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Earth's Structure
Geology is the study of planet earth, including its structure and composition.Constructive forces build and shape the surface (for example: mountains) and destructive forces erode and wear away the features. Uniformitarianism is the idea that geologic processes that operate today also operated in the past. Mountains and canyons are a part of geologic processes that worked well over a long period of time. The earth can be divided into 3 layers, the crust, mantle, and core. The layering is different due to density. The crust is thin compared to the other layers and is made up of silicates. It is the outer layer of Earth's surface. There are two types of crust: continental and oceanic. Continental crust is less dense, but thicker than the oceanic crust. The mantle is a thick, hot, and solid layer of rock underneath the crust. It extends 2850 kilometers. The pressure and temperature increase with depth. The mantle, like the crust, is composed of silicates. The mantle has been divided into 3 layers: the lithosphere (relatively cool, rigid rock that is the uppermost part of the mantle and the bottom of crust). It is about 100 kilometers thick. Below the lithosphere, there is the asthenosphere, a layer of softer, weaker rock that flows slowly. The bottom layer of the mantle is the mesosphere, the strong part of the mantle.The core is a large sphere of metal that occupies Earth’s center. It is mainly composed of iron. Pressure in the core increases greatly with depth. The core is divided into inner core and outer core. The flowing iron of the outer core produces an electric current that produces Earth's magnetic field. This is because of Earth's rotation. The inner core is solid because the high pressure is a more important factor than the temperature.
Minerals
Rocks and minerals might look similar at certain times, however when looked at closely, there is a distinct difference. A rock is a solid combination of minerals. A mineral is a naturally occurring, inorganic solid with a crystal structure and a characteristic chemical composition. Minerals are identified by different properties, including: crystal structure, color, streak, luster, density, hardness, fracture, and cleavage. In each mineral, atoms are arranged in a particular geometric shape, this is the crystal structure. A mineral's color can be deceptive because a small change in the composition can change the color of the mineral. Streak is the color of the mineral's powder. Luster is the way in which a mineral's surface reflects light. The different types of luster are silky, earthy, pearly, and vitreous. The density of a mineral depends on its chemical composition. Hardness is a mineral's resistance to scratching. Hard minerals can scratch a soft one, but not vice versa. Hardness is measured by Moh's Hardness scale. Fracture is how a mineral breaks and it is determined by the crystalline structure of the mineral and the bond between the atoms. Cleavage is the type of fracture in which a mineral tends to split along regular, well-defined planes where the bonds are weakest.
Geology is the study of planet earth, including its structure and composition.Constructive forces build and shape the surface (for example: mountains) and destructive forces erode and wear away the features. Uniformitarianism is the idea that geologic processes that operate today also operated in the past. Mountains and canyons are a part of geologic processes that worked well over a long period of time. The earth can be divided into 3 layers, the crust, mantle, and core. The layering is different due to density. The crust is thin compared to the other layers and is made up of silicates. It is the outer layer of Earth's surface. There are two types of crust: continental and oceanic. Continental crust is less dense, but thicker than the oceanic crust. The mantle is a thick, hot, and solid layer of rock underneath the crust. It extends 2850 kilometers. The pressure and temperature increase with depth. The mantle, like the crust, is composed of silicates. The mantle has been divided into 3 layers: the lithosphere (relatively cool, rigid rock that is the uppermost part of the mantle and the bottom of crust). It is about 100 kilometers thick. Below the lithosphere, there is the asthenosphere, a layer of softer, weaker rock that flows slowly. The bottom layer of the mantle is the mesosphere, the strong part of the mantle.The core is a large sphere of metal that occupies Earth’s center. It is mainly composed of iron. Pressure in the core increases greatly with depth. The core is divided into inner core and outer core. The flowing iron of the outer core produces an electric current that produces Earth's magnetic field. This is because of Earth's rotation. The inner core is solid because the high pressure is a more important factor than the temperature.
