Interesting facts about the mirabilite spring mounds near Great Salt Lake Marina

What are these white mounds and when did they form?

In late October 2019, as air temperatures started to cool to near freezing, unique mineral mounds began forming on the south shore of Great Salt Lake, just east of the Great Salt Lake Marina. They are not composed of common table salt (sodium chloride—NaCl), but mirabilite (hydrated sodium sulfate—Na2SO4•10H2O), also known as Glauber’s salt.

How do mirabilite mounds form?

When the sodium-sulfate-rich spring water hits the cold winter air, mirabilite crystals form and build up a collection of small terraces, similar in appearance to the travertine rimstone and dam terraces that form at Mammoth Hot Springs in Yellowstone National Park.

What conditions are needed for the mounds to form?

In the 1940’s, researchers investigated this area and reported finding a 3-6 foot thick mirabilite layer 30 inches down in the subsurface. Groundwater seems to be partially dissolving this mirabilite layer, which is then reprecipitated at the surface as the spring water emerges. Additionally, mirabilite is most stable and precipitates in sub-freezing dry environments. When temperatures rise above freezing, the impressive clear mirabilite crystals that form the mounds will dehydrate to form a white, powdery, easily eroded mineral called thenardite (Na2SO4). Furthermore, the mounds will only form if the area (at about 4194 ft) is above lake level, a rare occurrence until the past few years.

Why are there multiple mounds?

It is hypothesized that as the mounds grow, they eventually seal off their spring water source, causing the groundwater to find a new pathway to the surface, and thus, a new mound begins to form a few dozen yards away. As of January 2020, the beach has four mounds that have grown up to 3 feet tall and several yards wide.
   

How rare are mirabilite mounds?

The mineral mirabilite is quite common and found in saline lakes around the world, including the north arm of Great Salt Lake. In saline lakes, mirabilite crystals form in the water column, float to the surface, and are washed ashore to form an amorphous, slushy slurry or dune-like accumulations of crystals. However, spring-fed crystalline mirabilite mounds are rare―they have never before been scientifically documented at Great Salt Lake. Mirabilite-precipitating springs and the formation of terraced mounds have been documented in the Canadian Arctic, central Spain, and the Antarctic. These features are ephemeral; warmer spring temperatures will eventually turn the mirabilite to the powdery, easily eroded thenardite, if the rising lake level doesn’t erode the mounds first. These features may or may not reform again next winter.


Is there a Mars connection?

While Mars has conditions conducive to the formation of mirabilite (dry, cold, etc.), the mineral has not yet been documented there. Mars does have topographic mounds that some researchers believe may be related to saline groundwaters. In addition, orbital spectrometers have suggested the presence of sulfates on the surface. Because of these similarities, some researchers are interested in the growth of mirabilite mounds on Earth because they may serve as analogues for understanding geologic processes on Mars.


Don’t tread on me.

These mirabilite mounds are fragile and researchers are still actively studying them. Please do not walk on the mounds or collect samples. Besides, mirabilite is unstable at temperatures above freezing and dehydrates to form a white powder (thenardite), so the samples would not last more than a day.

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RARE MIRABILITE FORMATIONS FOUND ON GREAT SALT LAKE SHORELINE

One of the mirabilite mounds hanging over the water of the Great Salt Lake.

GREAT SALT LAKE STATE PARK — Park Rangers and Geologists have discovered four rare formations on the south shore of the Great Salt Lake – just north of the park and marina. Ranger Allison Thompson first noticed the salt formations in October 2019. As time passed, she noticed formations continue to grow and eventually she reached out to members of the Utah Geological Survey for their help.

After investigating, staff discovered that the mounds were, in fact, Glauber’s salt, also known as “mirabilite.” Researchers are particularly interested in the precipitation of mirabilite mounds because they may serve as analogues to similar features and conditions on Mars.

Mirabilite mounds are rare and have never before been documented at the Great Salt Lake. They have only been found at a few locations around the world – primarily in the Arctic.

Geologists have determined that the mirabilite is precipitating from warm, high salinity sulfate-rich springs, visible only when the lake level falls below an elevation of 4194 feet. A closer inspection of the mounds revealed that they are a built-up collection of crystallized terraces, similar in appearance to the travertine rimstone and dam terraces that form at Mammoth Hot Springs in Yellowstone National Park.

