Why does ice stay at the top of oceans instead of sinking to the bottom?
ice is colder than liquid water.
ice is warmer than liquid water.
ice is more dense than liquid water.
ice is less dense than liquid water.

Well ice is most definitely colder than liquid water but, unlike any other substance, ice is less dense than liquid water, that is the factor that causes it to float. But any other substance becomes more dense as it freezes

It covered the territory of land across eurasia from northeastern europe to the pacific ocean.