Minerals
Rocks and minerals might look similar at certain times, however when looked at closely, there is a distinct difference. A rock is a solid combination of minerals. A mineral is a naturally occurring, inorganic solid with a crystal structure and a characteristic chemical composition. Minerals are identified by different properties, including: crystal structure, color, streak, luster, density, hardness, fracture, and cleavage. In each mineral, atoms are arranged in a particular geometric shape, this is the crystal structure. A mineral's color can be deceptive because a small change in the composition can change the color of the mineral. Streak is the color of the mineral's powder. Luster is the way in which a mineral's surface reflects light. The different types of luster are silky, earthy, pearly, and vitreous. The density of a mineral depends on its chemical composition. Hardness is a mineral's resistance to scratching. Hard minerals can scratch a soft one, but not vice versa. Hardness is measured by Moh's Hardness scale. Fracture is how a mineral breaks and it is determined by the crystalline structure of the mineral and the bond between the atoms. Cleavage is the type of fracture in which a mineral tends to split along regular, well-defined planes where the bonds are weakest.
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Rocks and the Rock Cycle
Rocks are classified into three different categories, igneous, metamorphic, and sedimentary. Igneous rocks are made by magma (molten rock) from the mantle being pushed upwards. The magma cools and solidifies to form igneous rocks. There are two types of igneous rocks, intrusive and extrusive. Intrusive rocks form underground from hardened magma and they cool slowly, allowing crystals to grow large. They have a coarse-grained texture. Extrusive rocks form at the earth's surface and they cool very quickly. The crystals do not grow much and these rocks are fine-grained. Sedimentary rocks form over time as sediment is squeezed and cemented together. There are 3 classifications. Clastic rocks form from broken fragments of other rocks, chemical rocks form from when minerals precipitate out of solutions, and organic rocks that form from the cementing and compacting of shells and skeletons of certain creatures. Metamorphic rocks form when a rock is transformed by heat, pressure, or chemical reactions. They form under high pressure and temperatures deep underground. Foliated rocks are metamorphic rocks arranged with crystals in parallel layers. Rocks are constantly evolving, The rock cycle is a series of processes in which rocks change from one type to another. Forces within the earth and at the surface cause the rocks to constantly change form. One common example is a igneous rock pushed to the surface and broken into sand. Then it is carried to the ocean floor and it becomes a sedimentary rock. Then the sedimentary rock is pushed underground and change into a metamorphic rock. The rock cycle does not end here as it is continuous.
Plate Tectonics
The theory of plate tectonics states that pieces of the earth's lithosphere move slowly on top of the asthenosphere. The theory of plate tectonics explains the formation and movement of the earth's plates. Mapmakers noticed how the shapes of North and South America fit with the shape of Europe and Africa. Then, geologists discovered fossils of land-based plants and animals on continents separated by large oceans. Alfred Wegener hypothesized that continents were once joined in a single supercontinent which then broke into pieces and moved apart. The supercontinent was named Pangea. The continents eventually moved across earth’s surface in the continental drift. Now, there is evidence for this theory. The mid ocean ridge is a chain of underwater mountains and it had a remarkable feature a deep valley running along its crest. Seafloor spreading is a process by which new oceanic crust is created at mid-ocean ridges as older crust moves away. The ridge is a huge crack in the crust where magma is pulled upward. Ocean floor on each side of valley are moving apart, magma from the mantle wells up, solidifies, and forms new crust. As seafloor spreading occurs, old oceanic plates sink into the mantle in the process of subduction. As a plate sinks through, it forms a depression called a trench. Seafloor spreading creates new oceanic crust at the mid ocean ridges, while subduction destroys old oceanic crust at subduction zones.The evidence for seafloor spreading is, scientists sampled rocks on both sides of the mid ocean ridge and found patterns of parallel magnetic stripes on both sides. They showed the new ocean floor that was being added to both sides of the ridges.The theory of plate tectonics states that plates are always moving. Plate motions are the visible part of mantle convection as convection currents form in the mantle when hot rock rises at the ridges, cools, spreads out, and sinks back at subduction zones. There are three types of plate boundaries: divergent, convergent, and transform. At a divergent boundary, plates move away from each other. When the plates move apart, magma rises to fill the gap and it cools to form new rock at the edge of the plate. At a convergent boundary, plates collide. The most common type is when an oceanic plate is subducted beneath a trench. When oceanic crust collides with continental crust, the denser oceanic crust slides under the continental crust. At transform boundaries, plates slide past each other, moving in opposite directions. Geologists found that most mountains form along plate boundaries. Some form when two plates with continental crust at their edges collide along a convergent boundary. The crust buckles, folds, thickens, pushing up mountains. Mountains may also form when an oceanic plate collides with a continental plate. Mountains also form at divergent boundaries, such as the mid ocean ridges.
