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+--- Thread: Salt Polygons Are Caused by Convection (/showthread.php?tid=25805)
Salt Polygons Are Caused by Convection - DeathValleyDazed - 2020-11-24
Over at r/DeathValleyNP (reddit's forum for DEVA) some people were curious about the Badwater polygons. Rather than just spouting off like the non-expert I am as to why the polygons form I did some online research and discovered some new (Feb 2019) technical research on this topic performed at Badwater and Owens Lake. Here is the Conclusion from this research paper.
"Salt deserts are a common landform important for modeling climate-surface interactions and express a rich repertoire of patterns and dynamics. Here we have shown that, in order to model and understand the surface expression of salt deserts, it is crucial to consider it together with the subsurface dynamics. Specifically, we have explained the emergence of regular salt polygons, which are a common salt crust pattern, as the result of a convection process in the soil underneath. To prove the connection between surface and subsurface, we demonstrated consistent results from theoretical and numerical modeling, analogue experiments and field studies. We are able to explain the onset of pattern formation based on environmental parameters and the length scale expressed by the patterns. As such, we have shown how salt polygons are part of a growing list of geophysical phenomena, such as fairy circles, ice wedge polygons, and columnar joints, which can be successfully explained as the result of the instability of a dynamical process."
You can read the pdf document here:
http://salamandersociety.com/deathvalley/Salt-Polygons-2-2019.pdf
Or look at the site from which I obtained this pdf here:
https://www.researchgate.net/figure/Polygons-formed-by-salt-ridges-at-A-B-Owens-Lake-and-C-D-Badwater-Basin-in-Death_fig1_331034186
Now I'm off to learn more about "fairy circles, ice wedge polygons, and columnar joints" of which I know nothing even though I've probably crossed over them multiple times hiking around the Death Valley flats between the Panamint Mountains and The Black Mountains.
RE: Salt Polygons Are Caused by Convection - MojaveGeek - 2020-11-25
There's some great columnar jointing at Devil's Postpile. Giant's Causeway in Ireland is pretty famous. Here is some pretty cool columnar jointing in adesite I came across on Mt. Rainier last summer. Those joints are big - the sections are about a foot and a half to two feet across, and break off into chunks that are scattered around on the ground. All moss covered - this is on the aptly named Emerald Ridge.
![[Image: rainier_columns_shrunk.jpg]](http://www.media.mit.edu/~geek/webpix/rainier_columns_shrunk.jpg)
RE: Salt Polygons Are Caused by Convection - DeathValleyDazed - 2020-11-25
(2020-11-25, 05:03 PM)MojaveGeek Wrote: There's some great columnar jointing at Devil's Postpile. Giant's Causeway in Ireland is pretty famous. Here is some pretty cool columnar jointing in adesite I came across on Mt. Rainier last summer. Those joints are big - the sections are about a foot and a half to two feet across, and break off into chunks that are scattered around on the ground.
OK, who stacked the spaghetti straight up?
Seriously, MG, I appreciate your adding knowledge about the columnar joints. I've driven by The Devil's Post Pile several times now but am so anxious to get to DEVA I have not yet stopped in to take a peek. Your image of Mt. Rainier columns is amazing. Thanks for taking the time to post up this information.
RE: Salt Polygons Are Caused by Convection - Candace66 - 2020-11-25
On the topic of columnar joints, I got to visit the ones at the Gawler Ranges NP in Australia. They're reddish, and reportedly made of rhyolite. The largest formation of them, accessible via 4WD track and a short hike, is called The Organ Pipes:
Organ Pipes pics
RE: Salt Polygons Are Caused by Convection - DeathValleyDazed - 2020-11-25
(2020-11-25, 07:09 PM)Candace66 Wrote: On the topic of columnar joints, I got to visit the ones at the Gawler Ranges NP in Australia. They're reddish, and reportedly made of rhyolite.
