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86 Cards in this Set
- Front
- Back
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mechanical weathering
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break into smaller pieces with same composition
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chemical weathering
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chemical reactions alter composition
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mass wasting
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the transferring of rock and soil down slope under the influence of gravity
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erosion
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the wearing away of sediment and rock by running water, wind, glaciers and waves (ICE)
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freezing
where is this most effective on earth? |
involves the repeated freeze and thaw of water in the cracks and pores of rocks
result: frost wedging (an effective process for widening and extending cracks and breaking rocks into smaller pieces (expands by 9%) |
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pressure release
where is this most effective on earth? |
a common form of mechanical weathering of plutonic igneous rocks, these rocks form deep within the Earth and weather by pressure release when brought to surface
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salt crystal growth
where is this most effective on earth? |
produces enough force to break apart porous rocks. This process is effective mostly in arid and coastal regions.
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thermal expansion
where is this most effective on earth? |
heating/ cooling
cause differential volume changes in rocks. In deserts where temperatures vary 30oC daily, thermal expansion and contraction causes significant mechanical weathering. |
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abrasion
where is this most effective on earth? |
one block striking another
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What are the 3 chemical weathering processes and what do they do?
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Dissolution: minerals dissolve
Hydrolysis: water reacts to form new mineral with water as part of the new crystal structure Oxidation: reacts to form oxides |
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What is the weathered product of the mineral feldspar?
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clay is formed from the mineral Feldspar
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What is the definition of a sedimentary rock?
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rocks composed of sediment derived from pre-existing rocks
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Why are sedimentary rocks important?
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70% of earth's surface
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The process of creating sedimentary rocks begins with what? Followed by?
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Weathering
Then erosion, transport, deposition, and lithification |
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Weathering
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is the physical breakdown and/or chemical alteration of Earth materials at the surface.
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Erosion
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refers to the wearing away of sediment
and rock by water, wind, or ice. |
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Transport
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refers to the movement by water,
wind, or ice of eroded material from its place of origin to a new site where it is deposited as sediment. |
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Lithification
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Binding sediments together through compaction cementation
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What is the most important agent of sediment transport?
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Water: such as rivers, streams, waves and currents
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What information about earth history can we get from sedimentary rocks?
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climate
animals and plants environmental conditions atmospheric conditions |
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Most of the earths natural resources occur in sedimentary rocks: name 5 resources
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coal
oil iron uraninium |
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Size classification for clay
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finest
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Size classification for silt
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finer
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Size classification for sand
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fine
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Size classification for pebble
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coarse
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Size classification for gravel
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coarsest
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Size classification for bolder
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coarsest
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Which particle (clast) name occurs in which clastic sedimentary rock
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clay-found in shale
sand-found in sandstone |
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What is sorting and how does it occur?
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Well sorted: fine sand
Mod sorted: little rocks, gravel, sand Poorly sorted: big rocks, little rocks, sand, gravel |
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What is rounding and how does it occur?
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increase in abrasion
increase in transport distance increase working of sediment by wind or water currents |
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How are evaporate rocks (rock salt and rock gypsum) formed?
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Evaporation of water caused “super- saturation which triggers deposition of chemical precipitates
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What are "beds" of rock? Bedding planes, cross bedding
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bedding planes: separate strata
cross bedding: forms dunes |
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Name 3 or 4 sedimentary structures. What information do they provide?
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Strata: a layer of sedimentary rock or soil with internally consistent characteristics that distinguish it from other layers
Bedding planes: separate strata Cross bedding: reveal the direction of currents as well as their force |
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Lithification involves?
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the conversion of sediment into rock via two main steps:
1) compaction 2) cementation |
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Metamorphic
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Meta-change
morph-texture/shape |
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What are some natural resources associated with metamorphic rocks
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marble, asbestos, slate, gneiss, gems, coal
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What are the two primary things that happen to rocks as they are metamorphosed?
