Exogenic

Exogenic refers to processes or forces that originate outside or on the exterior of a system. In geology and geomorphology, exogenic processes are those acting on a planet’s surface, driven by external energy sources such as solar radiation, gravity, atmospheric dynamics, and hydrospheric processes. They contrast with endogenic processes, which arise from internal heat and tectonics, including volcanism and mountain-building.

On Earth, exogenic processes include weathering, erosion, transport, and deposition. Weathering alters rocks in place through physical disintegration and chemical alteration, while erosion removes material and transports it via water, ice, wind, or gravity. Deposition accumulates transported material, forming features such as river deltas, beaches, dunes, and alluvial plains. Mass wasting, glacial movement, and coastal processes also play major roles. Climate and atmospheric conditions control the rate and style of these processes, giving rise to diverse landforms over timescales from years to millions of years.

In planetary science, exogenic processes describe external forces acting on non-Earth bodies. On airless or tenuously held bodies, micrometeoroid impacts, solar wind, and cosmic rays weather surfaces and generate regolith, a process known as space weathering. On bodies with atmospheres or fluids, wind abrasion, precipitation, and erosion likewise modify surfaces. Exogenic processes help explain differences in terrain between planets and moons, such as the relative scarcity of tectonic features on some worlds, the presence of dunes on Mars, or the heavily weathered surfaces of airless bodies.

The term highlights the external origin of these processes, as distinct from endogenic internal activity, and is widely used in geosciences and planetary science to categorize surface evolution.