Where did the heat from inside the earth came from?
484046
Two main sources.  The first is that when the earth formed, it was very hot. The earth formed from a cloud of gas and dust, and then gained size from larger asteroids crashing into it for millions of years.  This left the early earth as a ball of lava. Because the earth is so large, it cools very slowly.\n\nSince the earth cooled from the outsize in, it eventually formed a crust, which insulates the inside even more, and slows down the cooling process. A good portion of the heat inside the earth is left over from its creation, about 4.5 billion years ago.\n\nThe other source of heat is the decay of radioactive elements inside the earth.  In the liquid early earth, the heaviest elements would have sunk to the middle. The earth's core is believed to be made mostly of iron, but there are traces of uranium and radioactive isotopes of  thorium, and potassium.
977025
Lord Kelvin back in the 19th Century showed that the Earth would have radiated all its original heat from formation long ago.  He therefore concluded that there must be nuclear processes occurring in the core which keep Earth's interior warm (who said nuclear energy was bad).  When these processes stop, the Earth will cool down.  I don't know (who does) but I expect that this will happen long before our sun's fuel is spent, although there's no need to worry - it won't be any time soon.\n\nIncidentally, it is extraordinary to think that we actually know remarkably little about the processes occurring in the core of the Earth and we have scarcely even scratched the surface in our exploration of our own planet.  We actually know far more about what happens in the core of the sun!
945885
Volcanoes are a result of the Earth trying to lose its internal heat. If the Earth's interior was cold, there would be no volcanoes. So how does a volcano form hey.\n\nWell, deep inside Earth, between the molten iron core and the thin crust at the surface, there is the mantle, a large layer of rock that is largely solid, but flows like plastic. When, for various reasons, rock from the mantle melts, it sometimes moves to the Earth’s surface through weak spots in the crust, releasing heat, gasses, and rock, what do you get when you put all this together..... you got it,  a volcanic eruption.\n\nVolcanoes erupt because magma is less dense than the solid rocks surrounding it in the mantle of the earth. As it nears the surface, gases expand and boil out of the rock, and this force of explosion propels lava from the vent. \n\nVolcanoes can occur by themselves or in belts and chains. The location of these volcanoes splits them into three groups. Rift volcanoes, subduction volcanoes, and hot spot volcanoes. This has a lot to do with plate tectonics, or moving of the segments of the earth's lithosphere. \n\n· Rift volcanoes occur where the plates are moving away from each other. They fill the separations with lava flows, creating new sea floor and mountain ridges beneath the waves. \n\n· Subduction volcanoes form where the plates collide and slide over each other. They create ridges and peaks. The Ring of Fire is a famous chain of volcanoes that rim the Pacific Ocean. About 1,000 live subduction volcanoes occur in this ring, and in any one-year, approximately 40 will be in some state of eruption. The Ring of Fire is composed of stratovolcanoes, which normally occur in chains, and account for over 95% of the world's active volcanoes.\n\nHot spot volcanoes are the exception to the rule of volcanoes occurring along plate margins. There are constant zones of magma within the earth in some places beneath the plates. The magma pierces through the plate. As time passes and the plates move, new volcanoes appear, and the extinct volcanoes are carried away with the drift of the plates. The common forms of hot spot volcanoes are shield volcanoes, like Mauna Loa of the Hawaiian Islands.\n\nMany factors determine the location, appearance, and amount of activity of each volcano. The location and consistency of magma determine the type of explosion, which determine the type of volcano that is formed. \n\nVolcanoes are both facinating and deadly examples of natures power. They are natural wonders that should be not just appreciated, but studied aswell. \n\nSorry this is long its just I studied volcanoes at uni and just find them fascinating.
