Lesson 5 - Oceanic-Oceanic Convergence Flashcards
What occurs when 2 oceanic plates meet?
One is forced under the other
Processes involved with subduction begin
Why may one plate be forced under another?
Higher density
Moving at higher speeds
What does the descending slab of ocean floor generate?
Friction
Heat
What does this lead to?
Partial melting of the crust
What is the name of the region in which this occurs?
The Benioff zone
Name + describe the type of magma formed by this melting process
Basaltic lava
Less dense than the mantle
How does this magma behave?
Rises up through fissures
By stoping (burning) it’s way through overlying rock
Eventually reaches surface
What forms at the surface as a consequence?
Volcanoes
What are some of these volcanoes referred to as + why?
Submarine volcanoes
Do not penetrate the ocean
What may happen to these volcanoes over time however?
Grow
Rise above sea level
Form islands (+ island arcs)
What are island arcs?
Characteristically curving lines of new volcanic land
Where can an example of these island arcs be found?
Aleutian Islands
Just off West coast of Alaska
Give 2 examples of nations which were formed as volcanic islands
Iceland
Japan
Typically, how severe are the eruptions of the volcanoes formed by oceanic-oceanic convergence?
Moderate to High
VEI 5-6
What is an ocean trench?
Deep underwater trench
Marks the point at which one plate was subducted beneath another
