Biogeochemical Cycles
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Rock Cycle
Water, Carbon, and Nitrogen Cycles
Rock Cycle
According to the CSET test guide, there will be a total of 50 multiple choice questions and three constructed response questions for CSET 122.
http://www.nature.nps.gov/geology/usgsnps/rxmin/rockchart.html
http://www.open2.net/sciencetechnologynature/worldaroundus/geologytooklit/rocktypes_embedded.html
http://www.learner.org/interactives/rockcycle/types3.html
http://www.as.uky.edu/academics/departments_programs/EarthEnvironmentalSciences/EarthEnvironmentalSciences/Educational%20Materials/Pages/VolcanoSongs.aspx
a. Compare and contrast the properties of rocks based on physical and chemical conditions in which rocks are formed, including plate tectonic processes
Igneous Rocks
Texture:
Rocks that form from molten magma are called igneous rocks. The magma, within the earth, experiences partial melting at various depths. This magma body will slowly rise towards the surface because it is less dense, more buoyant. Sometimes, this magma body breaks through the crust in some sort of volcanic activity. The magma that breaks through lost materials that escaped as a gas, and is now referred to as lava. Igneous rocks that forms and solidifies at the surface are called extrusive, or volcanic rocks. Rocks that solidifies and crystallizes inside the earth are called intrusive, or plutonic rocks. Examples of extrusive rocks are the Cascade Range and the lava flows of the Columbia Plateau, and many oceanic islands. Intrusive rocks are only viewable when a region experiences uplift and the overlying rocks are eroded away. Examples of places where you can find intrusive rocks is at Yosemite National Park.
So, when magma is very hot, the ions of the magma (usually made up of silicon, oxygen, aluminum, potassium, calcium, sodium, iron, magnesium, etc) are joining together and then breaking apart. As the magma cools, the ions move much more slowly and the forces of chemical bonds will join the ions together into an orderly, regular pattern, of a crystalline structure. Looking at the texture of igneous rocks tells us a great deal about the environment in which the igneous rock was formed. Factors that affect the texture of igneous rocks are the rate at which the magma cooled, the amount of silica present, and the amount of dissolved gases in the magma. Deep within earth, as magma slowly cools (may take hundreds of thousands of years), the ions are freely to move until they eventually join up with one of the existing crystalline structures. Since the magma cooled very slowly, then, crystals are able to grow into large sizes. However, if the magma cools quickly, then the ions quickly slow down and are not able to ready combine to form crystals. Thus, the solid magma has very small crystals. Then, you have magma that cools extremely fast and ions have no chance to organize themselves. These kinds of rocks are called glass. So, igneous rocks that cool quickly and have very small crystals that are not visible to the naked eye and have fine grade texture are said to have an aphanitic texture. A common feature in apahnitic rocks are voids, or holes where gas bubbles escaped when it quickly cooled. These openings in the rocks are called vesicles, so rocks that have this feature are said to have a vesicular texture (such as pumice). On the other hand, magma that cools slowly, far below the surface develop large crystals and are coarse-grained are said to have a phaneritic texture.
Magma that is deep within the earth may take tens to hundreds of thousands of years to harden. Different minerals crystallize at different temperatures. As a result, some minerals may crystallize early on and become quite large. And, if the magma moves up to the surface, than the minerals that haven't crystallized yet or had as much time to crystallize may be much smaller. These types of igneous rocks are said to have a prophyritic texture, which is a rock that has both large and small crystals. The large crystals are called phenocrysts and the smaller crystals are called groundmass.
Igneous rocks that are spewed out of a volcano and are cooled very quickly generates rocks that have glassy texture.
Igneous rocks that are composed of fragments that solidified and then cemented together tend to appear more like sedimentary rock than other igneous rocks. Igneous rocks composed of these fragments are said to have a pyroclastic texture.
Igneous rocks with a pegmatite texture may form in special conditions.Pegmatite texture means that the rocks has a coarse-grained, interlocking crystals all larger than a centimeter in diameter, and are found in the margins of large plutons in small masses or in veins. These types of rocks form in the late stages of crystallization where water and other volatiles make up a large amount of the magma. The large crystals of these types of rocks are not formed due to slow cooling, but instead due to the fluid-rich environment that helps crystalline growth.
Composition:
The composition of igneous rocks consists primarily of silicate minerals. The mineral makeup of igneous rocks are determined by the chemical composition of the magma where it crystallized. The eight elements that makes up magma are also the major components of silicate minerals. Silica within magma (silicon and oxygen) is the most abundant component of igneous rock. Magma is also composed of aluminum, calcium, sodium, potassium, magnesium, iron, titanium, and manganese. So, as magma cools and solidifies, these elements combine to form the two major groups of silicate minerals, either ferromagnesian silicates (dark), which are rich in iron and/or magnesium, and low in silica. Or, it may form nonferromagnesian silicate (light) which contains a larger amount of potassium, sodium, and calcium. They are much richer in silica than the dark silicates. Minerals of the dark silicates include olivine, pyroxene, amphibole, and biotite mica. Minerals of the light silicates include quartz, muscovite mica, and the feldspars.
