What it is
Our planet constantly emits energy in the form of heat, which propagates from deeper ground towards the surface. This is the so-called flow of heat or geothermal flow.
The Sun heats the Earth’s surface with a flow of heat that is almost 6,000 times greater than the heat from inside the Earth, however, the constant and continuous geothermal flow is an important source of heating for our Planet. With an average of 0.06 watt per sq. m, an overall amount of heat, equal to approximately 30,000 billion watts is radiated from the entire surface of the Earth.
The Earth gets hotter as we dig deeper in the ground, and this is a phenomenon that is well known to miners. Some of the deep mines and galleries reach temperatures that are near the boundary of human survival (which is not the case in caves, where the natural circulation of air and water remarkably lower the temperature, so that an increase in temperature related to depth is practically not felt). The Earth’s heat, is mostly due to energy freed in the decay process of the radioactive isotopes of some elements such as potassium, thorium and uranium. Due to the different thicknesses of the Earth’s crust and the different geological situations which can cause the rise of warmer materials from deeper zones, the geothermal gradient (i.e. the increase in temperature, due to greater depth) is not equal all over the World. On average, the temperature increases 2-3°C per 100 m in depth, but the increase can vary from 1° up to 5°C/100 m.
In order to measure the geothermal gradient, wells are dug at least 300 m deep (so that the effect of daily and annual variations in the temperature, due to climatic influences, is not felt). In these wells, special thermometers which record the temperature at the different depths are positioned.
The flow of heat is greater where the thickness of the lithosphere is less, as for example on the ocean ridges or in the continental rifting zones or in volcanic areas where different geological processes lead to rock melting, or in areas where there is slowly cooling magma in the subsoil.
Special reports
-
4 November 2009
Ecological house
At present, it is more and more difficult to assure the comfort standard...
13 May 2013
Small steps, great footprints
Have you ever wondered how much space is taken up by an apple or a steak?...
-
18 May 2011
Artificial photosynthesis
The history of science and technology is packed with discoveries and inventions inspired by nature...
27 September 2012
Over 7 billion people on Earth
Demographers have estimated that on 31 October 2011 world population...
-
18 January 2016
Ten years of oil demand
Eni has recently published the 14th edition of the 2015 World Oil and Gas Review...
10 September 2020
A simple and ingenious invention
There are objects so simple and ordinary that we forget their existence when we don't need them. Their presence is…
17 March 2020
Energy and renewable sources: what is the current status?
The unstoppable growth of renewable sources continues…
-
4 November 2009
Ecological house
At present, it is more and more difficult to assure the comfort standard...
-
13 May 2013
Small steps, great footprints
Have you ever wondered how much space is taken up by an apple or a steak?...
18 May 2011
Artificial photosynthesis
The history of science and technology is packed with discoveries and inventions inspired by nature...
-
27 September 2012
Over 7 billion people on Earth
Demographers have estimated that on 31 October 2011 world population...
-
4 November 2009
Ecological house
At present, it is more and more difficult to assure the comfort standard...
-
13 May 2013
Small steps, great footprints
Have you ever wondered how much space is taken up by an apple or a steak?...
From the Multimedia section
Facts
-
An artificial geyser
Electric and thermal power produced from geothermal energy depend on the existence of underground infiltrations...
A hydrogen house
In Settimo, a municipality close to Turin, the first Unité d’Abitation has been created...
Porto Marghera Hydrogen Park
In Porto Marghera (Venice), the Hydrogen Park was created. It is the biggest centre in the world for hydrogen production...
-
Hydrogen from the sugar cane
The Centro di Ricerca Interuniversitario per lo Sviluppo Sostenibile (CIRPS) carried out a study in Peru...
Some curiosities about methane hydrates
The melting of the ice cells, not only brings about the release of methane gas, but it also produces another…
The “wave-swallowing” dragon
Wave Dragon, that swallows waves and generates electricity is a plant...
-
Bio-climatic architecture
Solar energy is playing a vital role with reference to bioclimatic architecture...
The photovoltaic train
In Italy the PVTRAIN project by Trenitalia (co-financed by the European Union) plans...
The plant of Almeria
In the Tabernas desert, 30 km north-east of the Andalusia town of Almeria (Spain)...
-
16 May 2011
An artificial geyser
Electric and thermal power produced from geothermal energy depend on the existence of underground infiltrations...
A hydrogen house
In Settimo, a municipality close to Turin, the first Unité d’Abitation has been created...
-
Porto Marghera Hydrogen Park
In Porto Marghera (Venice), the Hydrogen Park was created. It is the biggest centre in the world for hydrogen production...
Hydrogen from the sugar cane
The Centro di Ricerca Interuniversitario per lo Sviluppo Sostenibile (CIRPS) carried out a study in Peru...
-
14 June 2011
Some curiosities about methane hydrates
The melting of the ice cells, not only brings about the release of methane gas, but it also produces another…
16 May 2011
The “wave-swallowing” dragon
Wave Dragon, that swallows waves and generates electricity is a plant...
-
An artificial geyser
Electric and thermal power produced from geothermal energy depend on the existence of underground infiltrations...
-
A hydrogen house
In Settimo, a municipality close to Turin, the first Unité d’Abitation has been created...
-
Porto Marghera Hydrogen Park
In Porto Marghera (Venice), the Hydrogen Park was created. It is the biggest centre in the world for hydrogen production...