Status Updates From Geology Underfoot in Yosemi...

Chapter 16, “Soda Springs”, starts with a concise explanation of how the isotopes of hydrogen and oxygen are crucial in understanding the climate record. Good to see here; I found the idea fascinating in «The Long Thaw» a few years ago.

Referring to tree stumps in Tenaya Lake and Mono Lake:
❝Each ring of stumps contains individuals with at least fifty growth rings, meaning that each drought lasted at least fifty years — they were megadroughts.❞
Disturbing, in an era of climate change that seems to be exacerbating drought in the western U.S.: droughts that lowered the height of these lakes for long enough for trees to grow unhindered for decades.

❝To illustrate this, we borrow an analogy from Jeff Mount’s California Rivers and Streams (a must-read for anyone interested in surface water).❞

❝The largest rock avalanche deposit in Yosemite Valley is located in Tenaya Canyon. […] The total volume of material is estimated to be about […] 34 million tons. […] The violence of such an event is almost unimaginable.❞
Imagine turning all that rock into dynamite. The largest atomic bomb released the energy of 50 megatons. Humans are capable of destruction far exceeding any terrestrial event.

❝Large boulders such as these are simply too big for the river to transport, even during floods, so they constrict it and are probably responsible for the river’s gentle character upstream of the constriction. Rock debris dams are relatively common in steep river canyons such as this.❞
I’ve seen this forever, and hypothesized such an effect, but I never traced it back to causes I could have understood.

❝[P]ark guidelines stipulate that no new building shall be placed on talus slopes.❞ Uhm, ya think?
Fascinating, if only for the frequent Yosemite enthusiast. First published in 2010, though. If only it had shown up in 1990 and I had found it?