Unit 4

clinate

is the most important factor influencing soil type and thickness. Soils that form in humid regions have plenty of moisture in the system, effective chemical weathering processes, and adequate precipitation. In humid regions, the topsoil has much of the soluble material leached out so the mineral content is stable, and there is likely plenty of organic matter to provide nutrients to vegetation. In arid to semi-arid regions, the topsoil contains less organic matter and more unstable minerals since there is little precipitation to leach them out. In tropical regions, chemical weathering is intense and leaching is more complete. The soils are mostly composed of aluminum hydroxides, with little nutrient value for agricultural crops.

parent material

is the underlying bedrock which provides the base material that was weathered to create the overlying soil horizons. Just as we classify rocks based on the mineral content and mode of formation, soils are characterized, classified, and mapped on the basis of their horizon development and elemental composition. The Soil Survey Division of the Natural Resources Conservation Service divides soils into 12 major soil orders and then further subdivides them into smaller groupings based on parent material, vegetation, and climate. Soil science is its own discipline, and many dedicated scientists have contributed valuable research regarding soil conservation and best management practices to retain and manage soil resources.

O horizon

is usually only a few centimeters thick and is composed of organic matter. Plant remains such as leaves, twigs, seed husks, and others in various states of decomposition are clearly visible in the upper part of this horizon, but in the lower part organic matter is more decomposed and is referred to humus.

slope steepness

plays a role in soil development; soils cannot accumulate and form easily on steep slopes, but can more readily on gentle slopes or flat topography. Slope aspect is another factor, in the Northern Hemisphere, north facing slopes receive less direct sunlight, have cooler temperatures, support different vegetation, and if in a cold climate, remain snow covered or frozen longer.

Eastern US

where precipitation is abundant, chemical weathering is intense, and there is a rich layer of organic matter to provide soil nutrients and humus, pedalfers form. Pedalfers are soils rich in aluminum (Al) and iron (Fe), are mostly fertile and productive, and contain stable minerals in the topsoil to provide structure and nutrients for vegetation. Since the development of these soils are controlled by climate, these soils also form in the Pacific Northwest where precipitation is abundant.

Western US

where precipitation is less, chemical weathering is not as prevalent so horizon development is less and the topsoil contains more unstable minerals. Soils that form in this region are called pedocals; with the primary elemental content of calcium (Ca). One of the primary minerals found in these soils is calcite, which can go into solution readily and precipitate in the subsoil forming irregular masses of caliche, a hard mass of clay material that stunts root development. In some arid regions, the evaporation of soil water leaves behind sodium salts creating alkali soils that are unable to support vegetation.

Inertinite

- oxidized remains of plants and fungi and is highly reflective; dark black substances in coal.

Liptinite

- spores, cuticles, waxes, resins and algae; usually a dark grey color with view visible characteristics in coal.

Vitrinite

- woody material such as branches, roots, leaves, or other visible pieces of plant material; usually dull brown to grey in color.

reservoir

A body of permeable rock containing oil and natural gas is called a reservoir. Several important factors must exist for hydrocarbons to accumulate and be extracted by geologists, including: source rock reservoir rock cap rock

glaciers

A glacier is a moving body of ice on land that flows downslope or outward from an area of accumulation. This definition of a glacier would not include frozen seawater found in North Polar region or drifting icebergs; icebergs may have come from a glacier at one point, but the critical aspects of this definition are "moving" and "on land". Glaciers are divided into two general categories: mountain or valley glaciers that exist as narrow bodies of ice, generally associated with mountain ranges (picture A below); and continental glaciers that cover most or all of a land mass, such as the Greenland glacier (picture B below) or Antarctic glacier.

soil profile

Depending on the degree of soil development, soil is composed of distinct layers called horizons. These horizons differ in texture, structure, composition, and color. From the surface, the soil horizons are:

dry lake beds

Dry lake beds, especially the salt flats of the Great Salt Lake, have been used for automobile speed trials because they are the most level surfaces above sea level. Rogers Dry Lake in California is used as the landing strip for the space shuttle and is home to Edwards Air Force Base. Smaller playas, such as the picture below from Death Valley, California, hold water during the monsoon season but the water is saline from the dissolved salts; one of the many reasons settlers headed west into California had so much trouble crossing the area. Playas are also known for a variety of salts and useful clays, mineral resources found in their sediments.

erosion

Erosion is an ongoing natural process, and is usually slow enough for soil formation to keep pace, but human practices add to the problem. Removing natural vegetation by plowing, overgrazing, overcultivation, and deforestation all contribute to soil erosion. Soil erosion destroys fertility, eroded soil settles in lakes and streams clogging waterways, and deposits excess sediment, pesticides, and nutrients in our water. The U.S. has one of the most advanced soil conservation programs, we still lose an estimated 2 billion tons of topsoil every year to erosion.

glacier water resources

Glaciers make up one water resource reservoir in the hydrologic cycle where water is stored for an extended period of time, but even this water eventually returns to its original source, the oceans. Many glaciers at high latitudes, as in Alaska, northern Canada, and Scandinavia, flow directly into the oceans where they melt, or icebergs calve and drift out to sea where they eventually melt. At low latitudes or areas remote from the oceans, glaciers flow to lower elevations where they melt and the liquid water enters the groundwater system or it returns to the oceans as runoff through streams and rivers. In addition to melting, glaciers lose water by a process called sublimation, when ice changes from a solid directly to a vapor without an intermediate liquid phase. Glaciers can release water vapor directly to the atmosphere, where it will eventually condense and fall as precipitation, returning to the oceans.

gravity

Gravity causes water in streams to flow down slope. The motion of the water is a kind of energy (kinetic energy) that causes the stream to erode rock, transport and deposit sediment, and modify the shape of its valley.

