Rift Valley notes

• • When the rocks of the earth’s crust are pulled apart or compressed by the movement of plates, they often crack.
• These cracks are called faults.
• Faults often occur in parallel sets as the stress that produces them operates over a large area.
• Pressure and tension often causes the land at either side of a fault to move up or down.
• If the land is being stretched, land may sink downwards along a fault.
• In this case the fault is called a Normal Fault.
• A Rift Valley or Graben can form at a normal fault.
• It forms when a block of land slips down between sets of parallel faults. This is due to stretching of the earths crust.
• Stretching and faulting of the crust is occurring as a hotspot of magma is rising underneath the crust, pushing it up and stretching it.
• The African Rift Valley is over 5,000 km long and it varies from 30 to 100 km wide.
• The East African Rift Valley runs from the Red Sea in the North to Mozambique in the south.
• Lava escapes through the fractured crust in places to form volcanoes such as Kilimanjaro.
• In Ireland Lough Neagh occupies a rift Valley.