thousand miles of ocean, huge amounts of water will be deposited as rain in these parts. This could have a cooling effect on the temperature there.

WATER DEPTH ANOMALY IN GULF OF ADEN

This project seeks to study the water depth anomalies in the Gulf of Aden and its rifted continental Margins. The oceanic crust adjacent to continental rifted margins often shows anomalous water depth (bathymetry) and subsidence history compared to the predictions of ocean lithosphere plate theory. These water depth anomalies are important both for their implications for geodynamic theories of lithosphere temperature structure and also for deep-water oil and gas exploration at rifted continental margins.

A broad region of positive anomalous bathymetry is observed on the young oceanic crust against the Yemen rifted margin in the Gulf of Aden. One proposed hypothesis for explaining this anomalous bathymetry is that the young oceanic lithosphere is underline at depth by relict thicker continental lithosphere with a deep temperature structure different to that of oceanic lithosphere. More mundane explanations for these bathymetric anomalies are that the oceanic crust could simply be thicker than usual or could be underlain by very thin continental crust so giving shallower bathymetry though isostasy. This study therefore uses satellite gravity inversion to map crustal thickness and ocean-continent transition location in the Gulf of Aden and its rifted continental margins. Bathymetric anomalies corrected for sediment loading and lithosphere age is compared with crustal thickness determined from gravity inversion.

1.0 Introduction
The Gulf of Aden within the Red Sea divides the gulf and the horn of Africa. It presents a unique ecosystem and resources that deserves scientific attention. It is characterized by dense, salty water formed by net evaporation with rates up to 1.4 - 2.0 m yr-1 (Hastenrath  Lamb 1979). Approximately three million barrels of oil is being transported daily through the Gulf of Aden. In the olden days, and even now, this Gulf used and still provide a considerable amount of sea food for the inhabitants of the surrounding arid lands (Al Saafani 2008). This Gulf is on the other hand important in transport and livelihoods of the people in the region. It serves as a highway for international trade between east and west. Its importance is fundamental to the fact that the present and future generations of peoples dependence on fishing is at stake. 

The Gulf of Aden is a small oceanic basin bounded by young conjugate passive margins well preserved beneath a thin postrift sedimentary cover (Leroy et al 2004). It is an important characterized by the processes of rifting, and break-up of continental lithosphere and evolution of young oceanic basin. According to Marcos (1970), the Gulf of Aden is characterized by a deep convection in the northern section that leads to the formation of a deep water mass flowing out into the Gulf of Aden underneath a layer of less saline inflowing water.

The existence of the Arabian monsoon is a phenomenon that dominates the region and affects the general oceanography and meteorology of the region. Heileman and Mistafa (2008) confirm that a northeast monsoon winds extend well into the Gulf of Aden and the southern Red Sea during winters, causing a seasonal reversal in the winds over this entire region. The prevalent seasonal monsoon reversal and the local coastal configuration combined during summer season forces a radically different circulation pattern composed of a thin surface outflow and an intermediate inflowing layer of Gulf of Aden thermocline water and a drastically reduced outflowing deep layer (Patzert 1974). The general surface circulation within the basin is cyclonic.
   
2.0 Geological Background of the area
The Gulf of Aden comprises the southern limit of the Arabian plate that started to drift away from Africa around 17.6 million years ago. It is a young ocean basin formed by the rifting of Asia from Africa. Its opening is usually considered as the westward propagation of a lithosphere crack from the Carlsberg ridge to the Afar volcanic area, which now represents the centre of a broad anomalous region with low S-wave mantle velocity, high elevation and much more evidence of mantle plume activity Lucazeau et al (2008). It has a well-defined continental margin, small oceanic basin, and an active mid-ocean ridge (Sheba) in the center characterized by a rift valley and fracture zone. The geophysical survey of the basin, reveals continental, oceanic domains and ocean continent transition (OCT) domains with distinct morphological and sedimentological characteristics (Leroy et al 2004)

