Learning Objectives (LO) What we ll learn today:!

Transcription

1 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!

2 Mountain Building

3 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

4 Crustal rocks can be bent, stretched, and broken deformation is caused by directed stresses

5 Stress describes the sense of forces acting on a rock Stress can be: Tensional (stretching) Compressive (shortening) Shear (side-to-side)

6 Styles of rock deformation that result from stress! Joints: Fractures without displacement Folds: Bending deformation of rocks Faults: Fractures with alongfault displacement

7 Strain is the change in the shape or the volume of a rock caused by an imposed stress San Andreas Fault, California

8 Temperature Confining Pressure Rate of Strain What factors govern the amount and type of deformation? Presence of Water Composition of the Rock

9 Faults Fault planes are edges of a broken block of crust

10 Major Types of Faults Dip-Slip and Strike-Slip faults Dip- Slip Faults Strike- Slip Faults

11 A dip-slip fault separates a hanging wall from a footwall

12 Dip-Slip Faults Reverse Normal

13 Normal Faults

14 Folds

15 Fold Terminology Anticline Syncline Plunging Anticline

16 Syncline: convex downward with younger rocks in the center of the fold Anticline: convex upward with older rocks in the center of the fold

17 Evolution of a fold into a reverse fault

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19 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

20 Volcanic Mountains

21 Volcanic Mountains

22 Volcanic Mountains The Cascades of the Pacific Northwest

23 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

24 Fold and Thrust Mountains Compressive stresses cause: Low-angle thrust faults High uplifted mountain ranges Folding of rock layers

25 Fold and Thrust Mountains The Himalayas Collision of India with Eurasia caused compressive stresses. These stresses raised the Himalayas and Tibet.

26 70 Million Years in 2 Minutes: The Himalayas Forming

27 Earth s Tallest Mountains: The Himalayas

28 Fold and Thrust Mountains The Appalachian Fold Belt Folds belts in Pennsylvania

29 The Appalachian Fold Belt

30 The Appalachian Fold Belt

31 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

32 Fault Block Mountains

33 Fault Block Mountains: Tensional Stresses

34 Basin and Range Province, Western USA

35 Basin and Range Formation

36 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

37 Crustal Extension Formed the Basin and Range Province Horst and Graben structures result from crustal extension

38 Action Items for Tuesday October Read Chapter 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!