Page 434 - Geosystems An Introduction to Physical Geography 4th Canadian Edition

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Orogenesis, or mountain building, is the result of plate interactions and related processes that thicken and uplift the crust, such as folding, faulting, and volcanism. Combined with weathering, erosion, and isostatic adjustment, these
processes produce the striking landscapes of Earth’s mountain ranges (GIA 13.1). Collisions of Earth’s plates produce three distinct kinds of orogenesis (GIA 13.2).
MAJOR MOUNTAIN RANGES AND OROGENIES
The mountain ranges we see today have roots deep in geologic time—some, such as the Appalachians, have repeatedly been formed, eroded away, and uplifted again as Earth’s plates interacted over hundreds of millions of years.
13.1
Three Sisters, Canadian Rockies, Alberta
[Bradley L. Grant/Getty Images.]
Rocky Mountains:
Formed mainly during the Laramide orogeny, 40–80 m.y.a., but also during several earlier orogenies, beginning 170 m.y.a. (including the Sevier orogeny)
Klamath Mountains, Oregon
[Spring Images/Alamy.]
Formed during the Nevadan orogeny, with faulting 29–35 m.y.a. (older batholithic intrusions date to 80 to 180 million m.y.a.)
Identify: What geologic event triggered the Alleghany orogeny, which formed the Appalachians?
Mount Katahdin, Maine
[WIN-Initiative/Getty Images.]
Appalachian Mountains:
Formed during the Alleghany orogeny, 250–300 million years ago (m.y.a.), when Africa and North America collided. Includes folded Ridge and Valley Province of the eastern United States and extends into Canada’s Maritime Provinces.
French Alps
[Calin Tatu/Shutterstock.]
Alps:
Formed during the Alpine orogeny, 2–66 m.y.a., and continuing to the present across southern Europe and the Mediterranean, with many earlier episodes (see Figure 13.15)
Sierra Nevada and Klamath Mountains:
Andes:
Chimborazo, Ecuador
[Michael Mellinger/Getty Images.]
Himalayas, Pakistan
[Microstock Man/Shutterstock.]
Himalayas:
Formed during the Himalayan orogeny, 45–54 m.y.a., beginning with the collision of the Indian and Eurasian plates and continuing to the present.
Formed during the Andean orogeny over the past 65 million years, the Andes are the South American segment of a vast north–south belt of mountains running along the western margin of the Americas from Tierra del Fuego to Alaska.
Visit the Study Area in MasteringGeographyTM to explore mountain building.
Visualize: Study geosciences animations of Assess: Demonstrate understanding of subduction zones and plate boundaries. mountain building (if assigned by instructor).
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