A plateau is a large, elevated landform defined by its expansive, relatively flat summit surface and one or more sides that drop off steeply to the surrounding lower terrain. Often described as a “tableland,” this geological feature rises abruptly above the adjacent landscape, distinguishing it from a plain. Plateaus are found on every continent and are products of immense geological forces that work over millions of years, shaping the crust through uplift and erosion.
Defining Plateaus and Their Physical Characteristics
Plateaus are primarily defined by their geomorphic characteristics, which set them apart from other highland features like mountains. The defining feature is the low relief across the top, meaning the summit area exhibits minimal change in elevation over a large distance. This flatness is in stark contrast to the rugged, high-relief peaks and valleys found in mountain ranges.
The elevation of a plateau is significant, often rising hundreds of meters above sea level or the surrounding land. The Tibetan Plateau, for instance, averages over 4,500 meters (about 14,800 feet). The edges are typically marked by steep cliffs or escarpments, which can be deeply dissected by rivers that have carved canyons into the elevated block.
The Geological Processes of Formation
The creation of a plateau is the result of three main geological mechanisms: tectonic activity, volcanic action, and long-term erosion. The formation process often takes place over millions of years, involving the slow but powerful movement of the Earth’s crust. Each mechanism results in a different type of plateau structure and composition.
One of the most common formation processes is tectonic uplift, or crustal shortening, which occurs when continental plates collide or converge. This immense pressure causes large, flat expanses of the Earth’s crust to be pushed upward as a single block, creating high-altitude plateaus. The underlying rock structure is often dense and compressed, with the movement raising the land without significantly folding the rock layers on the summit.
Volcanic activity can also construct vast plateaus through the successive outpouring of highly fluid basaltic lava. These lava flows, often extruded from long fissures rather than a central cone, spread out across the landscape, accumulating layer upon layer. As the lava cools and solidifies, it builds up an extensive, thick platform of rock, resulting in a type of landform known as a lava plateau.
Erosional processes play a significant role in shaping and sometimes defining a plateau. Uplifted plains are subjected to long-term weathering by water, wind, and ice, which carves deep valleys into surrounding softer material. This dissection leaves behind elevated, resistant blocks of rock with flat tops, giving rise to dissected plateaus.
Classification of Plateaus and Global Examples
Plateaus are commonly classified based on their surrounding geographical environment. Intermontane plateaus are those partially or completely enclosed by fold mountains, often representing the highest and most extensive examples globally. The Tibetan Plateau, situated between the Himalayas and the Kunlun Mountains, is the most famous example, formed by the collision of the Indian and Eurasian tectonic plates.
Continental Plateaus
Continental plateaus are surrounded by plains or oceans. The Colorado Plateau in the Western United States is a prime example, known for its deep canyons like the Grand Canyon.
Volcanic Plateaus
Volcanic plateaus, also called lava plateaus, are defined by their composition of solidified flood basalts. The Deccan Plateau in central India illustrates this type, formed by massive fissure eruptions that spread lava over a vast area.
Environmental and Human Significance
The elevated nature of plateaus creates unique environmental conditions that influence regional climate and support specialized ecosystems. High altitude means temperatures are lower, and their position often causes a rain shadow effect on the leeward side. This results in distinct microclimates, fostering biodiversity with flora and fauna adapted to the conditions.
Plateaus hold significant economic and cultural value. Many regions are rich in mineral resources, including deposits of coal and iron, which support mining activities. Volcanic plateaus often feature fertile soil derived from weathered lava, making them highly productive agricultural areas. The dramatic landscapes, such as deep river gorges, also attract tourists and have served as historical centers for indigenous communities.