Plate Boundaries & More Flashcards
What are plates driven by?
Plates are driven by cooling Earth in a heat transfer process called convection
What provides additional force to move plates?
Gravity
Plates moves due to:
- Differences in density
- Convection currents
Convection currents:
- Warm material rises form inside the Earth to the surface. then cools and sinks
- As it does this, it pulls the overlying plate with it in the direction the current is moving
How fast are the plates moving every year?
1-10 centimeters per year
What are the tectonic plates (lithospheric plate)?
- The 100 km thick surface of the Earth
- Contains crust and part of the upper mantle
- It is rigid and brittle
What is the asthenosphere?
- The hotter upper mantle below lithospheric plate
- Can flow like silly putty, but is a SOLID
The three types of boundaries:
- Divergent
- Convergent
- Transform
Divergent plate boundary:
- Plates are moving away from one another
- This occurs on the ocean floor along the mid-ocean ridges
- Lava moves out of the rift valley along the mid-ocean ridges
How do divergent boundaries affect crust?
New crust is generated as the plates pull apart
Where do divergent boundaries occur?
Ocean floors and continental interiors
Earthquakes on divergent boundaries are?
shallow and small
Two types of ridges?
Fast-spreading and slow-spreading
Convergent plate motion:
- Two plates move toward each other
- Can be ocean to ocean, ocean to continent or continent to continent
- Oceanic crust is more dense, so it always sinks under or subducts
Two continental plates crunch together and form?
high mountains
Convergent- ocean to ocean features & example:
Island arc & trenches, ex: Marianas
Convergent- ocean to continent features & example:
Mountains & trench, ex: Cascades
Convergent- continent to continent features & example:
Folded mountains, ex: Himalayas
Convergent boundary earthquakes:
Shallow, intermediate and deep
Shallow convergent earthquakes:
The most destructive of these occur between the plates on the plate boundary
Intermediate and deep:
Occur only within the subducting oceanic lithosphere
Transform plate boundary:
- Plates slide past one another
- This occurs along a fault (crack in earth’s crust)
- Transform faults can be found along the mid-ocean ridge
How is the lithosphere affected by transform plate boundaries?
It is neither produced nor destroyed as the plates slide horizontally past each other
Two different types of faults and examples:
- Strike-slip fault, example: San Andreas fault
- Transform fault: a strike-slip fault between two spreading ridges allows the two plates to move apart
Types of stress:
- Extension
- Compression
- Shear
Extension:
Faults and regional thinning
Example: Basin & Range
Compression:
Makes faults and folds
Example: Andes Mountains
Shearing:
Displaces layers horizontally and can result in strike-slip faulting
Example: San Andreas fault
Types of faults & examples:
- Normal, ex: basic & range african rift
- Reverse, ex: himalayas & rocky mountains
- Strike-Slip, ex: san andreas
