Geology 105 USC Midterm 1 Spring 2018 – Flashcards
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What are the layers of the Earth?
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Crust, mantle, liquid iron outer core, solid iron inner core
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What kind of collision is Everest?
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Two continental plates, which are not denser than each other, so they just smush together
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What are the steps of the scientific method?
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Observation, question, research, hypothesis, experiment, analyze data/observations, conclusion
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Hypothesis
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explanation of observations and experiments, proposed for further testing
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theory
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set of hypotheses that has survived repeated challenges and has accumulated a substantial body of observational support, everything is a theory and theories can never be proved
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Scientific model
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representation of some aspect of nature based on a set of hypotheses and established theories
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what is one of the most important tests of a scientific explanation?
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to compare its predictions with its observations
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What is the difference between continental and oceanic crust?
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Oceanic crust is thin and dense, and continental crust is thick and has a lower density due to its silica content
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What is Isostasy?
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The flotation principle that says that the crust floats on the underlying denser mantle, and that topography is controlled by the thickness and density of the crust
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"The Present is Key to the Past"
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a guiding principle in geologic research but not a hypothesis, theory, or model
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What is the layered Earth an example of?
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Scientific model, which explains observations like the topography of the crust
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How did we come to estimate the Earth's density? What does it imply about the inner core
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Through Eratosthenes estimating the volume of the Earth at a radius of 6370 km, Isaac Newton estimating the mass of the Earth by measuring its gravitational force, Henry Cavendish eventually determined the Earth's density to be 5.5 kg per m^3. Because granite, a prominent component of the Earth's crust is only 2.7 kg per m^3, it implies that the core is of a greater density
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What are meteorites?
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Primordial pieces of the solar system that have fallen to Earth, made up of iron and nickel with densities of 8 kg per m^3 (3x greater than the density of granite). Emil Wiechert in 1896 made a hypothesis has a dense core surrounded by a mantle.
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Wiechart's hypothesis
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Emil Wiechert made a hypothesis in 1896 that Earth has a dense core surrounded by a mantle, this was tested by probing the Earth with seismic waves (like a CAT scan), further testing confirmed that the outer core was liquid
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What is the Earth composed of?
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A core of liquid and solid iron , a solid mantle of mainly olivine, a crust which is solid and rich in silica and aluminum,
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What does Earth's magnetic field do?
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It protects us from solar wind and allows us to have an atmosphere, life may not have evolved on Earth without it (life also plays a role in keeping the Earth's surface cool from solar wind by sequestering carbon)
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Earth's system
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Open system that exchanges energy and mass with it's surroundings driven by the sun and heat from the mantle
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The Climate System
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involves interactions among the atmosphere, hydrosphere, biosphere, cryosphere, and lithosphere, interacts with other systems because climate depends on hydrosphere, cryosphere, biosphere, etc.
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The Plate Tectonic System
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Involves interactions among the lithosphere, asthenosphere, and deep mantle, driven by convection within the mantle, interacts with other systems through because the biologic material under pressure forms oil, releasing green house gases into the atmosphere
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Geodynamo system
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involves interactions between the inner and outer cores, interacts with other systems because the magnetic field protects the atmosphere
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atmosphere
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gaseous envelope extending from the Earth's surface to about 100 km up
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What is the theory of "Continental Drift" and what evidence do we have to support it?
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A theory presented by Alfred Wegener that proposes that the continents rest upon moving plates. This theory is backed up by evidence in the fit of continents around the Atlantic, geologic match-ups between the continents, similar fossils on widely separated continents, and similar past climates in regions at vastly different latitudes.
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What are the three types of plate boundaries?
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Divergent (spreading ridges or seafloor spreading) Convergent (subduction zones) Transform (strike-slip faults)
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Explain the processes at work in Divergent plate boundaries
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The plates move apart, and the deeper mantle wells up and cools to form new lithosphere (oceanic crust and mid ocean ridges).
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Explain the processes at work in Convergent plate boundaries
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The plates move together resulting in a subduction zone where one plate slides beneath the other and is recycled into the deep mantle.
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Describe the primary differences between the crust and the lithosphere
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The crust is defined by its silicate rich, less dense composition while the lithosphere is defined by its rigidity.
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What are the types of convergent plate boundaries?
