Mention erosional remnants and we tend to think of sea stacks, free-standing buttes and other solitary rock formations that have withstood the forces of wind, water and ice. Some of these landforms, especially mesas and buttes, are protected by a resistant cap of basalt or other non-porous rock while others are igneous plutons or laccoliths, uncovered as their encasing sediments have eroded away.
In reality, all natural landforms are erosional remnants, the current product of underlying geology, tectonic forces and erosion, modified by climate and vegetation. Highlands may represent areas of uplift, volcanism or resistant geologic strata but remain subject to the forces of erosion and, eventually, will wear down to a level plain. Stream valleys and canyons, while seemingly stable during our brief lifespan, are continually molded by floods, deposition, landslides, rock falls and periods of drought; depending upon the interaction of these factors, they may deepen, widen, clog with erosional debris or fill with water behind a natural dam of ice or soil.
Human activity hastens erosion in a number of ways. Deforestation augments erosion on hillsides, the drainage of wetlands increases flooding along river valleys and the construction of highways disrupts natural drainage, increases runoff and, in mountainous regions, hastens the occurrence of rock slides. As we witnessed during the Dust Bowl years, poor farming practices can dramatically augment soil erosion and the over-grazing of natural grasslands continues to threaten those regions. And, of course, our contribution to global warming will significantly affect erosional processes as glaciers retreat, sea levels rise and weather patterns change.
