Geology of the Ragged Mountain Reservoir

On this video 'field trip,' PVCC Geologist Callan Bentley shows off some of the cool Grenvillian "basement" rocks exposed at Ragged Mountain Reservoir near Charlottesville.

[@clintonmorris8222]

A very thorough and informative video. Thanks!

[@A-K_Rambler]

Thank you for Sharing!

[@Curated_Properties_Explores]

Just found your VA Geology video a couple days ago and diving in on the others now. Learning so much about my adopted state's geology. Have been exploring creek and river beds and finding really unusual rocks. Some I've seen in WA state (granites) and others in Colorado and Utah along faults. But here, so many unusual types in a relatively small area that I feel driven to learn more! Thank you for all the informative videos on VA and West VA, etc. Looking forward to more as you explore!

[@frannysinclair2613]

Thanks for pointing out the various contacts in the rocks. I enjoy hearing your comments on the geology of the eastern portion of our continent. My area of the hill country if Texas does not have much of interest since it is mostly limestone. Love watching you and Nick for some very interesting and informative lessons on the formation of our country.

[@tc5427]

Thank you Prof Bentley for such an informative video. Question why would the “blob” of darker more mafic material have smaller crystals than the surrounding granite? I would assume they are same temperature and thus cooled at the same rate…?

[@callanbentley]

"Same temperature" doesn't mean same rate. In general felsic minerals melt/crystallize at lower temperatures than mafic ones, so if you have an overall granitic magma, it could be significantly below the temperature at which mafic minerals are stable in a molten form - they "need" to crystallize at these lower temperatures while the ions that will eventually make their felsic counterparts are still swimming about, willy-nilly.

[@gwiz0042]

The peninsula rock outcrop tends to have a copper-color patina on it. Any idea what causes that?

[@callanbentley]

It's weathering (oxidation) of biotite rich layers.