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Rock ID With Willsey, Ep #4: Volcanic Rocks (andesite, dacite, rhyolite)

Shawn Willsey: Geology Explained

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Curious about some rocks you found? Confused about tuff, sandstone, basalt, or diorite? This engaging video series by geology professor Shawn Willsey helps you learn to identify common rocks. We cover each major group of rocks, showcase basic types, and interpret the fascinating stories of rocks in this immersive series.

Here in Episode #4, learn to describe and identify these common volcanic rocks: andesite, dacite, and rhyolite with geology professor Shawn Willsey.

Support these educational videos! Your generous support allows me to create more videos. Send support via:

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Click on the three dots above and then the "Thanks" button.
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Shawn Willsey
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Twin Falls, ID 83301

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Link to PDF of document: https://drive.google.com/drive/folder...

00:00 intro
00:30 overview
06:30 andesite
08:20 samples
10:42 dacite
11:46 samples
14:08 rhyolite
15:25 samples

20 Comments

@MrFmiller 3 years ago

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

@w4lauppe 3 years ago

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

@remorrey 3 years ago

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

@bobbycraigue725 5 months ago

Felsic = fel (feldspar) + sic (silica).
Mafic = magnesium + ferric/iron-rich.
Shawn Willsey, We greatly appreciate your geology videos! It’s hard for me being so old…it is like learning an entirely new language.

@roneldridge7991 3 years ago (edited)

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.

@stevengeorge5605 3 years ago

Thank you, Shawn!

@MountainFisher 3 years ago

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.

@stevenwolfson8699 3 years ago

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.

@Smiley_ASMR 2 years ago

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!

@spikes1092 1 year ago

The archaeological community thanks you

@stevebrooks1355 3 years ago

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

@rnayduch 11 months ago

Excellent series on rock ID. Thank you Dr Willsey

@BP_in_OR 3 years ago

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.