V. Geological and
Biological Information on Crater Lake Area
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E. Points of Geological Interest
in Crater Lake National Park
6. Llao Rock
This great mass of dacite (a sluggish lava) was
produced from a vent somewhere on the upper slopes of Mazama and hardened after
moving only a mile or two. The dacite filled in a former explosion crater. This
rock rises nearly 2,000 feet above the water--the highest vertical precipice on
the rim- -and was formed by the most massive single flow apparent in the caldera
wall, with a maximum thickness of 1,200 feet.