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Ocean-Ocean Convergence; occurs when two oceanic plates converge, forming a deep-sea trench and a volcanic island arc. Ocean-Continent Convergence; occurs when an oceanic plate subjects and a volcanic belt of mountains is formed at the continental plate margin. Continent-Continent Convergence; occurs when two continental plates collide, the crust crumples and thickens creating high mountains and a wide plateau.
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What are the types of transform plate boundaries?
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Mid-Ocean Ridge Transform Fault; occurs when spreading centers are offset by mid-ocean ridge transform faults where the two oceanic plates slide horizontally past each other. Continental Transform Fault; occurs when two continental plates move past each other, similarly to the mid-ocean ridge movement. (Examples include The San Andreas Fault in California)
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What are the main elements of the Earth's Magnetic Field?
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At the Earth's surface it looks like a simple "dipole" (two-pole) magnet. The north magnetic pole is displaced from "true north" by 11.5°. The magnetism is generated by "geodynamo", the convection process of the Earth's inner and outer cores. The direction of the magnetic field spontaneously flips from north to south at irregular intervals due to changes in convection within the outer core.
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What is an Isochron map?
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A map that shoes the age of the earth's crust by using color to denote age.
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What is the Geomagnetic Time Scale?
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A process that uses the irregular polarity reversal of the Earth's magnetic field (preserved in rock layers) to date the Earth rocks.
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What is Relative Plate Motion?
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The motion of one plate relative to any point on another plate boundary.
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How do scientists go about calculating the speed of plate movements?
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First, the rate of plate motion must be measured using the equation: Rate=distance/time. Methods: Mapping of magnetic anomalies Seafloor drilling GPS Remember: movement is not constant!
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What are the six points of the Rock Cycle?
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1. Rifting - dense rocks diverge, creating a basin at the spreading center. 2. Rifting+Spreading continues - magma rises to fill the space. 3. Subsidence of Continental Margin - leads to formation of sedimentary rock. 4. Subduction - formation of igneous rocks. 5. Closing of Ocean Basin - metamorphosed rocks form and mountains are created. 6. Erosion - new sedimentary rocks are formed. *Then the cycle begins anew*
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What are Extrusive Igneous Rocks?
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Formed outside the Earth's crust. Magma extruded at the surface that solidifies to form fine-grained or even glassy volcanic rock: lava flows.
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What are Intrusive Igneous Rocks?
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Formed within the Earth's crust. Includes forms such as dikes, tabular intrusions (sills) and plutons.
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Where and why does Melting occur within the earth?
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At Mid-Ocean Ridges, in Mantle Plumes, Above Subduction Zones, and in Zones of Mountain Building. Melting is a result of decompression of mantle rock in the Earth's crust.
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Explain the processes at work in Melting at Mid-Ocean Ridges
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Melting of mantle peridotite beneath the MOR. Produces Basalt Magma (low content of SiO2, high content of Fe and Mg). Most voluminous magmatism on Earth.
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Explain the processes at work in Magmatism in Mantle Plumes
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Plumes rise from the core-mantle boundary at nearly 3000 km depth. They start melting at depths oaf about 100km and produce basalt magma. Plumes can occur in the ocean or beneath continents.
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Explain the processes at work in Subduction Zone Magmatism
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Melting at 100-200 km depth in the Earth's mantle. The melting is a result of the addition of water carried down the subduction zone to hot mantle peridotite where the water lowers the melting temperature. Magma is water-rich, and causes explosive eruptions. Magma is silica-rich with a higher viscosity than basalt. It creates tall volcanoes (start-volcanoes).
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Explain the processes at work in Magmatism in Zones of Crustal Thickening
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In areas of thickened continental crust, like the Himalayas, melting of crustal rocks produces granitic magma.
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What are the types of extrusive rock?
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Low-viscosity magma (flows easily): Pahahoe (ropy lava), Aa (blocky lava), and Pillow Lava. High-Viscosity Magma (flows slowly): Tuff (ash), and Pyroclastic breccias
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What is Folding?
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Curved streaks of rock resulting from intense compression that bend rock layers (bedding) into folds.
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What is Faulting?
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Rock layers (bedding) broken on an Azia, splitting the rock and displacing it along discontinuities.
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What is Sedimentary Deformation?
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Forces that manipulate rocks during or after formation.
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What are the three basic Types of Tectonic Forces?
