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.