Plate Tectonics & related landforms Flashcards
What are the 3 types of tectonic plate margins?
Conservative (passive)
Constructive (divergent)
Destructive (convergent)
What is a conservative (passive) tectonic plate margin?
A plate margin where two tectonic plates are moving past one another with no addition or destruction of plate material.
Give an example of a conservative (passive) plate margin.
The San Andreas Fault in California - Pacific & North American plates.
What is a constructive (divergent) plate margin?
A plate margin where new crust is formed as the plates pull away from eachother. Often found at mid-ocean ridges.
Give an example of a constructive (divergent) plate margin.
The Mid-Atlantic Ridge - Including the North American plate & Eurasian plate, as well as the South American plate & African plate.
What is a destructive (convergent) plate boundary?
A plate margin where crust is destroyed as two plates converge. Usually associated with island arcs or young fold mountains.
What is a convection current?
The movement of magma below the crust, in a cyclical manner, which determines the direction of the plate margin movement.
What is a rift valley?
A lowland region (valley) which forms at contstructive boundries, created by collapsed crust into the low-pressure zone left by erupting magma.
Give an example of a rift valley?
The Great RIft Valley of East Africa.
How long is the Great Rift Valley of East Africa?
6,400km
How deep is the Great Rift Valley of East Africa?
1,500m deep.
What is said to happen as a result of the Great Rift Valley of East Africa continuing to move apart?
It will eventually flood with sea water and become a new ocean seperating Africa into two.
Give an example of a destructive (convergent) plate margin.
Where the Nazca plate subducts the South American plate.
When was the theory of a magma plume first developed?
1970s.
What are magma plumes?
Localised heating in the lithosphere from radioactve decay causing a plume of magma to rise through the mantle and ‘eat’ into the plate above the hot spot.
How do volcanic islands form from a magma plume?
While hot spots are fairly stationary, the tectonic plates continue to move, taking with it volcanoes which have formed, providing new, untouched crust to form new volcanoes. Over millions of years a chain of islands can form.
What is an example of a hot spot island chain?
Hawaii.
How long has the Hawaiian hot spot been active for?
Around 70 million years.
How long is the Hawaiian hot spot volcanic island chain?
6,000km
