Friday Rocks #10: Stretch Pebble Conglomerate

Here we have a stretch pebble conglomerate that records strain undergone by the rock. Stress on the rock has flattened and stretched the pebbles, giving them a long lozenge shape in cross section.

Forgive me, but I could not find my notes on this formation. I know that I took this photo outside of Death Valley, California.


On Climate Change, Glaciers, and the Rock Record

Paul Hoffman (Department of Earth and Planetary Sciences, Harvard University) is one of the best orators I’ve seen. When I saw this talk by Paul Hoffman at McGill last year I was completely blown away. Not by the science, but by his skill as a story-teller. Paul Hoffman didn’t just tell us why we know the climate is changing, he told us the history of how we got to where we are today in our understanding of climate and Earth’s history. He started with the history of our understanding of glaciers, through the development of the “Snowball Earth” hypothesis, and the importance of the geologic record in climate science.

The talk is about an hour long and well worth it. Find it at the link below.

Paul Hoffman at McGill Redpath Freaky Friday Talk

Friday Rocks #9: Pinnacles Volcanic Formation

Photo by Tim Sherry

The Pinnacles Volcanic Formation, south of Hollister, California, hosts flow banded rhyolites, rhyolite breccias, and massive rhyolite. Pinnacles is separated from similar rocks of the Neenach Volcanic Formation, which sits on the opposing side of the San Andreas Fault. These unique volcanic formations give geologists a “piercing point” for determining at least some of the offset on the San Andreas Fault, namely the offset since the volcanics were deposited in the Miocene. Using the Pinnacles and Neenach piercing points, geologists know that there has been at least 314 km of displacement on the San Andreas Fault since the Miocene.

Matthews, Vincent. “Pinnacles-Neenach correlation: A restriction for models of the origin of the Transverse Ranges and the Big Bend in the San Andreas fault.” Geological Society of America Bulletin 84.2 (1973): 683-688.

Friday Rocks #8: Eureka Valley Sand Dunes

Photo by Tim Sherry

Wow, almost forgot about today’s Friday Rocks! because thesisjail, so this one is quick.

The Eureka Valley Sand Dunes in Eastern California are “booming” sand dunes. Under the right humidity conditions and if enough sand avalanches downslope, soundwaves from the falling sand are amplified and making booming sound.