Felsic igneous rocks are composed of light-colored silicates, felsdspar and quartz (silica). These rocks have a granitic composition and make up the continental crust. Igneous rocks that contain the dark silicate minerals and plagioclase feldspar are said to have a basaltic composition. These rocks contain a high amount of ferromagnesian minerals and are called mafic. Intermediate igneous rocks have an andesitic composition and is found in between the felsic and mafic groups. They consists of around 25% dark silicate minerals and the rest is plagiocalse feldspar. These kinds of igneous rocks are created in the volcanoes at the margins of continents. Ultramafics are rocks whose composition is composed almost entirely of ferromagnesian minerals. Ultramafic's are rare at Earth's surface. An example of an ultramafic rock is the peridotite.
Silica content can be used as an indication of the composition of igneous rocks. Rocks high in silica have very small amounts of iron, magnesium, and calcium; whereas, rocks that have little silica have quite a bit of iron, magnesium, and calcium. The amount of silica in the magma also effects how viscous the magma will be. Magma with a high amount of silica will very viscous (sticky, produces explosive volcanic events). Magma with a low amount of silica will not be very viscous (not sticky, volcano lava will just flow).
Sedimentary Rocks
Composition:
The major component of sedimentary rocks tend to be clay minerals and quartz. Clay is the most abundant product of chemical weathering of silicate minerals. Quartz is abundant because it is very resistant to chemical weathering. So, when igneous rocks are weathered/eroded down, the quarts crystals are freed. Feldspars and micas are also commonly found in sedimentary rocks. Looking at the particle sizes of the minerals is the primary method of distinguishing sedimentary rocks. Boulders (>256 mm), cobble (64-256 mm), pebble (4-64 mm), granule (2-4 mm), sand (1/16 to 2 mm), silt (1/256- 1/16 mm), clay (<1/256). By looking at the types of particles and their sizes in the rocks, we can tell a lot about the how and in what environment a sedimentary rock was formed. Particles are sorted as they are carried by wind and water. The larger and stronger the current, the larger the particle that can be carried. Sedimentary rocks are formed by the accumulation of particles that are broken down through chemical or mechanical weathering and are then transported and settled are called detrital sedimentary rocks. Examples of detrital sedimentary rocks include shale, sandstone, siltstone, conglomerate, and breccia. Chemical sedimentary rocks are formed from the ions dissolved in the solution of lakes and seas. Eventually, the ions precipitate out to form chemical sediments. Examples of chemical rocks are halite, limestone, dolostone, and chert. Chemical sediments can be formed by organic or inorganic deposits. Coal is a sedimentary rock that is made up of organic material, such as leaves and wood, that have been chemically altered. Coal formed from plants that was buried millions of years ago. Because dead plants decay in an oxygen-rich environment, we know that these dead plants had to have formed in an oxygen-deficient environment. Bacteria in this oxygen-deficient environment works to break down the plants, but are eventually destroyed by the acids released in the plants. So, the partial, decayed plants begin to build up in many layers, creating peat. The peat then slowly changes into lignite coal. As these layers build up, temperature and pressure increases, which initiates a chemical reaction the forms water and gas. As pressure builds even more, water and gases are pressed out and the amount of fixed carbon increases. The lignite becomes bituminous coal. Through pressure and temperature, perhaps caused by mountain building, then bituminous coal becomes anthracite, a metaphoric rock. Anthracite is a clean-burning fuel, but isn't really mined since it isn't widespread and difficult to extract.
Environment:
By studying sedimentary rocks, we can tell a lot about the conditions under which it formed, such as the environment, origin, and the method that it formed under. Sedimentary rocks may be made out of sediments that traveled very far, or it may be formed in one spot (in a lake or stagnant swamp, for example). The different environments in which sediments may form in are continental, marine, or transitional.
A continental environment is a place where the climate affects the erosion or deposition of sediments, either through streams, glacial ice, or wind. Streams are the most influential force for eroding and depositing sediments.
There are different kinds of continental environment:
-Floodplains: Large quantities of sediments are dropped when flood waters flood a valley floor
-Alluvial Fan: When a rapid stream emerges from a mountainous area onto a flat region, it drops sediments in a cone shape.
-Glaciers pick up and transport large amounts of sediments and despot them, unsorted, when they retreat.
-Dune: Wind depots are called eolian and can carry sediments at great distances. These deposits are well sorted. If the wind is not obstructed by vegetation, then the sand is able to accumulate into hills called dunes.
-Playa lakes: These form in desert basins after a heavy rainfall or snowmelt occurs. They leave behind evaporates and deposits.
Marine Environment is divided into two environments based on depth. Shallow marine environments reaches to a depth of 200 meters and extends from the shore to the continental shelf. The sediments deposited in these environments is based on the elevation, water depth, water temperature, climate, and distance from shore. Because there is constant erosion taking place at the shore, the marine environment receives a large amount of land-derived sediment. In warm environments, carbonate-rich muds are the dominant sediment. Coral reefs are associated with a shallow marine environment. Deep marine environment extends from the continental shelf to the floors of the deep sea. Tiny particles may stay afloat in the water for a long time before settling out and falling to the ocean floor.
