1. Education

Stop 6, Putnam Peak Basalt: The Setting

By

Stop 6 is at 38°31.042´N, 122°03.361´W on route 128. This view is across the road. (more below)
Lava visitors from far away
Photo (c) 2006 Andrew Alden, licensed to About.com (fair use policy)
The Putnam Peak Basalt is a widespread lava flow that occurs as landslide blocks in this locality, but elsewhere it is in coherent beds. Stop 6 is a pullout next to some large blocks of basalt. These rocks were recently shown to be the same flows mapped as the Lovejoy Basalt in the Sierra Nevada—that is, they were erupted more than 200 kilometers away and flowed all the way here, probably in just weeks, around 16 million years ago. This gigantic flood basalt is thought to be one of the first products of the great eruptive center that lies under Yellowstone today. Its eruption is part of an age of prodigious volcanism in the Miocene, as the crust of the western United States broke up forming the Basin and Range province between eastern California and central Utah. We will see more of the Lovejoy later in the trip. At the time of the eruptions, the Coast Ranges did not exist and the Sierra was a range of low hills next to a wide coastal lowland.

Day 1, Coast Range: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9

Day 2, Sierra Nevada: 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18

Day 3, Sierra Nevada: 19 | 20 | 21 | 22 | 23 | 24 | 25 | 26 | 27 | 28

Day 4, Coast Range: 29 | 30 | 31 | 32 | 33

©2014 About.com. All rights reserved.