Wednesday, April 16, 2008

Under the Volcano: Changing the Emphasis

The classical and long-familiar view of Yosemite Valley from the end of the Wawona Tunnel has become so iconic that it is easy to forget how spectacular the individual elements of the view would be in any other setting (see Standing Underneath Volcanoes from a few days ago) . Since getting my first digital camera in 2001, I have been to Yosemite Valley 22 times, and I always take the same picture! It's true that every visit is different, with different clouds and light conditions, but it is hard to stand in front of one of the great panoramas of the world without trying to fit it all into a single picture. So, during the last few visits I tried to zoom in on a few of the pieces that make for such a rich tapestry.

Today, our view is of the lowermost Cathedral Rocks next to Bridalveil Fall (which at 620 feet provides the scale for the picture). The triangular shape of the cliff results from intersecting vertical joint sets. The cliffs are composed primarily of El Capitan granite (about 102 Ma), which is a coarse-grained, white to light-gray biotite granite and biotite granodiorite containing quartz (gray glassy looking grains), orthoclase feldspar (white grains), and biotite mica (black grains)..

Exfoliated Sentinel Dome can be seen at the top of the photograph. The Glacier Point Road pulls to within a quarter mile or so of the summit, and it is an easy climb for an incredible payoff of a view (see some future post!).

Update on the Earthquake Watch: didn't feel any of them today, but the Historical Geology Class got to see an incoming quake on the seismometer this evening. It was probably the 6.5 magnitude quake in the Andreanof Islands in the Aleutian chain. 29 years and 364 days to go....

1 comment:

Silver Fox said...

Quite a nice zoom in of Bridalveil Falls - Yosemite is such a great place for photos.

[Hmm... Haven't been there since 2000 in non-digital days. Grew up in Sacto - we went there often. Have a hard time getting past the increase in crowds, nowadays.]

Great granite!