For #MountainMonday here is colorful Mount Perry, a peak in the northern Black Mountains of Death Valley National Park.
The hike to Mount Perry's summit starts at Dante's View and is pretty much "uphill both ways", with a distance of 8.5 miles. From Dante's View one first loses about 800 feet in elevation — and then has to gain it back. And the same on the way back out of course. 🤪
I've got some neat-o rock pix from near Death Valley. (Rock thread!)
These are from a pass will outside the park, between Chicago basin and Pahrump, NV. But this rock unit occurs in a remote part of Death Valley, too.
These particular rocks were float, not attached to bedrock.
This rock is part of a very old (>500 MYA) pre-Cambrian unit. It is pretty well silicified and has fractures filled in with more resistant minerals. They stand proud after erosion of wraker stuff.
Here is another example from same location. Also float.
This rock is a Cambrian carbonate from the Bonanza King formation. It is limestone/dolomite.
This rock was deposited in limey mud ooze. Built up in layers. (Horizontal in this image). Then fractured and those fractures eroded through dissolution.
Note how some of the straight-line fractures do not go all the way through the rock. Very orthogonal.
Now I'm gonna show you a special kind of rock. It is called "my favorite rock right now".
(Every geologist has one. Everyone should have one.)
This rock is a mix of rougher grayish carbonate and more smooth buff-colored carbonate-cemented mudstone parts.
The carbonate is a mix of limestone and dolomite. Dolomite formation is funky. Happened way after limstone deposited. Wetting and drying with magnesium-rich fluids changed composition. Dolomite holds finer structures.
Let's take a closer look at that carbonate rock, especially the gray dolomite parts.
There is A LOT of fun detail in there. Zoom in close and check it out. Those little tiny channels are called microkarren. They form from super thin sheets of liquid (like dew) condensing and dissolving bits of rock as it creeps down due to gravity.
Here is an image of pyramid-like star dunes in the western part of Mesquite Dunes in Death Valley during a windstorm. These are accessible from the Mesquite Dunes parking area. It is usually pretty crowded.
But we are going to check out the far eastern area of Mesquite Dunes. There is a small parking area over there that is rarely visited. You can wander into the dunes and interdunes and find some especially interesting features....
Here is a picture of two crescent shaped barchanoid dunes in the E Mesquite sand dunes. The wind went from image right (S) to image left (N). The steep face indicates the downwind side.
There are smaller transverse ripples. The steeper face of the ripple also indicates downwind direction from image right to left.
Ripples are easier to make. They indicate most recent sand grain moving wind direction. Dunes are harder, they indicate a bigger wind that moved lotsa sand.
At the western star dune area of Mesquite Dunes, the sand isn't moving very much. The dunes shift shape, but don't move much. The big star dunes make a local wind pattern that moves sand around the peak of the big star dunes. So the center is locked in place and the arms might move around a bit.
At the eastern end of Mesquite Dunes, the transverse dunes move around. Usually north, then south, back and forth. So the bulk sand doesn't leave area but it moves more here.
In the eastern part of Mesquite Dune field, it seems like a simple story. Sands all bulk move in one direction.
But when you walk out there it is beautifully complex.
Look at these transverse ripples going up this barchanoid dune as you'd expect. Dune creeping image left (S) to right (N). Cool.
But then look at the ripples in front of slip face. They indicate hyper-local grain transport away and to right from camera. (To NW). Bizarre!
Dune influencing wind direction!
Here is another part of sand deposition story. It is a little creosote bush trapping sand the downwind part.
From looking at ripple patterns, we can see wind direction was from image back left to image front right.
As the wind wraps around the bush, there is a dead zone behind the bush. Right there the wind decrease and drop their sand load, building up that little fine sand pile behind the bush.
Wind and depostion in this area are going every which way. Very complicated.
Here is an example of former deposition layers inside a dune, maybe very slightly cohesive from dampness or sats, now being re-exposed by wind.
These were paper-thin and fragile. (And very satisfying to crunch by hand.) They were like sugar wafers. A little stronger wind and they will either carve up or get blasted away.
As blow-out basins expand and coalesce, you get interdune landscapes like this with little remnant mesaa. Those are areas that were between the coalescing blow-out basins
Eventually. They will erode down too. But by then maybe blow out basins will start on the next laya level down.
This is why Death Valley National Park is such a nice analog for Titan science. It has a lot of processes going on that modifies the landscape. Pluvial (rainfall), fluvial (overland flow), karstic (dissolving and underground flow) and eolian (wind), lacrustine (lake), and evaporitic (chemical precipitation).
And depostion and erosion happening.
Its really neat wandering out here and trying to imagine how Titan would be similar or different, and why.