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Classroom presentations to accompany Understanding Earth , 3rd edition. prepared by Peter Copeland and William Dupré University of Houston. Chapter 21 Deformation of the Continental Crust. Deformation of the Continental Crust. Deformation of continental crust.

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classroom presentations to accompany understanding earth 3rd edition

Classroom presentations to accompany Understanding Earth, 3rd edition

prepared by

Peter Copeland and William Dupré

University of Houston

Chapter 21

Deformation of the Continental Crust

deformation of continental crust
Deformation of continental crust
  • Since continents are not destroyed by subduction, we look here for the ancient history of Earth.
  • orogeny: sum of the tectonic forces (i.e., deformation, magmatism, metamorphism, erosion)that produce mountain belts
mountains and mountain building
Mountains and Mountain Building

Mountains are one part of the

continuum of plate tectonics—the most

evident one.

Example: Limestones at the top of Mount Everest.

structures of continents
Structures of continents

1) Continents are made and deformed by plate motion.

2) Continents are older than oceanic crust.

3) Lithosphere floats on a viscous layer below (isostasy).

age of the continental crust
Age of the Continental Crust

Blue areas mark continental crust

beneath the ocean

Fig.21.2

continental characteristics
Continental characteristics

• Granitic-andesitic composition

• 30–70 km thick

• 1/3 of Earth surface

• Complex structures

• Up to 4.0 Ga old

three basic structural components of continents
Three basic structural components of continents

• Shields

• Stable platforms

• Folded mountain belts

shields e g canada
Shields (e.g., Canada)

• Low elevation and relatively flat

• ”Basement complex" of metamorphic and igneous rocks

• Composed of a series of zones that were once highly mobile and tectonically active

stable platforms
Stable platforms

• Shields covered with a series of horizontal sedimentary rocks

• Sandstones, limestones, and shales deposited in ancient shallow seas

• Many transgressions, regresssions caused by changes in spreading rate

mountain belts
Mountain belts

• Relatively narrow zones of folded, compressed rocks (and associated magmatism)

• Formed at convergent plate boundaries

• Two major active belts: Cordilleran (Rockies-Andes), Alps-Himalayan

• Older examples: Appalachians, Urals

mountain types
Mountain types

Folded—Alps, Himalaya, Appalachians

Fault block—Basin and Range

Upwarped—Adirondacks

Volcanic—Cascades

indian subcontinent collides with tibet
Indian subcontinent collides with Tibet

40–60 million years ago

Fig.21.6b

accretionary wedge and forearc deposits thrust northward onto tibet
Accretionary wedge and forearc deposits thrust northward onto Tibet

Approximately 40–20 million years ago

Fig.21.6c

main boundary fault develops
Main boundary fault develops

10–20 million years ago

Fig.21.6d

effects of subsidence on venice
Effects of subsidence on Venice

Raised sidewalk

Fig.21.18