Transitional Environment is the region between the marine and the continental environments. One example of this region are beaches where you can find sediment deposits of sand and gravel. Ocean currents and waves move sand around and creates spits, bars, and barrier islands (offshore bars and reefs are called lagoons). Sediment build up into the sea when rivers experience a drop in velocity and drop their sediments produces deltas.
Metamorphic Rocks
Heat, pressure, and chemically active fluids are the the driving agents for creating metamorphic rocks. The degree of metamorphism and the contribution of each of the driving agents changes from one environment to another.
Texture:
Unlike sedimentary or igneous rocks that have random orientation of mineral grains, metamorphic minerals exhibit a parallel alignment of elongated minerals. When we view sedimentary or igneous rocks, they pretty much look the same no matter how you observe the rock. But with metamorphic rocks, looking at one side will look differently than viewed from another side. These types of metamorphic rocks is said to have foliation, which refers to a planar arrangement of mineral grains within a rock (foliation does occur in sedimentary rocks and few types of igneous rocks, but it's a very strong characteristic found in metamorphic rocks). Foliation is produced by compressional stresses and causes the mineral grains to form parallel alignments.
Different types of foliation:
Slaty cleavage is one type of foliation where the planar surface along the rocks splits into slabs if hit and smacked apart. Slaty cleavage can develop in low-grade metamorphic environment where beds of shale (a sedimentary rock) are folded and forms slate. With further deformation, recrystallization takes place. Narrow parallel zones develop and it is along here where the slate splits.
Schistosity is another type of foliation that takes place under higher temperature environments. The platy minerals begin to grow larger and exhibit a planar or layered structure.
Gneissic textured rocks occurs in high-grade metamorphic events. The ion migration results in the segregation of minerals. These rocks do not split as easily as slates and schists.
Metamorphic rocks that do not exhibit the foliated texture are referred to having a nonfoliated texture. These types of metamorphic rocks tend to develop in environments where deformation is minimal and the parent rock contains minerals that have equidimensional crystals (quartz, calcite). When a calcite, such as limestone, undergoes metamorphism, the grains recrystallize to form larger interlocking crystals. The new rock, marble, displaces the large equidimensional grains that are randomly ordered. Another texture takes place in rocks that have large grains surrounded by fine-grained minerals (porophyroblasts).
Environment:
Most metamorphism takes place in a plate margin region, and may be associated with igneous activity. There are different types of metamorphism:
Contact or Thermal- takes place when rocks are surrounded by magma and are essentially baked. Because the rocks are baked, they end up with hard, fine-grained metamorphic rocks called hornfels. The region where they are altered is called the metamorphic aureole. The size of the aureole depends on mineral composition of the host rock and how much water is available. Contact metamorphism does not involve direct pressure, so the crystals within the metamorphic aureole are somewhat randomly oriented. Hornfels can form from a variety of materials. Large grains of metamorphic minerals, such as garnet, may form giving the hornfel a porphyroblastic texture. Marble and quartzite are two metamorphic rocks that can form through contact metamorphism.
Hydrothermal- chemical alternation can occur when hot, iron-rich fluids circulate through cracks that develop in rocks. This type of metamorphism is closely linked to igneous activity and take place alongside contact metamorphism in regions of large plutons. As the magma cools and solidifies, the ions that are not organized in a crystalline structure and the water are expelled, called hydrothermal solution. This solution may chemically alter the host rock and the ions may even precipitate out to form mineral deposits. The fluids may even penetrate permeable rocks, such as limestone. The solution may react with the carbonates and produce a calcium-rich silicate mineral that forms a metamorphic rock called skarn. Hydrothermal metamorphism is mostly found at the mid-ocean ridge region. As magma moves up and and forms the new sea floor, seawater moves through this hot crust. This seawater is heated and reacts, chemically, with the basaltic rocks. This results in converting ferromagnesian minerals into hydrated silicates. Metals may also form in this region and rise up, generating a particle-filled cloud called black smokers. As it mixes with the cooler seawater, sulfides and carbonate minerals that contains these metals precipitate out, and forms a metallic deposit.
Burial and Subduction zone of metamorphism- Let's start with burial metamorphism. This type of metamorphism occurs when sediments build up thick layers along a subsiding basin. Low-grade metamorphism takes place within the deepest layers (and the depth varies from one location to another). Pressure and heat are the driving forces for recrystallization. Subuction may carry rocks and sediments down to great depths along convergence boundaries, called subduction zone metamorphism. This type of metamorphism is different from the burial metamorphism in that deformation of the rock now takes place and the rocks are metamorphosed.
