MountainsBy Jeanie Lacob 2014

The North Face of

Mount Everest

Himalayas, Northern India

What are mountains?

• A landform that reaches a high elevation.

• For a hill or mound to be classified as a mountain, its summit, or highest point, must be more than a few hundred meters above the land around it.

Mt. Fuji in Japan

Mountain Systems

• Most mountains do not stand alone, they are part of a group of mountains.

• A group of mountains with the same general shape and structure is called a mountain range.

• Groups of mountain ranges form into what are called mountain systems.

• Some scientists break up mountain systems into two major groups, called belts.

• These belts, shown below are called the Eurasian-Melanesian belt and the Circum-Pacific belt.

How are mountains formed?• When tectonic plates collide, land features

that start as folds and faults can eventually become large mountain ranges.

• Mountains exist because tectonic plates are continually moving around and colliding with one another.

Sierra Nevada in California

How do mountains change?

• Over millions of years, mountains change and take on different forms.

• Mountains change as the crust is either built up or worn away by various processes.

How do mountains change?Some mountains have steep slopes. The peaks are sharp and jagged and the valleys are narrow.

These mountains are often called “young” because they are formed from new crust.

• As time passes, a mountain’s peak is worn down by weather conditions which make the peak more rounded and the slopes become less steep. These mountains are sometimes called “mature” mountains.

San Bernardino Mountains of California

Some mountains continue to be worn away for a very long time. These “old” mountains are almost flat and have no jagged peaks. They have rolling hills and the valleys between these mountains are wide.

For example the Appalachian Mountains

How are mountains classified?

• Mountains are classified based on how they formed.

• There are three main types:– Volcanic– Folded– Fault-block

Appalachian Mountains in the U.S.

Volcanic Mountains

• Formed from lava or debris, such as ash or rocks, thrown out of a volcano.

• They are built up from eruptions that occur over thousands or even millions of years.

• Mount Fuji in Japan is a volcanic mountain.

Folded Mountains• Mountains formed by the folding of rock layers.• Most are formed at convergent boundaries where

continents have collided.• They form when rock layers are squeezed together and

pushed upward.• .

Folded Mountains• The highest mountain ranges in the world are made up

of folded mountains.• Example: Himalayas in Asia

Upwarped folding:Black Hills,South Dakota

"Hog backs" looking north along edge of Colorado Front Ranges west of Boulder, CO.

Anticline: fold of rock that bends upward in an arch

Syncline : a fold of rock that bends downward in the middle to form a “U”

Anticline or syncline? syncline

The famous Rainbow Basin ________ near Barstow, CA

syncline

Folded Mountains

Appalachian Mountains

Fault-Block Mountains• Formed when tension causes large blocks of the

Earth’s crust to drop down relative to other blocks.• Mountains that have sharp, jagged peaks.• Example: Sierra Nevada Mountains in California

Fault-Block Mountains• Formed when tension causes large blocks of

the Earth’s crust to drop down relative to other blocks.

Fault-Block Mountains

• Mountains that have sharp, jagged peaks.

• The Grand Tetons in Wyoming & the Sierra Nevada in California are fault-block mountains.

Fault-Block mountains: Teton Range, Sierra Nevada

Mountains that have sharp, jagged peaks.

Grand Tetons, Wyoming are examples of fault block mountains.

What are Plains?

• Large, flat areas that are just above sea level.• They slope gently over great distances.• They can form from uneven land being worn

down by weather conditions or from material being deposited in a large body of water .

• There are two types of plains:– Coastal (located in

coastal areas)– Inland (located inland)

The Great Plains in Montana

What are Plateaus?• Have much higher elevations than plains, yet they are

also large, flat areas.• The same forces that build mountains form

plateaus.

Island in the Sky Plateau, Canyonlands National Park Utah

What are Plateaus?• Many have canyons, which are steep-sided

valleys formed by a river.

The same forces that build mountains form plateaus.

Colorado Plateau