|
Geologic Trip, Mammoth
Area Owens Gorge The Owens Gorge is a steep-sided canyon
that has been cut by the Owens River through thick deposits of the Bishop
Tuff between Lake Crowley and Bishop, California. The pillars that line the
walls of the gorge, as shown in this photo, are formed by columnar jointing
within the Bishop Tuff. The Bishop Tuff was deposited in this area
during the eruption of
the Long Valley volcano 760,000 years ago when 150 cubic
miles of superheated ash was expelled from the volcano. Some of this eruptive material flowed down the flanks
of the volcano as clouds
of hot volcanic ash and some of these ash flows extended south down the Owens Valley as
far as Big Pine. The Volcanic Tableland that covers much of the
Owens Valley from Lake Crowley to Bishop is formed from these ash flows. The Bishop Tuff over
the Volcanic Tableland was welded into an extremely hard rock while the ash
flows were still hot. _____ |