Flashcards on geology – Geology
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What is the average rate at which temperature increases with depth in earth's crust?
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30 degrees Celsius/Km
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T or F: Metamorphic rocks result from the recrystallization of existing rocks while they are still in a sold state.
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TRUE
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Which of the following rock represents the highest metamorphic grade?
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Gneiss
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The parent rock of quartzite is...
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Sandstone
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Which mineral is commonly used to determine a metamorphic P-T path?
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Garnet
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What is the order of events oldest to youngest?
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B- youngest because it is the top layer C and D- next youngest because they are right under B F- oldest because it is an anticline FAEDCB
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Write a statement reflecting the principle of original horizontality?
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Sediments are deposited generally in horizontal layers
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The study of the layers in sedimentary rock is known as...
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Stratigraphy
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The principle of superposition states that...
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Undisturbed sediments get progressively younger from bottom to top layer
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The size of magnitude 8 earthquake is how much larger than that of a magnitude 6 earthquake?
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100X
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Earthquakes that originate at depths greater than 100 km are associated with.........plate boundaries.
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Convergent
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Structures built on what suffer the most damage in an earthquake?
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Wet mud or sand
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The dip of a layer in a geologic formation can vary between...
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0-90 degrees
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What mountain chain runs along the eastern margin of North America?
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the Appalachians
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The Carolina Piedmont is made of...
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Island arc rocks accreted to North America
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What does not hold up mountain belts...
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High intensity belts
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Which layer in the earth does not transmit s waves...
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Outer core
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Where is the earth's magnetic field produced?
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The liquid inner core
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Seismic tomography can detect relatively warm regions of the mantle because seismic waves
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Travel more slowly through these regions
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Lithification
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the process of sediments becoming rocks
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Lithification Processes
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Compaction Cementation Diagenesis Recrystallization
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Compaction
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reduces pore space
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Cementation
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chemical precipitation of mineral material between grains binds sediment into hard rock
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Diagenesis
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chemical and physical processes that change sediments to sedimentary rock
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Recrystallization
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pressure and temperature increase with burial
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Metamorphism
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change affected by pressure, heat, and water that results in a moe compact and more highly crystalline condition
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metamorphic rock
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rock that has undergone changes in texture, mineralogical, or/and chemical compositions in the solid state
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Do rocks remain in a solid state during metamorphism?
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yes
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Pressure......the space available for mineral growth because of the.....
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decreases;density
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Increases mobility of elements
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heat
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Act as a catalyst during metamorphism and aids the exchange of ions between growing crystals
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fluids
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The intensity of metamorphism
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metamorphic grade
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The amount of change during metamorphism depends on
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the grade and duration of metamorphism and the composition of the rock
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Lineation
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linear feature or element of a rock that occur as the product of tectonic, mineralogical, sedimentary, or geomorphic processes
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Foliation
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a set of flat or wavy parallel planes produced by deformation
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Are most minerals stable over a relatively narrow range of pressure and temperature?
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yes
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Describe metamorphism
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Index minerals, grade, and facies
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what type of metamorphic zones
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New England
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Relative dating
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how old a rock is compared to surrounding rocks
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Absolute dating
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the actual number of years since the rock was formed
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Steno's laws
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Principle of superposition, original horizontality
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principle of superposition
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in a sequence of undisturbed layered rocks, the oldest rocks are on the bottom
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principle of original horizontality
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layered strata are deposited horizontally or nearly horizontally (parallel to earth's surface)
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Fossils
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something dug up
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Paleontology
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the study of life in the past based on the fossil remains of plants and animals
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used to determine relative age and the environment of deposition
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fossils that are preserved in sedimentary rocks
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fossils play a key role in this
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correlation
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T or F: No single area records a complete record of earth's history
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TRUE
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John Drayton
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SC geologist who founded USC
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T or F: USC department of geology is the second oldest in the US
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TRUE
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Continental Drift
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latest fossil finds linked ancient africa to the carolinas
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Sara Samson found what in Batesburg SC?
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trilobite from an ancient sea 400 million years ago that was thrust up onto this continent and stayed behind when the sea opened again to form the modern atlantic ocean
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Unconformities
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surfaces where erosion has removed rock layer "missing time"; a buried surface of erosion
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Cross-cutting relationships
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geometry of rock bodies and relationship with adjacent bodies allows geologists to place rock units in relative chronological order, used for relative dating
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sequence stratigraphy
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stratigraphic analysis in which the major geologic units are bound by unconformities; used widely with seismic data, especially in petroleum exploration
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geologic timescale
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divisions in the worldwide stratigraphic column based on variations in preserved fossils
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Absolute geochronology
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add numbers to the stratigraphic column which was originally based on fossils and correlation, based on the regular radioactive decay of some chemical elements
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Isotopic Dating
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radioactive elements (parents) decay to stable, non-radioactive elements (daughters), rate of decay occurrence is constant and known
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T or F: If we know the rate of decay and the amount present of parent and daughter we can calculate how long this reaction has been occurring.
