Vicky Veritas

Slickensides

Slickensides form on rocks in fault planes as the rocks scrape past each other. They are polished surfaces with parallel (to fault motion) striations or grooves called slickenlines. This can happen suddenly during an earthquake, or gradually during creep.

Below are some slick (and famous) slickensides with mirror surfaces from San Francisco. More detail on these slickensides from Callan Bentley’s great AGU blog, Mountain Beltway: https://blogs.agu.org/mountainbeltway/2015/12/28/corona-heights-fault-san-francisco/

Bonus: See a collection of slickensides and more information from our own Andrew Alden @alden https://www.thoughtco.com/gallery-of-slickensides-4122857

#slickensides #slickenlines #EarthQuakeFaults #rocks #geology #ScienceMastodon @geology

Corona Heights Fault, San Francisco

At the end of the AGU Fall meeting, Callan visits the Corona Heights "mirror" fault, renowned for its gorgeous slickensides. Explore the site in photos in GigaPans.

Mountain Beltway
Dec 20, 2022 at 8:26pmWeb
Show threadJessTheGeologistDec 21, 2022
@vickyveritas what a beautiful fault! 🤩
Show threadVicky VeritasDec 21, 2022
@DrRocktagon Tis! Thank you!
Show threadTim N7KOMDec 21, 2022

@vickyveritas @DrRocktagon last week I uploaded an old video of that fault, the Corona Heights Faults, to my YouTube channel. I think this is circa 2011 maybe 2012... That's @keepitrheol giving everyone the lowdown.

https://youtu.be/ApczXVI_h7g

Corona Heights Fault Slickensides | San Francisco Geology

YouTube
Show threadVicky VeritasDec 21, 2022
@tsherrygeo @DrRocktagon @keepitrheol Priceless, Tim! Thank you.
Show threadberndandewegDec 21, 2022
@tsherrygeo @vickyveritas @DrRocktagon @keepitrheol is Corona Heights Fault parallel to Hayward etc? The it would be dextral as well.. I was trying to figure that out by the structures on the fault plane.
Show threadVicky VeritasDec 21, 2022
@berndandeweg @tsherrygeo @DrRocktagon @keepitrheol It’s motion is a bit oblique right lateral, but the Corona Heights fault is thought to be San Andreas related. Region-wide, the SAf and Hayward (Calaveras and others ) are right-lateral strike slip. Good question! Thanks, Bern!
Show threadTim N7KOMDec 21, 2022

@berndandeweg @vickyveritas @DrRocktagon @keepitrheol

Oriented NE-SW

Show threadChristie RoweDec 23, 2022
@tsherrygeo @vickyveritas @DrRocktagon I just want to point out that Jamie and I still have those jackets. Anyone want to Fault Party @ Corona Heights around AGU in 2024?
Show threadTim N7KOMDec 23, 2022
@keepitrheol @vickyveritas @DrRocktagon 🙌🙌🙌
Show threadLaura HollisterDec 23, 2022
@tsherrygeo @keepitrheol @vickyveritas @DrRocktagon Can Ryan and I join?
Show threadTim N7KOMDec 23, 2022
@Xeno_lith @keepitrheol @vickyveritas @DrRocktagon yes!
Show threadLaura HollisterDec 23, 2022
@tsherrygeo @keepitrheol @vickyveritas @DrRocktagon Woo hoo! 🎉 🎈
Show threadTim DawsonDec 23, 2022
@keepitrheol @tsherrygeo @vickyveritas @DrRocktagon We totally need a AGU Corona Heights fault party in 2024. Maybe AGU should sponser and rent out the Randall Museum as event space.
Show threadChristie RoweDec 31, 2022
@timblor @tsherrygeo @vickyveritas @DrRocktagon Past years we just wander down to get some margaritas around Market and Castro which is a great way to find out whether people feel like they know what they saw or not!! I've definitely failed as a guide a few times, before I realized that some people imagine faults only in cross section with an offset marker. Seeing a messy anastomosing set of slickensides in a volume of messy breccias and no clear offset markers doesn't always click.
Show threadBarry GoldmanDec 21, 2022
@vickyveritas @alden i found one yesterday in Rosendale NY
Show threadVicky VeritasDec 21, 2022
@barrygoldman1 @alden Nice, Barry! Thanks for sharing it.
Show threadBarry GoldmanDec 21, 2022
@vickyveritas @alden limestone
https://blackskimmer.blogspot.com/2022/12/my-third-species-of-calcite-growth-this.html
My Third Species Of Calcite Growth, This Time Possibly Grown By a Biofilm Of Algae and Who Knows Who Else!

 I found these blobby calcite growths on a Limestone outcrop in Rosendale, NY, (North East  North America) right behind the (defunct) Rosend...

Show threadVicky VeritasDec 21, 2022
@barrygoldman1 @alden Thanks, Barry!