GREAT SALT LAKE — One of the strangest and most striking places in Utah — an enormous oddity that scientists say was created accidentally by human engineering — is getting a bit of a remodeling job.
Union Pacific Railroad is beginning a bridge-building project to replace a small portion of a causeway that's been blamed for a half-century of disruption in the natural circulation of the Great Salt Lake.
Experts say the railroad causeway built across the lake in 1959 led to the formation of a vast plate of hardened salt covering hundreds of square miles — probably one of the largest man-made objects on Earth. It surrounds and evidently underlies nearly the entire north arm of the lake.
"The construction of the causeway has created the necessary conditions for the salt to form," said Andrew Rupke of the Utah Geological Survey who has been conducting studies on the so-called salt crust that developed in the last 56 years.
In a written statement, Union Pacific acknowledged that the "causeway is a factor in the condition of the north arm, but we have not conceded that the causeway is the sole cause of those conditions. There are other factors that contribute" to the problem.
To someone flying over the lake's north arm in a helicopter, shoreline areas look surprisingly like an Arctic coastline with broken chunks of sea ice. Scientists standing on the salt crust could be mistaken for explorers heading to the North Pole.
Almost everything in the region is some shade of white. No living things — plants or animals — are visible for many miles in every direction. It's essentially a landscape made up almost entirely of hardened salt and water that's at the theoretical limit of extreme saltiness.
The overall impression? It has the appearance of a weird, alien planet.
"Alien is probably a fair way to describe it," Rupke said. "It's definitely not like any place that we've worked."
Rupke and Utah Geological Survey scientist Taylor Boden have been drilling into the hardened salt to measure its thickness and chopping out chunks of salt for laboratory analysis. Normally, most of it is under water.
"The low level of the lake has provided us with a unique opportunity to study the salt crust," Rupke said, "so we're taking advantage of that."
The "salt crust" is a vast sheet of salt, hard as a rock, like pavement extending over the region and under the 20-mile-wide north arm. In places it's just a few inches thick. Previous studies have found places under the waters of the lake's north arm where the hard deck of salt is far, far thicker.
"Eight feet thick of salt," Rupke said. "Previous studies suggest that the salt crust is under the entire north arm of the lake."
Under the water, the salt crust is like the hard floor of a swimming pool with virtually no silt, mud or organic material. The vast pavement of salt — in or out of the water — is what gives the region its strangeness and even a sort of beauty.
"I've never worked in any place quite like it," Boden said. "It has a stark beauty to it that is seen nowhere else that I've ever been."
The region's lonely scenery — so stark and unusual — could easily be mistaken for a unique natural wonder. But scientists say it is not a work of nature. They say it resulted from the causeway's division of the lake into two distinctly different bodies of water. Due to its impact on water circulation, experts say, the causeway lowered the salt concentration in the south arm and raised it dramatically in the north arm. For many years, the north arm has been as salty as nature will allow.
"The salinity levels of the north arm are 26, 27 percent," Rupke said. "At that point there's just so much salt in the water that you start forming salt crystals."
When the 20-mile long railroad short-cut was built across the Great Salt Lake, stretching from Promontory Point to the western shore of the lake, it isolated the north arm from sources of fresh water. Crucially, the three major rivers that flow into the Great Salt Lake — the Jordan, the Weber and the Bear — all feed the south arm.
For 56 years, the north arm has received nearly all its water from the south arm through openings cut into the causeway. A railroad bridge crosses one large opening near the west end of the causeway. There were also two box culverts, but Union Pacific closed the culverts in the last couple of years because of stability and maintenance issues.
Around the world, salt lakes are formed when a lake has no outlet. Salts and other minerals are flushed in from the mountains by rivers; centuries of evaporation make the lake water saltier and saltier. But since 1959, the south arm has had an outlet: some of its water flows north, under the causeway and into the north arm. That set up an unnatural condition in which south arm salts are flushed into the north arm; the south arm became relatively less salty while evaporation in the north arm created an extreme salt environment.
The discrepancy has created some interesting visual effects. On the south side, the rocks of the causeway are black. But on the north side there's a white bathtub ring on the rocks at the water's edge. It's pure crystallized salt.
The water in the lake's north arm has a distinctly red or pink tinge. It's due to a salt-loving species of bacteria, Boden said. "Apparently it tolerates extraordinarily high salinity levels and is able to exist in this harsh environment."
The salt crust itself seems hostile to life. Its surface is littered with the carcasses of beetles, grasshoppers, praying mantises and other insects that are seemingly preserved in salt.
North arm water also has a strange look to it at times because — often — it's unusually smooth. On a day when light winds generate millions of ripples on the south arm, the water just across the causeway can be perfectly flat — as smooth as glass. Boden said it's because north arm water is so dense with salt.
"It's heavy. It doesn't move," Boden said. "It takes quite a wind to get it stirred."
The scientific studies by Boden and Rupke are aimed at getting baseline data so experts can monitor the salt crust as it changes over time.
"The ecology here, the environment out here is a delicate balance," Boden said.
It's possible the studies might influence state and federal policies. The discrepancy in saltiness affects the biology of the lake, which supports millions of migrating birds every year as well as the multi-million dollar brine shrimp industry. Several industrial operations on the lake also depend on the lake's salts and minerals.
"Salinity levels throughout the lake matter," Rupke said. "I mean they matter to industry, they matter to the ecology and to the various organisms that live in the lake."
Union Pacific's plan is to create a new 150-foot-wide opening in the causeway. A new 180-foot railroad bridge will be built to span the opening. It's not clear how much of an impact there will be on water and salt circulation.
In the company's written statement, Union Pacific said the project would mitigate the effects of reduced circulation between the two arms of the lake. "The new bridge is designed," the company said, "to replace the loss of water and salt transfer that resulted when it was necessary to close two large box culverts in the causeway that were failing."
The company commenced work on the project on Oct. 1 and plans to complete construction by the end of 2016.
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