Volcanic Eruptions

San Francisco Volcanic Field

Reported to have eruptions every several thousands of years from hot spots forming under the earths lithosphere, San Francisco's east side of the field is expected to have activity again in future, but not any time soon.

The field has mostly basalt cinder cones, but there are lava domes made up of rhyolite and dalcite as well. Can you tell what is what in the picture of the San Francisco Volcano Field? Why would the volcanoes be made of basalt and the domes be made of rhyolite? Thoughts?

Sunset Crater

The last time this young volcano erupted was less than a thousand years ago. Paleomagnetic evidence is said to point to a time frame of 1080 and 1150. At the time of eruption the ash and lapilli covered more then 2100 sq km forcing the local natives, the Sinagua Indians, to flee their homes.

Geronimo (San Bernadino) Volcanic Field

This is actually right in my playground. It last saw activity anywhere between 3.4 and 0.3 million years ago. Its volcanoes and fissures influence the formations of the area. In fact copper mining wouldn't be possible without the volcanic activity of 60 million years ago. 

The influence of volcanic activity can be seen all across the state of Arizona, from my home town of Morenci to the Grand Canyon. Even if my local volcanic fields haven't been active in recent history, and aren't as exciting as what you may find in Kilauea, their past history is pretty amazing. The lava flows from Hawaii are similar to what they would have been in Arizona.

The video link on the Kilauea eruption from 2018 is a good refresher for things found in this weeks' reading. Also, there is a lot of great information in all the links provided, so if you have time, give them a peek. I hope you enjoyed this week's blog.