According to Al Saafani (2008), the Gulf of Aden is approximately 900 km in length and varies in width from 26 km at Bab el Mandab to about 320 km at Ras Asir. The middle region is the deepest at approximately between 20002500m and the shallow area is less than 1000 m. It has an average depth of 1800m, which increases from west to east. The Gulf of Aden is therefore a modern analogue for the early stages of mature margins (Lucazeau et al 2008), such as the Atlantic margins. The conjugate margins of the Encens Sheba survey area were formed during the last period of rifting. The thickness of the oceanic crust of the Gulf of Aden varies from 4.8 to 8.4 km, as interpreted from a seismic refraction survey (Cochran, 1982). In these margins, the actual thermal regimes can be analyzed directly by means of surface heat flow, seismic tomography or regional isostasy, and compared with the observed tectonic and magmatic styles.

Through the ArabiaSomalia Plate, successive Jurassic and Cretaceous rifting episodes have created major basins (Leroy et al 2004 Cochran, 1982). These basins have a predominant eastwest to northwestsoutheast orientation. Seafloor spreading is more recent in the western part of the Gulf of Aden than in its eastern part according to previous magnetic anomaly studies, and that a magnetic quiet zone corresponds to an area of thinned crust (Leroy et al 2004). The structures and evolution of the Gulf of Aden margins are related to successive development of the formation of the Gulf of Aden during the Oligo-Miocene and the continental margin of the Indian Ocean during the Early Cretaceous up to the Paleocene (Leroy et al 2004 Besse and Courtillot, 1988).

According to dAcremont et al (2004), during the Oligocene times, the Afro Arabian Plate began to separate due to the creation of two divergent basins, which both evolved in the development of two narrow oceanic basins that comprised of the Gulf of Aden to the south, between Arabia and Somalia and the Red Sea to the west, between Arabia and Africa (Nubia). The East African rift forms the third branch of the Afar ridgeridgeridge type (RRR) triple junction (dAcremont et al 2004 Wolfenden et al. 2004) that is still in the rifting stage. This later Oligo-Miocene stretching episode of the ArabiaSomalia Plate reactivated inherited structures of these Mesozoic basins (dAcremont et al 2004 Ellis et al.1996 Granath 2001 Bellahsen 2002).

3.0 Water depth anomaly in the Gulf of Aden and why it is shallower than it should be.
The water depth anomaly in the Gulf of Aden is shallower than it should be because of eddies, outflows and evaporation due to high and recent rise in sea surface temperatures (SST) during summers seasons. According to Bower et al (2005) the Saline, dense Red Sea Water (RSW) originates in the northern Red Sea because of an excess of evaporation over precipitation. It enters the Gulf of Aden (GOA) in the northwestern Indian Ocean as a dense overflow through the shallow Bab el Mandeb. The Red Sea Outflow Water (RSOW) is the entrained mixed product water that descends from the  INCLUDEPICTURE httpjournals.ametsoc.orgna101homeliteratumpublisheramsjournalsentities223C.gif  MERGEFORMATINET 150 m deep Hanish Sill in the northern BAM Strait, less dense fresher water. However, during winter, the Red Sea outflow transport is typically about two times the annual mean because of monsoon winds and seasonal fluctuations in buoyancy forcing. Outflow transport reaches a maximum ( INCLUDEPICTURE httpjournals.ametsoc.orgna101homeliteratumpublisheramsjournalsentities223C.gif  MERGEFORMATINET 0.6 Sv) in winter (OctoberMay), when prevailing monsoon winds over the region are from the south-southeast (Bower et al 2002).

