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Thrust faults and related structures in the crater floor of Mount St. Helens volcano, Washington

Geological Society of America Bulletin

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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

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Thrust faults and related structures in the crater floor of Mount St. Helens volcano, Washington
Series title:
Geological Society of America Bulletin
Volume
101
Issue:
12
Year Published:
1989
Language:
English
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
First page:
1507
Last page:
1519
Number of Pages:
13