Oceanography 2 Flashcards
What plate boundary is spreading?
Divergent
What is filled into the spaces left at a divergent boundary?
New crust
What boundary are most mid ocean ridges located at?
Divergent
What is a mid ocean ridge?
Giant undersea mountain range
Why does a mid ocean ridge sit on top of the mantle?
The new crust is warmer than surrounding crust and has lower density, it sits on top of the mantle creating the mountain chain.
What is a rift valley?
Valley that runs along middle of mid ocean ridge
What type of crust forms at divergent boundaries?
Oceanic
What type of rock is oceanic crust?
Igneous
Where on the mid ocean ridge is crust the youngest?
At the spreading center (the valley) and gets older the farther from the boundary
Why is sediment thin or non existent in ocean ridge areas?
Because it’s younger and has not had time to accumulate
What type of convection is found at mid ocean ridges and why?
Upwards convection because the heat rate is higher
What creates a mid ocean ridge?
Magma rises from partial melting of the mantle as the plates spread
What is a convergent boundary?
Two plates moving towards each other.
What happens at an ocean-ocean convergent boundary?
One plate is subducted. Often the colder and older plate foes under.
What happens at an ocean-continent convergent boundary?
The denser oceanic plate will subduct
What happens at a continent-continent convergent boundary?
Collision and deformation of pre existing continental rock. This pushes the rock up forming mountains.
What geological feature is found at continent-continent plate boundaries?
Mountains
What is a transform plate boundary?
One plate sliding past another
What is a transform fault?
A strike-slip fault at a transforming boundary. Occurs between sections of tectonic plates. Connects mid ocean ridges.
What is common along transform faults?
Earthquakes
What causes an earthquake?
The shaking caused by rupture and displacement of rock beneath the earths surface. Basically a rock becoming stuck on another rock and then the pressure builds and is suddenly released and releases a massiv amount of energy.
How do earthquakes happen?
1: the rock under stress becomes deformed
2: when it can no longer stand the deformation, it breaks down and two sides slide past each other
What determines the magnitude of an earthquake?
The extent of the area that breaks and average amount of sliding
Where on divergent plate boundaries are earthquakes popular?
A narrow zone close to the mid ocean ridges.
Are earthquakes abundant on subduction zones?
Yes
Where do most earthquakes occur?
Along transform faults
Are earthquakes on divergent and transform boundaries shallow or deep? Why?
Shallow, the crust is not very thick.