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: Folds: Faults: Fractures without Bending deformation Fractures with along- displacement of rocks fault displacement Strain is the change in the shape or the volume of a rock caused by an imposed stress

San Andreas Fault, California What factors govern the amount and type of deformation?

• Temperature

• Confining Pressure

• Rate of Strain

• 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 Anticline: convex upward with older rocks in the center of the fold

Syncline: convex downward with younger 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 • Collision of India with Eurasia Mountains caused compressive stresses. • These stresses raised the The Himalayas 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!