What Are Some Landforms and How Are They Formed?

Landforms are the physical features that make up Earth’s surface, from towering mountain ranges to gentle river deltas, and they are shaped by a handful of powerful processes: the movement of tectonic plates, volcanic eruptions, the slow grinding of water and ice, wind, chemical dissolution, and even the activity of living organisms. Some landforms grow over tens of millions of years; others, like a volcanic island or a sinkhole, can appear in a human lifetime. What makes the subject fascinating is how radically different forces can produce surprisingly similar shapes, and how a single landscape often bears the marks of several processes layered on top of each other.

Mountains, Rift Valleys, and Other Tectonic Landforms

The largest landforms on Earth owe their existence to plate tectonics. When two continental plates collide, the crust crumples and thickens, pushing rock upward into mountain belts. The Himalayas are the textbook example of this, but the effects of a collision can reach far inland. The Ancestral Rocky Mountains, stretching from British Columbia to northern Mexico, formed hundreds of millions of years ago as a response to the collision of two ancient supercontinents, Laurentia and Gondwana. That deformation began only after the two landmasses were fully locked together and the ocean between them had closed. A strikingly similar pattern is playing out today in Central Asia, where the ongoing collision of India with Eurasia has produced the Tien Shan range and an array of uplifts and basins deep within the continental interior.

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Where plates pull apart instead of colliding, the crust stretches and thins, and blocks of rock drop downward along faults to form rift valleys. The East African Rift System is the most active continental rift on the planet, and within it you can find horsts, which are blocks of crust bounded by normal faults that sit higher than the surrounding terrain. Horsts and the down-dropped blocks beside them (called grabens) give rift landscapes their characteristic staircase profile.

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At ocean-continent boundaries, subduction carries one plate beneath another. This process not only builds volcanic arcs along the overriding plate but also creates deep ocean trenches on the seafloor. Evidence from the Izu-Bonin-Mariana system in the western Pacific shows that when subduction first begins, the initial volcanism comes from decompression melting of the mantle. Only several million years later does the system settle into the kind of magmatism we associate with a mature volcanic island arc.

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Volcanic Landforms

Volcanoes themselves are landforms, and they come in a range of shapes depending on the type of magma feeding them. Shield volcanoes, like those in Hawaii, are broad and gently sloping because they erupt low-viscosity lava that flows long distances before cooling. Their shape evolves through distinct growth stages, influenced by how fluid the magma is, how fast it erupts, and how vents are arranged across the volcano’s surface. A volcano fed by a single central vent tends to be more symmetrical, while one with vents spread along a rift zone develops an elongated profile.

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Calderas are among the most dramatic volcanic landforms. They form when a large eruption partially empties a magma chamber and the overlying rock collapses inward, leaving a broad, roughly circular depression that can be many kilometers across. Yellowstone’s caldera and the one occupied by Oregon’s Crater Lake are well-known examples. The conditions for collapse depend on the geometry of the magma chamber: shallow, wide chambers require less pressure loss to trigger a collapse than deep, narrow ones.

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Modeling work supports this, showing that the underpressure needed for collapse scales with the square of the chamber’s depth for calderas of similar width.

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Rivers, Oxbow Lakes, and Alluvial Fans

Flowing water is one of the most effective sculptors of terrain. Rivers carve valleys, deposit sediment on floodplains, and continuously reshape their own channels. One of the most recognizable products of a meandering river is an oxbow lake. As a river snakes across flat terrain, it naturally forms loops. When a loop becomes extreme enough, the river can cut a shortcut across the neck of the bend, abandoning the old curve. Sediment builds up at the upstream and downstream junctions, sealing off the abandoned loop and leaving behind a crescent-shaped lake. Over time, the lake fills with fine sediment and organic material, becoming a wetland and eventually just a subtle arc visible from the air.

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Where a river leaves a confined channel, such as exiting a mountain canyon onto a plain, it spreads out and dumps its sediment load, building an alluvial fan. These fan-shaped deposits are especially common in arid and semi-arid regions. They behave differently from fan deltas, which form where a river enters a standing body of water. In a fan delta, the water slows so abruptly that nearly all the sediment drops out right at the river mouth, creating a pronounced bar and causing the channel to fill up quickly behind it. An alluvial fan on dry land, by contrast, experiences a more gradual loss of transport energy, so sediment spreads more evenly and the channel backfills less dramatically.

