Plate boundaries Flashcards
Cards on each type of plate boundary, how they form, what could form at each, and examples of each
Types of plate margins?
Constructive, destructive and conservative
Describe what occurs at a destructive plate margin?
When two tectonic plates converge, the older oceanic (basalt) denser plate is subducted below the less dense continental plate.
What is slab pull?
When one lithospheric plate subjects and is pulled down by gravity
What is ridge push?
When magma rises between converging plates, cools and forces them apart.
What forms when two oceanic plates converge?
The denser one subjects and island arcs occur
What is an island arc?
A chain of volcanic islands
Example of an island arc?
Mariana islands (offshore)
What is the Benioff zone?
The stretch of continental or island arcs at risk from earthquakes due to the rise of partially melted basaltic crust (which was subducted).
What landforms could occur at destructive boundaries?
-Fold mountains
-Island arcs
-Ocean trenches
Where do fold mountains occur?
Where two continental plates converge
Example of fold mountains?
Himalayas
Which plates are the Himalayas at?
Indo-Australian and Eurasion
Where do ocean trenches form?
Destructive plate boundaries (could be ether continental and oceanic or two oceanic)
Example of an ocean trench (two oceanic)?
Mariana Trench (Pacific subducts under phillipines plate)
Example of ocean trench (oceanic and continental)?
Peru Chile trench (Nazca subjects under South American plate)
If at a convergent boundary there are two continental plates, what happens?
Neither subduct due to low density
What occurs at a constructive plate boundary?
Two plates diverge, and plumes of mama rise through the lithosphere, causing ridge push
What landforms occur at constructive plate boundaries?
Rift valleys or Ocean ridges
How do ocean ridges form?
Divergent boundary in oceanic areas, Space between plates filled with basaltic magma to form a ridge
Example of ocean ridge?
Mid Atlantic ridge (Eurasion and North American) or Surtsey Ireland (this one goes above sea level)
How do rift valleys form?
Divergent boundary in continental areas, Brittle crust collapses into parallel faults to form a valley,
Example of a Rift Valley?
East African Rift Valley
What occurs at a conservative plate boundary?
Two plates slide past one another, either the same way at different speeds or opposite directions.
Example of a conservative plate boundary?
The san Andreas fault between Pacific and N. American plates.
