Michael J. Malaska Profile picture
Dec 27, 2021 28 tweets 11 min read Read on X
Going to thread up some pix from today's #geology hike at #VasquezRocks.
(Why are those rocks right there? We'll get to that...) 🧵 In midground, tilted sandstone rocks lit up by the setting s
Here is a descent into a canyon in S end of park. That's where the geology story gets really wild.
Here's a view of a tree from a ridge where I measured strike and dip of the layers using a compass. Yellow green fall foliage tree lt up by back-angle sun. In f
Here is a zoom out view of the scene. It is hard to tell in the photo, you really have to be there, but those layers bend. The strike changes from 180 degrees at left to about 160 degrees at right. This is the hinge axis of a subtle synclinal fold. Sandstone layers above a valley. A yellow geology field note
Here I am standing at another location on the same hinge axis. But am now looking up a valley with a reverse fault. Can you see the fault? Looking at rock layers up a steep valley. Youa are looking g
Here is an annotated zoom of that scene. See that straight line where the color of the rocks don't match up? Also that big rock face right in line? Yup! That is a fault!
If you click to expand the photo you can see where I added yellow lines to show the fault location. Zoom of tbe previous scene of light tan sandstone layers in
Here is hiking out of that area. This is roughly in line and to the west of that fault, and also sorta in line with that hinge. The hinge is no longer obvious, nor is the fault, so something has changed here. It is complex! Orange fall foliage trees n a  canyone. Sandstone layers in
Setting sun lights up some of the highest rocks of #VasquezRocks County Park.
(So....why are those rocks right there? Time for a little #Geology!) Setting sun lights up the red tilted rock layers of Vasquez
Maybe a better question, is not why those rocks are right there, but why aren't there other rocks in front of them or behind them?
It's counterintuitive, but Vasquez Rocks is a story of erosion, not uplift. Sandstone layers of Vasquez Rocks in the sun. In foreground,
#VasquezRocks is...a valley!!!
Whut? But those rock poke up, right?
OK, BUT look at the rocks to E (lower older strata), and the rocks to W (younger higher strata). They are both HIGHER!
(Pic shows lower strata hill at right)
Vasquez Rocks are weaker rock than surrounding hills!
So, #VasquezRocks eroded FASTER than surrounding hills. But some were a little less weak than others. So they poke up where other weak sandstones got worn down. Great example of differential erosion.
So that explains why some layers poke up more than others. They are less weak than the others.
(But the higher volcanic hills at E end of park are still much stronger...)
So tha explains layers, but why those layers there, but not in front or behind??
Well, gotta look at topo...
Here's a map I made using #QGIS of the #VasquezRocks area. The park boundary I roughly indicated in black (may not be super accurate.) I colorized ASTGTM2 dem data, to highlight topography in near the park area. What do you see?
("479" is near one of those Big Rocks)
There is an overall pattern of valleys running SW to NE, going up valley to the NE. This is part of a much bigger pattern in this area of Southern California. Is orthogonal to spine of several mountain ranges, themselves controlled by being parallel to big faulting.
Big picture.
But now look closely, inside park boundary. Two parallel valleys go up SW to NE, but that high stuff is right between them. Aha, they are a drainage divide! They were sorta protected from erosion into a deeper valley! So maybe not just stronger, but actually just lucky!
And you can see little green valleys on either side of the layer as the weaker sandstone erodes out (see! I told you they are weak!). So eventually, they gonna erode down, just slower than everything else*.
*except the stronger hills on either side.
But...there's one more thing. See this area I've highlighted in red outline? Look at the topo. It's kinda high (yellowish) and also about the same level in that outline area.
(ignore that same elevation area at S edge, that is CA Highway 14. nice and level. Built up and roadcut.)
We're gonna look closer. Fortunatly, I've got a field notebook entry from what that wierd long plateau thing looks like on the ground. Here is that location called "470" on the same map. Is right in that zone.
And here is a ground image from "Station_470". The view is looking S. (that high hill in back right above the layers? Yeah that's the less eroded stronger materials younger than Vasquez Rocks sandstone.)
Boy is that plateau FLAT! almost....flat like a streambed, amiright? view of high plateau. flat path, with few rocks. off to the
This plateau is part of the Pacific Crest trail, is a nice plateau so you see a nice view of Vasquez Rocks on one side, and then a really steep valley to the S.
(A lot of my distant shots of Vasquez Rocks are from this plateau.)
Notice that really really really red dirt...
Here is an even closer view of Station_470 rocks.
What the.....???
Those rocks are round! Like they travelled a ways! And dark! And full of little vesicles. Like the older volcanics that are uplifted and make up the hills on E end of park!!! rounded dark heavy rocks on trail. Evidence of erosion and t
Ohhhhh! So now we can put it together. That high plateau....used to be a VALLEY!
A long time ago, there was a valley (going NE down to SE) cutting through sandstone rocks. It carried volcanics from the E through the valley and plopped them here...
(must've been an impressive stream, some of those transported and redeposited rocks are pretty big. Not just gravels and cobbles....)
And it covered up sandstone at underneath the streambed. At some point, the stream shifted (my guess is just to S to make that deep valley). And left a filled valley of rounded volcanic rocks and gravels. Then erosion kept happening. And Vasquez Rocks sandstone is really weak..
So the sandstone eroded, but the stronger volcanic steambed fill DID NOT.
Differential erosion again!
Since the streambed didn't erode, but the landscape around it did, we get a remnant higher standing thin plateau!
Inverted topography!
#VasquezRocks #geology
By the way, this plateau really easy to get to. From the parking lots, just head S. Follow the largest trails (almost road sized) up to the top of the plateau. If the distance (0.5 km) and some rough-ish terrain isn't a problem, it is one of most accessible features in park.
This is why #VasquezRocks is such a wonderful park for #geology. It has great examples of layers, syncline, hinge axis, faults, differential erosion, inverted topography, and volcanics (all of you know where to look).
I love this place!
[/end thread] Sunset at Vasquez Rocks. Shadowed clouds with orange sky an