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Compressive forces: pushing forward together. Ductile outcome: folding Brittle outcome: faulting Tensional forces: pulling apart. Ductile outcome: stretching and thinning Brittle outcome: faulting Shearing (strike-slip) forces: moving laterally across (left lateral or right lateral) Ductile outcome: shearing Brittle outcome: faulting
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What is Brittle Deformation?
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Under conditions of pressure, a rock will fracture instantaneously along faults with low temperature and pressure.
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What is Ductile Deformation?
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Under conditions of pressure, a rock will bend (without breaking) and warp in folding zones with high temperatures and pressures.
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What is Strike and Dip and how are they measured?
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Strike: the direction of the intersection of a rock lawyer or fault surface with the horizontal surface. Strike angle is measured with respect to north. Dip is measured at right angles to the strike towards the tipping place. Dip angle is the acute angle at which the surface inclines from the horizontal.
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What is the Hanging Wall? What is the Foot Wall?
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These names came form miners who excavated ore along fault zones. They hung their haters on the "hanging wall" and stood on the "foot wall".
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What is Reverse Faulting?
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Reverse faulting is caused by compressive forces that squeeze and shorten a body in which the hanging wall moves upward but the foot wall moves downward.
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What is a Thrust Fault?
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A thrust fault is a reverse fault with a shallow-dipping fault plane in which the hanging wall moves upward and the foot wall moves downward.
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What is Oblique-Slip Faulting?
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Oblique-slip faulting is caused by a combination of forces that lead to a fault that slips on multiple planes.
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What are the three fault types?
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Dip-Slip: normal, reverse Strike-Slip: right-lateral, left-lateral Oblique-Slip: combination
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What are the two basic types of Folds?
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Anticline: folds upward (Older rocks are nearer its axis) Syncline: folds downward (younger rocks are nearer its axis)
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What is Geologic Mapping?
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A cross section of rock formations that allows for observation of rock layers within it.
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What is a Dome?
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A pattern of geologic mapping in which the oldest bed is in the core and the flanking formation are successively younger and dip away from the core.
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What is a Basin?
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A pattern of geologic mapping in which the youngest formations are found in the core, flanked by successively older strata that dip toward the core.
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What are joints?
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Cracks along which there has been no movement.
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What are tensional tectonics?
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Extension of continental crust that occurs on normal faults having high dip angles in the upper crust that flatten in depth, forming curved fault surfaces.
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What is a Downfaulted Block?
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A Structure that results from tension and slippage on normal faults. Rift valleys are large-scale examples.
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What are Compressive Tectonics?
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Compression of continental crust occurs on thrust faults with low dip angles.
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What are Overthrust Structures?
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Compressive forces fracture rock layers and thrust them horizontally over a section of the same rock. Eventual erosion of the topmost layers reveals the older layers.
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What are Shearing Tectonics?
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Shearing of continental crust occurs on a nearly vertical strike-slip fault.
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What is the Spiral of Geologic Time?
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A mode of representation of geological times in which the eras get older the farther into the spiral one looks.
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What is the Arrow of Geologic Time?
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A mode of representation of geological times in which a division of arrows of time into continuously smaller arrows each elaborate on a specific period of time.
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What are the Two Types of Geologic Ages?
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Relative age: Geologists use their understanding of rock stratification and fossils to determine the relative ages of rock layers (example: Rock A is younger than Rock B) Absolute Age: Geologists use Isotopic clocks to determine the absolute ages of rock layers (Rock A is 122 million years old)
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Who's is Nicholas Steno and what did he propose?
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Nicholas Steno was an Italian Geologist that found shark teeth at varying depths in sedimentary rock and saw that he could compare time through observing the strata of these rocks. This is called the Stratigraphic Record.
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What is the Stratigraphic Record?
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the study of strata (layers) in rocks. These principles establish relative ages in sedimentary rocks: 1. Principle of Original Horizontality: sediments are deposited by gravity as nearly horizontal beds. 1. Principle of Superposition: each sedimentary layer in an undisturbed sequence is younger than the one below and older than the one above.
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What is the Fossil Record?
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Fossils are the remains of organism in geologic formations, by studying the distribution of these fossils in layers of sedimentary rock the relative ages of the rocks can be attained.
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Who was William Smith and what did he propose?
