Tuesday, October 7, 2008

Hydrovolcanism within the Mono Basin

On my eastern Sierra trip, I saved the best hydrovolcanism for last. Mono Lake is a remnant of Pleistocene age Lake Russell. If you are a bird watcher, the lake is an important pit stop for birds on the flyway and three times saltier than the ocean. Over 13,000 years ago the lake was more than 800 ft deeper than present when Black Point (second photo) erupted. Black Point received its name for obvious reasons since it produced basaltic lava. I wish I had time to venture out to the area, but I did not. So I will just have to make another trip to see the fissures and palagonitic soil.

The current lake level is regulated because starting in 1941, the Los Angeles Department of Water and Power (LADWP) began diverting water from streams that filled the lake, this dropped the lake level dramatically, enough so to damage the gull population at the lake. So to make a long story short, LADWP, must now allow some water to be released back into the lake. For the full story, I recommend the book, Storm over Mono Lake, by John Hart. Instead my focus on Mono Lake for this blog entry is Paoha and Negit Islands. Negit Island (photo 3) is a 1,600 year old andesitic volcano that has had activity as recently as 270 years ago. Paoha Island (photo 4) is problematic, made up of lake mud sediments, it may be a bulge from unerupted magma or could have been caused by local faults in the area. Anyways, it dates around 300 years old.

My first photo is Panum Crater, the youngest volcano in the Mono Craters chain that erupted around 600 years ago. It is a type of volcano known as a tuff ring. Usually tuff rings are monogenetic but the geologic history of Panum Crater is more complex. The eruption started with a tuff ring, then a dome was built, but collapsed sending a debris avalanche into Mono Lake, then a second dome formed. In my photo, I show the place where the dome collapsed through the tuff ring into the lake. If ever in this area, there is a short trail that can be taken to the top of Panum Crater. The reward is great views of Mono Lake, the Mono Craters and the June Lake/Mammoth Lakes Area and a hike through obsidian.

Also recommended when in Lee Vining is the Mono Lake Committee store and the National Forest Visitor Center, which has great exhibits on Mono Lake and a balcony to view the lake. If hungry when passing through and wanting an old style burger or ice cream cone, eat at the Mono Cone. If gourmet food is in order, then stop at the Whoa Nelli Deli, try the fish tacos, they are tasty.

1 comment:

Silver Fox said...

Nice post about Mono Lake - and nice photos!