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TRUE
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Alpha decay
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loss of 4He
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Beta decay
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neutron to proton
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Electron capture
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proton to neutron
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half-life
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time required for half of a radioactive isotope to decay to the daughter product
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Is the half-life constant?
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yes
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What does GPS do?
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allows measurements of processes such as plate motion
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Deformation
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strain
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change volume or shape of rock by
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Deform
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force applied to rock
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stress
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How do we measure deformation?
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Sedimentary rocks, lava flows, metamorphic rocks
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Are many features within rock bodies either planar or linear?
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yes
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Dip
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angle of steepest descent of the bed from the horizontal, angle between inclined plane and horizontal
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strike
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at right angles to the dip direction; formed by intersection of a horizontal plane and an inclined plane
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Tectonic Stress
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any change in original shape or size of an object in response to stress acting on the object
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Elastic deformation
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temporary change in shape or size of a body that is received when the stress is removed
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Ductile deformation
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permanent change in shape of size of a body that is not recovered when the stress is removed
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brittle deformation
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the body undergoes little change under the stress, until it breaks suddenly
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brittle strain
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fracture, break, upper crust rocks, earthquakes
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elastic strain
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return to original shape
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plastic strain
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ductile flow, keep deformed shape, lower crust and mantle rocks
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strength
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ability of an object to resist deformation
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symmetrical folds
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vertical axis planes
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asymmetrical folds
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inclined axial planes
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plunging folds
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dipping axis
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overturned folds
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both limbs dip the same direction
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folds
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caused by compression, permanent, plastic deformation
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anticline
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up-arched fold with oldest strata in the middle
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syncline
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down-arched fold with youngest strata in the middle
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domes
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circular anticlines
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basins
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circular synclines
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monocline
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a bend or flat uniformly dipping layers
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utah monocline
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San Rafael Mountain
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Where does most of the world's petroleum and natural gas production come from?
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anticlinal traps
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Joints
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fractures without displacement
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brittle deformation are otherwise known as
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faults
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faults
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fractures with movement along fracture (fault plane)
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reverse fault
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compression, hanging wall up
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normal fault
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extension, hanging wall down
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strike-slip fault
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shear, slide sideways
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Lewis thrust fault in Glacier National Park
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reverse fault
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Right-lateral strike-slip fault
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San Andreas Fault
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Mountains are found near...
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hot spots and plate boundaries
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T or F: Continental rocks are generally older than oceanic rocks.
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TRUE
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Where does the lithosphere float?
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on a viscous layer below the continents called the asthenosphere within the earths mantle
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What make up the continental components?
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Stable cratons shields platforms
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what are folded mountain belts otherwise known as?
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orogens
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Archean cratons
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High-grade metamorphic terrains, granite-greenstone terrains
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The crystalline basement is composed of....
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metamorphic and igneous rock
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magmatic differentiation
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magma transferred from the mantle to continents at subduction zones
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continental accretion
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buoyant fragments of crust attached to continent as the result of plate motions
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How much has the volume of the continents increased by for the past 4 Ga?
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2 km^3/yr
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Hot spot ex
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mid plate- Hawaii
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Plate boundary ex
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iceland
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divergent boundaries
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oceanic spreading centers, world's longest mountain ranges
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divergent boundaries ex
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continental rifts include the E. African Rift and the US Basin and Range
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convergent boundaries
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ocean-ocean boundaries which are island arcs; ocean-continent boundaries which are volcanic arcs
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ocean-ocean boundaries ex
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Japan, Phillippines, Carolina slate belt
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ocean-continent ex
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Andes
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what is known as the door to the Andes?
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Torres Del Paine (Patagonie)
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what is the world's highest active volcano?
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Ojos Del Salado (4500 m basement)
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what is the highest point in the Cordillera Blanca?
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Huascaran in Peru
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What constitutes the furthest point from the center of the earth due to high elevation?
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summit of Chimborazo
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what is an example of a continent- continent collision result?
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himalayan mountains and tibet plateau as well as the appalachian mountains
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The Wilson Cycle
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repeated opening and closing of ocean basins
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what is an arc?
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continental collision
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Where do the Appalachians extend from?
