A landform is a fundamental, naturally occurring physical feature of the Earth’s surface or terrain. These features range dramatically in size, from small hills to massive continental shields and deep ocean trenches. The scientific discipline dedicated to understanding how these features originate and evolve is known as geomorphology. Geomorphologists study the processes that create and change the Earth’s topography over geologic time.
What Constitutes a Landform
A landform is defined by its characteristic shape, physical attributes, and composition, forming an identifiable part of the overall landscape. These features are categorized by specific physical qualities, including elevation, slope steepness, orientation, and underlying material, such as rock exposure and soil type. Importantly, a landform is a singular, recognizable element of topography, unlike broader geographic concepts such as a desert or a forest, which are defined by climate and vegetation.
Landforms exist across a vast range of scales, from micro-scale features like small sand dunes to macro-scale structures such as entire continents. The structure involves the arrangement and composition of the rock and sediment materials that make up the feature. This structural foundation determines the feature’s resistance to modification.
A landform is distinct from a general geological structure because it relates specifically to the external shape and surface expression of the Earth’s crust. For example, a fold in rock layers is a geological structure, but the resulting mountain range is the landform. The presence of a defined surface shape is the primary criterion for classification.
How Geographers Classify Landforms
Geographers categorize landforms based on location, scale, and relief, which describes the variation in elevation and slope. Location separates terrestrial landforms (on continents) from submarine landforms (beneath the ocean’s surface). Submarine features include mid-ocean ridges and deep-sea trenches, while terrestrial features cover all exposed landmasses.
Landforms are also classified by their order or scale, a hierarchy based on size and complexity. First-order landforms are the largest, encompassing continents and major ocean basins. Second-order landforms, such as mountain ranges, plateaus, and plains, are the broad features found within these divisions.
Classification by relief organizes the primary continental features into four main types: mountains, plateaus, hills, and plains. Mountains are defined by high elevation and steep slopes. Plateaus are elevated regions characterized by a large, relatively flat surface, indicating significant uplift.
Plains are characterized by low elevation and generally flat relief, forming expansive areas. Smaller, third-order landforms, such as valleys, canyons, and deltas, combine to shape the larger second-order features.
Processes of Landform Creation
Landforms are shaped by the continuous interplay between two major types of geomorphic processes: endogenic and exogenic. Endogenic processes originate within the Earth, driven by internal heat, and are largely constructive. They are responsible for the initial creation and uplift of major landmasses.
The mechanisms of endogenic processes include volcanism, which brings molten material to the surface, and diastrophism, the large-scale deformation of the crust. Diastrophism includes folding, faulting, and plate tectonic movements, which build up the Earth’s surface. Orogeny, the process of mountain building, results from the pressures of colliding tectonic plates.
Conversely, exogenic processes originate outside the Earth’s surface, driven by solar energy and gravity. These external forces are largely destructive, constantly working to break down and level the relief created by endogenic forces. The collective action of these forces is often referred to as denudation.
Exogenic processes include weathering, the physical and chemical breakdown of rock material in place, and erosion, the subsequent transport of this material by agents like wind, water, and ice. Deposition occurs when transporting agents lose energy, settling the eroded material to create features like floodplains and deltas.