Have you ever wondered where mountains come from? There are
areas all over our country and others where the ground is flat and seems to go
on forever. Then there are areas, like in east Tennessee, where we are
surrounded by mountains. But why do some areas get mountains, and where did
they come from? There are three different ways that mountains can be formed,
and their name comes from how they were made.
Fold Mountains are formed
when the earth’s tectonic plates push against each other. A tectonic plate is a
large slab of rock that sits on top of the Earth’s mantle. These can actually move
around very slowly – just a few inches a year. When they crash into each other,
the edges buckle and fold. These edges create the mountains. Some examples of
fold mountains are the Rockies in the west United States and our very own
Appalachian Mountains in the east.
Fault-Block
Mountains are caused when giant cracks in the earth, called faults,
pull apart. When the rock layers on either side of the fault move, we get
earthquakes. Large blocks on the sides of the fault can be forced up and tilted
sideways, and on the opposite side the rocks can tilt in. The Sierra Nevada
Mountains in California are an example of this.
A Volcanic Mountain
starts out as a crack in earth called a vent. While the surface of the earth is
cool and hard, far beneath the surface (30 km and deeper) can be 1000⁰, hot enough to melt rock. This
melted rock is called magma. When the magma finds its way to the vent, it spews
its way out as lava flows, rock, and ash. Over time, a volcanic mountain builds
up, creating the familiar cone shape. Examples of these are Maunaloa and
Kilauea in Hawaii.