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alabama to newfoundland
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island arcs collided with the north american plate forming the blue ridge mountains and piedmont provinces otherwise known as the carolina slate belt when?
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500-350 my
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carolina gold belt mineralization within carolina slate belt happen when?
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450 my
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africa and north america collide for Pangea and the Appalachian (folded mountain belts) mountain chain known as the Valley ad Ridge fold belt
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300 my
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T or F: the appalachians are a cross-section.
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TRUE
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What were associated with the collision 300 mya?
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Granites
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Pangea begins to break apart
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235 mya
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atlantic ocean began to open with option of mafic flood basalts
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195 mya
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what were the triassic rift basins that formed along the Atlantic margin of the US filled with?
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red beds and basalt lava
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during what period would columbia have been considered beachfront property (also when the dinosaurs were extinct)?
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Late Cretaceous era
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stress compression
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convergent
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stress tension
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divergent
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stress shear
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strike-slip
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strain
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measure of the amount of deformation including any change in shape of size in response to sress
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what are brittle deformations?
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faults
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what explains why earthquakes occur?
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elastic rebounds
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elastic rebound
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return of rocks to original shape after earthquake
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Elastic rebound theory
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energy is store din rocks as they bend and when rock strength is exceeded, they break and snap back or "rebound" causing an earthquake
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body waves include
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s and p waves
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s wave
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shear waves, cannot travel through liquids or gases, secondary waves
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p wave
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fastest, compression, like sound waves, primary waves
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surface waves
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damage structures and include rayleigh waves and love waves
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rayleigh waves
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like water waves
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love waves
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shear waves
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seismology
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the study of earthquakes
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magnitude
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the amount of energy release by an earthquake
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amplitude
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of magnitude 6 wave is 10X larger than a magnitude 5
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energy
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released by a magnitude 6 is 30X larger than by magnitude 5
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what was the larges earthquake magnitude that was measured?
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9.5
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slip
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the amount of ground displacement in an earthquake
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seismic waves from an earthquake......from the focus and arrive at distant seismographic stations at different times
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move out concentrically
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at least..... recording stations are necessary to determine the location of an epicenter
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3
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use....to calculate distance
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P&S waves arrival times
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focus
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hypocenter
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where do the largest earthquakes occur?
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convergent boundaries
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what are earthquakes away from boundaries called?
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intraplate earthquakes
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where were two examples of intraplate earthquakes?
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New Madrid, Missouri; Charleston, SC
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what can be used to identify paleo-earthquakes?
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"sand blows" volcanoes and fissures
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what base of structures are the most sturdy during earthquakes?
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solid bedrock
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what bases are the weakest during earthquakes?
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adobe and mud-walled structures
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are steel and wood framed structures flexible and strong during earthquakes?
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yes
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what are seismic sea waves also known as?
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tidal waves
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how far is the center of the earth below us?
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6400 km
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what is the fishbowl experiment?
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when waves move from one material to another, they change speed and direction and seismic waves can be used to tell us about the interior of the earth
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are seismic waves refracted like light from air to water?
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yes
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earths inner core is....?
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solid
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what is the core composed mostly of
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iron with some nickel and sulfur
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geotherm curve
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temperature increases with depth
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seismic tomography uses.......to create 3D images of Earth's interior
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travel times
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do seismic waves slow down in hot rocks?
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yes
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what is the crust/mantle boundary called?
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MOHO- Mohorovicic
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what was the asthenosphere discovered by?
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low Velocity zone and it is weak and partially molten
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lithosphere contains....
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rigid plates and the crust and upper mantle
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Kimberlite Pipes Types
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Peridotite Coesite Diamonds
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peridotite
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inclusions from mantle
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coesite
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high pressure quartz
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diamonds
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high pressure carbon
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most of the earth's heat is generated by.....
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radioactive decay
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is the earth cooling off?
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yes
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isostasy
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because himalayas have a "low density root" the mountains float like iceburgs
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ability of the lithosphere to bend under weight where isostasy is regional
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flexure
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what is gravity used for?
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mineral and gas exploration
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valuable minerals are associated with...
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high density igneous rocks
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oil found with lows density was found in?
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the salt domes
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Earth has a....magnetic field
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dipole
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inclination
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deviation from horizontal
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declination
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angle between geographic N and Magnetic N
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northern light are produced by the interaction of.......and the........
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solar radiation;earth's magnetic field
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magnetization
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when hot magma cools below curie temperature, magnetic mineral are frozen in the direction of the earth's field
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magnetometers can be used to....
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detect magnetic ore bodies