45840
Could be. There is so far no way to know the temperature of the earth's core. We know from drilling that the temperature increases about 1 degree Fahrenheit for every 60 feet in depth. Of course, there is considerable variation in this from region to region, since it depends on the thickness of the crust, volcanic activity, ocean depth, etc. Anyway if you extrapolate that towards the core, it would give you an answer much greater than 12,000 degrees F. Most sources estimate about 7500 Kelvin or 13,040 F. We can attempt to model the core to calculate the temperature but since we don't know for sure what it is made of, and cannot reproduce the extreme pressure, it is hard to really know the temperature.
918513
Heat transfer in the Earth's atmosphere is dominated by radiation effects, rather than thermal conduction or convection.\n\nIt's complicated, but on average the Earth's surface is a few tens of degrees warmer than the surface of the Moon, which receives the same amount of sunlight, and of course has no atmosphere.
678414
If you are talking about the sun's surface, then the earth's core is hotter than it, because the earth's core is 15,000 C while the sun's surface is 5,000 C only. But if you compare the earth's core with the sun's core, then the sun's core temperature is estimated to be 14,000,000 C - 15,000,000 C.
86122
I was taught in school that it is due to radioactive decay of elements in the core.  That is pure bullcrap.  If it were true, every time a volcano exploded, there would be radioactive toxins spread out across the world.  Others say gravity pushing on the substances create heat and liquification of earth.  This may be somewhat true.  If you put a piece of solid ice in a chamber and put extreme pressure on it, it turns to liquid.  There must be some other source of internal heat generation though.  I have never found a satisfactory answer to date.  I really don't think anyone knows, just like gravity is still a big mystery.
1173782
Even though I like Oz's answer, it is actually the flow of magma in the Earth's mantle on average about 30 miles below the surface, where molten rock flows from high to low, nearing the earth's outer core where the temprature reaches to near 10000 degrees F.  Another heating element (or actually energy element, that has a side effect of heating) is radioactive decay.  Though most of the Earth's heat energy is released throught the much thinner parts of the crust that makes up the ocean floors.
364422
In physics, heat is defined as energy in transit. Generally, heat is a form of energy associated with the motion of atoms, molecules and other particles which comprise matter. Heat can be created by chemical reactions (such as burning), nuclear reactions (such as fusion taking place inside the Sun), electromagnetic dissipation (as in electric stoves), or mechanical dissipation (such as friction). Heat can be transferred between objects by radiation, conduction and convection. Temperature, defined as the measure of an object to spontaneously give up energy, is used to indicate the level of elementary motion associated with heat. Heat can only be transferred between objects, or areas within an object, with different temperatures.
989327
Naturally occurring earthquakes\n\nMost naturally occurring earthquakes are related to the tectonic nature of the Earth. Such earthquakes are called tectonic earthquakes. The Earth's lithosphere is a patch work of plates (see plate tectonics) in slow but constant motion caused by the heat in the Earth's mantle and core. Plate boundaries glide past each other, creating frictional stress. When the frictional stress exceeds a critical value, called local strength, a sudden failure occurs. The boundary of tectonic plates along which failure occurs is called the fault plane. When the failure at the fault plane results in a violent displacement of the Earth's crust, the elastic strain energy is released and elastic waves are radiated, thus causing an earthquake. It is estimated that only 10 percent or less of an earthquake's total energy is ultimately radiated as seismic energy, while most of the earthquake's energy is used to power the earthquake fracture growth and is eventually converted into heat. Therefore, earthquakes lower the Earth's available potential energy and thermal energy, though these losses are negligible. To describe the physical process of occurrence of an earthquake, seismologists use the Elastic-rebound theory.\n\nThe majority of tectonic earthquakes originate at depths not exceeding a few tens of kilometers. Earthquakes occurring at boundaries of tectonic plates are called interplate earthquakes, while the less frequent events that occur in the interior of the lithospheric plates are called intraplate earthquakes.