Warm Up 12/3Warm Up 12/31. The type of deformation in which the object permanently

changes size and shape without fracturing is called ____.a. stress deformation c. brittle deformationb. elastic deformation d. ductile deformation

2. Folding is usually the result of ____.a. tensional stresses c. shear stressesb. compressional stresses d. faulting

3. Which of the following combinations should favor folding rather than faulting?a. high temperature and high confining pressureb. high confining pressure and low temperaturec. low confining pressure and low temperatured. high temperature and low confining pressure

Answers: 1) d. 2) b. 3) a.

Types of MountainsTypes of Mountains

Chapter 11, Section 2Chapter 11, Section 2

MountainsMountains

• Orogenesis – the collection of processes that produce a mountain belt

• Mountains are classified by the dominant processes that have formed them.

Major Physiographic Provinces of Major Physiographic Provinces of the U.S.the U.S.

Landforms of the U.S.Landforms of the U.S.

Folded MountainsFolded Mountains

• Mountains that have formed primarily by folding are called folded mountains

• Compressional stresses are the major force that forms folded mountains

• Thrust faulting is also a major component in folded mountains, which are often called fold-and-thrust belts

• Examples: the Appalachians, the northern Rocky Mountains, and the Alps

Folded MountainsFolded Mountains

Fault-Block MountainsFault-Block Mountains• Large-scale normal faults are associated with

structures called fault-block mountains• The mountains form as large blocks of crust are

uplifted and tilted along normal faults• As the crust is stretched, a block called a

graben, which is bounded by normal faults, drops down

• Grabens produce an elongated valley bordered by relatively uplifted structures called horsts

• Examples: Teton Range (Wyoming), Sierra Nevada, and the Basin and Range Province

Grabens and HorstsGrabens and Horsts

Sierra Nevada MountainsSierra Nevada Mountains

Proposal for Proposal for Formation Formation

of the Basin of the Basin and Range and Range ProvinceProvince

Basin and Range ProvinceBasin and Range Province

Concept CheckConcept Check

• What is a horst?

• A horst is an uplifted block bounded by normal faults.

Domes and BasinsDomes and Basins

• Broad upwarping in basement rock may deform the overlying cover of sedimentary strata

• When upwarping produces a circular or elongated structure, the feature is called a dome

• The oldest rocks of a dome form the core of the mountains

• Downwarped structures having a circular shape are called basins

• Large basins usually contain sedimentary beds sloping at low angles, the basins are usually identified by the age of the rocks composing them (youngest form the center)

Black Hills – Black Hills – Domed Domed MountainsMountains

Black Hills, South DakotaBlack Hills, South Dakota

Michigan BasinMichigan Basin

Concept CheckConcept Check

• Where are the oldest rocks found in a dome?

• In the center or core of the dome.

AssignmentAssignment

• Read Chapter 11, Section 2 (pg. 314-316)

• Do Section 11.2 Assessment #1-6 (pg. 316)