Physical Geology

Chapter 11

Part 2 – Mountain Building

Definition• A mountain is the most extreme type of

deformation• Relatively small “wrinkles” in the earth’s

crust may soar from 1 to 8 km above sea level

• A mountain is a piece of land that is higher than a hill and stands much higher than the land around it.  Mountains have steep sides and a pointed or rounded top.  The top of a mountain is very cold.  Mountains are created over long periods of time by tremendous forces of the earth.

Range – a group of adjacent mountains related by shape and structure

System – a group of adjacent ranges

Belts – the two major mountainous regions of the world; Eurasian-

Melanesian & Circum-Pacific belts

How do mountains form? It’s all plate tectonics!

Types of Mountains• Folded

and Plateaus

• Faulted• Domes• Volcanic

Blossom Peak, Post Falls, Idaho

Folded Mountains

• Compression stress squeezes up accordion-like folds

• May also result in formation of uplifted, broad, flat plateaus

• Himalayas, Rockies, Appalachians, Urals, parts of the Alps

Types of Folds

Plateau

Faulted Mountains

• Vertical movement at fracture zones

• Tilted blocks, lift or drop at single faults

• Uplift at double faults

• Sierra Nevada, Tien Shan, western foothills of the Rockies (Basin/Range region)

Typical Fault Block Mountains

Fault block valley

Fault block ridge

Death Valley

Basin and Range

Domes and Basins

• Gentle upwarping or downwarping of crustal rock produce domes and basins

• Erosion of these structures results in an outcrop pattern that is roughly circular or elongated

• Black Hills, Adirondacks, Stone Mountain

Domes and Basins

sandstone

limestone

Crystalline

Metamorphic

core

Volcanic Mountains

• Eruptions of gases, magma, cinder/ash and pulverized surface material

• Piles of expelled material form cones that may stand out from surrounding terrain as mountains– Shield cones– Cinder cones – Composite cones