\n\nWhere the crust is thicker and colder, earthquakes occur at greater depths of hundreds of kilometers along subduction zones where plates descend into the Earth's mantle. These types of earthquakes are called deep focus earthquakes. They are possibly generated when subducted lithospheric material catastrophically undergoes a phase transition (e.g., olivine to spinel), releasing stored energy—such as elastic strain, chemical energy or gravitational energy—that cannot be supported at the pressures and temperatures present at such depths.\n\nEarthquakes may also occur in volcanic regions and are caused by the movement of magma in volcanoes. Such quakes can be an early warning of volcanic eruptions.\n\nA recently proposed theory suggests that some earthquakes may occur in a sort of earthquake storm, where one earthquake will trigger a series of earthquakes each triggered by the previous shifts on the fault lines, similar to aftershocks, but occurring years later, and with some of the later earthquakes as damaging as the early ones. Such a pattern was observed in the sequence of about a dozen earthquakes that struck the Anatolian Fault in Turkey in the 20th Century, the half dozen large earthquakes in New Madrid in 1811-1812, and has been inferred for older anomalous clusters of large earthquakes in the Middle East and in the Mojave Desert.\n\nInduced earthquakes\nSome earthquakes are the result of a number of anthropogenic sources, such as extraction of minerals and fossil fuel from the Earth's crust, the removal or injection of fluids into the crust, reservoir-induced seismicity, massive explosions, and collapse of large buildings. These seismic events caused by human activity are referred to by the term induced seismicity. They however are not strictly earthquakes and usually show a different seismogram than earthquakes that occur naturally.\n\nA rare few earthquakes have been associated with the build-up of large masses of water behind dams, such as the Kariba Dam in Zambia, Africa, and with the injection or extraction of fluids into the Earth's crust (e.g. at certain geothermal power plants and at the Rocky Mountain Arsenal). Such earthquakes occur because the strength of the Earth's crust can be modified by fluid pressure. Earthquakes have also been known to be caused by the removal of natural gas from subsurface deposits, for instance in the northern Net
1142164
Jupiter's internal energy is  the release of heat trapped when it formed
860799
The core generates heat from the long-lived radioactive isotopes in it.  At the temperature gradient which would be big enough to carry it all away by conduction, most of the mantle would be above its melting point.  So as the heat built up in the early part of the Earth's history, the mantle softened and began to convect.  We now have a stable temperature profile from the core to the crust, and a stable balance between conduction and convection to carry away all the heat exactly as fast as it is generated.
157317
The Earth can be divided into three large sections: the mantle, inner core, and outer core. The inner core is at the center of the earth. The pressure and temperature of the earth increases as one moves closer to the center. The inner core of the earth is about 7000 degree Celsius.
235856
http://www1.eere.energy.gov/geothermal/glossary.html#g\n\nGeothermal\nOf or relating to the Earth's interior heat.\n\nGeothermal Energy\nThe Earth's interior heat made available to man by extracting it from hot water or rocks.\n\nGeothermal Gradient\nThe rate of temperature increase in the Earth as a function of depth. Temperature increases an average of 1° Fahrenheit for every 75 feet in descent.\n\nGeothermal Heat Pumps\nDevices that take advantage of the relatively constant temperature of the Earth's interior, using it as a source and sink of heat for both heating and cooling. When cooling, heat is extracted from the space and dissipated into the Earth; when heating, heat is extracted from the Earth and pumped into the space.
51474
Actually, the very center of the earth is solid, composed mostly of iron and some nickel.  It's a solid because of the extreme pressures at the center of the earth (solids typically have denser crystal structures than their liquid forms).  It's very, very hot down there, but the effect of the pressure keeping the core solid outweighs the tendency of high temps to melt it.  Higher up, away from the inner core, the outer core is in fact molten, and this is due to the very high temperatures.  Here, the effect of the high temperatures outweighs the effect of the high pressures (not as high as in the inner core), and the material exists in its less dense, liquid form.
877741
Basically energy derived from steam or heat escaping from deep underground.  Kinda like harnessing "Old Faithful".\nHTH
1156287
it's the core of the earth. lava. melted rock.etc