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New mineral can form at the expense of the old one and the rock texture is changed in size, shape and orientation of constituent mineral
AKA COMPOSITION and TEXTURE can change |
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What are 5 factors that determine what metamorphic rocks are produced?
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Heat
Pressure Chemically active fluids Parent rock Time |
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What's the difference between regional and contact metamorphism? What variable influences each and where each process is likely to occur
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Regional metamorphism- the most important variable is a combination of heat, pressure and chemically active fluids; likely to occur near convergent plate boundaries and subduction zones
Contact metamorphism-HEAT is most impt variable; likely to occur under lava flow, igneous intrusion boundaries |
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What is the relationship between mineral alignment and direction of applied stress?
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The mineral alignment is due to differential pressure or the stress that is not applied equally to all sides of the rock body
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What's the difference between confining (lithostatic) pressure and differential (directed) pressure?
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Lithostatic-pressure IS applied equally
Differential-pressure is NOT applied equally |
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What does foliated and non-foliated mean?
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Foliated: parallelism of platy minerals
Non: a metamorphic texture, no orientation of minerals |
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What affect does heat have on NON-foliated rocks?
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Rocks begin to look igneous (Gneiss)
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Which rocks represent low grade, intermediate grade and high grade metamorphism?
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Low: Slate
Mid: Phyllite High: Schist |
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What is the geothermal gradient?
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An increase in temperature with depth
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What is lithostatic pressure?
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An increase in pressure with depth, pressure can be caused by weight of overlying rock
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What is the protolith for quartzite? For marble? For slate?
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Protolith: parent rock
Quartzite-Sandstone Marble-Limestone Slate-Shale (mudrocks) |
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What is an earthquake?
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Release of energy caused by slippage along a fault, fracture
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Where in the world do most earthquakes occur?
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Pacific belt
(80% occur here) |
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What is the difference between earthquake "magnitude" and "intensity"?
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Magnitude: estimates amount of energy released at the sources (focus) of the earthquake
Intensity: a measure of the degree of earthquake shaking at a given locale based in the amount of damage |
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What factors might affect earthquake "intensity"?
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AMOUNT OF ENERGY RELEASED
distance from the epicenter local geology types of buildings population density construction employed duration of shake |
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What are some of the hazards associated with earthquakes?
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ground shaking
fires broken water mains down electric poles tsunami ground failure panic/psychological |
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What is the difference between elastic and plastic deformation?
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Elastic: This type of deformation is reversible. Once the forces are no longer applied, the object returns to its original shape.
Plastic: This type of deformation is irreversible. However, an object in the plastic deformation range will first have undergone elastic deformation, which is reversible, so the object will return part way to its original shape. |
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Why do most earthquakes have a "shallow" origin, i.e. < 100 km
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shallow rocks are cool and brittle
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Why are deep earthquakes less common and why are earthquakes at spreading centers especially shallow and low magnitude?
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shallow earthquakes are more dangerous than deep ones
Shallow-focus depths <70 km Intermediate-focus depths of 70-300km Deep-focus depths >300 km |
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Know the difference between the focus and epicenter of an earthquake
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focus: point within Earth where fracturing begins where energy is first released
epicenter: the point on Earth's surface directly above the focus |
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Know how seismic waves travel through the earth
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S waves: slow, travel in solids, move materials perpendicular to the directions of travel
P waves: fast, travel in all 3 stages of matter, vibrate back in forth in all directions |
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What does seismic activity (earthquakes) reveal about Earth's mantle and core?
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Since shear waves cannot pass through liquids, this phenomenon was original evidence for the now well-established observation that the Earth has a liquid outer core
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What does the time lag between P and S arrival times allow us to determine?
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how far away the away the source of the quake is from the recording station
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How do we find the epicenter of an earthquake?
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you need to look at your seismogram and you need to know what at least two other seismographs recorded for the same earthquake
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How do variations in the composition of the land surface (dry soil, wet soil, rock) effect building damage (intensity) during earthquakes?
