John Rivers, age 12, of ‑Albany, New York, for his questions
What caused the Great Salt Lake?
Andy rates the Great Salt Lake of Utah as one of the wonders of the Western World, First there is the wonder of its beauty. Then there is the fact that its waters are from four to seven times as salty as ocean water, yet it has no outlet to the sea. Lastly, there is the fascinating geological history which created it.
The great lake is roughly 75 miles long and 50 miles wide. Its size and its shorelines vary with the rainfall. It is sot like a precious jewel amid the jagged peaks and snowcapped towers of the Rockies. The region is arid and. the sky above it almost always brilliant blue. The lake reflects this heavenly blue like a mirror. Twice a day, its benutg becomes a breathtaking spectacle. The dawn and sunset tint the rim of mountain peaks with rainbow colors. This radiance, too, is reflected on the mirror‑calm lake.
The Great Salt Lake we know today is but a ghost of its former self. It is a mere puddle remaining from a huge lake which covered this area thousands of years ago. We call the older lake Lake Bonneville, and in its day it was a body of fresh water. Lake Bonneville covered an area ton times as large as the Great Salt Lake. The average depth of the Great Salt Lake is 15 to 18 feet. Old Lake Bonneville was, in places, more than 1, 040 feet deep.
The old lake covered the present lake and a vast region around it. The shorelines left their fingermarks on the cliffs and slopes of the Rockies which once surrounded it. We can still trace its beaches, its coves and its deltas, These telltale signs of an ancient shoreline are now far from water. They have been part of the dry land for thousands of years.
Lake Bonneville was fed by streams of rain and melting snow which tumbled down from the high Rockies. Its waters were drained off by the Snake River, which met the beautiful Columbia River and hence drained into the Pacific Ocean. This outlet to the sea kept water flowing through Lake Bonneville and . it and made it a lake of fresh water,
The climate and the surface of the earth are always changing, Some time in the distant past, the region became drier. The surface of the earth heaved and the lake lost its gateway to the sea.
The old lake shrank and shrank. The only way it could get rid of surplus water was by evaporation. .few rivers and several streams still feed it with water from the melting snows. But there is no outlet,
Running water always dissolves salts and other chemicals from the rocks through which it flows. Normally, this load of chemicals is carried by streams and dumped into the sea. The Great Salt Lake has no outlet to the sea. Hence, its load of chemicals grows year by year.