Boundary Types Flashcards
Destructive/Convergent Boundary
This occurs when oceanic and continental plates move together. The oceanic plate is forced under the lighter continental plate. Friction causes melting of the oceanic plate and may trigger earthquakes. Magma rises up through cracks and erupts onto the surface. An example is the Nazca Plate being forced under the South American Plate.
Constructive/Divergent Boundary
A constructive plate boundary occurs when plates move apart. Volcanoes are formed as magma wells up to fill the gap, and eventually new crust is formed.
An example of a constructive plate boundary is the mid-Atlantic Ridge.
Collision Boundary
Collision zones form when two continental plates collide. Neither plate is forced under the other, and so both are forced up and form fold mountains.
Conservative Boundary
A conservative plate boundary occurs where plates slide past each other in opposite directions, or in the same direction but at different speeds.Friction is eventually overcome and the plates slip past in a sudden movement. The shockwaves created produce an earthquake. This occurs at the San Andreas Fault in California.
Continental Crust
The relatively thick part of the earth’s crust which forms the large land masses. It is generally older and more complex than the oceanic crust.
Oceanic Crust
The relatively thin part of the earth’s crust which underlies the ocean basins. It is geologically young compared with the continental crust and consists of basaltic rock overlain by sediments.
Plate Margin
The boundary of one of the plates that form the upper layer (the lithosphere) and together cover the surface of the Earth.
Transboundary
A transboundary river is a river that crosses at least one political border, either a border within a nation or an international boundary. The country of Bangladesh has the greatest number of these rivers.
