rocks and weathering

Tectonic plate

Large slabs of lithosphere that move over the asthensophere

Plate boundaries

The lines along which tectonic plates meet

Sea floor spreading

The process by which new oceanic crust is formed at divergent boundaries

Subduction

The process by which one tectonic plate is formed beneath another

Continental drift

The slow movement of continents across the earth’s surface

Plate tectonic theory

Theory that describes the large-scale motion of seven large plates and the movements of a number of smaller plates of the earth’s lithosphere

Divergent/ constructive boundary

Plates move apart

Conservative

Plates slide past each other

Convergent (destructive) boundary

Plates move towards each other

Ocean ridges

Underwater mountain ranges formed by sea floor spreading

Subduction

Occurs on convergent boundaries where oceanic crust is forced beneath the oceanic crust

Ocean trenches

Deep depressions in the ocean floor formed at subduction zones

Volcanic island arcs

Chains of volcanic islands formed parallel to a subduction zone on the oceanic crust

Fold mountain building

Occurs at convergent boundaries where continental plates collide causing the crust to fold upwards

Example of a fold mountain

Himalayas

Anticline

An upward arching fold

Syncline

A downward arching fold

Faults

Fractures in the earth’s crust

Three physical weathering processes

Freeze- thaw, salt crystal growth and heating/cooling

Freeze thaw weathering

Water seeps into cracks, freezes, expands and widens the crack causing the rock to break apart

Heating/cooling weathering process

Repeated expansion and contraction of rocks due to temperature changes

Dilation weathering process

The removal of overlying rock which reduces pressure causing the underlying rock to expand and fracture

Three chemical weathering processes

Hydrolysis, hydration and carbonation

Hydrolysis weathering process

The breakdown of minerals by reaction with water, often forming new clay minerals

Hydration

The absorption of water into the mineral structure, causing expansion and weakening

Carbonation

The reaction of carbonic acid with certain minterals to form soluble bicarbonates

5 general factors affecting the type and rate of weathering

Climates, rock type, rock structure, vegetation and relief

3 factors affecting the type and rate of weathering

Temperature, rainfall, Peltier diagram