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More from @mike_malaska

Jan 14, 2022
This is one of the greatest images taken by humankind. It is the first (and only) time we ever landed on an Ocean World.

There is A LOT you can learn by looking a this image.

What did we see? What can we learn?
(thread)
🧵
Wow. Look at that sky. It's all orange. It's a moon that has an ATMOSPHERE. Orange stuff is from filtered, scattered light coming down through a chemical-laden atmosphere.

(No surprise, the probe came down through the atmosphere on a parachute.)
en.wikipedia.org/wiki/Atmospher…
The Huygens probe was not a lander. It was an atmospheric probe. It was, however, designed to survive a soft landing on the surface.
So it's primary goal was learning more about Titan's complex atmosphere. The landing was a really nice added bonus.
en.wikipedia.org/wiki/Huygens_(…
Read 33 tweets
Dec 25, 2021
"Decollage!" You ever hear a common word and you start wondering about it's origins?
The word "Decollage" is from french verb "decoller" - opposite of french verb "coller" - which means to glue or stick.
English translation is "take off" but maybe "unstick-ify" better.
(and when you were a kid, you made a "collage". Sticking stuff together on construction paper with glue sticks, right?)
So...here's where I ponder. I worked in France for 3 years doing solid-bound organic synthesis. We used the french words "accrochage" and "decrochage" to mean "attach" and "unattach" the molecules from their solid support. But the French verb "accrocher" means "to hook".
Read 4 tweets
Oct 31, 2021
This is hilarious!
"Because everyone knows that carbon can only have four bonds, right?"

(Well, that's kinda not true....)
[thread]
...and yes, I do find this photo hilarously nerdly. And am just gonna riff off it here.

It was drilled into my head in organic chemistry that "carbon can only have four bonds" and "Haha, you drew a pentavalent carbon! That is WRONG! Points off!"

But...it can have five bonds!
And how that works is very interesting, and maybe one of the most important things in the Universe for organic chemistry.

Carbon can have 4 sp3 hybridized orbitals around it in tetrahedral geometry. But, if you stick a proton on it, it can rearrange.
Read 20 tweets
Jun 5, 2021
“Astronomy and Astrology are pretty much the same thing.”
And with that, I’ve pretty much pissed off every amateur and professional astronomer. But, there are really strong and provable connections.
Strap in for a long thread, and a wild ride. [1/n]
(with side links to explore)
Astronomy makes observation of the heavens, and predicts/explains physical properties and timing of those objects.
Astrology makes observations of the heavens, and predicts/explains spiritual or human-centered properties and timing.
(Starting data same, applications different.)
Looking at history, astronomy and astrology pretty much the same until 1700's, when the Science and beliefs kinda split out. Astrology goes way back. Prolly every culture had their own “sky-watcher” to look at heavens and figure out what to do.
(en.wikipedia.org/wiki/Archaeoas…)
Read 33 tweets
Jun 4, 2021
Well, this is great news!
FDA approval for vaginal yeast infections!
fiercepharma.com/pharma/scynexi…
This comes from the company that I (and many others) helped found, back in 2000-ish. I was not directly involved in this, but my colleagues (led by a former post-doc of mine) made this happen.
I sat in on some of the meetings, and worked for the same client (Merck) on parallel projects.
This started as a modified derivative of a natural product molecule called enfumafungin.
Read 8 tweets
Nov 16, 2020
I learned something today in #astrobiology that just totally blew my mind.
There are microbes that eat....air. And can live on just....air.

[thread]
These microbes live in cold deserts...I mean really brutal cold deserts. Barren rocky ridges (not even tundra) in Antarctica.
There's really no free water - very dry. And dark for 6 months, too. So these microbes live where there isn't enough water for photosynthesis producers.
They live on the trace amounts hydrogen gas (H2) in the atmosphere (about 190 parts per BILLION), and CO (20 parts per BILLION). So these things are living on tiny tiny tiny amounts of stuff.
But...they are still living.
Read 16 tweets

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