| Abstract: | A lava dome was built in the crater of Mount St. Helens by intermittent intrusion and extrusion of dacite lava between 1980 and 1986. Spectacular ground deformation was associated with the dome-building events and included the development of a system of radial cracks and tangential thrust faults in the surrounding crater floor. These cracks and thrusts, best developed and studied in 1981-1982, formed first and, as some evolved into strike-slip tear faults, influenced the subsequent geometry of thrusting. Once faulting began, deformation was localized near the thrust scarps and their bounding tear faults. The magnitude of displacements systematically increased before extrusions, whereas the azimuth and inclination of displacements remained relatively constant. The thrust-fault scarps were bulbous in profile, lobate in plan, and steepened during continued fault movement. The hanging walls of each thrust were increasingly disrupted as cumulative fault slip increased. -from Authors |
| Genre: | Article |
| ProdID: | 70015304 |
| Citation Author: | Chadwick, Jr, W. W.; Swanson, D. A. |
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| Citation End Page: | 1519 |
| Citation Issue: | 12 |
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| Citation Language: | English |
| Citation Larger Work Title: | Geological Society of America Bulletin |
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| Citation Number Of Pages: | 13 |
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| Citation Search Results Text: | Thrust faults and related structures in the crater floor of Mount St. Helens volcano, Washington; 1989; Article; Journal; Geological Society of America Bulletin; Chadwick, Jr, W. W.; Swanson, D. A. |
| Citation Start Page: | 1507 |
| Citation Volume: | 101 |
| Citation Year: | 1989 |
| Type: | citation/reference |
| Text: | Thrust faults and related structures in the crater floor of Mount St. Helens volcano, Washington; 1989; Article; Journal; Geological Society of America Bulletin; Chadwick, Jr, W. W.; Swanson, D. A. |
| URL (THUMBNAIL): | http://pubs.er.usgs.gov/thumbnails/outside_thumb.jpg |
| Date Other: | Sun, 1 Jan 1989 00:00 -0600 |
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