Rocks are classified into three different categories, igneous, metamorphic, and sedimentary. Igneous rocks are made by magma (molten rock) from the mantle being pushed upwards. The magma cools and solidifies to form igneous rocks. There are two types of igneous rocks, intrusive and extrusive. Intrusive rocks form underground from hardened magma and they cool slowly, allowing crystals to grow large. They have a coarse-grained texture. Extrusive rocks form at the earth's surface and they cool very quickly. The crystals do not grow much and these rocks are fine-grained. Sedimentary rocks form over time as sediment is squeezed and cemented together. There are 3 classifications. Clastic rocks form from broken fragments of other rocks, chemical rocks form from when minerals precipitate out of solutions, and organic rocks that form from the cementing and compacting of shells and skeletons of certain creatures. Metamorphic rocks form when a rock is transformed by heat, pressure, or chemical reactions. They form under high pressure and temperatures deep underground. Foliated rocks are metamorphic rocks arranged with crystals in parallel layers. Rocks are constantly evolving, The rock cycle is a series of processes in which rocks change from one type to another. Forces within the earth and at the surface cause the rocks to constantly change form. One common example is a igneous rock pushed to the surface and broken into sand. Then it is carried to the ocean floor and it becomes a sedimentary rock. Then the sedimentary rock is pushed underground and change into a metamorphic rock. The rock cycle does not end here as it is continuous.
Plate Tectonics
The theory of plate tectonics states that pieces of the earth's lithosphere move slowly on top of the asthenosphere. The theory of plate tectonics explains the formation and movement of the earth's plates. Mapmakers noticed how the shapes of North and South America fit with the shape of Europe and Africa. Then, geologists discovered fossils of land-based plants and animals on continents separated by large oceans. Alfred Wegener hypothesized that continents were once joined in a single supercontinent which then broke into pieces and moved apart. The supercontinent was named Pangea. The continents eventually moved across earth’s surface in the continental drift. Now, there is evidence for this theory. The mid ocean ridge is a chain of underwater mountains and it had a remarkable feature a deep valley running along its crest. Seafloor spreading is a process by which new oceanic crust is created at mid-ocean ridges as older crust moves away. The ridge is a huge crack in the crust where magma is pulled upward. Ocean floor on each side of valley are moving apart, magma from the mantle wells up, solidifies, and forms new crust. As seafloor spreading occurs, old oceanic plates sink into the mantle in the process of subduction. As a plate sinks through, it forms a depression called a trench. Seafloor spreading creates new oceanic crust at the mid ocean ridges, while subduction destroys old oceanic crust at subduction zones.The evidence for seafloor spreading is, scientists sampled rocks on both sides of the mid ocean ridge and found patterns of parallel magnetic stripes on both sides. They showed the new ocean floor that was being added to both sides of the ridges.The theory of plate tectonics states that plates are always moving. Plate motions are the visible part of mantle convection as convection currents form in the mantle when hot rock rises at the ridges, cools, spreads out, and sinks back at subduction zones. There are three types of plate boundaries: divergent, convergent, and transform. At a divergent boundary, plates move away from each other. When the plates move apart, magma rises to fill the gap and it cools to form new rock at the edge of the plate. At a convergent boundary, plates collide. The most common type is when an oceanic plate is subducted beneath a trench. When oceanic crust collides with continental crust, the denser oceanic crust slides under the continental crust. At transform boundaries, plates slide past each other, moving in opposite directions. Geologists found that most mountains form along plate boundaries. Some form when two plates with continental crust at their edges collide along a convergent boundary. The crust buckles, folds, thickens, pushing up mountains. Mountains may also form when an oceanic plate collides with a continental plate. Mountains also form at divergent boundaries, such as the mid ocean ridges.
