Landforms Found At Plate Boundaries (hazards) Flashcards
What landforms are found at divergent oceanic-oceanic boundaries?
Ocean ridge
Transform faults
Pillow lavas
Black smokers
Rift valleys
What landforms are found at divergent continental-continental boundaries?
Rift valleys
What landforms are found at convergent oceanic-oceanic boundaries?
Ocean trenches
Subduction zones
Volcanoes
Island arcs
What landforms are found at convergent oceanic-continental boundaries?
Ocean trenches
Subduction zones
Volcanoes
Fold mountains
Batholiths
What landforms are found at convergent continental-continental boundaries?
Collision zones
Fold mountains
What landforms are found at conservative boundaries?
Off-set landforms
Fault scarps
Describe and explain ocean ridges.
They are very long chains of mountains, up to 300km long. They occur when mantle rises, breaks through the crust and cools as new land.
Describe and explain transform faults.
They displace the ridge sideways by tens or hundreds of kilometres. As they slip, energy is released in the form of earthquakes.
Describe and explain pillow lavas.
Magma erupting directly on to the sea bed is cooled rapidly, forming rounded mounds.
Describe and explain black smokers.
Sea water seeps into rifts and is superheated. As it rises towards the surface it causes chemical changes in the basaltic rocks. Superheated jets of water sometimes re-emerge on the ocean floor containing metal sulphides. These features support unique and highly specialised organisms and ecosystems.
Describe and explain rift valleys.
The continental crust must be thin considerably for rifting to occur. Crust has been stretched, causing faulting and forming a sunken valley known as a graben - as the rift widened, magma erupted at the surface.
Describe and explain ocean trenches.
Subduction causes a deepening of the ocean at the plate boundary, and forms an ocean trench. They are long, narrow depressions with depths of 6000-11,000m. The denser plate subducts at a 45° usually asymmetric, with steepest side towards the continent.
Describe and explain island arcs.
When two oceanic plates meet, the slightly denser one will subduct under the other, creating a trench. As the descending plate melts, magma rises to the surface and forms chains of volcanic islands.
Describe and explain volcanoes.
Magma created by hydration melting of the subducted plate creates volcanoes.
Describe and explain subduction (Benioff) zones.
Faulting and fracturing occur in the zone, where the descending plate is at an angle close to 45°. This process releases vast amounts of energy in the form of earthquakes.
Describe and explain batholiths.
Plutons of magma rise to the surface because they are less dense than the surrounding mantle. When they cool and solidify they form igneous intrusions. The biggest of these are called batholiths and can be 100’s of kilometres in dimension.
Describe and explain fold mountains.
As an oceanic plate converges on a continental plate, these sediments and rocks crumple, fold and are uplifted along the leading edge of the continental plate. In addition, the continental crust is buckled and uplifted, and vast amounts of molten material are injected into it. The result is mountains.
Describe and explain collision zones.
When two continental plates converge, little if any subduction takes place. This is because the two plates have similar densities.
Describe and explain off-set landforms.
River valleys and channels may have ‘dog-legs’ along their course. These mark the location of a fault which has moved causing dislocation of the original course.
Describe and explain fault-scarps.
May be some vertical displacement too. Sections of plate may be punched up or slide down. Recent movement can be shown by a band of different coloured rock that hasn’t had time to be weathered.
