Our planet constantly emits energy in the form of heat, which is propagated from deeper areas to the surface : this is the so-called heat flow or geothermal flux . The heat of the sun warms the earth's surface with a flow that is almost 6,000 times greater than that produced inside the Earth , but the geothermal flux , constant and continuous , is an important source of heating for our Planet : with an average of 0.06 watts per m2 , the entire surface of the Earth radiates an amount of heat equal to about 30 trillion watts.
That the Earth becomes warmer deep down is a phenomenon well known to the miners in some mines and tunnels deep temperatures are reached at the limit of human survival ( not so in the caves , where the natural circulation of air and water drops the temperature substantially , so that the increase of temperature with depth is hardly perceptible ) . The heat of the Earth is for the most part due to the release of energy in the processes of decay of radioactive isotopes of some elements such as , for example, potassium , thorium and uranium . Due to the varying thickness of the crust and the different geological situations , which may cause the slope of the hottest materials from deep zones , the geothermal gradient (ie the increase of temperature with depth ) is not equal in all the Earth : in average temperature increases of 2-3 ° C per 100 m of depth , but the increase can vary from 1 up to 5 ° C/100 m . To measure the geothermal gradient are carried out at least 300 m deep wells ( so as not to be affected by changes daily and annual temperature due to climatic influences ) , in which it is being hauled special thermometers that record temperatures at different depths.
To find the most suitable areas for the exploitation of geothermal resources, it makes use of surveys that are conducted both on surface and underground, it seeks to understand what are the geological, hydrogeological, and thermal capacity of the geothermal system. Among the investigations of the surface are provided for the examination of the thermal conditions of the subsoil and the location of possible reservoirs. First, we measure the geothermal gradient at various points in the area and looking for obvious manifestations such as fumaroles and hot springs. In this regard, they can become valuable the data provided by the chemical analysis of water and gas. The location of a reservoir is the most complex part of the exploration as it requires to integrate the results of all geological, volcanological, geochemical and geophysical surveys carried out previously.
The survey is conducted underground , then , realizing a well that finally allows you to verify the assumptions made in the field above.
Referring to the theory of " plate tectonics " (according to which the earth's crust is divided into twenty macro-areas , called " plates " , which each year moving average of a measure that goes from zero to 18 cm ), the hottest geothermal areas of the globe, they...