Page 432 - Geosystems An Introduction to Physical Geography 4th Canadian Edition

396 part III The Earth–Atmosphere Interface
Horst Graben (upfaulted block) (downfaulted block)
◀Figure 13.13 Faulted landscapes. [(b) Neal Herbert.]
(a) Pairs of faults produce a horst-and-graben landscape.
(a) DEM shaded relief map with the Basin and Range Province within the red outline.
States and Canadian Maritime Provinces— formed during the Alleghany orogeny, 250–300 million years ago (m.y.a.), associated with the col- lision of Africa and North America
• Rocky Mountains of North America—formed mainly during the Laramide orogeny, 40–80 m.y.a., but also during several earlier orogenies, begin- ning 170 m.y.a. (including the Sevier orogeny)
• Sierra Nevada and Klamath Mountains of California—formed during the Nevadan orogeny, with faulting 29–35 m.y.a. (older batholithic in- trusions date to 80–180 million m.y.a.)
• Alps of Europe—formed during the Alpine orog- eny, 2–66 m.y.a., principally in the Tertiary Period and continuing to the present across southern Europe and the Mediterranean, with many earlier episodes (see Figure 13.15)
• Himalayas of Asia—Himalayan orogeny, 45–54 m.y.a., beginning with the collision of the India and Eur- asia plates and continuing to the present.
(b) Horsts and grabens result from normal faults in Canyonlands National Park, Utah.
120° W 42° N
40°
38°
36°
120°
118°
116°
114°
Alluvial fans
Bolson
Horst
Playa Graben (central salt pan) Bajada
(b) Parallel faults produce a series of ranges and basins. Infrequent precipitation events leave alluvial fan deposits at the mouths of canyons; coalesced alluvial fans join to form a bajada.
118°
116°
114°
42°
40°
38°
36°
(c) A playa in Death Valley, California.
Playa
(d) Parallel mountain ranges, bolsons, and playas in Nevada.
▲Figure 13.14 Landforms of the Basin and Range Province. [(a) gSFC/NASA. (c) Robert Christopherson. (d) Bobbé Christopherson.]
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