CH 11 Mountain Building

1
CH 11 Mountain Building

• Deformation all changes in the original shape
  and/or size of a rock body
• Stress - force per unit of area acting on a
  solid
• Strain change in shape of volume in a body of
  rock as a result of stress
• 3 factors that influence the strength of a rock
  and how it will deform
• Temperature and pressure, rock type, and time
• See pages 308 - 309

2
3 Types of Stress

• Tensional pulling apart in opposite
  directions (stretches)
• Compressional squeezed (shortens)
• Shearing rocks grind/slide past each other
  (distorts only)

3
Folds

• A bend in the rock resulting from stress
• anticline upfolding or arching of rock layers
• syncline - downfolding or troughs of rock
  layers
• monocline - a step-like fold in mostly
  horizontal rock layers

4
Joints and Faults

• Joints a break in the rock with no movement
• Fault a break in the rock with movement
• 4 Fault types
• 1. Normal from tensionhanging wall moves up
• 2. reverse from compressionHW moves down
• 3. Thrust from compressionlow angle reverse
• 4. Strike slip from shearingmoves horizontally

5
Mountain Types

• Orogenesis mountain building processes
• Classified by the processes that formed them
• Folded mountains
• From folding due to compression
• ex Appalachians, Alps
• Fault Block mountains (Horsts and Grabens)
• From huge uplift along faults
• ex Tetons
• Domes and Basins
• From upwarping due to magma rising
• ex Black Hills

6
Mountain Formation

• Convergent Boundaries
• Most common means
• From compression
• Three convergent boundary types
• Divergent Boundaries
• Along mid-ocean ridges
• Fault block mountains
• Non-boundary Mountains
• Hot spots
• Upwarped and fault block mountains

7
Vocab

• Accretion when crustal fragments collide with
  and stay connected to a continental plate
• Terrane a crustal block bounded by faults
  whose geologic history is distinct from
  surrounding blocks
• Isostacy the crust is floating on mantle in
  gravitational equilibrium
• Isostatic adjustment the response of the
  crust due to deposition or erosion