FE explanation please probably an easy one

First of all, I live on a mountain in North wales, so the earth is far from flat

My question is: Where do volcanoes get their magma/lava from and how come its liquid rock if on the other side of the earth there is nothing? Surely theres not a heat source underneath the earth as the sun is above the earth (moving upwards at 9.8ms) So yeah, molten rocks, how come?

They get it from inside Earth's mantle, presumably.

soo how thick is the earth?

No one knows. It could be a few hundred km, it could be a few thousand.

so what about P-wave earthquakes? RE belief is that they come from the other side of the world and travel across a tangent until they reach the other side

EDIT: Also what about global warming? surely the ice wall will soon melt and the continents will slide off the earths face? If the government are conspiring against it, why do they want this to happen? If they told the world the true fate of global warming im sure they'd stop quicker

so what about P-wave earthquakes? RE belief is that they come from the other side of the world and travel across a tangent until they reach the other side

Perhaps they do, Earth is not one sided.

As for the global warming question, a quick use of the search feature will yield better answers than I can give.