View is toward the east across the northern part of Long Valley Caldera. The caldera rim extends east from the Glass Creek flow (lower left) to Bald Mountain and Glass Mountain in the far distance. Lookout Mountain is behind the tree.

The volcanic rocks of both Bald Mountain and Glass Mountain were erupted before the caldera-forming eruption. Bald Mountain consists of a lava domes and flows of rhyodacite composition that were erupted between 3 and 2.5 million years ago. Glass Mountain consists of a 1,000 m sequence of lava domes, flows, and welded pyroclastic flows of rhyolite composition that were erupted between 2.1 and 0.8 million years ago.

Lookout Mountain and the Glass Creek flow were erupted after the caldera-forming eruption. Lookout Mountain is a rhyolite lava flow that was erupted within about 100,000 years of the caldera-forming eruption. Glass Creek flow was erupted about 600 years ago during the Inyo eruptions.