Copyright Information: All images are in the public domain and available for free. If you use this image, credit NOAA/NGDC, M.R. Mudge, U.S. Geological Survey. |
A view of the reverse fault in a roadcut on the west side of French Gulch just south of the Sun River in Lewis and Clark County, Montana, as it appeared in 1966. This reverse fault places the lower beds of the Castle Reef Dolomite (light gray) onto the Flood Shale member of the Blackleaf Formation (dark gray). The fault dips 60 degrees W, and the overlaying strata dip about 50 degrees W. The black shales beneath the fault are badly crumbled, whereas the carbonate beds above it are undisturbed. Image Credit: M.R. Mudge. U.S. Geological Survey Through the study of faults and their effects, much can be learned about the size and recurrence intervals of earthquakes. Faults also teach us about crustal movements that have produced mountains and changed continents. Initially a section of Earth's crust may merely bend under pressure to a new position. Or slow movement known as seismic creep may continue unhindered along a fault plane. However stresses often continue to build until they exceed the strength of the rock in that section of crust. The rock then breaks, and an earthquake occurs, sometimes releasing massive amounts of energy. The ensuing earth displacement is known as a fault. This slide set describes the mechanism and types of faulting. It illustrates a variety of fault expressions in natural and manmade features. |
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