Geology
Geology studies the solid Earth, the materials that make it, the processes that reshape it, and the deep history recorded in rocks.
What geology studies
Geology is the science of the solid Earth. It asks what Earth is made of, how rocks form and change, why mountains rise, why earthquakes and volcanoes occur, how landscapes wear down, and how the planet has changed through time. A geologist might map an ancient shoreline, analyze a mineral crystal, study landslide risk, or read climate clues from a sediment core.
Rocks, minerals, and the rock cycle
Rocks are made of minerals, glass, organic remains, or fragments of older rocks. Igneous rocks form from cooling magma or lava, sedimentary rocks form from deposited material or chemical precipitation, and metamorphic rocks form when heat, pressure, or fluids alter existing rock. The rock cycle describes how these types can transform as they are buried, melted, uplifted, weathered, or eroded.
Plate tectonics
Plate tectonics gives geology one of its central frameworks. Earth's outer shell is divided into moving plates that interact at boundaries. Plates can spread apart, collide, slide past one another, or sink into the mantle. These motions help explain ocean basins, mountain belts, volcanic arcs, earthquakes, and the changing positions of continents.
Reading deep time
Rocks preserve evidence of environments that no longer exist: river channels, coral reefs, volcanic eruptions, desert dunes, ice sheets, and seafloors. Fossils, layering, magnetic signals, and radioactive decay help geologists place events in order and estimate ages. This record is incomplete, but it is rich enough to reconstruct major chapters of Earth history.
Surface processes
Weathering breaks rocks down chemically and physically. Erosion moves material by water, wind, ice, waves, or gravity. Deposition builds new layers in river deltas, beaches, lakes, deserts, glaciers, and deep oceans. These processes create landforms, expose older rocks, shape soils, and influence habitats and human settlement.
Hazards and resources
Geology helps people understand natural hazards such as earthquakes, volcanic eruptions, landslides, subsidence, floods, and coastal erosion. It also guides the search for groundwater, metals, industrial minerals, geothermal energy, building stone, and fossil fuels. The same knowledge that finds resources is also needed to reduce environmental harm and manage land responsibly.
Tools of geology
Geologists combine field observations with laboratory analysis, maps, remote sensing, geophysics, drilling, computer models, and chemical measurements. A hand lens and field notebook still matter, but modern geology also uses satellites, seismic waves, isotope dating, electron microscopes, and large geospatial datasets.
Why it matters
Geology connects everyday life to deep Earth processes. It explains the ground under buildings, the minerals inside electronics, the water stored in aquifers, the risks along faults and slopes, and the long carbon cycle that influences climate. It also gives a sense of scale: human history is recent, but human decisions are now leaving signatures that future rocks may record.