Tectonics Flashcards
Earth’s outer shell is broken into _____ that move and interact in response to forces ____ the earth
lithospheric plates, within
A single plate includes
crust (oceanic or continental or both)
uppermost rigid mantle
Plates can move between ___ cm/year
0-10cm/year
defn Plate boundaries
Places where two plates meet
Are volcanoes randomly distributed? where do they happen?
No, plate boundaries
Describe the age of rocks as the result of divergent boundaries
Divergent boundaries can exist on land but mostly exist on the seafloor
New oceanic crust is made in the middle because hot rocks rise up, melt and fill in the gaps creating new oceanic crust. These are called quenches
Rocks get older as you move perpendicualrly away from the ridge
Quenches
New crust made my divergent boundaries
Hot rocks rise up, melt, create new oceanic crust
Mid ocean ridge
A row of subsea volcanoes that wraps around the world produced because of sea floor spreading
What geologic hazards are likely to occur at a divergent plate boundary>
Earthquakes
Volcanoes
Why does the oceanic plate subduct>
More dense (thicker)
Ocean continent covergent boundary
Oceanic crust subducts beneath continental plate
Deep trench forms ar boundary
Leading edge of cont crust gets compressed and deformed, producing mountains
Arc of volcanoes occurs on land above subducting plate
How can we find fossilized sea creatures on tops of mountains?
Sea floor that has formed mountain peaks
Ocean-ocean convergent boundary
two oceanic crust plates collide
Older, colder, denser plate subducts
Arc of volcanic islands forms on the overriding plate
Continent-continent convergent boundary
Produces very large mountains
Ex. Everest
Himalayan Mountains
Convergences of Indian and Eurasian plates
In which boundary is no crust created or destroyed?
Transform
Where do transform boundaries commonly form?
Along spreading cenres (divergent boundaries) to relieve stress
The San Andreas Fault is a ____
transform fault
What makes the plates move?
Heat is the source of power for plate movement
Heat is slowly being released to the surface of the earth through ____ in the ____
convection in the mantle
Tectonic plates likley move because of the realtively __ density of ____ and the relative ___ of the ____
high density of oceanic lithosphere and the realtive weakness of the asthenosphere
What causes plate movement? 2
- Plates pulled down into trenches (subduction zone)
- Plates driven down the slope from the ridge to trench by gravity
How do we know where the continents used to be?
We can look at the similarity of fossils and rocks on different continents
Geological evidence of pangea 2
- Rocks of the same age and type are found on continents that are now separated by oceans
- Ancient mountain belts have also been split across divergent boundaries