Porosity and Permeability

Hydrocarbons are trapped in holes within reservoir rock, called pores. As porosity, the total volume of pores increases, the amount of petroleum in a reservoir increases. However, the size of pores and degree that they are connected - known as permeability, will control the ability for petroleum to pass through the rock. If permeability is low, the pores are poorly connected and hydrocarbons cannot be extracted. If permeability is high, the pores are well connected and much of the petroleum in the reservoir can be extracted. The combination of porosity and permeability determine whether or not a hydrocarbon reservoir is economic to develop. In the figure below, the two boxes have equal porosity; however, the permeability of the box on the left is significantly higher than the permeability of the box on the right - In addition to porosity and permeability, the viscosity of the fluid will determine how easy the hydrocarbons can be extracted. Viscosity is the resistance of a fluid to flowing. Water has a low viscosity while maple syrup has a high viscosity. The lower the viscosity, the easier the hydrocarbon is to extract.

shallow coal mines

In open pit mines, shallow coal resources are mined by removing the overlying sediment, called overburden, with heavy machinery including large drag lines (see pictures below). The coal is then extracted and transported to a power facility for combustion and the open-pit is refilled with the overburden material that had been extracted. Because underground mines are significantly more expensive to operate, generally only higher grade coals such as anthracite and bituminous coal are extracted this way. In East Texas, most of the coal resources are lignite grade and occur at depths less than one hundred feet; therefore, open-pit mining is used; any lignite resources at greater depths are currently not economical to mine in East Texas.

source rock

In order for petroleum reserves to accumulate, organisms that would eventually become oil and gas settled to the bottom of the sea or lake bed with other fine-grained material such as clay or fine-grained carbonate. The transition from various types of largely solid organic material in the original sediment, to the liquid and gas of petroleum and natural gas contained within the rock involved both heat and some pressure. The heat source was generally just the natural internal heat of the Earth and the pressure was supplied by the overlying sediments. The resulting shale or limestone would eventually be known as a source rock, the rock that originally contained the organic material that has become oil or natural gas. However, because the source rocks are fine grained, their permeability is low and therefore the oil and gas would be difficult to extract from them. Most source rocks beneath the Earth's surface are saturated with water.

coal mining

In order to use coal as an energy resource, it must first be extracted from the ground by various mining processes. For thousands of years, humans have utilized coal as a fuel source to burn for heat. Peat is often dug out the ground by hand with shovels (see pictures below) and then dried to remove the excess water before burning. Peat has been used for centuries as a heat source. There is an estimated 4 trillion m3 of peat in the world, covering approximately 2% of global land area. Peat also functions as one of the most efficient carbon sinks on the planet. - Higher grades of coal require much more extensive mining operations, either in open pit mines or in underground mines. If the coal is deep in the subsurface, underground mines are used, where workers physically mine out layers of coal and then transport them to the surface.

Soil Degradation

In the context of geologic time, soils form rapidly. Although weathering processes are continually breaking down rock into sediment, and sediment is part of soil structure, but for practical purposes soil is a non-renewable resource, at least in the human dimension of time. Any soil losses that exceed the rate of soil formation and any reduction in soil fertility or production are causes for concern. Any process that removes soil or makes it less productive is defined as soil degradation. - Globally, an area the size of China and India combined has suffered soil degradation from agricultural activities and overgrazing, mostly in Asia, Africa, and Central and South America.

glaciers globally

The vast majority, almost 90%, of Earth's ice mass is in Antarctica, while the Greenland ice cap contains 10% of the total global ice mass. The Greenland ice cap is an interesting part of the water cycle. The ice cap became so large over time (about 600,000 cubic miles) because more snow fell than melted. Over time, as the snow got deeper, it compressed and became ice. The ice cap averages about 5,000 feet in thickness, but can be as thick as 14,000 feet. The ice is so heavy that the land below it has been pressed down into the shape of a bowl. In many places, glaciers on Greenland reach to the sea, and one estimate is that as much as 125 mi3 of ice calves (break off) into the ocean each year—one of Greenland's contributions to the global water cycle. Ocean-bound icebergs travel with the currents, melting along the way. Some icebergs have been seen, in much smaller form, as far south as the island of Bermuda.

oceans

The water cycle describes how water moves through the various reservoirs, but much more of Earth's water is not transitioning from one reservoir to the next - most of it resides in the largest reservoir, the oceans. The oceans are the ultimate base level for much of the water that precipitates from the atmosphere, flows through rivers and lakes across the surface, and percolates through soils, sediments, and aquifers as groundwater. Although it is impossible to accurately measure the volume of water in the oceans at any given time, the U.S. Geological Survey (and others) estimate that the world's oceans hold 321,000,000 cubic miles (mi3) of the the Earth's water, approximately 96.5%. It is also estimated that the oceans supply 90% of the evaporated water that goes into the atmospheric reservoir of the water cycle.

Nonmetallic Mineral Reserves

The yearly per capita consumption of nonfuel mineral resources in North America exceeds 10 tons, 94% of which is nonmetallic, with the major bulk being construction materials. The nonmetallic minerals are subdivided for convenience into three groups based on their use in industry, agriculture, and construction.

lignite

has a high moisture content and breaks apart easily (picture B below). Of all the ranks of coal, lignite contains the least amount of carbon. Sometimes called brown coal, lignite is mainly used by electricity generating plants. Many plant fragments are easily recognized in hand sample. Geologically speaking, lignites are relatively young coals, mostly occurring in Tertiary and Mesozoic rocks.lignite coalcoal has a high moisture content and breaks apart easily (picture B below). Of all the ranks of coal, lignite contains the least amount of carbon. Sometimes called brown coal, lignite is mainly used by electricity generating plants. Many plant fragments are easily recognized in hand sample. Geologically speaking, lignites are relatively young coals, mostly occurring in Tertiary and Mesozoic rocks.

Anthracite coal

has the highest carbon content, burns slowly, and makes a great heating fuel for homes. The United States has about 7.3 billion tons of anthracite, most of which can be found in Pennsylvania. Anthracite contains over 90% carbon and burns with a smokeless flame.

industrial minerals

include those that contain specific elements or compounds that are used in the chemical industry such as sulfur and halite; and those that have important physical properties such as materials used in ceramics and abrasives. Sulfur is one of the most important industrial compounds and is obtained as a by-product of petroleum refining and from the tops of salt domes (see picture below). More than 80% of domestic U.S. sulfur is used to make sulfuric acid, used in phosphate fertilizers.