Regional Metamorphism- Most metamorphic rocks were produced during regional metamorphism during orogenic event. During a mountain building episode, large amounts of Earth's crust are deformed along a convergent place boundary. This typically takes place when oceanic lithosphere is subducted during collision and continental volcanic arcs are produced. Rocks are shortened and thickened as a result of the folding that is taking place. This deformed rock often results in being lifted high above sea level to form a mountain terrain. In addition, inside the mountain, temperature becomes so high that rocks begin to melt. As a result, the magma forms bodies large enough to rise and intrude the overlying metamorphic and sedimentary rock. Thus, the core of a mountain consists of metamorphic rocks intertwined with igneous rock bodies.
Impact Metamorphism- takes place when a meteorite smacks into the Earth's surface. Energy from the impact is transformed into heat energy and shock waves that passes into the surrounding rocks. These nearby rocks are shattered and may even melt. The products from impacts are called impactiles and include a mixture of fragmented rocks and glass-rich eject (similar to volcanic bombs). Quartz and diamonds may be found in these regions. Finding these two minerals tells us that very high pressure and temperature (as great as within the earth) occurred briefly at the surface of the earth.
Geologists noticed that groups of minerals could be used to determine the environment (temperature and pressure) in which the metamorphic rocks underwent. Rocks that contained the same assemblage of minerals formed in very similar environments (think of this as with flowers. Flowers grow in similar environment). These types of minerals belong to the same metamorphic facies. Some metamorphic facies include hornfels, green-schist blueschist, and amphibolite. So, knowing these metamorphic facies helps because each facies underwent the same conditions and in similar tectonic settings.
b. Identify common rock-forming minerals (e.g., feldspars, quartz, biotite, calcite) using a table of diagnostic properties
http://www.sdnhm.org/kids/minerals/games/index.html
c. Identify common ore minerals as sources of copper, iron, lead, zinc, cement, halite, gypsum, and uranium
http://www.nature.nps.gov/geology/usgsnps/rxmin/rockchart.html
http://www.open2.net/sciencetechnologynature/worldaroundus/geologytooklit/rocktypes_embedded.html
http://www.learner.org/interactives/rockcycle/types3.html
http://www.as.uky.edu/academics/departments_programs/EarthEnvironmentalSciences/EarthEnvironmentalSciences/Educational%20Materials/Pages/VolcanoSongs.aspx
a. Compare and contrast the properties of rocks based on physical and chemical conditions in which rocks are formed, including plate tectonic processes
Igneous Rocks
Texture:
Rocks that form from molten magma are called igneous rocks. The magma, within the earth, experiences partial melting at various depths. This magma body will slowly rise towards the surface because it is less dense, more buoyant. Sometimes, this magma body breaks through the crust in some sort of volcanic activity. The magma that breaks through lost materials that escaped as a gas, and is now referred to as lava. Igneous rocks that forms and solidifies at the surface are called extrusive, or volcanic rocks. Rocks that solidifies and crystallizes inside the earth are called intrusive, or plutonic rocks. Examples of extrusive rocks are the Cascade Range and the lava flows of the Columbia Plateau, and many oceanic islands. Intrusive rocks are only viewable when a region experiences uplift and the overlying rocks are eroded away. Examples of places where you can find intrusive rocks is at Yosemite National Park.
So, when magma is very hot, the ions of the magma (usually made up of silicon, oxygen, aluminum, potassium, calcium, sodium, iron, magnesium, etc) are joining together and then breaking apart. As the magma cools, the ions move much more slowly and the forces of chemical bonds will join the ions together into an orderly, regular pattern, of a crystalline structure. Looking at the texture of igneous rocks tells us a great deal about the environment in which the igneous rock was formed. Factors that affect the texture of igneous rocks are the rate at which the magma cooled, the amount of silica present, and the amount of dissolved gases in the magma. Deep within earth, as magma slowly cools (may take hundreds of thousands of years), the ions are freely to move until they eventually join up with one of the existing crystalline structures. Since the magma cooled very slowly, then, crystals are able to grow into large sizes. However, if the magma cools quickly, then the ions quickly slow down and are not able to ready combine to form crystals. Thus, the solid magma has very small crystals. Then, you have magma that cools extremely fast and ions have no chance to organize themselves. These kinds of rocks are called glass. So, igneous rocks that cool quickly and have very small crystals that are not visible to the naked eye and have fine grade texture are said to have an aphanitic texture. A common feature in apahnitic rocks are voids, or holes where gas bubbles escaped when it quickly cooled. These openings in the rocks are called vesicles, so rocks that have this feature are said to have a vesicular texture (such as pumice). On the other hand, magma that cools slowly, far below the surface develop large crystals and are coarse-grained are said to have a phaneritic texture.
Magma that is deep within the earth may take tens to hundreds of thousands of years to harden. Different minerals crystallize at different temperatures. As a result, some minerals may crystallize early on and become quite large. And, if the magma moves up to the surface, than the minerals that haven't crystallized yet or had as much time to crystallize may be much smaller. These types of igneous rocks are said to have a prophyritic texture, which is a rock that has both large and small crystals. The large crystals are called phenocrysts and the smaller crystals are called groundmass.
Igneous rocks that are spewed out of a volcano and are cooled very quickly generates rocks that have glassy texture.
