Which heat source continues to contribute to earth’s internal heat?

Radioactive decay, the heat source continues to contribute to earth’s internal heat .

Explanation:

The core of the Earth is still burning and what we see on the outer aspect is the mantle and crust that took millions of years to cool down. If we go deeper towards the core of the Earth, we’ll start experiencing the heat that still exists there.

Besides this, there’s a radioactive decay of the isotopes generate in the core area that exerted heat to the mantle and crust of the Earth. Thus, in this way the Earth’s internal energy sustains and sometimes results in the plate tectonics and other geological processes.

this is a good question! i'll do some research and come back when i have the answer!

less than one you can't create energy