B horizon

is also called the subsoil, and has fewer organisms and less organic matter than the topsoil. This horizon is also called the zone of accumulation, because soluble material from the topsoil is transported downward and accumulates in the subsoil in irregular masses.

A horizon

is also called the topsoil, and has more organic matter than the horizons below. Within the topsoil, there is a lot of biological activity from plant roots, fungi, bacteria, and worms. Because soil formation starts at the surface and works downward, the A horizon has been altered the longest and is the most changed from the parent material than the horizons below.

peat

is an accumulation of partially decayed vegetation or organic matter that is unique to natural areas called peatlands or mires (picture A below). Peat is harvested as an important source of fuel in certain parts of the world. Over time, the formation of peat is often the first step in the formation of other ranks of coal.

Time

is another important factor in soil development. Although it is difficult to state how quickly or slowly soils form due to differences in climate and parent material, the average time for soil development is approximately 2.5 centimeters (1 inch) per 100 years. Generally speaking, soil develops faster on unconsolidated sediment than it does on bedrock. Younger soils tend to be thinner with less horizon development than older soils.

organic activity

is important to soil formation; soils depend on organisms for their fertility and in return they provide a suitable habitat for many organisms. From the smallest bacteria and microbes to moles and other burrowing animals, they all contribute to soil formation and provide humus when they die and decompose by bacterial action. Burrowing animals also churn and mix soils, and their burrows provide avenues for the exchange of gases and water. Soil organisms, especially some types of bacteria, are extremely important in changing atmospheric nitrogen into a form of soil nitrogen suitable for use by plants.

E horizon

is not always present, but if it is, it presents as a pale layer with little carbon material. The E horizon is most often present in older, more mature soils, and is formed by the leaching of minerals by soil water flowing downward from the topsoil above.

concentration factor

A particular ore deposit may be described in terms of its concentration factor, its enrichment expressed as the ratio of the element's abundance. For example, aluminum is one of the most common elements in the Earth's crust, and has a crustal abundance of about 8%. A "good" aluminum-ore deposit contains about 35% aluminum; the concentration factor for profitable mining of aluminum ore is about 4. In contrast, deposits of some rare elements, such as uranium, lead, gold, and mercury, must have concentration factors in the thousands to be considered mineral resources. - Some elements are extremely common; over 98% of the Earth's crust is composed of only eight elements: oxygen, silicon, aluminum, iron, sodium, calcium, potassium, and magnesium. For most elements, the average crustal abundance is only a fraction of a percent. Copper, for example, is rather rare; its average crustal abundance is only 0.0058%. In some localities, natural geochemical processes have concentrated it in mineral deposits that are 2% to 4% copper. A deposit with a high concentration of a desired element is called a high-grade deposit. A deposit in which the mineral content is minimal but still exploitable is called a low-grade deposit. For either grade of deposit, localities where desirable elements are concentrated sufficiently for economic extraction are relatively rare.

factors in soil development

All soils form by mechanical and chemical weathering processes, but they differ in color, texture, thickness, and fertility. The factors that control soil development, the location in which the soils are forming, and how rapidly soil forming processes are occurring, all contribute to the type of soil that will develop in a particular location and climate. The most important soil forming factors are:

the atmosphere

Although the atmosphere may not be a great storehouse of water, it is the superhighway used to move water around the globe. Evaporation and transpiration change liquid water into vapor, which ascends into the atmosphere due to rising air currents. Cooler temperatures aloft allow the vapor to condense into clouds and strong winds move the clouds around the world until the water falls as precipitation to replenish the earthbound parts of the water cycle. About 90% of water in the atmosphere is produced by evaporation from water bodies, while the other 10% comes from transpiration from plants. There is always water in the atmosphere. Clouds are the most visible manifestation of atmospheric water, but even clear air contains water—water in particles that are too small to be seen. One estimate of the volume of water in the atmosphere at any one time is about 3,100 cubic miles, approximately 0.001% of the total Earth's water volume of about 332,500,000 mi3. If all of the water in the atmosphere rained down at once, it would only cover the globe to a depth of 2.5 centimeters, about 1 inch.

where to find oil and gas

Because hydrocarbons are lighter than water, they migrate upwards through the subsurface. Geologists look for areas beneath the ground where large accumulations of hydrocarbons are expected to occur; these areas are called hydrocarbon traps. Traps form when the layers of rock are not completely horizontal and promote the upward flow of hydrocarbons towards a confined area where they become trapped under a cap rock. Changes in the type of sedimentary rocks can produce traps where a more porous rock grades into a less porous rock, such as sandstone transitioning into a mudstone. Folds in the rock layers can provide domal structures or upward arched structures called anticlines that trap hydrocarbons. Faults are breaks in rock layers which may also produce structural traps where hydrocarbons can be trapped. Therefore, petroleum geologists are always looking for areas where changes occur in sedimentary rock that might provide locations for hydrocarbons to accumulate Another type of structural trap common in the East Texas area is a salt dome. A salt dome is a mound or column of salt that has risen toward the surface because it has a density that is lower than the rock above it. As we learned in the previous unit on Earth Processes, during the early Mesozoic era as the Gulf of Mexico was just beginning to open, vast layers of salt were deposited across the area which is now the Gulf Coastal Plains (see map below left). The salt was eventually covered by other sediments, and as the burial depth increased, the salt began to deform and flow like a high-viscosity fluid under pressure. These columns of salt are referred to as diapirs (see figure below right), and these diapirs prevent the migration of hydrocarbons in the subsurface, allowing valuable resources to collect around and near the salt domes.

coals

Coal is generated from compressed or lithified remains of plants deposited in a low oxygen environment. Most coal began forming in swamps or bogs where plants grew in great abundance and accumulated in thick deposits. Because the accumulations of plant remains were so thick and the water flowing through the swamps was moving so slow, the oxygen in the water was rapidly used up and bacteria were not able to decompose the plant matter as they would on the land surface or in shallow soils. In the geologic past, coal has formed from the late Devonian when land plants evolved to present day humid environments where organic matter accumulates. The United States holds the world's largest estimated recoverable reserves of coal. In 2013, U.S. coal mines produced approximately one billion short tons of coal and more than 90% of this coal was used by U.S. power plants to generate electricity through steam turbines. In 2012, 1,016.4 million short tons of coal were mined in 25 states, generating approximately 37% of the 4 trillion kilowatt hours of electricity generated in the United States.