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Adobe and mud-walled buildings
are most susceptible and nearly always collapse The taller=more likely to be destroyed In mountainous areas, earthquake-triggered landslides have caused destruction and many deaths. |
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What is liquefaction?
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the tendency of surface material under a building foundation to lose its internal cohesion and fail during and earthquake shaking
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What are seismic gaps?
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Areas with no fault movement for a long time; high probability of future earthquakes
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What structure and what stresses result in crustal shortening? Crustal lengthening?
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compressive: Shortens the distance
between two points (clay)? extensional: Lengthens the distance between two points shear: Strain is parallel but opposite directions |
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What plate boundary(s) are associated with each of the 3 stresses?
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compressive: reverse (high angle) and thrust (low) angle faults
extensional: normal faults shear: strike slip faults |
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Be able to tell the difference between a left and a right lateral strike slip fault
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In picture on slideshow:
Left: left side moves toward you, right moves away Right: right side moves toward you, left moves away |
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What fold type has the oldest rocks in the middle of the fold (where the fold axis is)?
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Dome
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Be able to identify a dome, basin, anticline, syncline, plunging anticline, plunging syncline, and the two fault types in block diagram
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Dome: oldest layer in center, youngest outside
Basin: youngest layer in center, oldest outside Anticline: an upward fold Syncline: a downward fold Plunging anticline: An anticline that when folded was also titled to that it disappears beneath the present surface at one end of the ridge. plunging syncline: The remnants of a downfold that now extends above the surface' when folded it was also tilted so that the feature disappears beneath the existing ground surface at one end |
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What is a horst?
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up-thrown blocks
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What is a graben?
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down-thrown blocks
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What is the difference between elastic and plastic strain?
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elastic: rock returns to original shape when
stress is removed plastic: rocks permanently deformed (bent) |
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What is isostasy and isostatic rebound?
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isostasy: Adding weight to “super- structure causes hull to sink, and removing weight causes hull to rise.
isostatic: High mtns = thick crust Low mtns. = thin crust |
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What is the difference between relative and absolute age dating?
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Relative: relative ages establish the sequences of events without establishing exactly when they occurred
Absolute: absolute ages establish when an event took place |
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Who was James Hutton?
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Father of modern geology
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What are the 7 geologic principles used in relative age dating?
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Uniformitarianism
Superposition Original horizontality lateral continuity cross cutting relationships inclusions faunal (fossil) succession |
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What uniformitarianism?
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Earth processes today are the same ones that operated in Earth's history
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Principle of superposition
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younger rocks are formed on top of the older ones
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Principle of original horizontality
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Sedimentary rocks are deposited in horizontal layer parallel to Earth's surface
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Principle of lateral continuity
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layers are continuous until encountering an obstruction or extended in all directions until thinning to zero
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Principle of cross-cutting relationships
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intrusive rocks or geologic features, such as faults that cut across rock must be younger than rock they cut through
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Principle of inclusions
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this states that objects enclosed in rock must be older than the rock surrounding it
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Principle of faunal (fossil) succession
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fossils of different organisms first appear at different times, fossils of related organisms change in the same fashion in progressively younger rocks every place they occur, and fossil species disappear from the rock record everywhere when they become extinct and do not reappear in young rocks
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What are the 3 unconformities?
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1) disconformity: a gap between two sedimentary layers that are parallel to each other
2) Angular unconformity: the meeting of two layers that are inclined at different angles to one another 3) nonconformity: separate sedimentary or volcanic rocks from underlying plutonic-igneous or metamorphic rocks |
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What is an index fossil and what are 3 criteria that make it useful for age relative age dating
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fossil that is particularly used for relative age dating
1) wide distribution 2) easily recognized 3) short span of existence |
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What is an isotope?
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atoms of an element that have the same number of protons and different number of neutrons (and different atomic masses)
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What is the definition of a half-life?
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The amount of time it takes for 1/2 of the parent to turn into the daughter isotope
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