why is the earth's interior really hot?

Answer 1

The hundreds of miles /kilometer thickness of outer surface is a very good insulation.

This is my help from Washington, D.C. USA.

Answer 2

OK so some of you guys need to crack open a geology book.

Radioactive decay and pressure. Its more complicated than that but that's the gist of it. Rock is a very poor conductor of heat, molten or solid. The planet has been able to stay warm for so long from large quantities of radioactive decay (past and present) because the heat travels very slowly through the rocks. Pressure also plays an important part in maintaining that heat. Look up how pressure affects temp. If you put water under enough pressure, it will boil without any heat source at all.

Answer 3

Earth's interior is heated mainly by radiation. The decay of radioactive isotopes generates most of the heat in the core of the earth. Another source of heat comes from accretion when in-falling meteorites impacted the earth

Answer 4

The constant rotation of the planet keeps the interior in motion. The outer crust cooled billions of years ago and insulates the interior from the relatively cool surface temperature. The centrifugal force of rotation keeps the magma moving and is responsible for the movement of the tectonic plates. As these plates rub together they produce enormous heat and as they subduct carry that heat into the core.

Answer 5

Two reasons:
1► Fission. There are many radioactive elements.
2► Residual heat from the time the Earth was born.

Answer 6

Pressure.

Answer 7

because it is filled with liquid hot magma

Answer 8

it's because of the energy of the earth
it's all concentrated there