types of coal

Coals are ranked based on the degree of coalification, their level of organic metamorphism, and their maceral content. Macerals are the original organic sediment that makes up the coal; definite classification of macerals usually requires a microscope, however, the general appearance of each maceral type and their relative abundance is often enough to determine the type of coal in a hand specimen. Relative maceral composition changes with coal maturity as various maceral types are destroyed by heat and pressure; the deeper the coals are buried below the surface, the increase in coalification, and the conversion of the macerals. Macerals (picture below right) can be divided into three main categories:

zone of saturation

In the subsurface, when all the pore spaces are filled with water, this area is known as the zone of saturation. The top of the zone of saturation is known as the water table, and once water reaches this zone, it continues to flow slowly from areas of higher pressure to areas of lower pressure. A permeable underground rock layer saturated with slowly moving groundwater is an aquifer. Aquifers can either be unconfined, with an impermeable layer underneath that holds the water in place against the force of gravity (picture A below), or they can be confined between two impermeable layers (picture B below). Gravity and pressure drive the movement of groundwater; additions to the water table are referred to as recharge, subtractions from the water table, either from springs or by pumping at a water well, are referred to as discharge. - The most effective aquifers are deposits of well-sorted and well-rounded sand and gravel. Limestones in which fractures and bedding planes have been enlarged by solution are also good aquifers. Shales, and many igneous and metamorphic rocks, make poor aquifers because they are typically impermeable, unless fractured (see porosity table and pictures of porosity in various media above).

glaciers and the water cycle

Just because water in an ice cap or glacier is stored for an extended period of time does not mean that it does not have a direct effect on other aspects of the water cycle and the weather. Ice is very white, and since white reflects sunlight (and thus, heat), large ice fields can determine weather patterns. Air temperatures can be higher a mile above ice caps than at the surface, and wind patterns, which affect weather systems, can be dramatic around ice-covered landscapes. As a water resource, a large part of the water in some countries such as Nepal, Tibet, and Pakistan comes from melting glaciers. Even in the United States and Canada, some areas depend partly on water stored in glaciers.

lake

Lakes are bodies of water in landlocked basins that are formed by many different geological processes. For example, the geologic origin of the Great Lakes (except Lake Superior) is glacial (see map A below left), Crater Lake is volcanic (picture B below center), and the Great Salt Lake (picture C below right) is located in a fault basin. Lakes are not important quantitatively in the global water balance, holding less than 0.4% of all continental freshwater; however, they are of great importance for local agriculture and recreation and as a source of water. It is significant that 80% of all water in lakes worldwide is held in fewer than 40 large lakes. - Lakes are important as a source of freshwater, and salt lakes can be useful for transportation and mineral extraction. Whether a lake is fresh, salt, or dry depends on the balance between precipitation (P), runoff (R) into the lake from the surrounding area, evaporation (E), and outflow (O) from the lake to other sources. If a condition exists where P + R = E + O, the result is a freshwater lake. If P + R = E and there is no outflow, the result is a salt lake with a chemical balance that is similar to the oceans. In the southwestern United States, the condition exists where P + R < E + O, producing a dry lake bed called a playa.

Loess soils

Loess soils are aeolian soils formed from windblown silt composed of silicate and carbonate materials. The sediment is derived from glacial deposits and desert processes. Loess soils cover about 20% of the United States and 10% of Earth's land area. These soils are the most fertile and productive soils worldwide and are generally concentrated in the grain producing areas of most continents. In the U.S., they are found in the Pacific Northwest, Mississippi River Valley, and the central Great Plains (see map below left). In the picture below, the high bluffs along the Mississippi River near Vicksburg are composed of loess soils and sediments. The soils and sediments are stabilized by the humid climate and thick vegetation (picture below right). - Loess derives its fertility from its loamy texture, allowing roots to penetrate easily. It retains moisture well, providing adequate water for plant uptake. Many of the minerals in loess soils are small and not yet weathered. As they break down, they slowly release nutrients into the soil that plants can use. The most extensive loess deposits are in China, covering 310,000 square miles and are several hundred meters thick (see map below, left). It was enormously important to Chinese history as the cradle of Chinese civilization and silt eroded from the soil is responsible for the great fertility of the North China plain. Conservation efforts over the past 20 years have worked to teach farmers best management practices to mitigate erosion and flooding downstream (picture below right).

fossil fuels orgin

Most natural energy resources are associated with fossil fuels such as coal and petroleum products. Fossil fuels are energy resources that are the remains of organisms preserved in rocks. The fossil in fossil fuel is organic matter that was once part of a living organism. The energy in fossil fuels is originally sunlight, captured as chemical energy by photosynthesis in ancient plants. Organic molecules from plants give energy, measured in calories, to organisms (humans, other animals) that consume them. Plants eventually die; and their excess organic remains, which contain their stored energy, become buried in the ground. Large quantities of such material, preserved, compacted, and sealed off by sedimentation, create a potential energy resource. If the buried organic material has a sufficient concentration of stored energy, we can later burn it and use the energy generated to produce such things as electricity and fuel. All fossil fuels are preserved organic material: coal comes mainly from plant remains; oil and natural gas forms from a mixture of mostly aquatic organisms.

fossil fuel

Most natural energy resources are associated with fossil fuels such as coal and petroleum products. Fossil fuels are energy resources that are the remains of organisms preserved in rocks. The fossils in fossil fuel are organic matter that was once part of a living organism. The energy in fossil fuels is originally sunlight, captured as chemical energy by photosynthesis in ancient plants. Organic molecules from plants give energy, measured in calories, to organisms (humans, other animals) that consume them. Plants eventually die; and their excess organic remains, which contain their stored energy, become buried in the ground. Large quantities of such material, preserved, compacted, and sealed off by sedimentation, create a potential energy resource. If the buried organic material has a sufficient concentration of stored energy, we can later burn it and use the energy generated to produce such things as electricity and fuel. All fossil fuels are preserved organic material: coal comes mainly from plant remains; oil and natural gas forms from a mixture of mostly aquatic organisms.

