Mountain Building

1
Chapter 20

• Mountain Building

2
Crust-Mantle Relationship

• Topography change in elevation
• Used to determine elevation of earths crust
• 70 below sea level
• Density
• More dense (oceanic crust) surface will sink
  less dense (continental crust) surface will float

3
Isostasy

• Isostasy displacement of mantle by continental
  and oceanic crusts
• Crust are in equilibrium because of gravity
  pushing downward and buoyancy pushing upward
• Getting into and out of a boat

4
Isostasy Erosion

• Erosion
• As mountains are eroded ? mass decreases roots
  become smaller because they are pushing upward to
  make up for the loss of mass
• Isostatic rebound slow process of earths crust
  rising as the result of the removal of mass from
  the crust
• Seamounts individual volcanic mountains formed
  from plates moving over hot spots

5
Orogeny

• Orogeny process that forms mountain ranges
• Orogenic belts broad, linear regions of
  deformation associated with plate boundaries
• Convergent boundaries
• Oceanic-oceanic convergence
• Crust of island arc forms roots
• Displacement of mantle by roots that provides
  buoyancy for a mountain peak

6

• Oceanic-continental
• As continental plate pushes upward, orogeny
  occurs
• Roots form to support mountains formed
• Magma forms and pushes up sediments causing
  metamorphosed rocks to form
• Continental-continental
• Magma that forms due to collision results in
  batholiths
• Marine sedimentary rock forms

7
Appalachian Mts.

• Divided into regions based on rocks
• Early formation
• 700-800 million years ago due to convergence
• Figure 20-11 on page 533

8
Divergent-Boundary Mts.

• Magma rising from ocean ridges is forced upward
  causing an upward push in the lithosphere forming
  a gently sloping mountain range
• Ocean-ridge rocks
• Igneous rocks
• Pillow basalts formed from magma rising and
  pushing through dikes and erupting on seafloor

9
Nonboundary Mts.

• Uplifted mountains
• Large regions of earth slowly forced upward
• Uplift is not well understood
• Adirondack Mts plateaus
• Fault-block mountains
• Large pieces of crust are tilted, uplifted, or
  dropped downward between large faults
• Grand Tetons Basin Range Province
• Volcanic Peaks
• Formed by hot spots
• Hawaii

10
Closure

• Use the following terms to create a concept map
  that contrasts the mountain types discussed in
  this section
• uplifted mountains
• solitary volcanoes
• form as a result of hot spots
• result from tension
• form at divergent boundaries
• show little structural deformation
• ocean ridges
• fault-block mountains

11
Answer to Closure