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GEOL 470
Structural Geology
OUTLINE
Dr. Jeff Amato
Geological Sciences
8/26/08
Why structure is important
An example of structural analysis
Earth 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
Structural
analysis
of
a
pizza…
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, joints
Foliations, lineations, shear zones
Structures are found at every scale
Plate, mountain, outcrop, hand sample, thin section
Summary:
Structural geology is important to society
Helps 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
Crust
Mantle
Crust=
low density
rock
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
Asthenosphere Solid: flows
under stress
Outer Core
Liquid
Inner Core
Solid
Plates are
moving
Convection!
Oceanic crust
vs.
Continental crust
Why are the oceans deep,
and the continents at high
elevations?
What is density? (r)
mass (g)
r=
volume
3
(cm )
Density of different materials
Water:
Quartz:
Rocks:
Iron:
Lead:
Gold:
1
2.3
8
11
19
g/cm3
g/cm3
2-3.5 g/cm3
g/cm3
g/cm3
g/cm3
Density of different materials
Quartz:
Gold:
2.3
19
g/cm3
g/cm3
r = 0.9 g/cm3
r = 1.0 g/cm3
Less dense continental
crust floats on denser
mantle.
0 (km)
10
20
30
40
50
Oceanic crust
(3.0 g/cm3)
Continental crust
is less dense than
oceanic crust.
Continental crust
(2.8 g/cm3)
Mantle
(3.4 g/cm3)
Horizontal distance not to scale
Moho
discontinuity