future of fossil fuels

Natural gas occurs with petroleum, in coal beds, as shale gas, and as methane hydrates. It is an important fuel, a major feedstock for manufacturing plastics and fertilizers, and a potent atmospheric gas, although it emits far less CO2 than burning either petroleum or coal. The U.S. shale gas revolution has fueled an economic revolution. It is responsible for many positive outcomes in North America including the creation of jobs, cheaper electricity, and lower heating bills for many. It holds promise for reducing dependence on foreign oil by replacing liquid fuel-powered transport with electricity from natural gas or compressed natural gas. Much of this conversion will take decades and great cost to accomplish, but the promise is there. Many authorities even project that the United States will become almost self-sufficient in energy by 2030, fueled in part by natural gas, shale gas, shale oil, tar sands, and deep water discoveries. The future of coal-derived energy in the United States is optimistic as well. Coal constitutes 80% of U.S. energy stores, but only 18% of its usage. The electric utilities today consume about 90% of coal production, compared with 19% 60 years ago. A potential key element in coal's economic future lies in its use in manufacturing a substitute for oil and gas. The technology is in place to make methane from coal, what is known as syngas (synthesis gas), and has been used on a large scale to manufacture petrochemicals, including methanol and ammonia.

water/ocean cycel

Oceans also move massive amounts of water around the world and greatly influence the water cycle. The Kuroshio Current, off the coast of Japan, is the largest ocean current. It can travel between 25 and 75 miles a day, at a rate of 1-3 miles per hour, and extends more than 3,300 feet deep. Closer to home, the Gulf Stream (see map below) is a well known stream of warm water in the Atlantic Ocean, moving water from the Gulf of Mexico across the Atlantic Ocean towards Great Britain. At a speed of 60 miles per day, the Gulf Stream moves 100 times as much water as all the rivers on Earth. Coming from warm climates, the Gulf Stream is part of the heat transfer in the oceans from near the equator to higher latitudes. Cornwall, at the southwest corner of Great Britain, is sometimes referred to as the "Cornish Riviera" because of the milder climate attributed to the water movement of the Gulf Stream. As the Gulf Stream waters circulate through the North Atlantic, they sink and drag colder waters back toward the equator, providing much needed cooler water inputs to lower latitudes. - Of course, nothing involving the amount of water in the reservoirs of the water cycle is really permanent, even the amount of water in the oceans. Over the "short term" (geologically speaking) of hundreds of years, the oceans' volumes don't change much. Over much longer time periods, the amount of water does change and has many times in the past. During the last Ice Age, sea levels were lower because more of Earth's water was stored in extensive glaciers that advanced across the continents. Glaciers covered almost 1/3 of Earth's land mass, and oceans were about 400 feet lower than they are today. This allowed humans and animals to cross over into North America from Asia across the (now underwater) Bering Strait, as shown on the map below left. - During warmer cycles, the water columns in the oceans expand and glacial ice melts and flows across the continents into the oceans. During the last global "warm spell" about 125,000 years ago, sea level was approximately 18 feet higher than they are today. Five million years ago, the oceans could have been up to 165 feet higher as shown by the red line on the map above right.

rivers

Of all the agents that shape the Earth's surface, running water is the most important. Streams and rivers are responsible for producing a vast array of erosional and depositional landforms in both humid and arid regions. Many terms are used to describe streams, such as creeks, brooks, rills, rivers; but all refer to a channelized body of water that flows across the landscape in response to gravity. Streams are the most important geologic agent on the Earth's surface; they may vary in size and appearance, but the principles that control them are the same:

reservoir rock

Oil and gas, because they are less dense than water, tend to float or migrate upward and may become trapped in more permeable rock bodies. As a result of these geologic processes of migration and trapping, oil and natural gas move to places where people can extract them. The oil and natural gas must migrate to a permeable rock, but must not migrate all the way to the surface. If they do, they could be lost by weathering to the atmosphere. In some cases, migration to the surface does happen, in which case the natural petroleum (or gas) spring is called a seep. Sandstones, limestones, and dolomites, depending on porosity and permeability, make excellent reservoir rocks.

difference in drop sizes

On average, the 48 continental United States receives enough precipitation in one year to cover the land to a depth of 30 inches. However, not all rain droplets are created equal! The clouds floating overhead contain water vapor and cloud droplets; most of these droplets are too small to fall as precipitation, but they are large enough to form visible clouds. Most of the condensed water in clouds does not fall as precipitation because their fall speed is not large enough to overcome updrafts which support the clouds. For precipitation to happen, first tiny water droplets must condense on even tinier dust, salt, or smoke particles, which act as a nucleus. Water droplets may grow as a result of additional condensation of water vapor when the particles collide. If enough collisions occur to produce a droplet with a fall velocity which exceeds the cloud updraft speed, then it will fall out of the cloud as precipitation.

Drilling for Oil

Once potential traps for hydrocarbons have been identified, geologists must find a way of getting them out of the ground, which usually involves the installation of a well. The first oil wells were dug by hand and were limited to shallow depths; however, with the industrial revolution in the late 1800's new technology allowed for mechanical drills to be employed (picture B below center). In the early 1900's, oil wells were made by repeatedly lifting and dropping a heavy weight which would physically chip away at the rock (picture A below left), which was a slow process but enabled people to drill much deeper than could be dug by hand (picture A below left). Today, most petroleum wells are rotary drilled, where a drill bit is rotated on the end of a series of pipe and cuts through the rock (picture C below right). - Until recently, petroleum wells were drilled straight down into the Earth until they reached a depth where geologists suspected an oil reservoir might exist; however, with rapidly advancing technology in the 21st century, drilling can now be directed through the subsurface, such that wells can now be drilled horizontally through the ground at great depths so that geologists can exploit much smaller oil reservoirs that were overlooked in the past.

parent

Parent material is important in soil formation, but the same rock type can yield different soils in different climatic regimes and, in the same climatic regime, the same soils can develop on different rock types. Parent material contributes the initial elemental content in the soil, since the minerals that are weathering are contributing the elements found in the soil. Continued chemical weathering will cause some elements to mobilize, but others will remain as stable minerals in the soil. Rock type does exert some control on soil development, rocks composed of minerals stable at the Earth's surface will weather slower than those unstable at the surface. For example, the minerals in basalt are unstable in surface conditions and will weather more rapidly than the minerals in granite.

