How Earth's surface is broken down, shaped, and carried away over millions of years.
Two related but distinct processes that together reshape every landscape on Earth.
The disintegration or decomposition of rocks in situ — right where they are, without significant movement. It prepares rock material for erosion.
The picking up and moving of weathered material by agents like water, wind, ice, or gravity. It transports material from one place to another.
Weathering and erosion are critical parts of the Rock Cycle. Igneous rock weathers → fragments erode → sediment deposits → sedimentary rock forms → heat & pressure creates metamorphic rock → melts into magma → erupts as igneous rock again. This cycle runs continuously over millions of years.
Each operates through fundamentally different mechanisms and produces distinct effects on rocks.
Rock is broken into smaller pieces without changing its chemical composition. The same minerals exist — just in smaller fragments. Greatly increases surface area for later chemical weathering.
The chemical composition of rock minerals is permanently changed. Produces new secondary minerals like clays, iron oxides, and soluble salts. Dominant in warm, wet environments.
Living organisms — plants, animals, fungi, bacteria — directly or indirectly break down rocks. Often combines physical and chemical mechanisms.
Five major forces that transport weathered material across Earth's surface.
Running water — in rivers, streams, and overland flow — is the most powerful agent of erosion on Earth's surface, responsible for carving most landscapes we see today.
Wind erosion is most powerful in arid and semi-arid regions where vegetation is sparse and loose particles are exposed. The Sahara, Arabian, and Thar deserts are prime examples.
Glaciers — masses of moving ice — are extraordinarily powerful erosion agents. Though slow (meters to km per year), they carry enormous volume and can erode rocks that no other agent can.
Waves are the primary agent reshaping coastlines worldwide. A single large wave can exert pressures of 30–40 tonnes per m² against a cliff face.
Gravity pulls weathered material downhill. Mass movement occurs when the downslope forces exceed the forces holding material in place. Often triggered by rain, earthquakes, or human activity.
Real-world examples where weathering and erosion have created spectacular landscapes.
446 km long, up to 29 km wide, 1.6 km deep. Carved by the Colorado River over ~5–6 million years. Exposes nearly 2 billion years of Earth's geological history in its walls.
4,478m pyramidal peak formed by 3 corries (cirques) eroding backward from three sides. Classic example of a horn or arête junction. Sits on the Swiss-Italian border.
137m tall sea stack in Orkney, Scotland. Formed as waves eroded a sea cave through a headland to create an arch, which subsequently collapsed, leaving this isolated stack.
Iconic mesas and buttes in the Navajo Nation. Resistant sandstone caprock protected the tower from erosion while surrounding softer rock was stripped away by millions of years of wind and water erosion.
World's longest known cave system — over 670 km of mapped passages. Formed by carbonation: slightly acidic groundwater dissolved the limestone bedrock over millions of years.
Piopiotahi — 15km long, 290m deep glacial fjord. The valley was carved by glaciers, then sea levels rose as ice melted, flooding the trough. Sheer cliff walls rise 1,200m straight from the water.
All major weathering and erosion processes, their features, and real-world examples at a glance.
Weathering is the first step in creating soil — one of Earth's most vital resources.
It takes roughly 1,000 years to form 1 cm of topsoil. Soil supports 95% of the world's food production and is home to 25% of Earth's biodiversity. Weathering is the foundation of all soil formation.
CLORPT — the 5 soil-forming factors (Hans Jenny, 1941)
The dominant weathering process depends heavily on temperature and precipitation.
Human activity has dramatically accelerated natural processes — in many cases beyond recovery.
Weathering is the in-situ breakdown of rock — no movement occurs. Erosion is the transport of that broken material by wind, water, ice, or gravity. Weathering always happens first, then erosion moves the material. Think of weathering as breaking a building into rubble, and erosion as a truck carrying that rubble away.
Running water (rivers) is generally considered the most powerful and widespread agent of erosion on Earth's surface — responsible for most of the valleys, plains, and landscape relief we see. However, glaciers are more powerful per unit area and have shaped enormous areas during ice ages. Wind is most significant in deserts, and waves dominate coastlines. The "most powerful" depends on the environment and timescale considered.
Water is unique in that it expands by approximately 9% when it freezes. When water seeps into cracks in rock and freezes, this expansion exerts enormous pressure — up to 200 MPa (megapascals) — on the surrounding rock. Over many freeze-thaw cycles (common in mountain and periglacial environments), the crack progressively widens until the rock eventually shatters. This process, called ice wedging or frost action, is most effective when temperatures fluctuate repeatedly through 0°C.
Limestone (calcium carbonate, CaCO₃) dissolves in slightly acidic water. CO₂ in the atmosphere and soil dissolves in rainwater to form weak carbonic acid (H₂CO₃). This acid reacts with limestone: CaCO₃ + H₂CO₃ → Ca²⁺ + 2HCO₃⁻. The calcium and bicarbonate ions are carried away in solution. Over millions of years, this process (called carbonation) dissolves along joints and bedding planes to create cave systems, sinkholes, limestone pavements, and karst landscapes. When water drips inside a cave and CO₂ escapes, the reaction reverses and calcium carbonate is deposited as stalactites (from ceiling) and stalagmites (from floor).
A U-shaped valley (glacial trough) is a wide, flat-floored valley with very steep, nearly vertical sides — shaped exactly like the letter U. It forms when a glacier occupies and erodes a pre-existing V-shaped river valley. The glacier is far wider than the river, so it erodes the valley sides as well as the floor. Glacial abrasion and plucking widen and deepen the valley floor while the sides are steepened. When the glacier eventually melts, it leaves behind this characteristic U-profile. Classic examples: Yosemite Valley (California), Glencoe (Scotland), Lauterbrunnen (Switzerland).
This seems counterintuitive given the lush vegetation, but tropical rainforest soils (oxisols / laterites) are highly weathered and most nutrients are locked in the living biomass, not the soil. The intense heat and rainfall cause extreme chemical weathering that leaches almost all nutrients out of the soil. What nutrients do exist are rapidly recycled directly from decomposing leaf litter back into plant roots — the trees basically grow on each other rather than on soil nutrients. When rainforest is cleared, the soil is typically only productive for 2–3 growing seasons before becoming infertile wasteland — which drives further deforestation.
Cliff erosion rates vary enormously depending on rock type, wave energy, and sub-aerial weathering. Soft rock cliffs (clay, shale, glacial till) can retreat 1–10+ meters per year — Holderness Coast in Yorkshire, England (soft glacial till) retreats at ~2 meters/year — one of the fastest in Europe. Hard rock cliffs (granite, quartzite) may retreat only a few centimeters per century. The White Cliffs of Dover (chalk) retreat at ~20–25 cm/year. Climate change and rising sea levels are expected to significantly accelerate coastal erosion rates this century.
Regolith is the layer of loose, unconsolidated material — rock fragments of various sizes — that sits directly on top of bedrock, produced by weathering. It has no organic content and no biological activity. Soil is a much more developed material that has been further processed by organisms, water, and time to develop distinct horizons and contain organic matter, nutrients, and living organisms. You could say: regolith → (with organisms + time) → soil. The Moon is covered in regolith (lunar regolith) but has no soil because there are no organisms to develop it.