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Over long periods of time, mountains are created by tremendous
forces in the earth with a steep top usually shaped up to a peak or
ridge. Mountains occur more often in oceans than on land; some
islands are the peaks of mountains coming out of the water. Mountains

are formed by volcanism, erosion, and disturbances or uplift in the
earth's crust. Most geologists believe that the majority of mountains
are formed by geological forces of heat and pressure producing

changes under the Earth’s crust and movements in the earth's crust.
They call this movement plate tectonics.

Figure 4.4. A plain

Plains are broad, nearly level stretches of land that have no great

changes in elevation. Plains are generally lower than the land around
them; they may be found along a coast or inland. Coastal plains
generally rise from sea level until they meet higher landforms such as

mountains or plateaus. Inland plains may be found at high altitudes.
Plant life on plains is controlled by the climate. Plains are usually
well populated because the soil and terrain are good for farming, and
roads and railways are easily built between rural towns and cities.

A flood plain is the floor of a river valley beyond the riverbed. A
flood plain is formed of mud, sand, and silt that are left behind when
the river overflows its banks.

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