Landforms are any geological feature on the earth’s surface. They can be as tall as mountains or as low as a floodplain. They can be created by a number of geologic events, usually involving plate tectonics, volcanic activity, or erosion. Most landforms are actually formed by a combination of events over millions of years. With its large landmass, examples of most landforms can be seen in the United States.
Mountain
Plate tectonics are the cause for most mountains. The collision of plates can create mountains by thrusting strata higher at the collision points. Volcanic activity can also create mountains by forming lava layers after repeated eruptions. In more rare circumstances, mountains can be formed by erosion of the surrounding area.
Plain
Plains are lowland areas that are flat with little change in elevation. Often, they are the remains of ancient sea beds that became thick with sediment, but glaciers may have smoothed the area as it passed over. Erosion of the surrounding area may also be responsible for the formation of plains. In humid areas, plains may grow forests, but in dry areas like the Great Plains region, they are covered by grasslands.
Plateau
Plateaus are highland areas that are separated from the rest of the landscape by steep slopes. They can cover a large area. Some plateaus are formed as a result of repeated volcanic eruptions that caused a build-up of lava. Some plateaus, like the Ozark Plateau, were pushed up during a series of mountain building events. During such events, strata folds and breaks to raise some strata higher than others.
Alluvial Fan
An alluvial fan is a fan-shaped bed of sediment that has been flattened by the pressure of slow running water at a point where it spreads out. Usually these occur at the mouth of a river or stream, where the water empties into a large opening. Alluvial fans are referred to as active if they are still being created by running water. They can also be found in deserts or mountains, where the water source that created them has since dried up.
Canyon
A canyon is a deep valley or gorge, usually formed by running water. The running river erodes the bank and the rock underneath. Eventually, a deep gorge is formed with cliffs on either side. A split between mountain peaks may also be referred to as a canyon.
Delta
When a river empties into a larger body of standing water, a river delta is formed. They are usually found at the mouth of a river. Generally triangular, much like an alluvial fan, the deltas gain their shape from the deposited sediment. Unlike alluvial fans, deltas generally have a shallow slope, while alluvial fans have a steep slope.
Floodplain
Floodplains are low, flat areas that run adjacent to a river. They are prone to flooding, when the banks of a river overflow. In most cases, the area was formed by river sediment. This formation continues when the river floods and deposits more sediment.
Hill
A hill is a landform with a higher elevation than the adjacent terrain. They usually have some form of a summit and can be formed in a variety of different ways. Some are moraines that were created by glaciers. Some are the cinder cones of an ancient volcano. Most hills were created by the same fold and fault method that creates mountains. Many hills were mountains at some point, but erosion has taken its toll on their height.
Levee
A natural levee is an earthen wall or embankment along a waterway. It regulates water levels and prevents a water body from overflowing its banks. They are created when the water rises, loses momentum, and deposits sediments on the bank. Many modern levee systems are man-made.
Meander
A meander is the bend in a river. It is formed by a pattern of gradual sediment build-up and erosion. A series of meanders cause a river to flow from side to side. This gives a river a winding pattern.
Mesa
A mesa is a flat highland with steep slopes. Mesas are generally remote in their elevation. Often, they may be surrounded by flat plains. They are similar to plateaus in many ways, but they do not cover as large an area as a plateau.
Mouth
The mouth of a river is where a river empties into a larger body of water. This larger body of water may be an ocean or lake, but it may also just be a larger river. For example, the Missouri river’s mouth can be found where the river joins the Mississippi. As the river waters flatten and spread sediment at the mouth, alluvial fans and deltas may form.
Valley
A valley is a long depression in the land. Valley systems can run for miles through mountains and hills, and they often slope down to a river or other source of running water. Most valleys are formed when running water erodes rock, but there are also those that are formed by glaciers and plate movement.
Waterfall
Waterfalls are places where a flow of water continues over a steep cliff or high rock formation. Its creation can happen in a number of different ways, depending on how the cliff was created. Some of them, like Niagara were created by glaciers. In many cases, the surrounding rock was damaged by earthquakes or erosion.
Moraines
Moraines were formed during the ice age through the movement of large glaciers. As the glacier moved, it carved rock and deposited debris. These areas of deposited rock and debris are called moraines.
Sand dunes
Sand dunes are caused by a combination of wind and water erosion. Surrounding rock is gradually eroded by rain and wind. The sand that results from the erosion process is blown by the wind to form sand hills. Dunes can come in a variety of shapes and heights, depending on wind patterns.
Fault
A fault is a crack in the earth’s surface. Adjacent rock may be pushed to an uneven position. Some faults may be more horizontal, while others are vertical. During plate movement or volcanic activity, faults can shift dramatically.