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56 Cards in this Set
- Front
- Back
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What stresses result in crustal shortening? Crustal lengthening? |
Shortening=Compression
Lengthening= extension |
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> / < |
> hangingwall
< footwall |
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What type of fold has the oldest rocks in the middle of the fold (where the fold axis is)? |
Anticlines |
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What type of fold has the youngest rocks in the middle of the fold (where the fold axis is)? |
Synclines |
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What do we call a one-limbed fold? |
Monocline |
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What type of fault has the hanging wall go up? |
Reverse fault
*In reverse* |
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What type of fault has the hanging wall go down? |
Normal fault |
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What is a Horst? |
Footwall |
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What is a graben? |
Hangingwall |
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What type of stress is associated with a Horst and graben? |
Extension |
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The denser the rock, the more energy will pass through because ^ density= |
^ velocity |
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Sudden increase in seismic velocity= |
Seismic discontinuity |
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Type of Seismic discontinuity |
Moho |
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Earthquakes originate at the ____ _____ |
Focus point |
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The ______ of an earthquake is located above the focus point, on the surface |
Epicenter |
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Which seismic waves are fastest? |
P |
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Which seismic waves are slowest? |
S |
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P and S waves are called _____ _____ |
Body waves |
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What does the time lag between P and S arrival times allow us to determine? |
The distance of the epicenter |
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What are two ways we measure earthquakes? |
1) Intensity (Merrali intensity scale)
2) magnitude (moment magnitude/Richter scale)
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In order to find the Richter Magnitude (moment magnitude) of an earthquake we must know 1) magnitude 2) ___________ |
Amplitude |
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3 reasons why surface waves are so destructive |
1) slower and more concentrated 2) on the surface 3) stay strong with distance |
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In order to find the epicenter of an earthquake you need a minimum of ____ points |
3 points |
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What type of geologic material is safe to build on in earthquake prone regions? |
Bedrock /solid rock= less shaking |
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How do anticlines affect seismic waves? How do synclines affect? Which is unsafe to build on? |
Anticlines= deflect outward
Synclines= deflect inward
Unsafe= synclines |
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______ _____- an area where there's stress being built up, where you would expect to see an earthquake but don't. |
Seismic gaps |
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Why are seismic gaps dangerous? |
There's a lot of strain |
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The outer most portion of the earth is broken up into sections that move in response to mantle convection |
Theory of plate tectonics |
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____________- relatively cool and brittle •earthquakes form here •mantle + crust |
Lithosphere |
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___________- plastic, ductile, flows easily •below lithosphere (litho floats on top) •mantle |
Athenosphere |
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What type of melting lowers melting temperature |
Flux melting |
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Who proposed the continental drift hypothesis? |
Alfred wegernerz |
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What evidence is there to support continental drift hypothesis? 4 things |
1) continents seem to fit together 2) similar geology 3) glacial evidence 4) similar fossils |
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Why was the continental drift hypothesis rejected?
B/c Wegenerz couldn't answer
And he did not know about |
"why continents drifted?"
And he did not know about mantle convection |
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Why did the land bridge hypothesis fail? |
Because it couldn't explain glacial evidence or fossils |
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_____ _____ Hypothesis- Sea floor is spreading •new ocean floor is being created at MOR and old ocean floor is being destroyed by subduction at deep sea trenches |
Harry Hess hypothesis |
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___________ - transfer of heat |
Convection |
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What region of the earth is the only place where earthquakes can be generated? |
Lithosphere (outermost portion of the earth) |
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what is the modern day evidence that supports the theory of plate tectonics? 5 things |
1. mid ocean ridge and trenches 2. seafloor ages that get older as you move away from the ridge 3. Heat flow 4. earthquake locations and magma production 5. Volcanic island chains- hot spots or mantle plumes |
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what two hypothesis merged into the present day theory of plate tectonics? |
continental drift and the seafloor spreading hypothesis |
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What changes do we see in the ocean floor, as we move away from the mid-ocean ridge? |
The rocks get older and there are changes in the paleomagnetism. |
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What is the driving mechanism for plate tectonics? |
Mantle convection |
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Why is the oldest ocean floor only 180 million years old, when continental crust can be 4 billion years old? |
because the ocean floor in continously subducting into the mantle |
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_________- oceanic plates go back into the mantle, evidence is an ocean trench |
Subduction |
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which crust type will never subduct and why? |
continental crust because it has a low density |
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What are the 5 types of plate boundaries? |
1. Ocean-Ocean divergent 2.Ocean-Continent convergent 3.Ocean-Ocean convergent 4.continent-continet convergent 5.transform |
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Mountain chains? |
Cc-cc convergent |
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Coastal mountain chains |
Oc- cc convergent |
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Volcanically active chains |
Oc- oc |
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Deep ocean trenches |
Oc- oc
Oc- cc |
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Deep valley |
Cc- cc divergent |
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MOR mountain ranges |
OC- OC divergent |
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Continental fit |
CC- CC divergent |
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Magma- all BUT 2 types |
Cc- cc convergent Transform |
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______ - ______ zone= Zone of shallow earthquakes you get at subduction zones |
Wadati Ben zone |
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At MOR mantle is decompression melting causing |
Magma |
