Download Foundations of Social Studies GEOGRAPHY

Foundations of Social Studies
GEOGRAPHY
LANDFORMS
A landform is any natural formation of rock or dirt. Landforms can be as large as a mountain range,
or as small as a hill; as “uninteresting” as a plain, or as fascinating as an arch. Geographers and
geologists study how landforms are created, how they evolve and change, and where they are
located.
A term which is synonymous with the term landforms is topography. For example, we might say
that the topography of an area is rough, if it is mountainous or hilly. We might say the topography is
smooth, if it is a plain or if we are talking about a valley which has been carved by a glacier. The
walls of many canyons have steep topography. If we are talking about a very large area, we would
not be surprised if it was described as having varied topography because it had a wide variety of
landforms.
Below is a list of some important basic types of landforms but there are many, many more.
arch
butte
dune
mountain
sinkhole
archipelago
canyon
gulf
peninsula
strait
atoll
cape
isthmus
plain
valley
basin
cliff
mesa
plateau
volcano
bay
delta
moraine
promontory
The Creation of Landforms
The great variety of landforms on earth are the result of two basic forces: internal forces – which are
those that come from deep inside the earth and push the landforms up, and external forces – which
are those present on the surface of the earth or in the earth’s atmosphere and which wear the
landforms down.
Internal Processes
The internal forces are usually called tectonic processes. The surface, or crust, of the earth is
made of about a dozen rigid slabs, called plates. These are much larger than the continents as
huge portions of the plates are under the oceans but still part of the same plate as the
neighboring continent. Through a process called plate tectonics, these giants slabs move slowly
across the surface of earth. As they do so, they grind past each other, push on top of each other
and, in some places, are torn apart. As the plates move, grind, split, crash, and crumple they
create some of the world’s largest landforms – mountain chain, plateau lands, and islands – by
pushing each other up. When it occurs it feels jarring to humans and are called earthquakes,
these changes in the plates happen very slowly, taking millions of years.
How are these giant tectonic plates able to move slowly across the earth? Underneath the rigid
layer of crust on which we live are deeper layers which are not solid. The earth’s crustal plates
are able to move slowly across these inner layers which consist of molten rock called magma.
Sometimes this magma is able to force its way up to the surface and form a volcano. This is
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especially common along the edges of some of the plates. Volcanism is another internal process
which shapes the landforms we see on the surface of the earth.
External Processes
The surface of the earth is subject to forces which change its shape. The most important forces
are weathering and erosion. Weathering occurs when rock surfaces decompose and begin to
break up. Erosion refers to the actual movement of the broken particles away from their source.
These two processes occur at the same time and result in the changing shape of land, that is, the
creation of landforms.
Weathering is caused by water on the surface of rocks, by plants whose roots break up rocks, and
even by animals. There are also many ways for erosion to take place once weathering has begun
to break a rock down. Rainfall, rivers, and glaciers, can all move those portions of rock which have
been weathered and carve the surface of the earth. Coastlines – along lakes, seas, and oceans –
are subject to erosion by the pounding of waves. Wind is another important erosional force.
Different types of rocks result in different types of landforms. This is because different minerals, of
which the rocks are made, erode in different ways. For example, if the surface area of a region is
made of limestone it is likely that there will be many caves because limestone erodes easily in water.
If a region is made of sandstone - large dunes, gravel deposits and steep cliffs may be expected.
Man can also effect the creation of landforms. As pollution and chemicals in the air mixes with
precipitation, the result is acid rain which can erode minerals more effectively and kill plant life. The
loss of plant life leads to increased erosion. Overgrazing of animals and deforestation can also lead to
increased erosion. Finally, man has the technological and mechanical ability – with the use of
machinery – to physically alter the landforms of the earth by digging, blasting, and moving huge
portions of the surface.
Physiographic Regions
Geographers divide the surface of the earth into huge regions based on the predominant type of
landform found in the region. These are called physiographic regions because they are based on
physical features. They are also sometimes called landform regions. The United States is usually
divided into 25 separate and distinct regions based on physical geography. The largest region in the
eastern US is the Coastal Plain. Two large regions make up most of the central United States. They
are the Central Lowland and the Great Plains. In the western United States the largest single region is
the Great Basin, but the Rocky Mountains cover nearly as large a territory.
In summary, the earth’s surface can be divided into regions based on the topography, or landforms,
which are found there. The topography is created by internal forces which push the land up and by
external forces which wear it down into different shapes. These shapes, called landforms, are based
on the type of rock of which they are made and the type of erosion which is wearing it down. Regions
based on physical features are sometimes called physiographic regions.
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