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Alluvial fans are also remarkably dynamic. Their channels shift position through avulsion, where the river suddenly abandons one path and opens a new one. Experimental work has shown that even under steady water and sediment supply, fans develop complex patterns of channel switching that mirror what happens in nature, distributing sediment across the fan surface over time.

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Glacial and Periglacial Landforms

Glaciers reshape landscapes on a grand scale, scooping out U-shaped valleys, grinding bedrock smooth, and depositing vast quantities of sediment as they melt. Among the most distinctive features left behind are eskers, sinuous ridges of sand and gravel that mark where meltwater rivers once flowed beneath or within the ice. Ireland’s central lowland preserves an extensive system of these ridges from the last deglaciation, less than 18,000 years ago. Not all ice-contact ridges form the same way. Some are subglacial tunnel fills left by rivers running under the ice sheet. Others formed parallel to the ice margin as moraines, marking where sediment piled up at the glacier’s edge. Telling one type from another matters if you want to reconstruct the history of how an ice sheet retreated.

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In regions with permafrost, the ground itself becomes a landform factory. Thermokarst landscapes develop when permafrost thaws and the ice-rich ground collapses, creating irregular depressions that often fill with water to become thermokarst lakes. In northeast Siberia’s Kolyma Lowland, thermokarst lakes formed during the early to mid-Holocene warm period. As the climate cooled after roughly 3,500 years ago, those lakes shrank and disappeared, and the ground beneath them refroze. The refreezing forced water-saturated sediment upward, building pingos, which are dome-shaped mounds of earth-covered ice that can stand tens of meters tall. Pingos are among the most visually striking features of Arctic terrain, and their presence tells you something specific about the thermal history of the ground beneath them.

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Coastal and Wind-Built Landforms

Coastlines are battlegrounds between land and sea, and they produce their own family of landforms. Sea stacks are isolated pillars of rock standing just offshore, separated from the mainland by wave erosion. Their formation is not as simple as waves just chewing through rock. Beaches play a surprising dual role in the process: a narrow beach at the base of a headland can actually accelerate erosion by acting as a natural sandblaster, grinding the cliff with wave-tossed sediment. A wider beach, on the other hand, absorbs wave energy and protects the cliff behind it. Along the curved flanks of rocky headlands, where pocket beaches tend to be narrow and crescent-shaped, the abrasive effect dominates. Over time, preferential erosion can cut a channel entirely through a headland, leaving its outermost section standing alone as a stack.

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Inland, wind builds landforms of its own, most obviously sand dunes. The shape a dune takes depends heavily on wind patterns and how much sand is available. When wind blows from two directions that differ by more than about 90 degrees, dunes tend to align lengthwise along the combined wind direction, forming long, sinuous ridges called linear or seif dunes. The meandering shape of these dunes is controlled by how tall they are and how long each wind direction persists. When sand supply is low and the wind regime is bimodal, unusual shapes can appear, including wedge dunes that have also been observed on Mars.

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Sinkholes and Karst Terrain

Where the bedrock is soluble, usually limestone or similar carbonate rock, water dissolves it from below to create a family of landforms collectively called karst. The most familiar karst feature is the sinkhole. Sinkholes can form gradually, as the ground slowly sags into a void beneath, or catastrophically, when a roof of rock or soil collapses without warning. In some regions, sinkholes develop above hydrothermal plumes where warm, chemically aggressive water dissolves bedrock at depth. The voids grow over time, their roofs either sagging downward under their own weight or giving way suddenly, filling with broken debris. These clusters of sinkholes serve as surface evidence of extensive dissolution happening underground that would otherwise be invisible.

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Karst terrain also produces caves, disappearing streams, and rugged pinnacle landscapes called tower karst, which are common in tropical regions with high rainfall and thick limestone beds. The process is slow in human terms but relentless: slightly acidic rainwater seeps into joints and bedding planes, widening them over thousands of years into networks of passages and chambers.

