Mountains and Mountain Building: Chapter 11 - PowerPoint PPT Presentation

1 / 24
About This Presentation
Title:

Mountains and Mountain Building: Chapter 11

Description:

Mountain Building. The formation of mountains is called . orogenesis. Mountains that are formed by compressional stresses are called . folded mountains – PowerPoint PPT presentation

Number of Views:182
Avg rating:3.0/5.0
Slides: 25
Provided by: MSCS151
Category:

less

Transcript and Presenter's Notes

Title: Mountains and Mountain Building: Chapter 11


1
Mountains and Mountain Building Chapter 11
2
Rock Deformation
  • Deformation is a general term that refers to a
    change in size or shape of rocks in the earth's
    crust.
  • Deformation occurs when stress, or a force over a
    given area occurs.
  • The amount of deformation that occurs and can be
    measured, either by a change in shape or volume
    of rocks in the earth's crust is referred to as
    strain.
  • The four factors that influence rock deformation
    are temperature, pressure, rock type, and time.

3
Temperature and Pressure
  • When rocks are near the earth's surface and
    temperatures and pressures are normal, rocks
    undergo brittle deformation and fracture.
  • When rocks are at great depths, the temperatures
    and pressures are very high.
  • Under extreme temperatures and pressures rocks
    can behave elastically.
  • When rocks are elastic the type of deformation
    that occurs is referred to as ductile deformation.

4
Rock Types and Time
  • Igneous Rocks like Granite and Basalt usually
    deform by brittle deformation. Sometimes they
    deform by ductile deformation.
  • Metamorphic Rocks are more likely to deform by
    ductile deformation.
  • Often times Sedimentary Rocks show that ductile
    deformation has occurred. One possible
    explanation for the ductile deformation is the
    sedimentary rocks folded before they hardened
    (lithification).
  • The longer stress is applied to rocks, the more
    deformation will occur.

5
Types of Stress
  • The three types of stress can be applied to
    rocks.
  • Tensional Stress When rocks pull apart.
  • Compressional Stress When rocks push together.
  • Shear Stress When rocks twist or push in
    opposite directions.

6
Stresses
7
Folds
  • Often times when Compressional Stresses and
    ductile deformation occurs during mountain
    building, rocks will fold or bend much like
    sheets of paper.
  • When a fold bends upward in an arching shape, an
    anticline forms.
  • When a fold bends downward in the shape of a
    trough, a syncline forms.
  • When a fold occurs in a step or stair-like
    fashion a monocline can occur.

8
Folds
9
Faults
  • Stresses can also cause a fault or fracture in
    the earth's crust to occur due to brittle
    deformation.
  • There are four main types of faults.
  • Normal faults these are caused by tensional
    stresses. When this occurs the head (hanging)
    wall moves down relative to the foot wall.
  • When discussing the relative motion of the
    earth's crust along faults, the hanging wall or
    head wall refers to the side of the fault that
    rests on the foot wall.
  • The foot wall is the side of the fault that
    appears to support the head wall or hanging wall.

10
Faults
  • Reverse Faults faults that are caused by
    compressional stress. In the case of a reverse
    fault, the hanging wall moves up relative to the
    footwall.
  • Thrust Faults these faults are low angle (less
    than a 45 degree angle) reverse faults.
  • All faults that move up and down (normal,
    reverse, and thrust faults) are referred to as
    dip-slip faults.
  • Strike-Slip Faults These faults move side to
    side.

11
Faults
12
Faults
13
Mountain Building
  • The formation of mountains is called orogenesis.
  • Mountains that are formed by compressional
    stresses are called folded mountains.
  • In folded mountains, compressional stresses can
    cause anticlines and synclines to occur, or they
    can produce reverse faults and thrust faults.
  • Examples of folded mountain ranges are the
    Appalachian Mountains, The northern Rocky
    Mountains, and the Alps in Europe.

14
Folded Mountains
15
Folded Mountains
16
Folded Mountains
17
Folded Mountains
18
Mountain Building
  • Mountains that are formed by tensional stresses
    are called fault-block mountains.
  • Most fault-block mountains are formed as a result
    of normal dip-slip faults.
  • When a normal fault occurs, a block of the
    earth's crust (the hanging wall) collapses,
    leaving behind a low-lying valley called a
    graben.
  • Graben is a German word for a ditch or trench.
  • The uplifted or higher elevated foot wall(s)
    is/are referred to as a horst(s).

19
Fault-Block Mountains
20
Fault-Block Mountains
21
Fault-Block Mountains
22
Mountain Building
  • Examples of fault-block mountains include the
    Teton Range of Wyoming, the Sierra Nevada Range
    of California, and the Basin and Range area of
    Nevada, Utah, and California.
  • A circular bulge or upwarping of the earth's
    crust is called a dome.
  • A circular dip or downwarping of the earth's
    crust is called a basin.

23
Fault-Block Mountains
24
Domes and Basins
Write a Comment
User Comments (0)
About PowerShow.com