Another geology-related diary. This location was visited on the afternoon July 31st, 2013, the same day as the visit to Devils Postpile and the tufa formations at Mono Lake.
Panum Crater is the remains of a rhyolitic volcano that erupted 600-700 years ago. It is located to the south of Mono Lake and represents one of the more recent eruptions of the Mono-Inyo crater sequence. (The uplifting of Paoha Island in Mono Lake and some other features around the lake are additional and more recent activity.)
Panum Crater is considered a textbook rhyolitic volcano in part due to the interior lava dome(s) that formed and built up never overran the surrounding tephra ring of ejected material. Therefore the dome and ring are clearly separate. (USGS link to page on Panum Crater with a nice explanation on crater formation and how the magma characteristics drive the volcano’s type and formation. And a link to the Wikipedia page on the Mono-Inyo Craters which provide some nice satellite and aerial photos of the formation along with further background.)
No real nature observations to add. It was afternoon and very little was stirring in terms of insects, birds, etc. And there are few plants growing on the dome and cone; some brush and a few pine trees that I guess have found pockets of soil.
A few closing comments regarding the hike itself. First, the outer ring is mainly loose pumice, sand, and small stone. It’s like walking on a beach, except in this case it’s a hilly beach. A bit tiring in the hot sun and altitude. The inner dome is rocky, and often uneven and thus you need to keep track of where you are putting your feet. And this area gets very hot in the sun and there is little to no shade anywhere. Make sure you have water, sun block, and the appropriate clothing on. (Though I expect anyone doing hikes out this way is already taking proper precautions.)