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Earthquakes
An earthquake is the movement of Earth’s lithosphere that occurs when rocks in the lithosphere suddenly shift, releasing stored energy. A seismic wave is a small portion of energy released during an earthquake is carried by these vibrations. A tsunami is a large sea wave generated by an underwater earthquake, volcano, or landslide. Stress is a force that squeeze rocks together, stretch or pulls them apart, or pushes them in different directions. An example of stress is deformation. As tectonic plates move, they cause stress in the crust, which in turn produces faults and folds. A fault is a break in a mass of rock along which movement occurs. The two slabs move in relation to each other. A fold is a bend in layers of rock. They form where rocks are squeezed together, but do not break. Rocks fold when they are under high temperature or pressure. Earthquakes occur because stress forces have exceeded the strength of rock. The focus is the location beneath Earth’s surface where an earthquake begins. The epicenter is the location on Earth’s surface directly above the focus. Forces cause the two sides of the fault to move past each other. Rocks may snag and remain locked because of friction and stress builds up. When rocks exceed their limit of stress they can bear, they break and grind past each other, releasing a lot of energy. There are 3 types of seismic waves: P waves, S waves, and surface waves. P waves are longitudinal waves. P waves compress and expand the ground. They are the fastest seismic waves and are the first to be detected at a distance. They can travel through both solids and liquids. S waves are transverse waves. They cause particles in materials they pass through to vibrate at right angles to the direction the waves move.They cannot travel through liquids. Surface waves develop when seismic waves reach Earth’s surface. They move slower than P and S waves, but usually produce larger ground movements and greater damage. Some are transverse, some are like ocean waves. To measure earthquakes and pinpoint their epicenters, geologists record seismic waves using seismographs. Earthquakes are measured in 3 different ways. The Richter Scale uses measurements of time and amplitude of seismic waves, but it is not used by geologists. The scale geologists use is the moment magnitude scale, it gives the measurement for the amount of energy released by an earthquake. The last scale is the Modified Mercalli scale. It is based on the intensity of the ground's shaking and damage. Most earthquakes are concentrated along plate boundaries, where many faults are found.
Volcanoes
A volcano is a mountain that forms when magma reaches the surface. Under certain conditions, small amount of mantle rock can melt, forming liquid magma. The magma rises upward through the crust, erupting at the surface as a volcano. Magma rises because it is less dense than solid rock. Magma is under pressure and contains gases. As magma approaches the surface, lower pressure allows gases to expand rapidly. An eruption occurs when gases bubble out through a crack in the crust, propelling magma to the surface. A magma chamber is a pocket where magma collects before eruption. Magma slowly accumulates until enough pressure builds up to start an eruption. Then, it rises to the surface in a narrow, vertical channel called a pipe. An opening in the ground where magma escapes to the surface is called a vent. A crater is a bowl-shaped pit at the top of the central vent. After an eruption, a volcano’s magma chamber and main vent might empty of magma, creating a shell. If the shell collapses inwards, it creates a depression, called a caldera. Volcanoes erupt explosively or quietly depending on characteristics of magma. Magma can vary in viscosity, or resistance to flow. The three factors that determine viscosity are temperature, water content, and silica content. A higher temperature and a higher water content will result in lower viscosity and a higher silica content will result in higher viscosity. Volcanoes that have very hot, low silica content magma erupt quietly. In a quiet eruption, lava erupts in a stream of low viscosity lava (lava flow). Hot, fast moving lava is known as pahoehoe and slow, cooler lava is known as aa. Explosive eruptions occur when there is a high silica content. Thick magma clogs volcanic pipe, causing enormous pressure to build up. When the volcano finally erupts, lava and hot gases are hurled outwards. Lava solidifies quickly and shatters into pieces. Most volcanoes occur along plate boundaries or hot spots in the crust. Volcanoes often form along a converging plate boundary where an oceanic plate is subducted into mantle. As it sinks through mantle, the plate causes melting. Magma forms and rises to surface. Volcanoes also form along divergent boundaries where magma rises to fill gaps between separating plates. A hot spot is a region where hot rock extends from deep within mantle to surface. There are three main volcanoes. A shield volcano is produced by quiet eruptions with low viscosity lava and is wide, flat. A cinder volcano occurs when an eruption is entirely ash and cinders and it forms a small, steep sided volcano. A composite volcano is a volcano that forms from an explosive eruption that produces combination of lava and ash.
