A landform is a natural feature of the solid surface of the Earth, defined by its shape, size, and location. These features are the result of geological processes that have acted over vast timescales, shaping the planet’s topography. Landforms are categorized based on their inherent characteristics and the forces responsible for their creation, whether those forces originate from within the Earth or from external agents like water and ice. The diverse array of landforms highlights the dynamic nature of our planet, ranging from the highest peaks on continents to the deepest trenches beneath the ocean.
Continental Landforms of High Relief
High-relief continental landforms are characterized by significant elevation above sea level and distinct, often steep, slopes. These features are primarily generated by tectonic forces that uplift, fold, and fault the Earth’s crust. Mountains are the most prominent examples, typically forming in long chains called ranges due to the collision of tectonic plates, such as the Himalayas. Volcanic activity also creates mountains, with magma rising from the mantle to build large, conical structures like Mount Fuji.
Plateaus are extensive, elevated regions that distinguish themselves from mountains by their relatively flat, table-like summit surfaces. The Tibetan Plateau, sometimes called the “Roof of the World,” is an intermontane example formed by immense crustal shortening from continental collision. Other plateaus, such as the Deccan Plateau in India, are volcanic in origin, built up from numerous successive layers of basaltic lava flows. These high-altitude, flat surfaces often end abruptly in steep escarpments, contrasting sharply with the surrounding lower terrain.
Continental Landforms of Low Relief
In contrast to high-relief areas, low-relief continental landforms feature minimal elevation and generally gentle slopes. These features often form through the accumulation of sediments or from long-term erosional processes that level the landscape. Plains are broad, flat, or gently rolling areas of low elevation, often formed by the deposition of sediment carried by rivers or glaciers. The Great Plains of North America are large depositional plains leveled by water and ice age processes.
Valleys are low-lying areas situated between higher landforms like hills or mountains. Deserts are another class of low-relief feature, primarily defined by their aridity, but structurally they are often broad, flat basins or plains covered by sand dunes or rock pavements. The low elevation and flatness of these landforms facilitate large-scale deposition.
Landforms Shaped by Water and Glaciation
A suite of landforms is created primarily by the erosional and depositional actions of external agents like moving water and ice. These features are often superimposed onto the larger continental landforms, adding fine-scale complexity to the landscape.
Fluvial landforms, created by rivers, include depositional features like deltas, which form where a river slows and drops its sediment load upon entering a larger body of water. Erosional processes carve V-shaped valleys and deep canyons, such as the Grand Canyon, where the river incises the land faster than the surrounding slopes can erode. Rivers also create meandering loops and floodplains by continuously eroding and depositing sediment laterally across their channels.
Glacial landforms result from massive ice sheets and valley glaciers grinding against the bedrock. Glacial erosion carves out distinctive U-shaped valleys and deep, bowl-shaped depressions called cirques high in the mountains. Depositional features include moraines, which are ridges of unsorted rock debris (till) left behind at the edges or terminus of a melting glacier. When these U-shaped valleys meet the sea and are flooded, they form deep, narrow inlets known as fjords.
Coastal landforms are shaped by the relentless action of waves, currents, and tides at the interface between land and sea. Erosional features include sea cliffs and wave-cut platforms, which form as wave action undercuts the base of steep shorelines, causing them to retreat. Depositional coastal landforms include beaches, which are accumulations of sand and sediment along the shoreline, and barrier islands, which are long, narrow strips of sand parallel to the mainland, protecting the coast from storm surges.
Submarine Landforms
Submarine landforms are features located entirely beneath the ocean surface, covering over 70% of the Earth’s solid surface. These structures are shaped by tectonic activity, volcanic eruptions, and the slow settling of marine sediments.
The Mid-Ocean Ridge system represents the longest continuous mountain chain on Earth, spanning over 40,000 miles beneath the sea. This volcanically active feature is where new oceanic crust is generated as tectonic plates slowly diverge. Away from the ridges, the deep-sea floor is dominated by abyssal plains, which are immense, flat, sediment-covered regions typically found at depths between 3,000 and 6,000 meters.
The deepest parts of the ocean are the oceanic trenches, which are long, narrow depressions formed at subduction zones where one tectonic plate is forced beneath another. The Mariana Trench, containing the Challenger Deep, is the deepest known point in the world’s oceans, plunging to nearly 11,000 meters. Closer to the continents are the passive continental margins, which include the continental shelf—a gently sloping, shallow extension of the continent—and the continental slope, which steeply descends to the abyssal plain.