Mountain Formation
Chapter 5.3
Mountains
1.Mountains
a.A mountain is a natural elevation of the
Earth’s surface rising abruptly to a
summit.
b.A mountain range is a group of adjacent
mountains with the same general shape
and structure.
i. For example: Mt. Everest is in the Himalaya
mountain range and Mt. St. Helens is in the
Cascade mountain range.
Mountains
a.A mountain system is a group of adjacent
mountain ranges.
i. The Smoky, Blue Ridge, Cumberland, and
Green mountain ranges make up the
Appalachian mountain system.
b.A mountain belt is a group of large
mountain systems.
i. The two major mountain belts on Earth are
the circum-Pacific belt and the EurasianMelanesian belt.
Plate Tectonics and Mountains
1.Plate Tectonics and Mountains
a.Scientists believe that these two major
mountain belts are formed by convergent
plate boundaries and that most mountain
were formed by colliding lithospheric
plates.
b.While some mountain belts do not lie
along active plate boundaries, evidence
suggest that these ranges formed where
plates collided in the past.
Plate Tectonics and Mountains
a.Mountains can form at the three types
of plate boundaries.
i.Continental-Oceanic
1.In this collision the oceanic crust subducts
under the continental crust forming high
mountains.
2.It is also believed that some of these
mountains are caused by terranes being
scraped off.
3.Volcanic mountains can also be formed at
this type of boundary.
Plate Tectonics and Mountains
i.Oceanic-Oceanic
1.In this collision the more dense oceanic
plate subducts under the less dense
oceanic plate and forms an arc of volcanic
mountains on the ocean floor.
ii.Continental-Continental
1.The Himalaya Mountains were formed by
two continents colliding. This can cause
severe earthquakes in the area. These
earthquakes still occur today.
Types of Mountains
1.Types of Mountains
a.Mountains are classified according
to the way the crust was deformed
and shaped.
b.Folded Mountains & Plateaus
i.Folded mountains are landforms
created when tectonic movements bend
and uplift rock layers. Basically,
tectonic movements squeeze rock layers
together.
Types of Mountains
i.Folding is evident in the rock layers of
mountains formed this way.
ii.Plateaus are large areas of flat-topped
rocks high above sea level and are
formed by the same force that forms
folded mountains.
Types of Mountains
1.Plateaus are formed when thick,
horizontal layers of rock are uplifted,
generally next to a mountain ranges.
2.The Tibetan and Colorado plateaus are
next to the Himalayan and Rocky
mountains.
Types of Mountains
a.Fault-Block Mountains & Grabens
i.Fault-Block mountains form where
faulting breaks the earth’s crust into
large blocks that become tilted, causing
some blocks to drop down relative to
other blocks.
1.An example of fault-block mountain is the
Sierra Nevada mountain range of
California.
Types of Mountains
i.Grabens are long, narrow valleys
formed by faulting and downward
slippage of crustal blocks.
1.Grabens are formed by the same
force that forms fault-block
mountains.
2.An example of a graben is Death
Valley in California.
Types of Mountains
a.Volcanic Mountains
i.Volcanic mountains are formed when
molten rock erupts onto the Earth’s
surface and can develop on land or
ocean floor.
ii.Most volcanic mountains are formed
on divergent plate boundaries and
along mid-ocean ridges.
Types of Mountains
i.Hot spots are pockets of magma
beneath the Earth’s crust that erupt
onto the surface.
1.The Hawaiian islands were formed (are
forming) over hot spots, and are the tips
of volcanic mountains that have breached
the surface of the ocean.
2.The main island of Hawaii is about 9km
tall with only 4km above sea level.
Types of Mountains
a.Dome Mountains
i. A dome mountain is a landform created
when molten rock pushes up rock layers on
the Earth’s surface and the layers then are
worn away in places, leaving separate high
peaks.
1.Examples include the Black Hills of South
Dakota and the Adirondack mountains of New
York State.