An earthquake is the movement of Earth’s lithosphere that occurs when rocks in the lithosphere suddenly shift, releasing stored energy. A seismic wave is a small portion of energy released during an earthquake is carried by these vibrations. A tsunami is a large sea wave generated by an underwater earthquake, volcano, or landslide. Stress is a force that squeeze rocks together, stretch or pulls them apart, or pushes them in different directions. An example of stress is deformation. As tectonic plates move, they cause stress in the crust, which in turn produces faults and folds. A fault is a break in a mass of rock along which movement occurs. The two slabs move in relation to each other. A fold is a bend in layers of rock. They form where rocks are squeezed together, but do not break. Rocks fold when they are under high temperature or pressure. Earthquakes occur because stress forces have exceeded the strength of rock. The focus is the location beneath Earth’s surface where an earthquake begins. The epicenter is the location on Earth’s surface directly above the focus. Forces cause the two sides of the fault to move past each other. Rocks may snag and remain locked because of friction and stress builds up. When rocks exceed their limit of stress they can bear, they break and grind past each other, releasing a lot of energy. There are 3 types of seismic waves: P waves, S waves, and surface waves. P waves are longitudinal waves. P waves compress and expand the ground. They are the fastest seismic waves and are the first to be detected at a distance. They can travel through both solids and liquids. S waves are transverse waves. They cause particles in materials they pass through to vibrate at right angles to the direction the waves move.They cannot travel through liquids. Surface waves develop when seismic waves reach Earth’s surface. They move slower than P and S waves, but usually produce larger ground movements and greater damage. Some are transverse, some are like ocean waves. To measure earthquakes and pinpoint their epicenters, geologists record seismic waves using seismographs. Earthquakes are measured in 3 different ways. The Richter Scale uses measurements of time and amplitude of seismic waves, but it is not used by geologists. The scale geologists use is the moment magnitude scale, it gives the measurement for the amount of energy released by an earthquake. The last scale is the Modified Mercalli scale. It is based on the intensity of the ground's shaking and damage. Most earthquakes are concentrated along plate boundaries, where many faults are found.
Volcanoes
A volcano is a mountain that forms when magma reaches the surface. Under certain conditions, small amount of mantle rock can melt, forming liquid magma. The magma rises upward through the crust, erupting at the surface as a volcano. Magma rises because it is less dense than solid rock. Magma is under pressure and contains gases. As magma approaches the surface, lower pressure allows gases to expand rapidly. An eruption occurs when gases bubble out through a crack in the crust, propelling magma to the surface. A magma chamber is a pocket where magma collects before eruption. Magma slowly accumulates until enough pressure builds up to start an eruption. Then, it rises to the surface in a narrow, vertical channel called a pipe. An opening in the ground where magma escapes to the surface is called a vent. A crater is a bowl-shaped pit at the top of the central vent. After an eruption, a volcano’s magma chamber and main vent might empty of magma, creating a shell. If the shell collapses inwards, it creates a depression, called a caldera. Volcanoes erupt explosively or quietly depending on characteristics of magma. Magma can vary in viscosity, or resistance to flow. The three factors that determine viscosity are temperature, water content, and silica content. A higher temperature and a higher water content will result in lower viscosity and a higher silica content will result in higher viscosity. Volcanoes that have very hot, low silica content magma erupt quietly. In a quiet eruption, lava erupts in a stream of low viscosity lava (lava flow). Hot, fast moving lava is known as pahoehoe and slow, cooler lava is known as aa. Explosive eruptions occur when there is a high silica content. Thick magma clogs volcanic pipe, causing enormous pressure to build up. When the volcano finally erupts, lava and hot gases are hurled outwards. Lava solidifies quickly and shatters into pieces. Most volcanoes occur along plate boundaries or hot spots in the crust. Volcanoes often form along a converging plate boundary where an oceanic plate is subducted into mantle. As it sinks through mantle, the plate causes melting. Magma forms and rises to surface. Volcanoes also form along divergent boundaries where magma rises to fill gaps between separating plates. A hot spot is a region where hot rock extends from deep within mantle to surface. There are three main volcanoes. A shield volcano is produced by quiet eruptions with low viscosity lava and is wide, flat. A cinder volcano occurs when an eruption is entirely ash and cinders and it forms a small, steep sided volcano. A composite volcano is a volcano that forms from an explosive eruption that produces combination of lava and ash.