Weathering and the Slow Breakdown of Rock

Not all landform-shaping processes are dramatic. Weathering, the gradual breakdown of rock in place, is quiet but pervasive. In cold regions, freeze-thaw cycles are a powerful agent: water seeps into cracks, freezes, expands, and pries the rock apart. Research in Antarctica’s Sør Rondane Mountains shows that where conditions are humid enough for regular summer freeze-thaw cycles, rock fragmentation proceeds relatively quickly. But most of those mountains sit in an arid zone where freeze-thaw is rare and mechanical breakdown is slow unless the rock contains salts. Salt weathering grows more intense over time as salts accumulate in rock pores, eventually reducing rock to particles as fine as silt.

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Weathering products feed into larger geomorphic cycles. The fine sediment created by salt weathering or freeze-thaw can be carried away by wind or water, contributing to dune fields, river sediment loads, and soil formation elsewhere. In this way, the breakdown of rock in one place builds landforms in another.

How Living Things Shape the Land

Biology is an underappreciated architect of landforms. Plants, animals, and even microorganisms alter sediment transport, stabilize or destabilize slopes, and redirect water flow in ways that leave lasting marks on the terrain. Researchers use the term “ecosystem engineers” for organisms whose physical activity reshapes their environment, and the feedbacks between living systems and earth-surface processes can create repeating landscape patterns. Vegetation on a hillslope, for example, traps sediment and slows erosion, which in turn supports more vegetation, which traps more sediment. The result can be distinct terraced or banded patterns visible from satellite imagery.

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These interactions run in both directions. Vegetation and animals respond to the physical landscape, but they also steer its evolution. Numerical modeling has shown that even small, temporary disturbances to vegetation cover, like a wildfire scar or a patch of overgrazing, can redirect large-scale, long-term landscape development by changing where water flows and sediment deposits.

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Tidal marshes and river channels are environments where biological and physical processes are particularly intertwined. Marsh grasses slow water flow and promote sediment deposition, building the marsh surface higher, while the network of tidal channels that feeds the marsh is itself shaped by vegetation patterns. Remove the vegetation and the entire system reorganizes.

Human-Modified and Impact Landforms

Humans have become a geomorphic force in their own right. Mining, agriculture, urbanization, and dam construction reshape terrain at scales that rival natural processes. Small-scale opencast mining, for instance, leaves behind a characteristic signature of excavated pits and spoil heaps that are easily recognized in the landscape. But the secondary effects can be even more significant: disturbed ground is vulnerable to accelerated erosion, altered drainage patterns, and slope instability that persist long after mining has stopped.

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At the other extreme of scale and origin, impact craters are landforms created in an instant when an asteroid or comet strikes a planetary surface. On Earth, erosion and tectonic recycling have erased most ancient craters, but they are spectacularly preserved on Mars and the Moon. Martian craters show a clear progression in complexity with size: small craters are simple bowls, but as diameter increases past a few kilometers, flat floors appear first, then central peaks, scalloped rims, and terraced walls. The central peak is produced by a rebound of the crater floor, not by material sliding inward from the rim, which overturns an older assumption about how complex craters form.

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Dating Landforms and Why It Matters

Understanding how landforms are created is one thing; knowing when they formed is another. For decades, geologists struggled to put reliable ages on features like glacial moraines, river terraces, and lava flows. The development of cosmogenic nuclide dating changed that. When cosmic rays from space strike minerals near Earth’s surface, they produce rare isotopes that accumulate over time. By measuring the concentration of these isotopes in a rock surface, researchers can estimate how long that surface has been exposed to the sky. The technique has been called transformative for geomorphology because it allows landforms to be dated directly and erosion rates to be measured over timescales relevant to soil formation, filling a gap that no previous method could address.

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Cosmogenic dating has been applied to everything from moraine boulders left by retreating glaciers to desert pavements and fault scarps. It has given researchers a way to test competing ideas about how fast landscapes erode, how quickly rivers cut through rock, and whether certain landforms are relics of past climates or are still actively forming today. Without methods like these, the story of how landforms evolve would remain largely circumstantial.