Petroleum and Natural Gas

Petroleum and natural gas are fluid fossil fuels. Petroleum, also called crude oil, is a liquid mixture of large, sometimes complicated hydrocarbon molecules. Crude oil is extracted from the ground and refined to create gasoline for combustion engines, motor oil, and also used in the manufacturing of plastics, paints, and insecticides. Natural gas is mostly composed of methane molecules (CH4) but may contain heavier molecules such as ethane, propane, or butane. Petroleum and natural gas are composed of hydrogen and carbon, known as hydrocarbons. They are generally the remains of microscopic animals that settled on the bottom of a lake or ocean and were buried beneath layers of sediment. As the sediment was buried and lithified, the organic remains were subjected to heat and pressure and the microscopic animals were transformed into hydrocarbons. Oil occurs as a liquid while natural gas may be liquid at great depths and under great pressure, but exists as a gas at or near the Earth's surface. The rocks that contain hydrocarbons in East Texas were deposited 70 to 200 million years ago in the Jurassic and Cretaceous periods, back when dinosaurs roamed the Earth. During these time periods, East Texas was covered by a shallow sea known as the Western Interior Seaway that extended from Texas up through the Great Plains and Canada. These much older rocks now occur at depths up to two miles beneath the East Texas region, requiring deep wells to be drilled into the Earth for petroleum geologists to extract the oil and gas.

Precipitation

Precipitation does not fall in the same amounts throughout the world. In the state of Georgia, it rains fairly evenly all during the year, around 40-50 inches per year. Summer thunderstorms may deliver an inch or more of rain on one suburb while leaving another area dry a few miles away. But, the rain amount that Georgia gets in one month is often more than Las Vegas, Nevada observes all year. The world's record for average-annual rainfall belongs to Mt. Waialeale, Hawaii, where the average annual rainfall is about 450 inches per year. A remarkable 642 inches was reported there during one twelve-month period (that's almost 2 inches every day!). Is this the world record for the most rain in a year? No, that was recorded at Cherrapunji, India, where it rained 905 inches in 1861. Contrast those excessive precipitation amounts to Arica, Chile, where no rain fell for 14 years, and in Bagdad, California, where precipitation was absent for 767 consecutive days from October 1912 to November 1914.

mineral reserves

Reserves are not static, because they are defined by the current economics and technology, as well as by the amount of a mineral that exists. In a free economy, a mineral deposit will not be developed at an economic loss, and prices will rise with demand. Consequently, low-grade deposits that are marginal or sub-marginal in today's economic climate may, if demand and prices rise, eventually become profitable to exploit. Advancements in technology also may increase reserves by lowering the cost of development or processing.

C horizon

contains partially altered bedrock with little organic matter. In a well developed soil, the upper horizons have been so altered that the parent material is unrecognizable but in the C horizon, weathered parent material is easy to identify. This horizon grades downward into unaltered bedrock.

importance of running water

Rivers are invaluable to not only people, but to life everywhere. Not only are rivers a great place for recreation, but people use river water for drinking-water supplies and irrigation water, to produce electricity, to flush away wastes, to transport merchandise, and to obtain food. Rivers are major aquatic landscapes for all manners of plants and animals. Rivers even help keep the aquifers underground full of water by discharging water downward through their streambeds. Globally, total withdrawals of water from surface streams amounts to about 2,400 cubic kilometers per year, with 82% used for agricultural irrigation. This amount is expected to increase to 20,000 cubic kilometers by the year 2050, which is beyond the dependable flow of the world's rivers. It is important to note that water is not equally distributed around the globe either; the availability of water resources will have an affect on population growth in the 21st century, either by choice in developed countries, or by natural means, most likely drought and famine, in developing nations.

spindletops

Salt domes were almost unknown until an exploratory oil well was drilled on Spindletop Hill near Beaumont, Texas in 1900 and completed in 1901. Spindletop was a low hill with a relief of about 15 feet where a visitor could find sulfur springs and natural gas seeps. At a depth of about 1000 feet, the well penetrated a pressurized oil reservoir that blew the drilling tools out of the well and showered the surrounding land with crude oil until the well could be brought under control. The initial production from the well was over 100,000 barrels of crude oil per day - a greater yield than any previous well had ever produced. - The Spindletop discovery ignited a drilling spree on similar structures across the Gulf Coast area. Some of these wells struck oil, and those discoveries motivated geologists to learn about the structures below that held such vast amounts of oil. Careful subsurface mapping of well data and later, the use of seismic surveys, enabled geologists to discover the shape of salt domes, develop hypotheses about how they form, and understand their role in petroleum exploration.

soil

Soil is a naturally occurring mixture of mineral and organic ingredients with a definite form, structure, and composition. The exact composition of soil changes from one location to another. The following is the average composition by volume of the major soil ingredients: 45% Minerals (clay, silt, sand, gravel, stones). 25% Water (the amount varies depending upon precipitation and the water-holding capacity of the soil). 25% Air (an essential ingredient for living organisms). 5% Organic matter or humus (both living and dead organisms). - A soil is composed primarily of minerals which are produced from parent material that is weathered or broken into small pieces. Beyond occasional stones, gravel, and other rock debris, most of the mineral particles are sand, silt, and/or clay sized sediments. These mineral particles give soil texture. Sand particles range in diameter from 2 mm to 0.05 mm, are easily seen with the unaided eye, and feel gritty. [One millimeter (mm) is about the thickness of a dime.] Silt particles are between 0.05 mm and 0.002 mm and feel like flour. Clay particles are smaller than 0.002 mm and cannot be seen with the unaided eye. Clay particles are the most reactive mineral ingredient in the soil. Wet clay usually feels sticky. Water and air occupy the pore spaces—the area between the mineral particles. In these small spaces, water and air are available for use by plants. These small pore spaces are essential to the life of soil organisms, to soil productivity, and to plant growth. The final ingredient of a soil is organic matter. It is comprised of dead plant and animal material and the billions of living organisms that inhabit the soil.

