Learning Objectives (LO) Lecture 13: Mountain Building Read: Chapter 10 Homework #11 due Tuesday 12pm What we ll learn today:! 1. Define the types of stress that are present in the crust! 2. Define the 3 stages of strain! 3. Compare volcanic, fault-block, and fold-thrust mountains! 4. Describe the origin of the Basin and Range Province!
Mountain Building
3 Types of Mountains Volcanic Mountains: Built by accumulation of volcanic materials Fold and Thrust Belts: Built by compression stresses Fault Block Mountains: Built by extensional stresses
Crustal rocks can be bent, stretched, and broken deformation is caused by directed stresses
Stress describes the sense of forces acting on a rock Stress can be: Tensional (stretching) Compressive (shortening) Shear (side-to-side)
Styles of rock deformation that result from stress! Joints: Fractures without displacement Folds: Bending deformation of rocks Faults: Fractures with alongfault displacement
Strain is the change in the shape or the volume of a rock caused by an imposed stress San Andreas Fault, California
Temperature Confining Pressure Rate of Strain What factors govern the amount and type of deformation? Presence of Water Composition of the Rock
Faults Fault planes are edges of a broken block of crust
Major Types of Faults Dip-Slip and Strike-Slip faults Dip- Slip Faults Strike- Slip Faults
A dip-slip fault separates a hanging wall from a footwall
Dip-Slip Faults Reverse Normal
Normal Faults
Folds
Fold Terminology Anticline Syncline Plunging Anticline
Syncline: convex downward with younger rocks in the center of the fold Anticline: convex upward with older rocks in the center of the fold
Evolution of a fold into a reverse fault
3 Types of Mountains Volcanic Mountains: Built by accumulation of volcanic materials Fold and Thrust Belts: Built by compression stresses Fault Block Mountains: Built by extensional stresses
Volcanic Mountains
Volcanic Mountains
Volcanic Mountains The Cascades of the Pacific Northwest
3 Types of Mountains Volcanic Mountains: Built by accumulation of volcanic materials Fold and Thrust Belts: Built by compression stresses Fault Block Mountains: Built by extensional stresses
Fold and Thrust Mountains Compressive stresses cause: Low-angle thrust faults High uplifted mountain ranges Folding of rock layers
Fold and Thrust Mountains The Himalayas Collision of India with Eurasia caused compressive stresses. These stresses raised the Himalayas and Tibet.
70 Million Years in 2 Minutes: The Himalayas Forming https://www.youtube.com/watch?v=hushoq6gv5y
Earth s Tallest Mountains: The Himalayas https://www.youtube.com/watch?v=pdrmh7rwupq
Fold and Thrust Mountains The Appalachian Fold Belt Folds belts in Pennsylvania
The Appalachian Fold Belt
The Appalachian Fold Belt
3 Types of Mountains Volcanic Mountains: Built by accumulation of volcanic materials Fold and Thrust Belts: Built by compression stresses Fault Block Mountains: Built by extensional stresses
Fault Block Mountains
Fault Block Mountains: Tensional Stresses
Basin and Range Province, Western USA
Basin and Range Formation https://www.youtube.com/watch?v=owjt_wjkrbo
Basin and Range Province Subduction of a seafloor spreading center about 25 millions year ago. After subduction extension continues on the continent. Horst and graben structures developed
Crustal Extension Formed the Basin and Range Province Horst and Graben structures result from crustal extension
Action Items for Tuesday October 13 1. Read Chapter 10 2. Complete homework assignment #11 What you should know from today:! 1. Define the types of stress that are present in the crust! 2. Define the 3 stages of strain! 3. Compare volcanic, fault-block, and fold-thrust mountains! 4. Describe the origin of the Basin and Range Province!