There have been recently numerous and new oceanographic observations in the Gulf of Aden along the northwestern Indian Ocean. Some studies have shown large, energetic, deep-reaching mesoscale eddies (Bower et al 2002) that contribute and influence the spreading rates and pathways of intermediate-depth Red Sea Water (RSW). The other important pieces of the thermal puzzle are the present-day topography, gravity, seismic velocities and all the geological aspects contribute to the shallowness. Comparison of salinity and direct velocity measurements (Bower et al 2002) indicates that the eddies advect and stir RSW through the Gulf of Aden and the anomalous water properties in the center of the anticyclonic eddy point to a possible formation site in the Somali Current System.

The exchange flow has a two-layer structure, with dense, saline RSW flowing out at the bottom, and less dense GOA surface water flowing toward the Red Sea in the upper layer. During summer (JuneSeptember), prevailing winds from the north-northwest drive a surface flow out of the Red Sea, and GOA water flows in via an intermediate layer sandwiched between the surface layer and a thin layer of outflowing dense RSW, producing a three-layer exchange flow. The overflow results from an excess of evaporation over precipitation in the entire Red Sea is estimated to be about 2 m yr_1.

The existence of mesoscale eddies and currents contribute to the water depth. Low oxygen water perists throughout a wide depth range in the intermediate waters of the Arabian Sea. The extensive exchange of water between the Red Sea, the Gulf of Aden and the Arabian Sea, the strong evaporation and the monsoonal winds that blow over the region, all assist in the formation of complex vertical structures in the water column of the Gulf of Aden (Al Saafani 2008). As argued by Yamanaka et al (2008), the resultant outflow from the Red Sea through the Gulf of Aden is considered to play a strong role in determining the properties of these intermediate waters

Several studies and research have been done to ascertain the reasons for shallowness in relation to water depth anomalies in this Gulf. Bower  et al (2005) conducted a study dubbed the Red Sea Outflow Experiment (REDSOX), which was the first comprehensive field study of the hydrography and circulation of both the descending Red Sea outflow plume, and the equilibrated RSOW in the GOA. The study aimed at achieving the following
describing the pathways and downstream evolution of the descending outflow plumes in the western Gulf of Aden, quantifying the processes that control the final depth of the equilibrated RSOW, and
Identifying the transport processes and mechanisms that advect RSOW and its properties through the GOA and into the Indian Ocean.

This study have revealed new large, energetic, deep-reaching eddies in the Gulf of Aden that fundamentally influence the spreading of RSW. With the use of Shipboat Acoustic Doppler Current Profiler (SADCP), measurements at 100 and 300 m reveal that currents in the Gulf of Aden were strong and organized into coherent eddy structures in February 2001 (Bower et al 2002). The most conspicuous feature is an energetic cyclonic eddy adjacent to the Somali coast in the southwestern part of the gulf.

From these studies we can deduce that the outflow waters reached neutral buoyancy where the bathymetric channels empty into the deep Tadjura Rift during winters and the northern channel was the source for the most saline, deepest and densest salinity maximum. Outflow currents are lower during summer due to evaporation. The outflow water reached neutral buoyancy somewhat upstream of the channel exits, with lower salinity, temperature, and potential density in comparison with winter (Bower et al 2002). It is also evident that the two deeper salinity maxima at nominal depths of 600 and 800 m, are initially more confined by the walls of the Tadjura Rift. Waters associated with both maxima are generally swept southward out of the rift through gaps in the southern rift wall and also along the continental slope.,

Other theories suggest that magma accumulation, heat and changing atmospheric pressure. Lucazeau et al (2008) alleges that accumulation of magma below the OCT crust could produce the expected thermal and density anomaly by advection of hotter and lighter material and release of latent heat. He further explains that another alternative is serpentinization of the continental mantle, which might be exposed and fractured in the OCT and then percolated by water flows, as observed at several locations on mid-ocean ridges. Al Saafani (2008) noted that the atmospheric pressure at mean sea-level is highest during January and lowest during July at Aden with a range of 10 m bar.
How to get the data to produce gravity inversion maps
There are several ways of getting data and deriving gravity inversion maps. The methods are presented here.