groundwater

Some rain and snow that falls on land runs off into streams, some evaporates back into the atmosphere, and some is absorbed by plants, but most of Earth's fresh water exists beneath the land surface as groundwater. Gravity causes water that enters the subsurface to percolate downward through soil, sediment, and porous rock, known as the zone of aeration. Eventually it reaches the zone where water fills all spaces or pores in rock and sediment; the volume of space within a body of rock or sediment that can be occupied by water is known as porosity. In the boxes below, porosity in solid rock depends on the size, shape, and arrangement of the material. Well-sorted sedimentary rock (box A below) has high porosity, but a poorly sorted one (box B below) has lower porosity. In soluble rock such as limestone (box C below), porosity can be increased by dissolution of bedrock by groundwater, and crystalline igneous or metamorphic rocks (box D below) can exhibit increased porosity values as a result of fracturing.

Origins of Mineral Deposits

Specific geologic processes must occur to concentrate minerals or native elements in a mineral deposit. The geologic processes responsible for many mineral deposits may be understood in terms of plate tectonics with mineral concentrations occurring in distinct tectonic settings (see table below). For example, the rich porphyry copper deposits of the Western Hemisphere were formed by igneous processes at convergent plate margins at the sites of former volcanic island arcs. On the other hand, deposits of tungsten, tin, some iron ore, gold, silver, and molybdenum originated by hydrothermal activity or by contact metamorphism accompanying the emplacement of granitic plutons within the continental lithosphere near convergent boundaries.

Reclamation of Mined Land

The General Mining Law of 1872 was important legislation in our nation's history as it helped establish the mining industry as a fundamental element in the U.S. economy. From 1872 to the early 1970's, the law has allowed approximately $250 billion worth of mineral material to be extracted by private corporations with no consideration for the environmental consequences of mining. The Surface Mining Control and Reclamation Act (SMCRA), passed in 1977, established the coordination of federal and state efforts to regulate the coal industry to prevent the abuses that had occurred in the past. These regulations apply to all lands - private, state, and federal. SMCRA established a fee that is charged on coal production that generates funds for reclaiming abandoned coal-mine lands. Federal reclamation standards and other safeguards established by SMCRA for the coal-mining industry have no counterpart for noncoal-underground and surface mineral mining on state or private lands. Although there are federal regulations for noncoal mining on federal lands, it is left to the individual state governments to codify safeguards and enforce noncoal-mine reclamation requirements.

mining earths resources

The General Mining Law of 1872 was important legislation in our nation's history as it helped establish the mining industry as a fundamental element in the U.S. economy. The original 19th century law allowed miners to stake a claim on potentially profitable public land and, should the claim prove to contain valuable minerals, to obtain a patent for $2.50 an acre and reap the profits. This law helped settle the west by enticing thousands of prospectors to seek their fortunes in gold, silver, and other valuable commodities. From 1872 to the early 1970's, the law has allowed approximately $250 billion worth of mineral material to be extracted by private corporations with no consideration for the environmental consequences of mining. During the environmental awareness decades of the 1960's and 1970's, the National Environmental Policy Act (NEPA), Surface Mining Control and Reclamation Act (SMCRA), and Comprehensive Environmental Response, Compensation and Liability Act (CERCLA) were passed to ensure that future mining activities would reclaim the land after mining operations ceased, and that mining activities would meet federal standards. Since the General Mining Law was enacted, it has been amended over 50 times and today's mining laws fill six volumes with thousands of rules and regulations.

american oil usage

The United States has about 4.4% of the world's population, yet consumes 28% of the world's energy supplies. Each day, Americans use some 3,000 products, including such things as gasoline, lubricating oils, jet and other fuels, fertilizer, makeup, synthetic fabrics, and pharmaceuticals, all of which are derived from petroleum. Even with conservation efforts, our consumption of petroleum generally increases annually, although there has been a decrease since 2008 because of a world-wide economic downturn, policies that encourage fuel efficiency in automobiles, and an increase in renewable fuels. By 2010, the United States was consuming 19 million barrels of oil per day, out of some 85 million barrels consumed worldwide. Of those 19 million barrels, about 10.4 million barrels were imported. Using the Energy Information 2010 average price of $74 a barrel of imported oil, nearly $740 million each day went to other countries to pay for petroleum resources. Although the United States is the third largest producer of petroleum (Saudi Arabia and Russia rank first and second, respectively), it is the most energy deficient of the largest oil producing countries. Since 1970, overall U.S. production has been dropping, and at the current rate of production, authorities vary in their expectation for the lifespan of U.S. reserves. Today, technological advances in drilling and extraction methods allow geologists to retrieve more oil from reservoirs that were once considered depleted.

amount of water

The amount of energy of the water in the stream, and therefore the amount of work it does, depends on its volume and velocity.

area around

The area occupied by the water in a stream is the stream's channel. A stream's valley is the region directly and indirectly eroded by the stream, and it extends well beyond the stream channel. A natural levee is a higher bank next to a stream where the stream has deposited sediment as it overflows or floods. The U.S. Army Corps of Engineers have installed artificial levees along major waterways to protect valuable infrastructure.

coalification

The degree of coalification can be measured by several parameters, including the amounts of carbon, hydrogen, oxygen, volatiles, and moisture present, and the calorific value (the amount of heat it will produce when combusted). As the rank of coal increases, the carbon content increases and volatile content decreases. Some common rankings are:

Economic Mineral Concentrations

The elements forming the minerals that make up Earth's crust exist in many forms in a great variety of rocks. The greater the quantity in place, the richer the deposit and the more economically feasible it is to extract and process the desired element. Locally rich concentrations of minerals are called mineral deposits. If they are sufficiently enriched, they may be mineral reserves, deposits of earth materials from which useful commodities are economically and legally recoverable with existing technology. Reserves of metallic minerals are called ores, and the minerals composing the deposits are referred to as ore minerals.

