2009 earthquakes

On 3 October 2009, a series of earthquakes up to magnitude 5.2 occurred on the eastern edge of the Golden Trout Creek volcanic field.

Tunnel volcanic center

3 phases of eruptive activity occurred at the Tunnel volcanic centre. A small cinder cone about 15 m high was constructed on a low ridge of quartz. Olivine-rich basalt erupted from the central vent adjacent to the quartz ridge and flowed over the low rim of the crater to the north and south, forming layers of porous basalt flows rich in gas bubbles and 3 m thick.

South Fork volcanic center

3 eruptive phases occurred at the South Fork volcanic center. Vesicular basalt flows, 3 m thick, were erupted to the west and southwest from the base of South Fork cone, west along Golden Trout Creek. These flows disappear under overlapping younger lavas from the Groundhog Center. Strombolian activity built a cinder cone, known as the South Fork Cone. The cone is 200 m above the present river. South Fork cone is breached on the north side.

Groundhog volcanic center

5 eruptive phases have been recognized at at Groundhog volcanic center:

1) In the first phase highly fluid basaltic magma was erupted from vents near the present western base of Groundhog cone. These flowed to the west along the north side of the valley of Golden Trout Creek and diverted the river. The lava flows filled a 270 m deep gorge at the junction with Kern Canyon almost completely.
2) The second phase were lava fountain eruptions from fissures on the south side of Toowa Valley.
3) The third phase of eruptions from the Groundhog center were black basaltic aa lava flows covering nearly 3 square miles of Toowa Valley. The eruptive vents were arranged in a circle around the Groundhog cinder cone.
4) The fourth phase of volcanic activity were lava fountains that built the 270 m high Groundhog cone itself, composed of scoria, ash and bombs. Spindle bombs of up to 2 m in diameter can be found from this eruption.
5) The last eruption of the Groundhog volcanic center erupted a single olivine-rich basalt lava flow, which erupted from the central vent inside the crater and flowed north through the breach.
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Source: R.W. Webb, Volcanic Geology of Toowa Valley, Southern Sierra Nevada, California. Geological Society of America Bulletin, April 1950, v. 61, p. 349-357

Little Whitney volcanic center

5 eruptive phases have been identified at Little Whitney volcanic center:

1) The first eruptions erupted a large basaltic lava flow, about 7 m thick, from fissures northeast of the present cinder cone. The lava flow reached 100 m from the vent and displaced a small river to the east.
2) During the second phase of activity, a large basalt flow was erupted.
3) The third phase built a small basaltic cinder cone on a bedrock ridge, extending southeast across the head of Little Whitney Meadow.
4) In the 4th phase, a smaller inner cone of scoria was built.
5) The last phase consisted of extrusion of a small basaltic lava flow from a breach in the souther wall of the outer cone. The flow reached about 50 m distance.