Chapter 5 Section 3 How are mountains classified? Objectives: Identify three types of mountains. Describe how they are formed.

Key Terms folded mountain: mountain formed by the folding of rock layers dome mountain: mountain formed when upfolds in rocks create a rounded structure that looks like a bowl turned upside down fault-block mountain: mountain formed when normal faults uplift a block of rock

Classifying Mountains Mountains are classified based on how they are formed. There are three main types of mountains. These are volcanic, folded, and fault-block mountains.

Classifying Mountains Volcanic mountains are formed from lava or debris, such as ash or rocks, thrown out of a volcano. Mt. Fuji is a volcanic mountain. Volcanic mountains are built up from eruptions that occur over thousands or even millions of years.

Mt. Fuji

EXPLAIN: How are mountains classified?

Folded Mountains When rock layers are subject to certain forces, they can become bent in a process called folding. Mountains formed by the folding of rock layers are called folded mountains. Earth’s continents move slowly on top of the upper mantle. Most folded mountains form when the continents collide.

Folded Mountains The movements of the continents squeeze rock layers together. Over millions of years, pressure builds up. The rock layers of the crust buckle and fold. Large upfolds, and anticlines, form folded mountains. The Himalayas in south central Asia and the Urals in Russia are folded mountains. The Appalachian Mountains in the United States are also folded mountains.

Mount Everest, in the Himalayas, is a folded mountain

Folded Mountains When some mountains fold upward they produce a shape that looks like a bowl that has been turned upside down. These mountains are called dome mountains.

Folded Mountains The rock layers in a dome mountain dip down and out in all directions from a center point. As the top layers of unfolded sedimentary rock are worn away, older igneous or metamorphic rock beneath is exposed. The upper rock layers of these dome mountains have been worn away unevenly. This has resulted in many separate peaks being formed.

The Black HIlls of South Dakota are dome mountains

2. DESCRIBE: How are folded mountains formed?

Fault-Block Mountains Fractures can form in Earth’s crust. These fractures may break the crust into large blocks. Sometimes faulting lifts these large blocks. One side of the fault slips past the crust on the other side. If the blocks are pushed up enough, a mountain is formed. Mountains formed in this way are called fault-block mountains.

Fault-Block Mountains The Grand Tetons in Wyoming are fault- block mountains. The Sierra Nevada in California are also fault-block mountains.

3. LIST: Name two fault-block mountain ranges in the United States.

Classwork CHECKING CONCEPTS Which type of mountain is usually formed by colliding continents? Which type of mountain is formed by vertical pressure? Which type of mountain is formed by upward thrusts of Earth’s crust?

Classwork THINKING CRITICALLY 4. CLASSIFY: Classify each mountain range listed as dome, folded, or fault-block. Explain your choices. Appalachian Mountains Grand Tetons Himalaya Mountains