I climbed Black Rock the other day for perspective on a writing assignment on the history of Lake Bonneville. What was Lake Bonneville? The short answer: A really big lake that covered about 1/3 of Utah until about 14,500 years ago.
The slightly less short answer: Bonneville was the latest in a 15-20 million year succession of lakes that have occupied the Bonneville basin of the Basin and Range physiographic province. Through a combination of flooding and changes in climate, the lake receded dramatically. The Great Salt Lake is Bonneville’s largest remnant, occupying the deepest areas of the basin.
Lake Bonneville’s currents and waves sculpted the unique topography of western Utah. The lake was just about the size of Lake Michigan, but deeper. In fact, at the lake’s highest level, my home in Tooele County would sit nearly 1,000 feet underwater. When you explore our vast deserts, you’re literally navigating the floor of this ancient water body. My pen name, Bonneville Mariner, derives from this notion.
And speaking of ancient, most people who write about Lake Bonneville use that word to describe it, and pronounce it dead and gone. Ancient it technically may be, though consider that we measure Bonneville’s life in thousands of years, not millions or billions, like most other geologic formations here. (hat tip: G. Atwood)
Dead and gone? Hardly. Which begs the question, when exactly did Lake Bonneville become the Great Salt Lake?
Think about, say, Lake Michigan. Say it starts drying up until about 1/12 of it is left in the deepest depression. It’s still a sizable body of water– still a really big lake. Would you rename it?
Lake Bonneville, as far as geologists can tell, never completely dried up (though it came close about 7,000 years ago). And while the Great Salt Lake covers only a fraction of the area Lake Bonneville did, it’s still the largest salt lake in the western hemisphere and the fourth largest terminal lake in the world. If you’d like a perspective on the scope of GSL’s reach, just paddle out on a surf board.
To be fair, Lake Bonneville wasn’t studied or named until several decades after pioneers named the Great Salt Lake. But this begs another question: were the GSL to rise over time back up to Lake Bonneville’s lowest major level (the Gilbert Level), would it still be the Great Salt Lake, or would it re-assume its previous (and rightful) name?