Monday, August 27, 2012

Salt Lake City: The Great Salt Lake and Antelope Island

If you look at this map of the United States, you will readily see the Great Salt Lake in Utah, the largest lake in the US west of the Mississippi River. Only the Great Lakes are larger. But this was not always so because the Great Salt Lake is a small remnant of the huge Ice Age Lake Bonneville, which encompassed 20,000 square miles. By comparison, the Great Salt Lake today comprises only 2,000 square miles. Still, it is massive enough that the entire state of Rhode Island and the Hawaiian Island of Oahu could fit inside the lake with room to spare.

The Great Salt Lake
Most lakes contain fresh water, but because it has no outlet, the Great Salt Lake is filled with water so salty that in some parts the salt content is 25%. Imagine filling a glass ¼ full of salt and then adding water to the top of the glass. The lake is divided into three parts--the southern arm, the northwest arm, and the northeast arm. Because it is so salty if you swim in the Great Salt Lake you can easily float. Some folks look like corks as they bob about in the water. 4.56 billion tons of salt are dissolved in the lake with about 2.2 tons of salt—about as much as would fill 70,000 railroad boxcars—added each year. Salts and other minerals are carried into the lake by three rivers and smaller streams that empty into the lake. Salt settles to the bottom of the lake and over time  can create large crystals like the one in the photograph below. 

Salt crystal from the Great Salt Lake
Situated in the Great Salt Lake is Antelope Island, named for the antelope that once roamed there.  It is the largest of the ten islands located in the lake, and is now a state park. Two-thirds of the island is formed of gneiss, a hard metamorphic rock that is about 2.7 billion years old, ten times as old as rocks from the age of early dinosaurs. 

Gneiss (pronounced as "nice") is a metamorphic rock with bands of minerals clearly visible.
Rock formations like this are common on Antelope Island.
For more than 100 years, bison have lived on Antelope Island. At present the population numbers between 500 and 700. Each year the bison are rounded up and checked by veterinarians. And to thin the population about 150 bison are auctioned each year. Otherwise, they roam freely. In addition to the bison, millions of native birds, including waterfowl reside there. And what about that salty water? Fish cannot survive in the lake because the water is too saline. But the lake is filled with tiny brine shrimp, an important component of the ecosystem that serves as food for the billions of brine flies that swarm around the lake, sometimes forming a black cloud. While adult brine flies live for only a few days they are the primary food source for the birds. In addition, dozens of species of bacteria, protozoa, and algae thrive in the lake. More than 400,000 acres of wetlands around the lake’s shore provides important nesting grounds for the multitude of birds that live on the island. Some of the species of birds that are dependent on these wetlands are the bald eagle, peregrine falcon, eared grebe, California gull, white-faced ibis, American white pelican, tundra swan, western sandpiper, snowy plover, American avocet, along with huge numbers of geese and ducks.

If you look very carefully, you can see tiny brine shrimp in this photograph. They are the small white creatures near the center and bottom.
This sign warns motorists to stay on the road and to keep away from the buffalo.
Some buffalo on the island form herds.
Others wander about alone.
Antelope Island is a Utah state park and is now accessible by automobile on a seven-mile causeway to the island.

Seven-mile causeway to Antelope Island
The Great Salt Lake at sunset

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