Types of Faults

Subduction Faults

• Oceanic plate moves under a continental plate

• Large elevation difference between mountains and water level

• Pressure of oceanic plate sliding underneath, causes the folding of crust.

• Results in adjacent lands being mountainous

• Ex. the Chile trench is 8 km deep and the Andes are 7km tall

Subduction fault

Extension Faults

• Two plates pull away from one another

– In the ocean - Molten rock fills in the seafloor as it spreads apart

Ex. The mid-oceanic ridge is the longest continuous landform region on Earth

Extension Faults

Extension Faults (cont’d)

• On land: this causes the land to either:

1) sinks as plates move away

- creates rivers and lakes

- e.g. Great Rift Valley in Africa,

Rocky Mountain trench

Rift Valley

Extension Faults (cont’d))

2) Rises as plates move away

(Horst/block Mountains)

eg. Table Mountain in Africa,

Grand Teton in US

Block Mountains

Collision Mountains

• Two plates collide into each other

• Both plates are continental

• No subduction takes place since plates are the same size and strength

• Continual crushing of the plates create a crumpling of land which create mountains

• E.g. Himalayan mountains

Collision Faults

Strike-Slip Mountains

• Plates side laterally beside each other

• Often sudden movements which cause earthquakes and volcanoes

• E.g. San Andreas fault

Strike-Slip Fault

Strike-Slip Faults