Water from the saline spring flowing through the top of a mirabilite mound.

As the mounds at the Great Salt Lake grow, they eventually seal off their spring source and a new mound will begin to form a few dozen yards away. Currently, the beach has four mounds that have grown up to 3 feet tall and several yards wide.

In addition to the requirement of saline spring waters with very specific chemical composition, mirabilite is only found in sub-freezing environments, such as those found in the polar regions of Earth.

When temperatures rise above freezing, the impressive clear mirabilite crystals that form the mounds at the Great Salt Lake will dehydrate to form a white powdery mineral call thenardite (NaSO4). As such, these mirabilite mounds will disappear with changing temperatures and the rising lake levels.

Staff at Great Salt Lake State Park will be offering guided tours of the mirabilite mounds to the public. These tours will be available this coming Saturday and Sunday (January 11-12, 2020) and will be available every half-hour each day between the 10 a.m. and 4 p.m. Those attending a guided tour are advised to wear water-resistant or waterproof boots as the lake water and mud can rise to mid-calf.

As research into these mounds continues, we are asking that members of the public do not damage these mounds or intentionally remove pieces of them.

An above view of one of the mirabilite mounds with a notebook shown for scale.

The four mirabilite mounds along the Great Salt Lake shoreline with the State Park gift shop in the background.

Utah’s fossil record is dino-mite!

Reporters Leia Larsen and Benjamin Zack sat down with James Kirkland to find out what Utah looked like 100 million years ago and learn about the discovery boom happening right now.

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www.standard.net

James Kirkland, the state paleontologist with the Utah Geological Survey, goes through the bones of a Mierasaurus on Nov. 21, 2017, at his lab in Salt Lake City. The fossils were recently found in Southern Utah and belong to a species of dinosaur that was previously thought to only live in what is now Europe.

Uniquely Utah: State employees compete to fill calendar with beautiful shots

fox13now.com

Employees with the Utah Department of Natural Resources work in every corner of the state, and every year they submit photos in the hope of being featured in an annual calendar.

Check out this week’s edition of Uniquely Utah:

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Living Rock from the Great Salt Lake, Now in our Permanent Exhibits

nhmu.utah.edu

In June of 2016, we added a new, living exhibit in the Great Salt Lake Gallery on the third floor of the museum. At first glance, the three stone-looking bumps in a tank aren’t as impressive as the Cretaceous monsters looming in the background. But their humble appearance masks what might be the most awesome creature on display: these lumpy guys are one of the oldest forms of life on Earth.

Utah aglow with new solar developments, rooftop systems

Did you see our 2016 Utah’s Energy Landscape is out? Read this feature on the new pub, and find the publication HERE.

deseretnews.com

Utah, identified four years ago by the U.S. Department of the Interior as one of six states in the country with prime solar potential, is riding a boom of new utility-scale developments harnessing the energy of the sun.

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Energy Success Stories: Discovering Utah’s Geothermal Potential

The Utah FORGE team collaborated with the Utah Governor’s Office of Energy Development to produce this video short highlighting Utah’s vast geothermal potential.

Check out the Utah FORGE Facebook to follow updates on the projects!

City seeks grant to stabilize blue clay slide area, purchase homes for demolition

stgeorgeutah.com

City officials are anxiously waiting to find out if they will receive a $1.6 million Federal Emergency Management Agency grant to purchase properties and stabilize a hillside that has destroyed homes and is threatening others.

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Utah Geologists win national award

heraldextra.com

The Utah Geological Survey recently garnered a 2016 National Award for Excellence from the Western States Seismic Policy Council (WSSPC) Board of Directors in partnership with the Northeast States Emergency Consortium (NESEC), the Central U.S. Earthquake Consortium (CUSEC), and the Cascadia Region Earthquake Workgroup (CREW).

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Low water in Great Salt Lake reveals ‘rocks that are alive’

We hope you all had a great and safe Thanksgiving! Who ate so much turkey that they feel like a turkey? I think I do. Here’s a little something to help you kickstart after a long, holiday weekend—
A couple of our geologists here at the UGS helped a team of researchers collect microbialites from Great Salt Lake for the Natural History Museum of Utah. Read more about these living rocks in this great write up.

sltrib.com

As Utah’s Great Salt Lake continues to drop during recent years of drought, something strange and wonderful is coming into focus in the shallows and exposed lake bed.

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