Geothermal Energy


As we are encountering the forthcoming crisis of fossil fuels depletion, many regions of the world started to depend on geothermal energy as an affordable, sustainable, reliable, and environmentally friendly solution. The heat of the Earth is available everywhere, and it can be used in a broader diversity of applications. However, historically, geothermal power has been limited to areas near tectonic plate boundaries. The amount of heat within 10,000 meters of Earth’s surface contains 50,000 times more energy than all the oil and natural gas resources in the world.

Resources of geothermal energy range from the shallow ground to hot water and hot rock found a few miles beneath the Earth’s surface, and down even deeper to the extremely high temperatures of molten rock called magma. Thermal energy is created by radioactive decay at the core of the Earth where the temperature may reach over 5000˚C. Then, this heat is transferred from the core to the surrounding rocks; the high temperature and pressure can cause some rocks to melt creating magma. The magma heats rock and water in the crust, sometimes up to 370˚C.

In certain areas, water seeping down through cracks and fissures in the crust comes in contact with this hot rock and is heated to high temperatures. Some of this heated water circulates back to the surface and appears as hot springs and geysers. However, the rising hot water may remain underground in areas of permeable hot rock, forming geothermal reservoirs. These, which may reach temperatures of more than 3500 Celsius can provide a powerful source of energy.

Geothermal reservoirs within 5 km of the Earth’s surface can be reached by digging deep wells and pumping the heated underground water or steam to the surface, and this is known as the hydrothermal resources. When the temperature of the pumped hot water or steam is around 105 Celsius and above, it can be used to turn turbine generators to produce electricity. While if it is lower in temperature, it can be used directly in spas or to heat and cool buildings, growing plants in greenhouses, drying crops, heating water at fish farms, and several industrial processes such as pasteurizing milk.

The areas with the highest underground temperatures are in regions with active or geologically young volcanoes. These “hot spots” occur at plate boundaries or at places where the crust is thin enough to let the heat through. The Pacific Rim, often called the Ring of Fire for its many volcanoes, has many hot spots.

More than 20 countries generate geothermal energy. The United States of America is the largest producer of geothermal power with more than 3,000 megawatts in eight States; 80% of this capacity is from the Geysers north of San Francisco in California. Iceland dominates the European geothermal market where there are at least 25 active volcanoes and many hot springs and geysers; many of the buildings and even swimming pools are heated with geothermal hot water.


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SCIplanet is a bilingual edutainment science magazine published by the Bibliotheca Alexandrina Planetarium Science Center and developed by the Cultural Outreach Publications Unit ...
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