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William smith was a geologist who proposed the Principle of Faunal Succession.
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What is the Principle of Faunal Succession?
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The Principle of Faunal Succession tells that fossils are deposited in a sequence and that the same fossils can be found at outcrops of different locations, thus one can see the same fossils in similar layers and deduce that the layers were laid at similar times.
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What are Unconformities?
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A surface between two rock formations that were not laid down in an unbroken sequence.
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What are the Three Types of Unconformities?
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Disconformities: Upper layers overlie an erosional surface developed on undeformed, still horizontal lower layers. Nonconformity: Upper layers overlie metamorphic or igneous rocks. Angular unconformity: Upper layers overlie lower layers that have been tectonically folded and subsequently eroded to be more-or-less flat
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What are Cross-Cutting Relationships?
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A process in which tectonic forces cause uplift, folding, and deformation of the sedimentary layers during mountain building under the sea. Then, a dike from molten lava shoots through sedimentary layers, or faults can also disrupt the sequence.
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What is the Relative Time Scale?
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A mode of representation of geological times in which the eras are based on definitions relative to one another.
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What are Relative Age Relationships?
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From field maps, a geologist makes a cross section, noting the characteristics of the strata and unconformities. These relationships are observed in relation to each other to garner relative age.
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What is Absolute Time?
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Using radioactive decay to find the actual, quantifiable age of a rock using atomic structure.
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What is Atomic Structure?
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The structure of an Atom. The number of protons in an element is constant, but the number of neutrons can change.
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What is a Mass Spectrometer?
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A machine that measures the radioactive atoms in elements. Atoms of some elements are found to be unstable, but are subject to spontaneous changes that make them stable. Calculating this process (radioactive decay) results in the Absolute age of a rock.
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Why are Radioactive Atoms called "The Clocks in Rocks"?
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Atoms of some elements are unstable, their spontaneous transformation into more stable atoms by radioactive decay gives the absolute age of a rock.
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What is Radioactive decay?
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Radioactive decay is the spontaneous transformation of unstable atoms into stable atoms. Radioactive decay is random, but on average, is continuous. Therefore, the percentage amount that decays over a fixed time is constant. The Time interval for the decay of hand the atoms is called the half-life.
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What are the most Radioactive Elements used in geologic dating?
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Uranium-238, Uranium-235, Potassium-40, Rubidium-87, and Carbon-14
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What are the Three Types of Radioactive Decay Processes?
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Alpha decay: the parent nucleus loses alpha particles to the daughter nucleus. Beta Decay: the parent nucleus loses a beta particle to the daughter nucleus. Electron Capture: the parent nucleus loses an electron to the daughter nucleus. (Not gone over in lecture)
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What are the longest intervals of geologic time called?
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The longest intervals of geologic time are eons. The eons so far have been: 1. Hadean 2. Archaen 3. Proterozoic 4. Phanerozoic
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cryosphere
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polar ice caps, glaciers, and other surfaces of ice and snow
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hydrosphere
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surface waters comprising all oceans, lakes, rivers, and groundwaters
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Moon and Earth layers
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moon composed of iron core and lighter matter, during differentiation, iron sank to the center and lighter material floated upward Formation of a chemically layered Earth was done through gravitational differentiation, in which iron sank to the center and lighter material floated upward to give us Earth as a zoned planet
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Moon features
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lunar Maria, the crater, is made from basalt the lunar highlands are anorthosite
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Terrestrial (rocky) planets
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Mercury Venus Earth-Moon system Mars Several of the moons of Jupiter and Saturn and some of the asteroids are comparable in size, composition, and structure to the terrestrial planets
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Venus
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similar size and composition to Earth, weak magnetic field and no plates, extensive volcanoes, very thick and hot atmosphere, no oceans landforms include the arachnoid, tesserae and corona
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Mars
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about half the diameter of Earth, no magnetic field which means it may be solid core, no plates, used to have active volcanoes and tectonics in the first billion years, thin and cold atmosphere, no surface water now but there may have been some once land features include the Valle Marineris (5 km deep), a frozen sea, alluvial channels
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Titan
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a moon of Saturn, larger than Mercury, rocky core with a water mantle and thick ice crust, nitrogen atmosphere and lakes of methane
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origin of the earth-moon system
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1. 4.5 bya a Mars-sized body impacted Earth 2. giant impact propelled a shower of debris into space 3. Earth re-formed as a largely molten body 4. Moon aggregated from the debris 5. impact sped up Earth's rotation and tilted Earth's orbital plane 23 degrees There are moon rocks that are 4.47 billion years old that support this
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Earth's Chemical Layering
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8 elements constitute 99% of Earth's mass: oxygen, iron, silicon, magnesium, nickel, calcium, aluminum, sulfur
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covalent bonding
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when one atom loses an electron and gives it to the other, most common form of bonding, ex. graphite, which bonds carbon atoms in hexagons organized in sheets (the weak bond is why graphite is so soft), ex. silicate materials linking in chains sheets or frameworks, quartz, mica
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Chelyabinsk Meteor
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Landed in Russia on February 15th, 2013. Chondrite body weighing 12k metric tons, entered at 19.2 km/s. Airburst equivalent to 500 kiltons of TNT. Only meteor to result in a large number of injuries (~1500), significant damage (~7200 buildings).
