Shastina

Shastina was formed during a VEI-4 eruption around 7650 BC that also involved activity at the summit of Mount Shasta and the Red Banks on Shasta's south flank.

Geological features

Shastina has the general form of a smooth-sided cone truncated by a one half-mile (0.8 km) diameter summit crater, but with several geological features which make it unique among other volcanoes in the Cascade Volcanic Arc. The most prominent feature when seen from lowland viewpoints is Diller Canyon, a large cleft carved into the western flank by pyroclastic flows and since expanded by erosion. It extends from the crater rim near 12,000 feet (3,660 m) down for over 7,000 vertical feet (2,100 m) towards the town of Weed in the valley below, and is by far the largest such feature found on any of the Cascade volcanoes. Unseen except by mountaineers and fliers are the three small crater lakes nestled among the cones and ridges of the summit crater, which rarely melt free of snow until late summer. Clarence King Lake at 11,755 ft (3,583 m) occupies the center of the crater, while Sisson Lake lies at 11,793 ft (3,595 m) on the eastern side. Highest of all is an unnamed lake at over 11,960 ft (3,645 m) on the south side of the cinder cone which forms Shastina's true summit. These lakes are the highest subaerial lakes in the entire Cascade Range, exceeded only by the subglacial lake beneath the ice of Mount Rainier's summit crater.