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What Are Fault Blocks And Horsts?
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If you thought fault blocks and horsts
are technical terms associated with a sport, we wouldn’t blame
you. That’s what they probably sound like. Well, they are not
terms used in sports but are terms applied in geography. Horsts
and fault blocks are two different types of plateaux. Before we
delve to find out what they are, let’s first take a look at what
plateaux are. Remember, plateaux and enclosed basins cover
forty-five of the Earth’s land surface.
A plateau is an area of flat upland usually
bounded by an escarpment (a parapet or wall) on all sides, but
sometimes surrounded by mountains. The latter ones are called
intermontane plateaux. For an area to be typically classified as a
plateau, it should have low relative relief and it should be at an
altitude. Plateaux are usually at an altitude. |
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Different types of plateaux
There are different kinds of plateaux. These include Tectonic
plateaux, intermontane plateaux, horsts, fault blocks and so on. As
mentioned earlier, plateaux that are enclosed within mountain ranges
are called intermontane plateaux. It is referred to as basin and
range in the United States and they may be found in the area between
the Sierra Nevada and the Rockies. Besides, this kind of landscape
is also found in Central Asia, Tibet, part of Szechwan and Mongolia.
Intermontane plateaux are also common in the Andes range of South
America. The highest navigable water in the world, Lake Titicaca,
which is located at a height of 12,500 feet, lies on such a plateau.
Intermontane plateaux, are usually associated with young fold
mountains. Fault block plateaux and horsts are also associated with
fold mountains. |
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Fold mountains
Fold mountains occur where extensive basins have been filled
with layers of sedimentary rock material. When subjected to
compressive forces, the layers react differently. Where the
sedimentary rock cover is folded over the basement, simple fold
mountains are created. Fault blocks and horsts are plateaux left
standing high when neighboring blocks have sunk. Horsts are usually
more distinctive than the larger fault block. A kind of plateau in
which the plateau has one steeper edge and a gently tilted surface
is known as a tilted block.
Fault blocks
Segments of the Earth’s crust that have been uplifted along
linear zones in the form of enormous blocks are fault blocks. They
are usually separated by valleys or basins. The Teton Range and the
Sierra Nevada of North America are some examples of fault-block
mountains.
Horsts
Horsts and grabens are elongated fault blocks of the Earth’s
crust that have been raised and lowered, respectively, relative to
their surrounding areas. They are usually surrounded on both sides
by steep faults.
Fault blocks that form horsts usually dip
away from each other, while those forming grabens dip toward each
other. More than one horst and graben may occur adjacently. They
often occur on the crests of domes or anticlines. Valleys that are
formed in grabens are called rift valleys. Some examples of horsts
are the Palestine Plateau and the Vosges of France and some examples
of grabens are the Dead Sea depression and the Death Valley. |
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