Normal faults develop in areas where the land is pulling apart or stretching. The tension in the crust increases until the rocks fracture. One block of land slips downward in relation to the block of land on the other side of the fault plane.
Fault blocks showing how land drops down
on one side of a fault plane, Myrna Martin
The hanging wall is the side of the fault above the fault plane where the ore deposit is located. When the ore erodes off the hanging wall it falls down onto ground of the footwall where miners found the ore.
A normal fault will have a hanging wall and a footwall. The term footwall is derived from miners finding mineral deposits where inactive faults have been "filled in" with mineral deposits at their feet.
Parallel faults can develop when land is pulling apart. The block of land in between the two parallel faults drops down creating a valley. Grabens are valleys that develop between these parallel faults.
East Africa Rift System
The East Africa Rift System is a 50 to 60 km wide earthquake zone of active volcanoes and faults. The African Plate is in the process of splitting apart forming many grabens.
Land dropping down in this rift area
The area where the grabens are located contain many lakes with lake bottoms below sea level. Lake Tanganyika is located in the area and is the second largest freshwater lake on Earth. It is possible the area may someday become an ocean if the African Plate continues to split apart.
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Earthquake Zones Find out where and why earthquakes occur and why there are earthquake zones.
Moment Magnitude Scale Find out why the moment magnitude scale is used to measure great earthquakes.
1964 Alaska Earthquake The Great Alaskan Earthquake find out why Good Friday saved many people's lives!
New Madrid Earthquakes The New Madrid earthquakes were a series of three very large earthquakes felt by people over almost 2 million square miles.
Normal Fault Find out why miners often find valuable ore in sites where these faults formed.
What Causes Earthquakes. Find out what causes earthquakes and other fascinating facts about when our planet shakes, rattles, and rolls.
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