A dissected plateau is a broad, elevated geomorphic feature severely eroded by water, transforming a flat upland into a rugged, high-relief landscape. The landform begins as a high, flat area, similar to any other plateau, standing significantly above the surrounding terrain. Over vast stretches of geologic time, this elevated surface is deeply cut by rivers and streams. The term “dissected” refers to this process of being deeply incised by the drainage network, which carves the original tableland into a complex pattern of valleys and ridges.
Defining the Dissected Plateau
The defining characteristic of a dissected plateau is its high relief, the large vertical difference between the valley floors and the highest points. A casual observer might mistakenly identify the terrain as a mountain range due to the steep slopes and sharp ridges, but its underlying structure reveals its true nature. Unlike folded or faulted mountains, the highest elevations across a dissected plateau tend to be uniform, representing the remnants of the original flat surface.
These flat-topped remnants, known as “interfluves,” are the areas of land between adjacent river valleys. The topography is dominated by deep, V-shaped river valleys and canyons that have cut down into the bedrock. Local relief can often exceed hundreds of meters; the Cumberland Plateau, for example, features areas with a vertical difference of up to 370 meters from valley bottom to ridge top.
The overall appearance is a rugged, irregular surface, where the original level plateau surface has been almost entirely replaced by hillslopes and steep escarpments. The layers of sedimentary rock—often sandstones, shales, and limestones—remain largely horizontal or gently tilted, a structural feature that distinguishes the dissected plateau from true mountain belts. This horizontal layering often controls the pattern of erosion, creating distinctive cliff-and-slope features within the valleys.
How Dissected Plateaus Form
The creation of a dissected plateau is a two-phase geological process. The initial phase involves the tectonic uplift of a large, relatively flat region of the Earth’s crust. This uplift is often the result of large-scale tectonic forces, such as the slow collision of continental plates or the thermal expansion of the underlying lithosphere.
The uplift raises the land high above sea level, which significantly increases the potential energy of any water flowing across its surface. The subsequent phase is fluvial erosion, where rivers and streams begin to cut downward into the elevated bedrock, a process known as downcutting. The increased gradient and speed of the water give it immense erosive power, allowing it to carve deep gorges and valleys.
For a true dissected plateau to form, the rate of tectonic uplift must first exceed the rate of erosion for a sustained period, creating the elevated platform. Once the plateau has reached a sufficient height, the erosional forces, particularly the downcutting action of the rivers, begin to dominate the landscape carving. This process is continuous, with water seeking the path of least resistance and exploiting any weaknesses in the rock layers.
The differing resistance of rock layers contributes to the rugged topography, as softer rocks like shale erode more quickly than harder rocks like sandstone. This differential erosion creates the steep-sided valleys and the characteristic remnants of the original plateau surface. The continuous action of water and weathering over vast timescales eventually transforms the broad, flat upland into the intricate network of ridges and ravines seen today.
Notable Global Examples
The Appalachian Plateau in the eastern United States is one of the most prominent examples of this landform, encompassing the Allegheny and Cumberland Plateaus. Located on the western side of the Appalachian Mountains, this region demonstrates the extreme relief and rugged terrain resulting from the deep incision of rivers into an uplifted block of rock.
The Colorado Plateau in the western United States offers another well-known illustration, containing the vast canyons carved by the Colorado River and its tributaries. This plateau was uplifted due to tectonic processes and subsequently subjected to intense fluvial erosion, creating iconic features like the Grand Canyon.
The Chota Nagpur Plateau in eastern India, formed by a combination of tectonic uplift and erosion, is characterized by undulating topography and deep valleys. Such areas are often rich in mineral resources, including iron ore and coal, due to the exposed geological layers.
Dissected plateaus frequently present challenges for human settlement and infrastructure development due to their steep slopes and irregular surfaces. However, the diverse topography and varied microclimates also support unique ecosystems, such as the rich biodiversity found in the narrow gorges of the Appalachian Plateau.