FOLD MOUNTAINS
HOW DO MOUNTAINS FORM???
(Write down what is in red)
The great mountain ranges of the world were created because of the constant
but very slow movement of the Earth's plates. When the plates of the Earth
collide the crust becomes high mountain ranges. The roots of the world's great
mountain ranges contain some of the oldest rocks on the surface of the Earth.
Some of these rocks are over 3.5 billion years old!! These rocks were once buried
deep inside the Earth and have been raised into mountains by the collisions of
the plates.
These plates travel at a very slow rate about 1 to 4 inches per year. The Indian
Subcontinent was a very fast mover, clipping along at over 4 inches per year.
When it slammed into the Eurasian plate over 24 million years ago the collision
built the highest mountain range in the world, the Himalayas. In fact, the
Himalayas are still climbing higher and higher today.
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FOLD MOUNTAINS
DEFINITION
Fold mountains are mountain ranges that are formed when two of the
tectonic plates that make up the Earth's crust push together at their
border. The extreme pressure forces the edges of the plates upwards
into a series of folds.
Fold mountains are created through a process called "orogeny." An
orogenic event takes millions of years to create a mountain range
because tectonic plates move only centimeters every year.
Fold mountains are the most common type of mountain on Earth.
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FOLD MOUNTAINS
DIAGRAM OF PLATES
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FOLD MOUNTAINS
EXAMPLE of Fold Mountains:
The Zagros Mountains are the largest mountain range in Iran and Iraq.
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FOLD MOUNTAINS
EXAMPLE of Fold Mountains:
Folded and faulted rocks at the Lizard, in Cornwall, England. Large scale
sideways compression, like you will see in the box demonstration.
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FOLD MOUNTAINS
TRY THIS AT HOME
Step 1
Build up several flat layers of dry
sand and flour in an empty
transparent box, with a piece of
board standing in one end. Do not fill
the box more than half full.
Step 2
Very carefully, push the board
across the box, so that it begins to
compress the sand and flour
layers, stopping at intervals to see
the result. Usually, the layers
buckle up into a fold, and some
of them become overturned.
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