Rock Identification with Willsey: Volcanic Rocks (andesite, dacite, rhyolite)

Learn to identify and describe andesite, dacite, and rhyolite (three common volcanic rocks) with geology professor Shawn Willsey. Part of my ongoing series on some easy and practical ways to identify and interpret rocks.

Support these videos! You can ensure these videos continue by providing support (travel logistics, content creation, etc.)

or Venmo @Shawn-Willsey (be sure to put two L's in last name)

or a good ol' fashioned check to this address:
Shawn Willsey
College of Southern Idaho
315 Falls Avenue
Twin Falls, ID 83303

[wlauppe]

Great informative series of rock lectures. Keep them coming.. Thanks

[MrFmiller]

Another outstanding video. You keep putting them out and I keep learning.

[roneldridge]

I’m chasing porphyritic dikes in my area for gold and Rhyolite in cascades for cool rocks, and I found my first tourmaline samples hiking east of cottage Grove in Andesite . A tremendous amount of work trying to identify them, this is definitely the best and less complicated way of explaining it.

[remorrey]

Really appreciate your videos. At 76 I'm still able to learn about the rocks we had in Southern Utah. Thank you.

[MountainFisher]

Interesting presentation Shawn. I used to live in Mammoth and Bishop for a couple of years and all kinds of volcanic rocks I didn't know the names of and now I do.

[stevenwolfson]

Thanks so much for putting these videos together! Great way to help folks at least being to differentiate the more subtle differences in rock groups.

[Rachel.]

Yay team! Terrific class that I must watch again to ... I hope... remember. Love the samples. Thank you Shawn!

[macking]

one reason knowing rocks is important “On San Miguel Island, rocks dating 50-30 million years ago contain well-rounded pieces of rhyolite that are chemically identical to the rhyolite found in similar age deposits in San Diego county. The inference is that these pieces of rhyolite reached the islands in a submarine fan deposit when the islands were positioned off the coast of San Diego. Analysis of the direction of the currents flowing at that time shows that they came from a southerly direction. However, the only possible source of these sediments is from the mainland, which lies to the east of the islands, giving geologists one more reason to believe that the islands have rotated 90-100 degrees in the last 20 million years.” (nps channel islands)

[Smiley_ASMR]

These are SO helpful for the igneous section of my petrology class!! I can look at charts and rocks all day but having you go through a few variations of each type and ways you can identify them is so so so necessary for me to remember it!!!! Thank you thank you thank you!

[nitahill]

Understanding how porphyry works has been a problem for me. I think your identification was extremely useful. You make things very understandable.

[leslie]

Thank you, Shawn, once again. I am having trouble remembering the names so I created this pneumonic:
Red Dogs Are Buffalo
For Ryolite Dacite, Andesite Basalt
Still working on one for
Granite, Granodiorite, Diorite, Gabbro
Maybe
Giant Giraffes Dig Gabbros! Haha

[stevebrooks]

Thanks Shawn
Started watching your vids when you did Bonneville Floods and area- always fun and informative I appreciate your joy at bringing info to us--- keep expanding my vocabulary 😀 I dig this rock shyte

[henryx]

Really like this lecture, Big thank you!

[branni]

Shawn your videos are so instructive and helpful. I've learned so much about the land and it's formation. Thanks again!

[davidk]

Thanks Shawn, great info. These are great companions to your field videos. Maybe link these to field videos where indicated.

[BP_in_OR]

There's some dark-toned Dacite up in the Cascades near where I live and it looks similar to the andesites you show in the vid except for the vague, faint purplish hue it has.

[labeef]

Love your channel Professor. Mega thanks for your expertise. I’ve learned a lot.😊😊😊

[markthomas]

Solid info, clear and quick presentation.

[grandparocky]

very much enjoying your series. Best rock ID videos I have seen!

[PlayNowWorkLater]

This is such a great series! So helpful.