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inner terrestrial planets
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small and rocky
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nebular hypothesis
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stars and their planets form by nebular contraction and condensation
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giant outer planets
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gaseous, with rocky cores
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small bodies (planets)
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dwarf planets - massive enough to be nearly spherical, like Pluto or Eris asteroids - planetesimals that never accreted to planets comets - aggregations of dust and ices that condensed in the outer, cooler regions of solar nebula meteoroids - small chunks of material, often broken off larger bodies
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pluto
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snowball of methane water and rock - not a planet : ( (a dwarf though!)
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Inner core
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inner sphere composed primarily of solid iron, extending from about 5150 km deep to the Earth's center at 6370 km
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minerals
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individual grains that have a simple, fixed chemical composition (denoted by an orderly, repeating fixed arrangement of atoms) and crystal structure, naturally occurring solid, internal structure reflects outer structure and exterior angles are the same as interior angles within the atomic structure
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porphyroblasts
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large crystals of new metamorphic minerals are called porphyroblasts, commonly contain inclusions (minerals that record stages in the history of the rock)
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P-T Path
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Pressure temperature path taken by rock, reflects pressure and temperature as it moves down (prograde path) and back up (retrograde path)
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metamorphic facies
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conditions of formation often defined by these, resulting rocks dependent upon temp and pressure and not as much the parent rock
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metamorphic mineral assemblages
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mineral assemblages in metamorphic rocks are controlled by rock composition, pressure and temp, and availability of water. can be used to infer the pressure and temp at time of metamorphism, provides info on depth of burial
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magmatic environments (for metamorphism)
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large intrusions like plutons rise into the crust and heat surrounding rocks, temperature increases but pressure does not in contact metamorphism, little or no deformation, neomineralization but no fabrics, ex. mid-ocean ridges, plutons related to subduction zone magmatism, plutons related to collision-related melting
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collisional environment (for metamorphism)
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crust is thickened by continental collision and rocks become buried and heated causing temp and pressure to increase, rocks start to melt in regional methamorphism, rocks become ductile and start to flow, sedimentary rocks are metamorphosed into slate, schist, or gneiss with increasing temperature
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subduction environment (for metamorphism)
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subducting sedimentary and volcanic rocks experience big increase in pressure and a small increase in temperature, broken and disrupted rocks form melanges, high/low temperature forms blueschist and eclogite facies (eclogite is at a greater pressure and deeper than blueschist)
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environments of metamorphism
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1. subduction zones, 2. continental collision zones, magmatic environments
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3 processes of metamorphic textures
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1. neomineralization - growth of new minerals, replacing ones that become unstable at high temperature/pressure 2. increase in grain size - grain growth 3. solid state flow of rock reorients minerals, causing *cleavage* or *foliation*
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evaporites (chemical sediment, type of sediment)
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precipitates formed with increasing concentration (like calcite, halite, and other salts), formed in areas with restricted circulation of water and hot climates (playa lakes in deserts, rift valleys, narrow seas like the Red Sea, the Mediterranean), crystalline in texture
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Properties of minerals
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color (may be misleading due to trace impurities that color it, like with ruby and sapphire which are corundum), streak, hardness, crystal shape and symmetry, cleavage, density
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What ways does organic sediment form fuel?
