The internal temperature of the earth increases with depth from the surface. Near the surface, the average geothermal gradient is about 25 degrees centigrade (77 degrees Fahrenheit) for every kilometer of depth. Some areas have much higher heat flows because of deep fault zones, rifting, magmatic intrusions, or active tectonic forces. The geothermal gradient can make conditions in deep mines quite uncomfortable and hot enough to explode rocks or bend steel.
The geothermal gradient of 25 degrees centigrade/kilometer is thought to be restricted to the upper part of the crust . If it continued at this rate uniformly from the surface, the internal temperature of the earth would be greater than 2,000 degrees centigrade within the lithosphere a temperature that far exceeds the melting temperatures for all rocks at that depth.
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The internal temperature of the earth increases with depth from the surface. Near the surface, the average geothermal gradient is about 25 degrees centigrade (77 degrees Fahrenheit) for every kilometer of depth. Some areas have much higher heat flows because of deep fault zones, rifting, magmatic intrusions, or active tectonic forces. The geothermal gradient can make conditions in deep mines quite uncomfortable and hot enough to explode rocks or bend steel.
The geothermal gradient of 25 degrees centigrade/kilometer is thought to be restricted to the upper part of the crust . If it continued at this rate uniformly from the surface, the internal temperature of the earth would be greater than 2,000 degrees centigrade within the lithosphere a temperature that far exceeds the melting temperatures for all rocks at that depth.
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Both extrusive and intrusive igneous rocks are derived from magmas. The temperature and pressure conditions in the crust and upper mantle influence the melting temperatures of the minerals in the rocks .
Temperature and pressure increase with depth from the surface and eventually reach a point at which rocks melt . The geothermal gradient is the rate at which temperature increases with depth. In the upper crust, the geothermal gradient is about 2 .5 degrees centigrade for every 100 meters (330 feet).
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