Igneous rocks that are composed of fragments that solidified and then cemented together tend to appear more like sedimentary rock than other igneous rocks. Igneous rocks composed of these fragments are said to have a pyroclastic texture.
Igneous rocks with a pegmatite texture may form in special conditions.Pegmatite texture means that the rocks has a coarse-grained, interlocking crystals all larger than a centimeter in diameter, and are found in the margins of large plutons in small masses or in veins. These types of rocks form in the late stages of crystallization where water and other volatiles make up a large amount of the magma. The large crystals of these types of rocks are not formed due to slow cooling, but instead due to the fluid-rich environment that helps crystalline growth.
Composition:
The composition of igneous rocks consists primarily of silicate minerals. The mineral makeup of igneous rocks are determined by the chemical composition of the magma where it crystallized. The eight elements that makes up magma are also the major components of silicate minerals. Silica within magma (silicon and oxygen) is the most abundant component of igneous rock. Magma is also composed of aluminum, calcium, sodium, potassium, magnesium, iron, titanium, and manganese. So, as magma cools and solidifies, these elements combine to form the two major groups of silicate minerals, either ferromagnesian silicates (dark), which are rich in iron and/or magnesium, and low in silica. Or, it may form nonferromagnesian silicate (light) which contains a larger amount of potassium, sodium, and calcium. They are much richer in silica than the dark silicates. Minerals of the dark silicates include olivine, pyroxene, amphibole, and biotite mica. Minerals of the light silicates include quartz, muscovite mica, and the feldspars.
Felsic igneous rocks are composed of light-colored silicates, felsdspar and quartz (silica). These rocks have a granitic composition and make up the continental crust. Igneous rocks that contain the dark silicate minerals and plagioclase feldspar are said to have a basaltic composition. These rocks contain a high amount of ferromagnesian minerals and are called mafic. Intermediate igneous rocks have an andesitic composition and is found in between the felsic and mafic groups. They consists of around 25% dark silicate minerals and the rest is plagiocalse feldspar. These kinds of igneous rocks are created in the volcanoes at the margins of continents. Ultramafics are rocks whose composition is composed almost entirely of ferromagnesian minerals. Ultramafic's are rare at Earth's surface. An example of an ultramafic rock is the peridotite.
Silica content can be used as an indication of the composition of igneous rocks. Rocks high in silica have very small amounts of iron, magnesium, and calcium; whereas, rocks that have little silica have quite a bit of iron, magnesium, and calcium. The amount of silica in the magma also effects how viscous the magma will be. Magma with a high amount of silica will very viscous (sticky, produces explosive volcanic events). Magma with a low amount of silica will not be very viscous (not sticky, volcano lava will just flow).
Sedimentary Rocks
Composition:
The major component of sedimentary rocks tend to be clay minerals and quartz. Clay is the most abundant product of chemical weathering of silicate minerals. Quartz is abundant because it is very resistant to chemical weathering. So, when igneous rocks are weathered/eroded down, the quarts crystals are freed. Feldspars and micas are also commonly found in sedimentary rocks. Looking at the particle sizes of the minerals is the primary method of distinguishing sedimentary rocks. Boulders (>256 mm), cobble (64-256 mm), pebble (4-64 mm), granule (2-4 mm), sand (1/16 to 2 mm), silt (1/256- 1/16 mm), clay (<1/256). By looking at the types of particles and their sizes in the rocks, we can tell a lot about the how and in what environment a sedimentary rock was formed. Particles are sorted as they are carried by wind and water. The larger and stronger the current, the larger the particle that can be carried. Sedimentary rocks are formed by the accumulation of particles that are broken down through chemical or mechanical weathering and are then transported and settled are called detrital sedimentary rocks. Examples of detrital sedimentary rocks include shale, sandstone, siltstone, conglomerate, and breccia. Chemical sedimentary rocks are formed from the ions dissolved in the solution of lakes and seas. Eventually, the ions precipitate out to form chemical sediments. Examples of chemical rocks are halite, limestone, dolostone, and chert. Chemical sediments can be formed by organic or inorganic deposits. Coal is a sedimentary rock that is made up of organic material, such as leaves and wood, that have been chemically altered. Coal formed from plants that was buried millions of years ago. Because dead plants decay in an oxygen-rich environment, we know that these dead plants had to have formed in an oxygen-deficient environment. Bacteria in this oxygen-deficient environment works to break down the plants, but are eventually destroyed by the acids released in the plants. So, the partial, decayed plants begin to build up in many layers, creating peat. The peat then slowly changes into lignite coal. As these layers build up, temperature and pressure increases, which initiates a chemical reaction the forms water and gas. As pressure builds even more, water and gases are pressed out and the amount of fixed carbon increases. The lignite becomes bituminous coal. Through pressure and temperature, perhaps caused by mountain building, then bituminous coal becomes anthracite, a metaphoric rock. Anthracite is a clean-burning fuel, but isn't really mined since it isn't widespread and difficult to extract.
