Warm Up 12/3 The type of deformation in which the object permanently changes size and shape without fracturing is called ____. a. stress deformation c. brittle deformation b. elastic deformation d. ductile deformation Folding is usually the result of ____. a. tensional stresses c. shear stresses b. compressional stresses d. faulting Which of the following combinations should favor folding rather than faulting? a. high temperature and high confining pressure b. high confining pressure and low temperature c. low confining pressure and low temperature d. high temperature and low confining pressure Answers: 1) d. 2) b. 3) a.

Types of Mountains Chapter 11, Section 2

Mountains 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 the U.S.

Landforms of the U.S.

Folded 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 Mountains

Fault-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 Horsts

Sierra Nevada Mountains

Proposal for Formation of the Basin and Range Province

Basin and Range Province

Concept Check What is a horst? A horst is an uplifted block bounded by normal faults.

Domes 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 – Domed Mountains

Black Hills, South Dakota

Michigan Basin

Concept Check Where are the oldest rocks found in a dome? In the center or core of the dome.

Assignment Read Chapter 11, Section 2 (pg. 314-316) Do Section 11.2 Assessment #1-6 (pg. 316)