Gravity
An appropriate method for producing gravity inversion maps is by modeling geological zones having anomalous density. It basically involves determining the top of the anomalous zone from non-potential fields data. For this case, for example, the westward continuation into the Gulf of the axial trough and linear magnetic anomalies of the Sheba Ridge is often used. A potential fields data is then used to derive the lower boundary of the geologic anomalous zones.

Figure 1 Gravity map
A lower boundary to an anomalous zone is formulated by predicting parameters representing the lower boundary within predetermined limits. Gravity and bathymetry profiles across the Carlsberg Ridge in the Indian Ocean are analyzed to investigate the isostatic compensation of this part of the Indian Ocean spreading ridge system. This is done by using a gravity inversion process on the potential fields data, such as measurements of gravity data andor magnetic data. These may be in both vector and tensor form. The potential fields data is compared to the predicted fields from the results of the inversion process to obtain a difference between the two. If the difference exceeds a predetermined value, the parameters representing the anomalous zone are adjusted to improve the fit. When the lower boundary limits are reached or the difference between the model and the data is less than the predetermined value or convergence is attained, the anomalous zone has been determined.

Bathymetry
The Gulf of Aden comprise two bathymetric channels that originate seaward of Perim Narrows and direct the dense RSW from the strait to the open ocean. One can use 3-D seismic array to map crustal stretching across and along the margins. User receiver functions can be used to retrieve crustal thickness and crustal composition along the margins. Another option is utilizing the ocean wave-shoaling photographic imagery. The instrument used for the acquisition of sea-surface image sequences is a ground-based nautical X-band radar with horizontal polarization. The device utilized during the experiments is a softwarehardware combination consisting of a commercial, navigational Furuno X-band radar antenna and radar device. In the case of datum determination, a tidal-gauge-measurement is used.
 SHAPE   MERGEFORMAT
Figure 2 Bathymetry map

Other cross-spectral techniques are employed to obtain an admittance function for isostatic studies. Synthetic topography and gravity profiles are computed for a cooling plate model are subtracted from the observed, to estimate the median valley signatures. The residual gravity anomaly over the ridge axis is mostly explained by the median valley topography with a uniform crustal thickness. Spatial profiles are developed using contours, seismic data or satellite imagery to create 3D maps. Then the profiles are created with a known parameter, a prerequisite for checking depth and depth inversions. Depth inversion occurs when an observation has a shallower depth than the observation directly preceding it.

The sonar instrument uses a transducer that is usually mounted on the bottom of a ship. The sound pulses are sent from the transducer straight down into the water where the sound reflects off the seafloor and returns to the transducer. It is claimed that acoustic penetration into the sea bed increases with decreasing frequency. The distance to the seafloor is calculated based on the time the sound takes to travel to the bottom and back to the surface. Water depth is estimated by using the speed of sound through the water. The sound pulses are sent out regularly as the ship of opportunity moves along the surface, which produces a line showing the depth of the ocean beneath the ship. This continuous depth data is used to create bathymetry maps of the survey area.

4.3 Age
The age is mapped by shipborne magnetometers which allow delineation of zones of normal and reversed magnetic polarity. The magnetic zones form distinct stripes on the map as the oceanic plates grow. Heat flow measurements are another method of age determination and inversion map production. The average value of heat flow measurements calculated from measurements and other collected data indicates that the age of basins and margins.

SHAPE   MERGEFORMAT
Figure 3 A map showing age
The thermal gravity anomaly can be conditioned using ocean isochrons from plate reconstruction models to provide the age and location of oceanic lithosphere (Chappell and Kusznir 2008). There is a relationship of water depth with age. The agreement in age from both heat flow and water depth data favors aids in age determination. The map production using all these characteristics helps in determining geologic events with respect to their dates. 