Candace you are fortunate to see those formations. In DEVA per the NPS fact sheet there exists rhyolite around the Strozzi's Ranch but while hiking the area i don't recall any "organ pipe" like formations.
[b]Strozzi’s Ranch Rhyolite "Tr[/b]"
Pliocene-Oligocene
Mostly resistant, gray, white, and tan, rhyolitic lava flows and volcanic domes, and subordinate ashflow and airfall tuff. Includes many rhyolite and lesser trachyte and comendite masses, many of them associated with calderas.
Eocene and Paleocene
Granitic intrusions and volcanics, not known to be represented by sedimentary deposits.
https://www.nps.gov/deva/learn/nature/geologicformations.htm
Does anyone know if columnar formations exist in DEVA?
I just happened to be watching the latest video on a YouTube channel named "Astrum" which focuses on space topics. He mentions and shows close ups of an area on Pluto called "Sputnik Planitia" where convection creates polygonal cells. You can see them at about minute 6:30 here:
https://youtu.be/GMIbZ2k_OtQ
DEVA is other worldly in more ways than one!
RE: Salt Polygons Are Caused by Convection - MojaveGeek - 2020-11-25
The Organ Pipes look awesome!
I don't know of any in DV but I'm not a geologist. I have seen some in the Red Cliffs area just outside St. George, though there we not anywhere near as good as the ones I saw on Rainier. And some nice stuff on the highway just a bit west of Yakima, WA. You need a place where there was volcanic flow with certain conditions of slow (?) cooling I think. We have lots of volcanics in DV but I don't know of any good flow areas. Anyone?
RE: Salt Polygons Are Caused by Convection - GowerGulch42 - 2020-11-27
(2020-11-25, 09:50 PM)MojaveGeek Wrote: The Organ Pipes look awesome!
I don't know of any in DV but I'm not a geologist. I have seen some in the Red Cliffs area just outside St. George, though there we not anywhere near as good as the ones I saw on Rainier. And some nice stuff on the highway just a bit west of Yakima, WA. You need a place where there was volcanic flow with certain conditions of slow (?) cooling I think. We have lots of volcanics in DV but I don't know of any good flow areas. Anyone?
There's volcanics of all shapes and sizes across the greater DV region, but I don't know of any with well-defined columnar jointing. They generally prefer a thick flow, and most of the basalts and other volcanics are pretty thin. Lots more rhyolites than just the rhyolite tuff at Strozzi.
I think the coolest columnar joints in the area are at Owens Gorge. It's not too common to find columnar jointing in welded tuff, but the Bishop Tuff is an uncommonly interesting volcanic unit!
RE: Salt Polygons Are Caused by Convection - Kauri - 2020-11-27
(2020-11-27, 12:46 PM)GowerGulch42 Wrote: I think the coolest columnar joints in the area are at Owens Gorge. It's not too common to find columnar jointing in welded tuff, but the Bishop Tuff is an uncommonly interesting volcanic unit!
I just googled Owens Gorge--wow! I've been to Mammoth many times, but never knew about that spot, so will need to check it out sometime.
RE: Salt Polygons Are Caused by Convection - DeathValleyDazed - 2020-11-27
(2020-11-27, 04:11 PM)Kauri Wrote:(2020-11-27, 12:46 PM)GowerGulch42 Wrote: I think the coolest columnar joints in the area are at Owens Gorge. It's not too common to find columnar jointing in welded tuff, but the Bishop Tuff is an uncommonly interesting volcanic unit!
I just googled Owens Gorge--wow! I've been to Mammoth many times, but never knew about that spot, so will need to check it out sometime.
Wow, Andrew and Candice, thanks for pointing out the Owens Gorge columns. This link has some stunning images of the formations. I had no idea these were there and have not heard of the Owens Gorge near Bishop. One reason I love this forum is how much I learn from all of you.
http://geotripper.blogspot.com/2010/09/columns-on-columns-other-jointing.html