Environment:
By studying sedimentary rocks, we can tell a lot about the conditions under which it formed, such as the environment, origin, and the method that it formed under. Sedimentary rocks may be made out of sediments that traveled very far, or it may be formed in one spot (in a lake or stagnant swamp, for example). The different environments in which sediments may form in are continental, marine, or transitional.
A continental environment is a place where the climate affects the erosion or deposition of sediments, either through streams, glacial ice, or wind. Streams are the most influential force for eroding and depositing sediments.
There are different kinds of continental environment:
-Floodplains: Large quantities of sediments are dropped when flood waters flood a valley floor
-Alluvial Fan: When a rapid stream emerges from a mountainous area onto a flat region, it drops sediments in a cone shape.
-Glaciers pick up and transport large amounts of sediments and despot them, unsorted, when they retreat.
-Dune: Wind depots are called eolian and can carry sediments at great distances. These deposits are well sorted. If the wind is not obstructed by vegetation, then the sand is able to accumulate into hills called dunes.
-Playa lakes: These form in desert basins after a heavy rainfall or snowmelt occurs. They leave behind evaporates and deposits.
Marine Environment is divided into two environments based on depth. Shallow marine environments reaches to a depth of 200 meters and extends from the shore to the continental shelf. The sediments deposited in these environments is based on the elevation, water depth, water temperature, climate, and distance from shore. Because there is constant erosion taking place at the shore, the marine environment receives a large amount of land-derived sediment. In warm environments, carbonate-rich muds are the dominant sediment. Coral reefs are associated with a shallow marine environment. Deep marine environment extends from the continental shelf to the floors of the deep sea. Tiny particles may stay afloat in the water for a long time before settling out and falling to the ocean floor.
Transitional Environment is the region between the marine and the continental environments. One example of this region are beaches where you can find sediment deposits of sand and gravel. Ocean currents and waves move sand around and creates spits, bars, and barrier islands (offshore bars and reefs are called lagoons). Sediment build up into the sea when rivers experience a drop in velocity and drop their sediments produces deltas.
Metamorphic Rocks
Heat, pressure, and chemically active fluids are the the driving agents for creating metamorphic rocks. The degree of metamorphism and the contribution of each of the driving agents changes from one environment to another.
Texture:
Unlike sedimentary or igneous rocks that have random orientation of mineral grains, metamorphic minerals exhibit a parallel alignment of elongated minerals. When we view sedimentary or igneous rocks, they pretty much look the same no matter how you observe the rock. But with metamorphic rocks, looking at one side will look differently than viewed from another side. These types of metamorphic rocks is said to have foliation, which refers to a planar arrangement of mineral grains within a rock (foliation does occur in sedimentary rocks and few types of igneous rocks, but it's a very strong characteristic found in metamorphic rocks). Foliation is produced by compressional stresses and causes the mineral grains to form parallel alignments.
Different types of foliation:
Slaty cleavage is one type of foliation where the planar surface along the rocks splits into slabs if hit and smacked apart. Slaty cleavage can develop in low-grade metamorphic environment where beds of shale (a sedimentary rock) are folded and forms slate. With further deformation, recrystallization takes place. Narrow parallel zones develop and it is along here where the slate splits.
Schistosity is another type of foliation that takes place under higher temperature environments. The platy minerals begin to grow larger and exhibit a planar or layered structure.
Gneissic textured rocks occurs in high-grade metamorphic events. The ion migration results in the segregation of minerals. These rocks do not split as easily as slates and schists.
Metamorphic rocks that do not exhibit the foliated texture are referred to having a nonfoliated texture. These types of metamorphic rocks tend to develop in environments where deformation is minimal and the parent rock contains minerals that have equidimensional crystals (quartz, calcite). When a calcite, such as limestone, undergoes metamorphism, the grains recrystallize to form larger interlocking crystals. The new rock, marble, displaces the large equidimensional grains that are randomly ordered. Another texture takes place in rocks that have large grains surrounded by fine-grained minerals (porophyroblasts).
Environment:
Most metamorphism takes place in a plate margin region, and may be associated with igneous activity. There are different types of metamorphism:
Contact or Thermal- takes place when rocks are surrounded by magma and are essentially baked. Because the rocks are baked, they end up with hard, fine-grained metamorphic rocks called hornfels. The region where they are altered is called the metamorphic aureole. The size of the aureole depends on mineral composition of the host rock and how much water is available. Contact metamorphism does not involve direct pressure, so the crystals within the metamorphic aureole are somewhat randomly oriented. Hornfels can form from a variety of materials. Large grains of metamorphic minerals, such as garnet, may form giving the hornfel a porphyroblastic texture. Marble and quartzite are two metamorphic rocks that can form through contact metamorphism.