Metallic Mineral Reserves

The geochemically abundant metals - aluminum, iron, magnesium, manganese, and titanium - have abundances in excess of 0.1% by weight of the average continental crust. Economically valuable ore bodies of the abundant metals, such as iron and aluminum, need only relatively small concentration factors for profitable mining and are recovered mainly from ore minerals that are oxides and hydroxides. Even though they are abundant, these metals require large amounts of energy for production. The scarce metals have crustal abundances that are less than 0.1% by weight of average continental crust. Most of these metals are concentrated in sulfide deposits, but the rarest metals occur in rare rock types. Included within this category are copper, lead, zinc, and nickel along with gold and platinum group minerals. The United States has all of these critical metals in the National Defense Stockpile, a supply of about 100 critical mineral materials valued at about $4 billion; this stockpile could supply the nation's needs for 3 years in a national emergency.

kinetic energy

The stream's kinetic energy can transport sediment (see picture below) by rolling, sliding, or hopping particles along the bottom (bed load), and by suspension in the water (suspended load). The chemical properties of water also permit it to carry sediment in solution (dissolved load).

Bituminous coal

contains very little moisture, has a high heat value, and is the most plentiful rank of coal available in the United States. It is used to generate electricity and produce coke, a coal residue used in the steel industry. These coals are black, hard, and bright compared to softer brown coals. A distinctive bedding or parallel banding usually develops in extensive deposits consisting of bright and dull layers of differing composition.

cap rock

To prevent the oil and natural gas from escaping to the surface, geologic structure or features must exist that trap the fuels. A proper trap must have impermeable rocks called cap rocks above the permeable ones, so that the fluids can migrate into the permeable rocks but cannot migrate out of the ground. The impermeable rocks prevent further migration. Tight shales, some limestones, and other impermeable layers function as cap rocks. Hydrocarbons are trapped in holes within reservoir rock, called pores. As porosity, the total volume of pores, increases, the amount of petroleum in a reservoir increases. However, the size of pores and degree that they are connected, known as permeability, will control the ability for petroleum, to pass through the rock. If permeability is low, the pores are poorly connected and hydrocarbons cannot be extracted. If permeability is high, the pores are well connected and much of the petroleum in the reservoir can be extracted. The combination of porosity and permeability determine whether or not a hydrocarbon reservoir is economic to develop.

water resources

Water resources in stream channels are important, and they provide abundant water to cities and municipalities, some many miles from the river's locations. There are strict and complicated laws that govern water rights and usage, and often times water supplies are dammed and metered out downstream. In many areas, particularly the western United States, consumption exceeds local water supplies. This necessitates importing water from other areas or mining groundwater. For example, about 75% of southern California's water is imported from sources more than 200 miles away. Two aqueducts import water from the Sierra Nevada region, and one aqueduct imports water from the Colorado River. Approximately 80% of this water goes to irrigation; California is the largest U.S. consumer of water, using almost as much as the two next largest consumers combined, Texas and Illinois.

velocity

When a stream's velocity or its volume increases, its ability to carry sediment increases, and it will erode material from its bottom and sides. The most dramatic changes in a stream's channel shape occur during flooding (see aerial photographs of Mississippi River at regular flow in 1991 and at flood stage during 1993 below). When a stream slows, or loses water by infiltration or evaporation, its capacity to carry sediment diminishes, and fluvial deposition occurs.

Tropical Soils

While these soils are not suitable for farming, they do contain rich deposits of aluminum minerals, collectively called bauxite (above right). Bauxite minerals are the primary source of aluminum ore, and the main export of Jamaica. During World War II, the United States sourced aluminum ore from rich deposits near Little Rock, Arkansas. Most of the aircraft built in the U.S. during the war used aluminum from this area. Today, other than recycled aluminum, the United States and Canada are dependent on foreign sources for aluminum ore.

communicatoin

While we are discussing groundwater as a separate water reservoir, in many cases there is constant communication between surface water and groundwater. Groundwater resources can be instrumental in maintaining base flow in stream channels, which can be critical for maintaining the ecological integrity of streams as surface water resources and habitat. Stream channels that gain water from groundwater are referred to as gaining streams (picture A below). In arid climates where there are permeable, water saturated rocks beneath the surface, groundwater seeping into stream channels may be the only source of water for rivers. The fabled oases of the Sahara and Arabian deserts occur where underground water is close to the surface or where it intersects the ground surface, forming a spring or watering hole. If a stream channel loses water to the groundwater system, it is referred to as a losing stream (picture B below). - Groundwater provides about 40% of public water supplies and 30% to 40% of all water used exclusive of power generation in the United States. It is by far the least expensive and most efficient source of municipal water, because obtaining it does not require the construction of expensive aqueducts and reservoirs. Groundwater usually requires far less cleaning and purification than surface water. Thirty-four of the largest 100 cities in the U.S. depend entirely on local groundwater supplies. Groundwater resources supply 80% of the water for rural domestic and livestock use, and it is the only source of water in many agricultural areas.

construction minerals

are aggregates such as crushed stone, sand, and gravel; and cement made from limestone and shale. Eighty percent of the aggregate is used in road building. Other major construction materials are clay, used for bricks and tile; and gypsum, the primary component of plaster and wallboard.

agricultural minerals

are important in the production of fertilizers and agricultural chemicals. Phosphate and potassium compounds are found in the Earth's crust. The largest economic deposits of phosphate compounds are found in marine sedimentary rocks in North Carolina and Florida, and other valuable deposits are found in Idaho, Montana, Wyoming, and Utah. The main U.S. supply of potassium comes from widespread non-marine evaporite beds in the subsurface beneath New Mexico, Oklahoma, Kansas, and Texas.

residual soils

are those that have developed in place on top of the underlying bedrock. The soil will have similar mineral content to the bedrock below. The organic matter in the soil will be derived from plants and animals living in the area. These soils take tens to hundreds of thousands of years to develop and are subject to removal by geologic processes.

transported soils

are those that have formed on transported sediments and they are described by their transportation mechanism. Alluvial soils are those that contain sediments transported by rivers. Aeolian soils contain sediments transported by wind, glacial soils would have been transported by ice. Volcanic soils contain sediments transported by volcanic flows.