1. Mountain building & the evolution of continents
Chapter 20
Mountain building & the evolution of continents
Mountain belts
Mountain building
Continental accretion
Uplift, Basin and Range , Southern Rocky mountains

2. Study questions
What is the geologic history of the Basin and Range province and southern Rocky mountains?
What is an accreted terrane and where do they originate? What is the connection with plate tectonics?
What is the geologic history of the Himalayas and Appalachians?

3. 1) Mountain belts “Orogeny” = mountain building
Mountain belts = continuous mountain ranges
Huge horizontal forces in the crust build mountains
Signs of such forces: folding, faulting, metamorphism, igneous activity

4. 1) Mountain belts
many “young” mountain belts ( < 100 million years old)
Paleozoic and Precambrian-age mountains (> 250 million
Yrs old)
mountain belts usually parallel folded/faulted ridges
sedimentary or volcanic rocks, usually intruded by igneous bodies
- Western Americas
- Himalayas (45 million yrs ago)
- NW Pacific, etc
- Appalachians
- Urals
Fig

5. 2) Mountain building Convergent Boundaries
Ocean-ocean boundaries (Aleutian-type)
Generates a
volcanic arc
Ocean-continent boundaries (Andean-type)
1st: a passive continental margin (like east coast of US)
2nd: turns into an active margin, subduction initiates
3rd: deformation, metamorphism: 2 parallel zones:
accretionary wedge and volcanic arc

6. Himalayas 2) Mountain building
Subduction zones (convergent plate boundaries)
Continental collisions (examples: Himalayas, Appalachians)
Himalayas
Fig ,14,15

7. Himalayas 2) Mountain building
Subduction zones (convergent plate boundaries)
Continental collisions (examples: Himalayas, Appalachians)
Himalayas
Fig

8. Appalachians 2) Mountain building
Subduction zones (convergent plate boundaries)
Continental collisions
Appalachians
Valley and Ridge Province in Pennsylvania
Fig. 20.4

9. Formation of the Appalachians

10. 3) Continental accretion
Small island arcs or “mini-continents”
can be added to continents
Accreted crustal blocks= terranes
Example: Western N. America
Fig
Fig

11. 4. Uplift, Basin and Range, Southern Rockies
Fig. 20.5
See Fig. 20.6

12. Northern Rocky Mountains, British Columbia
Deformed sedimentary rock from continental shelf deposits displaced by
low angle thrust faults toward the interior of Canada.

13. Basin and Range
Fault-block mountain ranges and
rift valleys

14. 4. Uplift, Basin and Range, Southern Rockies
Current uplift or subsidence in the U.S.

15. Sample MC Where are the oldest rocks in North America located?
A. in the Appalachian Mountains
B. in the Basin and Range province
C. in the Canadian Shield
D. in the Rocky Mountains

16. Sample MC
In which of the following settings were most of the rocks of the interior platform of North America deposited?
A. in a continental rift
B. in a deep ocean basin
C. in an extensive shallow sea
D. in a volcanic island arc

17. Sample MC
Why is the North American Cordillera topographically higher than the Appalachians?
A. because the Appalachians have undergone less erosion
B. because the Cordillera formed by continent-continent collision
C. because the main orogeny in the Cordillera was more recent
D. because the spreading rate of the East Pacific Rise is greater than the spreading rate of the Mid-Atlantic Ridge

18. Sample MC
Which of the following processes is responsible for the topography of the Basin and Range province in western North America?
A. normal faulting
B. strike-slip faulting
C. thrust faulting
D. upwarping

19. Sample MC
In which of the following regions is new material currently being added to the crust?
A. Appalachian Mountains
B. Canadian Shield
C. Cascade Range
D. Rocky Mountains

20. Sample MC
Which of the following mountain belts formed as a result of a collision between two continents?
A. Appalachians
B. Himalayas
C. Urals
D. all of these

21. Sample MC What type of faults are depicted in the cross section?
A. normal faults
B. strike-slip faults
C. thrust faults
D. cannot tell from the information given