4.4 Crust thickness
According to Lucazeau et al (2008), the high resolution 3-D forward modeling approaches reveal a possible crustal thickness and density distribution beneath.  The use of satellite remotely sensed imagery give precise information about the sediments and sea bed. The seabed, basement and mantle boundaries are defined by a series of triangular facets, whose size varies as the amount of constraining data changes. The sediment and basement boundaries and the base of the crust are defined by larger facets than those defining the bathymetry.

SHAPE   MERGEFORMAT
Figure 4 Crust thickness map
Another method is the use of a mechanical bed level detection in combination with DGPS. The bed level soundings are often performed by use of a vehicle moving through the surf zone. Alternatively the water depth can be measure by using the single-beam echo sounder. The sonar instrument is used to measure the crust thickness. The Instrument measures the vertical distribution of the Turbidity turbidity levels in the water column, transition from water column to bed based on the scattering of light from the suspended particles and the bed material particles and transition from water column to air.

5.0 How the data is collected for Satellite gravity inversion.
Analysis of satellite gravity data offers an opportunity to rapidly evaluate the sedimentary structure of basins. The accurate and evenly distributed measurements of the gravity field determined from satellite orbits contain information about the bathymetry, age, sediment thickness and crustal structure of the worlds oceans. The data is collected from satellite based methods.

Many organizations have carried out seismic surveys, opportunity vessels and satellite sensors to collect data for gravity inversion maps. These institutions have archived them and available to the general public. For instance, the sea level data from satellite based altimeters is used and obtained from, for example, Archiving, Validation, and Interpretation of Satellite Oceanography Data (AVISO) operations canter. AVISO distributes sea surface heights (SSH) and sea level anomalies (SLA) measured by Jason and ERS12 satellites (Al Saafani 2008) Jason and ERS12 altimeter data helped in better resolving the mesoscale variability and the data provides more homogeneous and reduced mapping errors than the individual data set. The National Oceanic and Atmospheric Administration (NOAA) as a federal US agency focused on the condition of the oceans have a lot of satellite data.

The measurements made by the sensors mounted on board satellites are used, especially, Seas Surface Temperatures (SST) and the sea level heights are measured by the satellite based altimeters and the sea winds measured by the scatterometer. Other profiling instrument such as the ConductivityTemperatureDepth (CTD), Expendable Bathythermograph (XBT) and Mechanical Bathythermograph (MBT) and the Ocean Station Data (OSD), obtained using reversing bottles attached with reversing thermometers are used (Al Saafani 2008).

The use of hyperspectral sensing as one of the Remote sensing remote sensing techniques can be used to generate maps of the seafloor. A model technique is the Hyperspectral Mapping (HyMap) that is widely used in bathymetry and sea floor mapping. This process involves transformation of subsurface reflectance to the bottom albedo. According to Heege et al (2003), the unknown input value of depth is calculated iteratively in combination with the spectral unmixing of the respective bottom reflectance. The unmixing procedure produces the sea floor coverage of three main bottom components and the residual error between the model bottom reflectance and the calculated reflectance. The final depth, bottom reflectance and bottom coverage is achieved at the minimum value of the residual error. The final step of the thematic processing classifies the bottom reflectance due to the spectral signature of different bottom types and species using a Fuzzy Logic method and assignment of individual probability functions for each defined sea floor component (Heege et al 2003).

The gravity inversion maps
Thermal Gravity anomaly
Thermal gravity anomaly is generated by the gravitational admittance that modifies the topography. The thermal gravity anomaly is attributed the early stages in the formation of divergent margins when the lithosphere experiences large changes in temperature which play a key role in the anomaly of the Gulf of Aden.  Evidence suggest that in this regions, thermal anomaly in the upper mantle that has persisted after continental break-up. According to Chappell and Kusznir (2008), the oceanic lithosphere thermal model is always used to predict the lithospheres thermal gravity anomaly.  In the deeper parts of the margin the heat flow is high and constant, but it decreases abruptly near the shelf-slope.