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plant material accumulates to form peat and coal (mainly carbon), marine plankton accumulate to form oil and gas (hydrocarbons)
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lithification
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compaction (reduction of pore space and removal of water), cementation (pore spaces filled with cementing minerals), diagenesis (alteration of original sedimentary material by heat and pressure
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texture and crystal grain size
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crystalline texture is composed of grains (which may have crystal faces and interpenetrate), grains grow with time during formation, large grains result from slow cooling in a melt, small grains occur when cooled rapidly (like at the surface)
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sedimentary texture
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rounded or angular grains, do not interpenetrate, separated by matrix
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pelagic limestone (carbonate rocks)
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dead micro-organisms settle out from the water column to form pelagic limestone, very fine-grained, skeletons are mainly calcite, ex. The White Cliffs of Dover
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main constituents of Earth's layers
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the continental crust is mainly granite (igneous - quartz and feldspar), the Earth's mantle is mainly peridotite (igneous - olivine), oxygen is the most abundant element
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bioturbation (type of sediment)
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disturbance of sediment deposits by living organisms
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carbonate rocks (type of sediment)
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reef limestone (in place accumulations of corals and the like), bioclastic limestone (re-sedimented carbonate material transported by currents, clastic sedimentary textures and structures), pelagic limestones (settling out of calcareous micro-organisms like foraminiferans, marine environments below the wave base)
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mudcracks (type of sediment)
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there's a floodplain and a flood and then the water recedes and all sediment is exposed to the sun, the water evaporates out and the smooth surface that was originally exposed cracks as it contracts (you can have rocks that preserve this)
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modern rippled sand (bedding)
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you can see ripples formed already even though it's not rock yet, if the flow continued the ripples would be captured in rock
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ripples (bedding)
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with modern ripples you can see ripples formed already even though it's not rock yet, if the flow continued the ripples would be captured in rock, with ancient ripple marks you can get a graded bedding due to a change in speed such as a river that gets at less and less of an angle causing water to flow slowly (fine sediment on top and coarse sediment on bottom)
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bedding (type of sediment)
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sedimentary rock feature, extremely distinct colored beds in layers in sedimentary rocks, settled from top down
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cross-bedding (bedding)
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difference in bedding and directional lines tells you past trends of how sediment was deposited
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alluvial deposits
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coarse grained, poorly sorted, with poorly developed bedding
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components of sedimentary rock that tells us the environment they were formed in
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grain size, composition, sedimentary textures and structures, longer the transport the smaller and smoother it will be
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medium grained sediment
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sand into sandstone, requires a medium energy transport mechanism (like wind, moderate rivers, deltas, fair weather beaches, tidal flats, submarine turbidity currents)
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fine grained sediment
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clay into shale, requires a low energy transport mechanism (slow-moving rivers, lakes and lagoons, flood-plains, deep seas)
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glacial till
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coarse-grained, very poorly sorted, no bedding, happens when the glacier retreats
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coarse grained sediment
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gravel into conglomerate, requires a high energy transport mechanism (like steep, fast flowing rivers, storm waves on beaches, glaciers)
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sedimentary rock cycle
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1. weathering 2. transport of sediment by water or wind 3. deposition 4. burial 5. lithification or diagenesis: converting rock to sediment
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types of sediment
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1. clastic sediment - particles of pre-existing rocks and minerals 2. chemical sediments - precipitated from seas or lakes (evaporites) 3. carbonate rocks - skeletal materials (shells, corals, etc.), mainly calcite 4. organic accumulations - coal and petrol (oil and gas)
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intrusive igneous rocks
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magma may be emplaced into the crust, the magma cools more slowly (years to millions of years), crystals have time to grow, rocks are medium or coarse grained with a crytalline
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plutonic rocks
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large intrusions of igneous rocks, cooled very slowly and coarse grained
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rock cycle
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1. begins with rifting with in a continent, sediments erode from continental interior and into rift basins, buried to form sedimentary rocks 2. rift and spreading continue, and a new ocean basin develops, magma rises from the asthenosphere at mid-ocean ridges and chills to form basalt (an igneous rock) 3. subsidence of the continental margin - sinking of Earth's lithosphere - leads to accumulation of sediment and formation of sedimentary rock during burial 4. oceanic crust subducts beneath a continent, building a volcanic mountain chain. the subducting plate melts as it descends. magma rises from the melting plate and mantle and cools to make granitic igneous rocks 5. further closing of the ocean basin leads to continental collision, forming high mountain ranges. rocks are buried or modified to form metamorphic rocks where continents collide. uplifted mountains force moisture-laden air to rise, cool, and release its moisture as precipitation. weathering creates loose material - soils and sediment - that erosion strips away 6. streams transport sediment away from collision zones to oceans, where it is deposited as layers of sand and silt. layers of sediment are buried and lithify to form sedimentary
