Term
| Where do earthquakes occur in the Pacific Northwest? |
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Definition
All of the above
- near the surface within the North American plate
- deep within the Juan de Fuca plate
- at the Cascadia subduction zone
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Term
| The recurrence interval of large Cascadia subduction zone earthquakes is _______. |
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Definition
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Term
| How did geologists determine the exact day of offset on the Cascadia subduction zone in 1700 AD? |
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Definition
| They had accurate tsunami logs from japan that recorded this event |
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Term
| Where is isostatic recovery from ice loading still occuring today in North America? |
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Definition
Only answers a and c are correct
- northern Great Lakes
- Hudson Bay, Canada
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Term
| An overturned fold will often evolve into a _____ with continued compressive stress. |
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Definition
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Term
| Which mineral group accounts for most of our extractable iron ore deposits in the world? |
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Definition
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Term
| Chert generally precipitates ______. |
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Definition
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Term
| Joints facilitate weathering because ______. |
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Definition
Only answers b and c are correct
- permit water and other chemical agents to penetrate below the surface
- provide more surface area for the weathering fron to attack
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Term
Why is olivine the dominant mineral in most beach sands?
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Definition
| Olivine is not the dominant mineral in beach sands |
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Term
| Which rock type will tend to produce sink holes in Florida from solution weathering? |
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Definition
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Term
| Frost wedging would be most prominent in: |
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Definition
| Sub-polar latitudes where temperature fluctuate around the freezing temperature during certain seasons. |
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Term
| Which soil horizon contains the highest organic content? |
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Definition
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Term
| H+ ions utilized in hydrolysis weathering reactions come from ______. |
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Definition
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Term
| Spheroidal weathering occurs because: |
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Definition
| Rounding occurs because the edges and corners of the rock surface offer more points of attack to chemical weathering processes than its planar surface. |
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Term
| Which of the following transport agents generally results in current (asymmetric) ripples? |
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Definition
Answers a and c are both correct
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Term
| What test would conclusively tell you that marble and limestone are both composed from the mineral calcite? |
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Definition
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Term
| The zig zag pattern of rock units that can be observed while flying over Pennsylvania is due to ______. |
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Definition
| Erosion of plunging (tilted) anticlines and synclines |
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Term
| Oolitles form from ______. |
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Definition
| Precipitation of calcite around sand grains oscillated by waves |
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Term
| Why do geochronologists not use the ratio of 14C/14N to determine the age of organic matter? |
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Definition
| Most of the 14N found in organic matter is naturally occuring and not the result of 14 C decay |
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Term
| If a horizontal layer of volcanic tephra lies between two horizontal sedimentary strata, the principle by which the relative ages of each of these layers could be determined is: |
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Definition
| The principle of superposition |
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Term
| According to the principle of inclusions: |
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Definition
Answers a and c are both correct
- a xenolith will be older than the plutonic body in which it is emplaced
- clasts within a conglomerate will be older than the rock itself
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Term
| According to the principle of cross-cutting relationships, if a fault is found cutting across sedimentary strata, the reasonable conclusion would be that: |
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Definition
| The fault is younger than the strata |
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Term
| The strike-slip fault shown below is _____. |
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Definition
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Term
| The half-life of a radioactive isotope refers to: |
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Definition
| the time it takes for half of the existing parent isotopes to decay to daughter isotopes |
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Term
| A nonfoliated metamorphic rock would likely form _____. |
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Definition
| From contact of pre-existing country rock with an igneous pluton |
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Term
| A minimum of _____ seismic stations are necessary to determine the focus of an earthquake. |
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Definition
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Term
| If an earthquake occurs, the ____waves are the second waves to arrive at the seismic station. |
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Definition
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Term
| In order to relieve stress buildup that would cause a Richter magnitude 6 earthquake, approximately how many magnitude 5 earthquakes would have to occur? |
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Definition
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Term
| High confining pressure is conductive to ______ deformation in rock. |
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Definition
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Term
| A high strain rate is conductive to _____ deformation in rock. |
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Definition
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Term
| According to the national earthquake hazard map, the Puget Lowland is a ____ risk region in the U.S. |
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Definition
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Term
| An eroding anticline (upwarped fold) will have the _____ rocks exposed along its axis. |
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Definition
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Term
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Definition
All of the above
- can have repeating strata exposed in a vertical cross-section
- can result in older rock units overlying younger units in a vertical cross-section
- results primarily from compressive stresses
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Term
| ______ is an example of elastic deformation. |
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Definition
Answers b and c are correct
- subsidence related to the filling of a reservoir
- isostatic unloading of the earth's lithosphere following deglaciation
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Term
| What kind of faults bound mountains and valleys of the Basin and Range province in Nevada and Utah? |
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Definition
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Term
| What kind of stress would you expect to cause this type of faulting? |
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Definition
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Term
| At what kind of plate margin would you expect to find this type of fault? |
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Definition
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Term
| What hypothesis did we discuss to explain Basin and Range tectonics (ie to explain why a divergent margin might be forming uner Nevada and Utah)? |
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Definition
| The spreading ridge was subducted under California and is now positioned under Nevada and Utah |
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Term
| What type of faulting would you expect to dominate the Canadian Rockies or Appalachian Mountains |
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Definition
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Term
| ______ is an example of elastic deformation. |
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Definition
| Isostatic unloading of the earth's lithosphere following deglaciation |
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Term
| In the geologic time lab we studied _____ fossil assemblages that we used as biostratigraphic indicators? |
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Definition
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Term
| In metamorphic rocks with foliation, the texture develops as a result of: |
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Definition
| The allignment of platy (flat) minerals perpendicular to the maximum pressure on the body of rock |
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Term
| In the sedimentary rock lab which chemical precipitate did we not observe in the laboratory? |
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Definition
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Term
| In laboratory you used the first arrival time of P-waves to determine the distance between a seismic station and the focus of the Nisqually earthquake. What is the most likely reason that the three arcs not intersect at location on point, assuming your measurements were accurate? |
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Definition
| The nisqually earthquake focus was 50 km below the surface and the arcs would not intersect at the surface. |
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