Thermal gravity anomaly parameters contain information on the state of isostacy for a surface topography feature. The sensitivity of the lithosphere thermal gravity anomaly and the predicted ocean depth from gravity inversion maps are always correlated. Variations of the sea floor bathymetry constitute a load distribution on the oceanic lithosphere. The presence of shallow-water sediments deposited after the opening of the Atlantic Ocean hints at lower subsidence than would have occurred in the absence of persistent thermalanomalies.
         
Figure 5 Thermal gravity anomaly maps (mgal) a) with sed and b) with sed and volcanic corrections.
As shown in figure , the curve along the gulf is more shallower than towards the ocean, hence reduction in water discharge, the latent heat due to high temperatures and eddies contribute to the water depth anomaly in the shores of Yemen.

Thinning Factor
The lateral density changes caused by the elevated geotherm in thinned continental margins such as the Gulf of Aden and adjacent ocean basin lithosphere yield important thermal gravity anomaly. According to Leroy et al (2004), magnetic quiet zone corresponds to an area of thinned crust. Lucazeau et al (2008) argues that the lithosphere in the deep margin should be locally hotter and more buoyant than any homogeneous margin. There are several methods to determine crustal depth, lithosphere thinning and the location of the ocean-continent transition at rifted continental margins using 3-D gravity inversion which includes a correction for the large negative lithosphere thermal gravity anomaly within continental margin lithosphere.

Figure 6 Thinning Factor maps a) with sed correction and b) with sed and volcanic corrections
Sediment Thickness
The sediment thickness can be obtained from geophysical studies and associated gravity inversion maps. For instance, a three-dimensional Bouguer anomaly map is produced for dimensional inverse approach to gravity data interpretation. The Bouguer anomalies along the axial portion of the rift floor, as deduced from the results of the regional and residual separation, are mainly caused by deep-seated structures.

Figure 7 Sediment Thickness map
The use of satellite remotely sensed imagery and hyperspectral remote sensing gives precise information about the sediments and sea bed. The seabed, basement and crust boundaries are defined by a series of triangular facets with their sizes varying as the amount of constraining data changes. In this case, the sediment and basement boundaries and the base of the crust are defined by larger facets than those defining the bathymetry.

Figure 8 Volcanic addition map (m)
Mantle Residual Anomaly
There are prominent slow anomalies within the Gulf of Aden and the entire Indian Ocean unlike the fast the central Atlantic and the older parts of the Pacific. Since most of the large slow anomalies define geoid highs, Leroy et al (2004) indicates that there is poor overall correlation between velocities in the upper mantle and the geoid because subduction zones in general are associated with geoid highs and regions of fast velocity below.
     
Figure 9 Mantle Residual Anomaly (mgal) a) with sed correction and b) with sed and volcanic corrections
These maps identify target area of study using satellite gravity inversion. The maps are compiled from seismic data, surface and wave data and contoured to produce the exact heights of the crust at various points. Embedded thermal correction and prediction of Gulf of Aden crust thickness is used to map crustal thickness. The map shows thickening of the crust from Red Sea and Gulf of Aden eastwards and northwards. This crust is inherent in the middle of the Arabian plate.

7.0 Summary
The water depth anomaly has been analyzed to describe the vertical and horizontal structure of Red Sea. The outflow water in the western Gulf of Aden, at the location where it is first injected into the open ocean is one contributor to shallowness despite the high atmospheric temperatures and eddies among the contributing factors. An important region for oil exploration and shipping, the application of 1km resolution imagery aids in the studies and development of this region.

This project is focused on how to create gravity inversion maps and the general application of satellite data in bathymetry, SST estimation, thinning and age determination. It is evident that the Gulf of Aden existing in the slow Indian Ocean margin is experiencing water depth anomalies especially during summers. Remote Sensing and Earth observation does not only cover the global and regional survey of geophysical parameters by satellite- or airborne radars, it also includes local observations by ground based radar techniques.