Landforms associated with plate tectonics

How are ocean ridges formed?

1. Two oceanic plates move apart in oceanic areas

2. The space between is filled with basaltic lava, forming a ridge

Which types of crust are ocean ridges formed between?

• oceanic & oceanic

How are ocean trenches formed?

1. An oceanic plate sinks below a continental plate OR an oceanic plate sinks below an oceanic plate

2. A deep section of the ocean, a deep ocean trench, is formed

Which types of crust are ocean trenches formed between?

• oceanic & oceanic

• oceanic & continental

How are rift valleys formed?

1. Plates move apart on the surface of the Earth

2. Areas of crust drop to create parallel faults to form the valley

How are fold mountains formed?

1. Rock layers are compressed as they have been forced together

2. The rock layers crumple, buckle, and fold

Which types of crust are fold mountains formed between?

• oceanic & continental

• continental & continental

How are island arcs formed?

1. During subduction at a destructive plate boundary, the descending plate melts

2. The melted material is also lighter and more gassy than the material already in the mantle, so it rises towards the surface through the crust as plutons (blobs of magma)

3. These eventually reach the surface as explosive volcanoes

4. This may form island arcs