As if i know bed rock is the deepest layer
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Under the bedrock,there is molten rocks known as magma.Magma is very hot.when the Earth was a big ball of burning gases,the rain happened for so many years and cooled the upper surface and formed land .But it couldn't cool the inner surface.That part is still as it was billions of years ago.that is magma.Magma comes out from the area where the soil is loose.That is the lava.