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Metamorphic rocks
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crystalline texture, may, for example, be buried by during mountain building processes and be heated and become ductile
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mineralization
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minerals deposited by fluids include quartz and calcite, include many economically valuable minerals like gold, silver, and ore
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clastic texture of sedimentary rocks
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grains deposited by water or wind
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classification of rocks by texture and origin
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1. Igneous rocks (temperature): crystalline texture, crystallize from a melt (magma) 2. Sedimentary rocks (erosional processes): clastic texture mainly, grains deposited by flowing water or wind 3. Metamorphic rocks (pressure): crystalline texture, growth of minerals in the solid state, form by modification of other types of rock
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igneous rocks
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form by solidification from a liquid (molten rock or magma), magma may crystallize within the crust (intrusive) or flow out at the surface as lava (extrusive)
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properties of rocks
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constituent minerals, grain-size, texture, organization and structure, all info that allows us to interpret how the rock formed
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polymorphs
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materials that have the same composition (ex. carbon) but have a different crystal structure and are therefore different
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ionic bonding
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sharing an outer electron, the strongest
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Atomic bonding in crystals
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atoms bond ionically, covalently, and metallically (the least common),
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Rocks
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aggregates, made up of different constituents and minerals (and non-minerals, like coal, which has plant matter), the Earth is made up of different rocks, aggregate means that the individual constituents retain their identity (so minerals are still identifiable)
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outer core
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liquid shell composed primarily of molten iron, extending from about 2900 km to 5150 km in depth
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Earth's internal heat engine
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inherited from the Earth's formation and generated by radioactive decay of elements like uranium, thorium, and potassium, heat drives convection and plate tectonics
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weather
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determined by solar energy, difficult to predict more than several days in advance, day-to-day changes
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climate
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longer-term daily and seasonal weather cycles, predictable over longer time scales
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Deep Mantle
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mantle beneath the asthenosphere, extending from about 400 km deep to the core-mantle boundary (about 2900 km deep), energized by Earth's internal heat
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asthenosphere
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weak, ductile layer of mantle beneath the lithosphere that deforms to accommodate the horizontal and vertical motions of plate tectonics
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lithosphere
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part of the climate system and the plate tectonic system, strong rocky outer shell of the solid Earth that comprises the crust and the uppermost mantle to an average depth of about 100 km; forms the tectonic plates
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biosphere
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all organic matter related to life near earth's surface - this geosystem is energized by solar radiation
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What is the "Lithosphere"?
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The outer 100km of the earth that is too cool to flow, comprised of the cool upper mantle and the overlying crust. It is brittle, rigid, and hard to move.
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What is Geological Time?
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The time-scale of interactions within the earth. These interactions take place over both relatively short time scales (such as weather or climate) or much longer time scales (such as the drift of tectonic plates and the convection of the mantle)
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What is some of the evidence for plate tectonics?
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Large-scale motions of the continents (continental drift). Distribution of earthquakes and volcanoes. Magnetic anomalies on the sea floor.
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What are the three types of plate movements?
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Divergence (moving apart) Convergence (moving together) Transform motion (moving sideways past each other)
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What are Lithospheric Plates?
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The Earth's lithosphere is broken up into large fragments that move around the surface of the globe, driven by the Earth's heat engine. Plate motion is made possible by the flow of the asthenosphere.
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What is the Asthenosphere?
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The hot upper mantle beneath the lithosphere, it can flow (over geologic time scales.) It is weak and flows freely with convection.
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What powers Earth's plate tectonics and where does this power come from?
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Plate tectonics are driven by heat (convection) inherited from the earth's formation and the radioactive decay of elements.
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Describe convection
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Convection occurs when heat is transferred through the earth in a circular flow. As the heat circulates upwards the cold goes down.
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Define "Anthropocene"
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The hypothetical age of human mass extinction
