Warm Up 12/3
1. 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
2. Folding is usually the result of ____.
a. tensional stresses
c. shear stresses
b. compressional stresses
d. faulting
3. 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)