Landforms
A landform is a natural feature of the land’s surface. Landforms can present unique
challenges and opportunities to the people living near them. For example, Switzerland
was a neutral nation in both World War I and World War II, when the rest of Europe was
heavily involved in both wars. The reason was Switzerland has very high mountains, and
nobody wanted to cross the mountains to invade Switzerland.
The people of Indonesia speak over 400 different languages. The reason is that landforms
separate people. Indonesia is spread out over hundreds of islands, and a lot of those
islands have steep mountains and hills that separate villages. Therefore languages change
with each village.
Why is the soil in the prairie of the United States so fertile? Landforms are the reason.
Glaciers acted like a bulldozer, pushing topsoil from Canada and leaving it on the prairie.
Tall Landforms
The tall landforms are landforms that are visible above the horizon. They include:
mountains, hills, volcanoes, mesas, buttes, plateaus, and alluvial plains.
A mountain is a landform that rises considerably higher than its surroundings (usually
more than 2,000 ft, 610 meters, above the sea level) and is wide at the bottom and usually
narrow at the peak. Pike’s Peak in Colorado is an example.
A hill is an area that rises above the surrounding land and has a rounded top. Hills are
generally lower than and usually not as steep as mountains. Be careful of the name. The
Black Hills raise several thousand feet from the surround prairies in the Dakotas. The
highest point is Harney Point at 7,242 feet. Unlike the name suggests, the Black Hills are
actually mountains. Mount Rainier is both a mountain and a volcano. A volcano is an
opening in the Earth’s surface through which molten rock, ashes, and gases from the
Earth’s interior escape.
An alluvial fan is a fan-shaped deposit of sediment. Alluvial fans are frequently located at
the base of a tall landform, such as a mountain. The alluvial fan may be caused by a lava
flow from volcanic activity or by erosion.
The next three landforms could be thought of as three sizes of the same type of landform.
They are all caused by the erosion of the surrounding land, and their distinguishing
features are flat tops and steep sides.
A butte is a small, raised area of land with steep sides. A mesa is a high, flat-topped
landform with cliff-like sides, and is larger than a butte. A plateau is a large, flat area that
rises above the surrounding land; at least one side has a steep slope. Plateaus are tricky.
Because they are quite large (several miles wide), it is hard to realize that they are above
the horizon, especially if you are standing on one.
Flat Landforms
Flat landforms are basins, plains, glaciers, and Valleys. Plateaus, mesas, and buttes are
also flat on the top, but have steep slopes, so they are included in the tall landforms
section.
A basin is an area drained by a river and its tributaries. Sometimes a basins are obvious
because they are surrounded by mountains or higher elevations. Sometimes basins are not
so obvious, because the river they drain into may be far away from where you are.
A plain is a large area of flat or gently rolling land, usually with little change in
landscape.
A valley is low land lying between hills or mountains, created by flowing water or a
glacier. It often has a stream or river running through it.
Basin
Plain
Valley
One of the principal causes of flat landform areas is glacier movement. A glacier is a
huge, slow-moving mass of snow and ice. Glaciers are not necessarily flat; some have
high piles of snow or ice on their surfaces. Glaciers act more as a flattener and grinder.
Below are photos from Glacier Bay National Park courtesy of the Park Service
Free Floating Glacier
Glacier Cruises
Glacier Entering Bay
River Landforms
This group of landforms is associated with rivers and moving water. They are part of the
river system or are created by the flow of rivers. Topics are tributary, mouth, canyon,
delta, flood plain, and valley.
A tributary is a river or stream that flows into a larger river. For example the Ohio and
Missouri Rivers are tributaries of the Mississippi River.
The point where a river enters a lake of sea is known as the mouth of the river. The
mouth of the Mississippi River is where it enters the Gulf of Mexico.
If the river sediment leaves a triangular plain at the mouth of the river, it is called a delta.
The Mississippi River has a large delta.
A canyon is a deep, narrow valley with steep sides. Rivers and streams create canyons by
erosion or just the constant movement of the water eroding at the underlying crust.
Sometimes the stream or river has dried up over time while at other times it still flows.
A flood plain is a broad plain on either side of a river. It is formed when sediment settles
on the riverbanks. This sediment eventually forms new land as the river continues to
move.
Grand Canyon, US Parks Service
Red River Basin, FEMA
Here is an illustration showing the different parts of a river landform.
Ocean and Lake Landforms
This group of landforms is usually associated with oceans or lakes, but they can occur in
other bodies of water. They can sometimes be found in rivers. These include: Peninsula,
Island, Archipelago, Isthmus, Bay, and Strait.
A peninsula is an area of land almost
completely surrounded by water. Florida
is a peninsula.
An island is an area of land
surrounded by water. Cuba
is an island.
An archipelago is a group of islands. The
state of Hawaii is an archipelago.
An isthmus is a narrow strip of
land that connects two larger areas
of land. Panama is an isthmus.
A bay is part of a sea or lake that extends
into the land. Hudson Bay is an example.
A strait is a narrow stretch of water
that connects two larger bodies of
water. The Bering Strait near Alaska.
Landform Combinations
Landforms are often seen in combinations. Take a look at this photo of Crater Lake.
Crater Lake was created in the top of a collapsed volcano. It is thought that a huge
volcanic eruption thousands of years ago drained all the magma from the volcano and
caused the sides to collapse in on themselves, leaving a giant basin that filled with water.
The island in the lake was created by later volcanic activity.
This is a photo from the NASA’s Earth from Space collection. It was taken by the Space
Shuttle. It is a photo of the northern end of the island of Madagascar, an area known as
Cape Ambre.
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