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How are mountains formed?
Why do mountains form?
Types of Mountains
Folded
Fault Block
Dome
Volcanic
Eroded plataeus
Mountains are made in several ways.
Let’s take a closer look . . .
• Folded Mountains - These are formed as layers of the earth react
to forces pushing in on either side, much as a piece of paper folds
when pushed together.
• Fault Block Mountains - These mountains form when faults or
cracks in the earth's crust force some materials or blocks of rock up
and others down.
• Dome Mountains - These mountains are the result of a great
amount of melted rock pushing its way up under the earth. Over
thousands of years the dome mountains form in the place where the
earth is pushed up.
• Volcanic Mountains - These are formed from the vast amounts of
lava that have hardened after spurting out of a volcano.
• Residual Mountains - These are mountains that are really plateaus
that have worn down from erosion.
Folded Mountains
• Folded mountains are formed when land is in
between two plates and those plates are pushing
toward each other. When this happens the land
begins to fold to form mountains.
• Layers of folded rock look like waves.
• They have upfolds and downfolds.
• An upfold is called an anticline and is a fold that
folds towards the sky and the bend is on top.
• A downfold is called a syncline and is a fold that
folds toward the ground.
Folded Mountains
Anticline
Syncline
Appalachians - the site of an
ancient continental collision
Folded Mountains - the Blue Ridge
Fault Block Mountains
• When continental plates push together, the
layers of rock may also crack and break;
and then they become forced up and down
along the breaks or faults as they are called
by geologists.
Cracks or faults
Strata originally deposited in horizontal layers become tilted.
Erosion occurs over time!
Magma rises toward the surface pushing up
the land above; later the above layers erode
leaving an igneous dome or pluton.
Sometimes called plutonic mountains from
Pluto, Roman god of the underworld.
Mt.Fuji, Japan
Three types of volcanic mountain
cones are:
• Cinder or Tuff Cones - small symmetrical cones formed
from cooled lava ejected into the air
• Composite or Strato volcanoes - very large and steep near
the summit and broad at the base; formed from layers of
“thick” viscous lava and layers of ash
• Shield volcanoes - very broad and flat and large ; formed
from “runny” (very low viscosity) lava that flows easily;
they look like a warriors shield lying on the ground from
distance
Active cinder cones
from Iceland-very
explosive
Note the relatively
small size as
compared to the
other types.
These are eroded cinder
cones in Idaho.
Mayon, Philippines
Mt. Fuji, Japan
Composite or Strato volcanoes are extremely
dangerous and explosive on a large scale.
Popocatepetl near Mexico City
Mt.. Vesuvius, Pompeii, Italy
Mount St.. Helens, Washington
Popocatepetl is a snow capped strato volcano that stands 13,776
(4200 m) above the surrounding basin. The name Popocatepetl,
meaning “smoking mountain”, was given to the volcano by the
Aztecs, and suggests that the volcano has long been active. Popo,
as it is often called, is built on an older volcano which adds 12,464 ft
(3800 m) to Popocatepetl's elevation.
Huge snow and ice
covered strato volcanoes
- Some of the sleeping
giants of the Cascade
Range
Mt. Ranier
Mt. St. Helens
Lahars- hot mud slides - how do you think they form?
Mauna Loa, Hawaii
- world’s largest
volcano.
Shield volcanoes are
characterized by
“runny” lava. The
lava will run for
miles; this causes a
broad and flat
volcano. These
volcanoes are not
very explosive.
Fountaining
produces Aa and
ground flows
produce pahoehoe!
When an area of highand remains standing above the general level
after rivers and other natural agents have lowered the surface of
the surrounding area, the name residual mountain is used. Sometimes
such highands are called 'mountains of denudation'. This term can
usually be applied to the mountain ridges associated with 'dissected
plateaux'. Included in this class are the mountain ridges of the
Highlands of Scotland, the Sierras of Central Spain, and the Mesas and
Buttes of the western plateau lands of the United States.
•Formed from eroded plateaus.
•Buttes, mesas, rock spires are common features.
Monuments Nat’l Park
The Southwest- USA
Goose Canyon
Mesa Verde
Canyonlands
Monuments Nat’l Park
Bibliography
http://ea.bemidji.msus.edu/truedson/psns/ch22b/tsld004.htm
http://volcano.und.edu/
http://www.americansouthwest.net/html
http://www-glg.la.asu.edu/~sreynolds/geologic_scenery/
http://www.homestead.com/parkview/Folded.html
http://www.pittsford.monroe.edu/Schools/Jefferson/Maps&Glob
es/Mountains.html
http://www.swparks.com/