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Wilson Butte erupted at the north end of the Inyo chain (note Highway 395 in lower right) between 1350 and 1200 years ago. Like the most recent series of lava flows erupted during the Inyo eruptions 650 to 550 years ago, the Wilson Butte dome (above) was erupted shortly after a period of explosive eruptions that generated pyroclastic flows, surges, and vertical eruption columns. Scientists have determined that during the most recent eruptive episode, significant explosive activity along the Inyo chain ceased before lava flows were erupted. If this pattern holds during the next eruption along the Mono-Inyo chain, the most serious hazards will occur early in the eruption; the risk from volcanic hazards would diminish significantly once lava begins spreading across the ground. Nevertheless, the steep sides of thick rhyolite lava flows like Wilson Butte can collapse to form small pyroclastic flows and surges as far as 5 km from the flow. During such collapse events and when gas is released from vents atop the flow, small ashy plumes may rise several hundred meters above the ground. |
