Answer: Magma originates in the lower part of the Earth's crust and in the upper portion of the mantle. Most of the mantle and crust are solid. Magma that cools quickly forms one kind of igneous rock. When igneous rocks undergo weathering and erosion, they are broken into smaller pieces of sediment. Once the rock has been weakened and broken up by weathering it is ready for erosion. Erosion happens when rocks and sediments are picked up and moved to another place by ice, water, wind or gravity. Mechanical weathering physically breaks up rock. ... The sediment is dropped, or deposited, in landforms. Over time, sediment accumulates in oceans, lakes, and valleys, eventually building up in layers and weighing down the material underneath. This weight presses the sediment particles together, compacting them. Water passing through the spaces in between the particles helps to cement them together even more. Some examples of sedimentary rocks are limestone, sandstone, siltstone, shale, conglomerate, and breccia. Most sedimentary rocks contain either quartz or calcite. Way down inside the Earth, it very hot and there is a lot of pressure. It's so hot and there is so much pressure that rocks that get pushed deep into the Earth actually change. This process is called metamorphism. ... Some rocks get pushed down so far underground that they melt and become molten rock called magma. It's so hot and there is so much pressure that rocks that get pushed deep into the Earth actually change. ... Igneous rocks like granite can turn into gneiss (pronounced 'nice') and sedimentary rocks like limestone can change into marble when they are pushed down into the hot pressure-cooker inside the Earth.
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