GEOLOGY Earth's geology spans four main layers: the solid inner core, molten outer core, mantle, and crust. Tectonic plates atop the semi-fluid mantle cause geological activity, forming mountains, valleys, and earthquakes at plate boundaries. Rock types-igneous, sedimentary, and metamorphic—reflect Earth's dynamic history through processes like volcanic eruptions, erosion, and pressure-induced changes. Fossil records within rock layers unveil evolutionary history, while minerals, such as quartz and feldspar, signify Earth's composition. Geological time, measured in eons, eras, and periods, illustrates the planet's ancient transformations and ongoing changes shaping its surface.