Hydrothermal- chemical alternation can occur when hot, iron-rich fluids circulate through cracks that develop in rocks. This type of metamorphism is closely linked to igneous activity and take place alongside contact metamorphism in regions of large plutons. As the magma cools and solidifies, the ions that are not organized in a crystalline structure and the water are expelled, called hydrothermal solution. This solution may chemically alter the host rock and the ions may even precipitate out to form mineral deposits. The fluids may even penetrate permeable rocks, such as limestone. The solution may react with the carbonates and produce a calcium-rich silicate mineral that forms a metamorphic rock called skarn. Hydrothermal metamorphism is mostly found at the mid-ocean ridge region. As magma moves up and and forms the new sea floor, seawater moves through this hot crust. This seawater is heated and reacts, chemically, with the basaltic rocks. This results in converting ferromagnesian minerals into hydrated silicates. Metals may also form in this region and rise up, generating a particle-filled cloud called black smokers. As it mixes with the cooler seawater, sulfides and carbonate minerals that contains these metals precipitate out, and forms a metallic deposit.
Burial and Subduction zone of metamorphism- Let's start with burial metamorphism. This type of metamorphism occurs when sediments build up thick layers along a subsiding basin. Low-grade metamorphism takes place within the deepest layers (and the depth varies from one location to another). Pressure and heat are the driving forces for recrystallization. Subuction may carry rocks and sediments down to great depths along convergence boundaries, called subduction zone metamorphism. This type of metamorphism is different from the burial metamorphism in that deformation of the rock now takes place and the rocks are metamorphosed.
Regional Metamorphism- Most metamorphic rocks were produced during regional metamorphism during orogenic event. During a mountain building episode, large amounts of Earth's crust are deformed along a convergent place boundary. This typically takes place when oceanic lithosphere is subducted during collision and continental volcanic arcs are produced. Rocks are shortened and thickened as a result of the folding that is taking place. This deformed rock often results in being lifted high above sea level to form a mountain terrain. In addition, inside the mountain, temperature becomes so high that rocks begin to melt. As a result, the magma forms bodies large enough to rise and intrude the overlying metamorphic and sedimentary rock. Thus, the core of a mountain consists of metamorphic rocks intertwined with igneous rock bodies.
Impact Metamorphism- takes place when a meteorite smacks into the Earth's surface. Energy from the impact is transformed into heat energy and shock waves that passes into the surrounding rocks. These nearby rocks are shattered and may even melt. The products from impacts are called impactiles and include a mixture of fragmented rocks and glass-rich eject (similar to volcanic bombs). Quartz and diamonds may be found in these regions. Finding these two minerals tells us that very high pressure and temperature (as great as within the earth) occurred briefly at the surface of the earth.
Geologists noticed that groups of minerals could be used to determine the environment (temperature and pressure) in which the metamorphic rocks underwent. Rocks that contained the same assemblage of minerals formed in very similar environments (think of this as with flowers. Flowers grow in similar environment). These types of minerals belong to the same metamorphic facies. Some metamorphic facies include hornfels, green-schist blueschist, and amphibolite. So, knowing these metamorphic facies helps because each facies underwent the same conditions and in similar tectonic settings.
b. Identify common rock-forming minerals (e.g., feldspars, quartz, biotite, calcite) using a table of diagnostic properties
http://www.sdnhm.org/kids/minerals/games/index.html
c. Identify common ore minerals as sources of copper, iron, lead, zinc, cement, halite, gypsum, and uranium
Water, Carbon, and Nitrogen Cycle
a. Illustrate the mechanism that drives the water cycle
The water cycle begins with the energy of the sun. The water cycle, also referred to as the hydrologic cycle, is a mental reference with what happens to water as it cycles through the earth. The large reservoir is the ocean because of the large solar radiation that is absorbed by the ocean, the water evaporates and gains energy. Because the ocean is so large, most of this water falls back into the ocean (short circuit). Very small amount of the water condenses into clouds and moves over land. So, you start with the transport from the ocean to the land (we are so concerned about the atmosphere as it is what transports the water). Some of it falls to earth in some form of precipitation, and then it splits off to different paths. A small amount infiltrates the ground (10 percent) and becomes groundwater. The crust consists of several layers, with some layers being porous and permeable while others are impermeable. As water moves through the permeable layer and reaches the impermeable layer, it begins to build up. We call this region the saturated zone. The region above this zone is called the unsaturated zone. The boundary between the two is called the water table.
Water may also be absorbed by the plant and released (transpiration) back into the atmosphere. 30 percent falls into rivers and eventually makes its way back to the ocean. Because water has different sized reservoirs and moves at different speeds, it spends very long in some reservoir and little in others. The ocean is so vast that it has a lot of storage. It takes a long time to move from one region to the next. Once in the atmosphere it takes a few days to get back into the ocean. In a river (no lakes), it takes a couple of weeks to get from the top of the mountain to get back to the ocean. One good thing about rivers is that if it's polluted, then it will clear out into the ocean. Water that infiltrates moves very slow. So, groundwater may take thousands, tens of thousands of years, to empty into river and then into the ocean or discharge directly into the ocean.
