A) 2 oceanic plates move away from each other

Bi) Magma rises from the mantle to fill the gap between the plates as they diverge.

1. Oceanic-oceanic plate divergence

P11. The Mid-Atlantic Ridge is found in the middle of the Atlantic Ocean cutting across Iceland, a volcanic island.

Bii) New sea floor is formed when the magma cools and solidifies. This process is called sea-floor spreading.

Bii) Magma rises at the zone of divergence/spreading zone to form a ridge of new ocean floor called mid-oceanic ridge.

1. Oceanic-oceanic plate divergence

Ci) The newly formed (youngest) rocks are closest to the middle of the ridge/plate boundaries.

Cii) At various points along the ridge, magma builds up above the ocean to form volcanic islands.

1. Oceanic-oceanic plate divergence

2. Continental–continental plate divergenceA)2 continental plates move away from each other

B)Stretched and causes fractures at boundaries

C)Land in between sinks and forms rift valley and volcanoes

2. Continental–continental plate divergence• Can result in the breakup of continents

• E.g. Great Rift Valley (East Africa)– a lowland with steep sides and flat valley

floor

– formed by Somalian boundary of the African Plate moving away from the Nubia plate boundary of the African Plate

– 6,000 kilometres long

– between 30 to 100 kilometres wide

• Can result in the formation of linear sea

• E.g. Red Sea and Gulf of Aden near the Great Rift Valley – Elongated/linear shape

– 1,900 km long

– 300 km at its widest

– Average depth of 500 m

– Evidence of tectonic

activity formation of

new volcanic island in

Red Sea

IMPT! P25 Rift valleys and block mountains

• A fault is a fracture in the rocks along which the rocks are displaced.

• The tensional forces result in parts of the crust being fractured.

• This process is called faulting.

FAULTING

• A rift valley is a valley with steep sides formed along fault lines. E.g. East African Rift Valley

Formation of Rift Valley

• A block mountain is a block of land with steep sides. It is formed when sections of the crust extend along fault lines and rock masses surrounding a central block sink due to tensional forces.

Block mountains