Figure 5. Pseudotachylyte. (sue' doe tack uh lite) A special kind of rock that is produced along a fault by frictional heating. Sudden fault motion can generate incredibly high temperatures which instantaneously melt a small volume of rock. The melted rock is injected into fractures in the adjacent rock, then solidifies. Most pseudotachylyte veins are very thin, measured in the millimeters. Though small, they are important. The presence of pseudotachylyte is evidence that there were sudden fault motions that produced sizable earthquakes in the geologic past. Show pseudotachylyte. (Photo by Henry Berry, Maine Geological Survey)

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Last updated on April 26, 2007

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