The Earth functions as a massive recycling plant where the lithosphere is constantly being reshaped through the rock cycle. This journey often begins with igneous rocks, which form from the cooling of molten material. When magma cools deep underground, it creates intrusive rocks like granite; if it erupts as lava and cools on the surface, it forms extrusive rocks like basalt. Over time, these rocks are exposed to the elements, where the forces of wind, water, and ice break them down into smaller fragments through weathering and erosion.
As these fragments, or sediments, are transported and deposited in layers—usually at the bottom of bodies of water—the process of lithification begins. Over millions of years, the weight of overlying layers squeezes the sediment, and minerals act as a natural glue, cementing the particles into sedimentary rocks like sandstone or limestone. This is the only stage of the cycle where we find fossils, as the gentle accumulation of debris can preserve the remains of ancient plants and animals before they decompose.
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