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Dr. Jeff Amato
Geological Sciences
8/26/08
GEOL 470Structural Geology
OUTLINE
Why structure is importantAn example of structural analysisEarth Structure
Time Scale
Why study structural geology?
How do we
explain the major features of the Earth?
Why are there mountains?
Matterhorn, Swiss Alps
How can solid rock flow like taffy?
Morcles Nappe, Swiss Alps
Where is the oil?
How do faults relate to earthquakes
Active mountain. front, Basin and Range Province, Nevada
Structural Hazards and Society
Structuralanalysisofapizza…
It all starts with field mapping
Brooks Range Foothills, AK
A basic tool: the geologic map
A structural cross section: Determine deep structure
from surface data
Summary:
Structures include:Folds, faults, jointsFoliations, lineations, shear zones
Structures are found at every scalePlate, mountain, outcrop, hand sample, thin section
Summary:
Structural geology is important to societyHelps to find resources and determine hazards
Summary:
Structural analysis is conducted through observation and interpretation:
Kinematics: What moved? How much? What direction?Dynamics: What forces and stresses were responsible?
Summary:
Geologic maps and cross-sections help visualize the big picture
Earth Structure
How many layers in the earth?
Two answers to this…
1) Compositional Classification
Each layer has same basic composition.
Crust
CrustMantle
Crust=low densityrock
Mantle = high density rock
Core= iron
2) Mechanical Classification
Each layer will consist of material that behaves the
same way under stress
Outer Core= liquid
Inner Core= solid
Mechanical Classification
Lithosphere Solid plates,resistant to flow
Plates are moving
Asthenosphere
Solid: flows under stress
Convection!
Outer Core
Inner Core
Liquid
Solid
Oceanic crust vs.
Continental crust
Why are the oceans deep, and the continents at high
elevations?
What is density? ()
mass (g)=
volume (cm3)
Density of different materials
Water: 1 g/cm3
Quartz: 2.3 g/cm3
Rocks: 2-3.5 g/cm3
Iron: 8 g/cm3
Lead: 11 g/cm3
Gold: 19 g/cm3
Density of different materials
Quartz: 2.3 g/cm3
Gold: 19 g/cm3
= 0.9 g/cm3
= 1.0 g/cm3
0 (km)Continental crust(2.8 g/cm3)
Mohodiscontinuity
Horizontal distance not to scale
Mantle(3.4 g/cm3)
Oceanic crust(3.0 g/cm3)
1020304050
Less dense continentalcrust floats on densermantle.
Continental crustis less dense thanoceanic crust.