Global Carbon Cycle
WILL POST PICTURE
Complicated chain of events. Each one of them controls the other one. On the one hand, if you have too much of CaCo3, then it's removed by sedimentation (shells) and so forth. The oceans are crucial, the very important role (for the last 500 my) of maintaining the amount of co2 in the atmosphere. They are the buffers of the amount of co2 in the atmosphere. They also, due to the generation of the H they control the acidity of the ocean. The ocean is slightly more the the alkaline side. If I have 20degree pure water, a very tiny amount of the molecules in the water, are breaking naturally form hydrogen and oxygen> they then join again. As many as splitting are joining. At any time there are 10+-7, the pH means the amount pH 7, means the amount of hydrogen atoms present in the water. So, what is bigger, 10=7 or 10-5, 10-5 means hundred more times of hydrogen. So, it's more acidic. So, 10-3 is more acidic. 10-7 is bigger than 10-10 (have less, 10 would be like soap). The ocean happens to be somewhere around 7.8. Doesn't change much. Why? Because of the carbon cycle. The system is buffered so well, that if anything changes seriously, the reactions just turn the other way so that it maintains a constant amount of HC)o- and H+. You may have heard that global warming is increasing the co2, that will drive the reaction and thus change the acidity of the acid. But it can't, the system is buffered and remain it's acidity. The bad news is that the ocean needs a lot time, a lot of time to do these things. So, the co2 content of the atmosphere could rise quite a bit, the ocean this whole time is consuming it. By the time the oceans regulate the co2, we might not be around to see it.
b. Compare the processes of photosynthesis and respiration in terms of reservoirs of carbon and oxygen
c. Identify the carbon reservoirs (i.e., physical and chemical forms of carbon in the atmosphere, oceans, biomass, soils, fossil fuels, and solid earth) and describe the movement of carbon among these reservoirs in the global carbon cycle
Quick Background: Pure carbon atom is fairly rare in nature, and is primarily found in diamonds and graphite. Typically, carbon is chemically bounded to other atoms to form compounds (carbon dioxide, carbon monoxide, calcium carbonate, etc). Carbon is also an essential building block of life and is found bonded to hydrogen and oxygen to form organic compounds, necessary to compose living things.
Carbon is found in the atmosphere primarily as the greenhouse gas, carbon dioxide. Many processes on Earth requires the use of carbon dioxide. Thus, carbon is constantly being moved in and out of the atmosphere. Carbon is able to move through all four of the Earth's major spheres (biosphere, atmosphere, hydrosphere, and lithosphere).
Plants absorb carbon dioxide (biosphere) from the atmosphere in order to produce organic compounds that is necessary for growth. Then, animals who consume the plants, use the organic compounds that was produced by the plant as a source of energy. Through the process of respiration in plants, carbon dioxide is returned to the atmosphere. In addition, when plants die and decay, their biomass is oxidized and carbon dioxide is returned to the atmosphere. Small amounts of carbon dioxide may be deposited as sediment (lithosphere) when plants decay. After a long period of time, this decaying plant material may form become a fossil fuel. Burning of this fossil fuel releases large quantities of carbon dioxide back into the atmosphere. Volcanic eruption (lithosphere) spews out gases such as water vapors and carbon dioxide. Some carbon dioxide combines with water vapors to form carbonic acid which attacks rocks of the lithosphere. This chemical weathering of rock produces bicarbonate ion, which is carried by groundwater and streams into the ocean. Marine life extracts the dissolved ion to produce its hard parts (shells, for example) of calcium carbonate. When these marine creatures die, their skeleton parts fall to the sea floor and eventually becomes compacted and forms a sedimentary layer, with limestone being the most abundant (lithosphere). Through shifts and changes on Earth, the limestone may be exposed at the Earth's surface. Through chemical weathering, the carbon stored in the rock would be released into the atmosphere as carbon dioxide.
d. Describe the nitrogen cycle as it relates to the atmosphere, soils as reservoirs, life processes, and pollution
Organisms need nitrogen in order to make amino acids, proteins, and nucleic acids. Except for bacteria, organisms cannot use nitrogen directly from the atmosphere. In the atmosphere, nitrogen exists in the gaseous stage (N2). A specific kind of bacteria (contains nitrogenase enzymes) is able to bind the nitrogen atoms to hydrogen atoms to form ammonia ion, NH3, in a process known as nitrogen fixation. Plants can only take in nitrogen as either ammonium ion or nitrate ion. Bacteria in the soil converts ammonia into nitrates and nitrites during nitrification. Producers can take these substances in and use them to make proteins and other molecules. Consumers eat the producers, who in turn, uses these proteins to make new proteins. When organisms die, decomposers return the nitrogen back into the soil as ammonia. Bacteria may again change the ammonia into nitrates or nitrites or into nitrogen gas (denitrification, which is internal respiration by bacteria).
Pollution: Soluble nitrogen in oceanic waters limits the amount of growth of certain types of bacteria. However, through artificial fertilizers that is added to crop-lands results in run-off of soluble nitrogen into oceans. The addition of soluble nitrogen results in eutrophication (increase in the amount of artificial or natural substance in an environment). Nitrogen-driven bacteria grows and depletes the water of oxygen to the point that organisms begin to die.
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