Chapter 9
Chapter 9: Crags, Cracks, and Crumples: Crustal Deformation and Mountain Building
Animation
An oblique air photo shows the San Andreas Fault displacing a creek flowing from the Tremblor Range (background) into the Carizzo Plain, California. The sketch shows what a geologist sees looking down on the San Andreas Fault. For more information, see “Recognizing Faults” starting on p. 248 and Figure 9.9c in your textbook.
A road cut in the Rocky Mountains of Colorado shows a fault offsetting strata in cross section. Note that the fault is actually a band of broken rock about 50 cm wide. The sketch shows what a geologist sees looking at the Rocky Mountain road cut. For more information, see “Recognizing Faults” starting on p. 248 and Figure 9.8 in your textbook.
The photo shows a thrust fault, on which a distinct layer has been offset. A geologist’s sketch emphasizes the offset. For more information, see “Recognizing Faults” starting on p. 248 and Figure 9.9b in your textbook.
What a geologist sees looking at a train of folds exposed in sea cliffs in eastern Ireland. Note that the axial planes of these folds are not vertical. For more information, see 9.5 Folds: Curving Rock Layers starting on p. 249 and Figure 9.12 in your textbook.
Layers of rock can wrinkle or contort into a series of wave-like curves that geologists call folds. Not all folds look the same—some look like an arch, some like a trough, and some have other shapes. This animation examines how two types of folds are formed. View 1 illustrates the formation of a flexural-slip fold, and View 2 shows the formation of a passive-flow fold. For more information, see 9.5 Folds: Curving Rock Layers starting on p. 249 and Figure 9.14 in your textbook.
What a geologist sees looking at a small fold formed by flexural slip. Note that the sedimentary beds maintain the same thickness around the fold. For more information, see 9.5 Folds: Curving Rock Layers starting on p. 249 and Figure 9.13 in your textbook.
What a geologist sees when looking at a small flow of folds exposed in northern Scotland. Note how rock flowed into the hinge zone of the fold. For more information, see 9.5 Folds: Curving Rock Layers starting on p. 249 and Figure 9.13 in your textbook.
A stream cut shows axialplanar cleavage; a geologist’s sketch of the stream cut. For more information, see 9.5 Folds: Curving Rock Layers starting on p. 249 and Figure 9.12 in your textbook.
The photo shows schistosity oriented at a low angle to the direction of shear. Note how large grains are all parallel to each other. A geologist’s sketch of the outcrop shows shear movement. For more information, see Section 9.6 Plate Foliation in Rocks starting on p. 253 and Figure 9.15a in your textbook.
When two continents collide, the resulting compression shortens and thickens the continental crust so that a large mountain range develops. This animation is a continuation of the 1e “Process of Subduction” animation.For more information, see Section 9.7 Uplift and the Formation of Mountain Topography starting on p. 254 and Figure 9.16 in your textbook.
The Himalaya Mountains and other important highlands of southern Asia are a consequence of the collision of India, a small but very old and strong block of continental lithosphere, with Asia about 55 million years ago. For more information, see Geology at a Glance: Collision of India with Asia on pp 256-257 in your textbook.