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When the first people arrived in the Great Basin thousands of years ago, the basin looked very different from today. Where today there are massive salt flats and deserts, there were prehistoric lakes, and an abundance of wildlife. There were two massive prehistoric lakes in the Great Basin - Lake Lahontan and Lake Bonneville. Pyramid Lake in Nevada is a relic of Lake Lahontan and today one can still see ancient watermarks and archeological sites where ancient Native Americans would hunt along its shores.

But the larger of the two was Lake Bonneville - it was the largest Late Pleistocene (ice age) prehistoric lake of the Great Basin. On the other side of North America, a prehistoric lake larger than the Great Lakes today combined called Lake Agassiz once spanned the land.

Salt Lake Was Once Part of Lake Bonneville

Lake Bonneville covered much of what is today western Utah (a third of all of Utah) and at its peak extended into Idaho and Nevada.

Today one can still make out its ancient shorelines that appear as shelves or benches protruding from the mountainsides above the valley floor. In total there are three named distinct shorelines (Stansbury, Bonneville, Provo) of the ancient lake that can be seen in the basin.

  • Where: Western Utah, Parts of Nevada and Idaho

At Lake Bonneville's peak, it was over 300 meters or 980 feet deep and spanned almost 51,000 km2 or 20,000 sq miles - about the size of what Lake Michigan is today. The lake was irregular in shape with many peninsulas and islands. It formed between around 30,000 and 13,000 years ago and didn't have an outlet for most of its existence. Over its life, its levels oscillated but reached its high watermark around 18,000 years ago.

  • Depth: 300 meters or 980 feet
  • Size: 51,000 km2 or 20,000 sq miles
  • Remnants: Sevier Lake, Utah Lake, and the Great Salt Lake

Today the Great Salt Lake is the largest of the remnants of Lake Bonneville with Utah Lake and Sevier Lake being the next largest. The climate is now too dry to support the large lake of the past.

Related: Here's What To Know Of The Ancient Sea That Flooded The Great Plains

Bonneville Salt Flats

Today there are many places where one can see the remnants of the prehistoric Lake Bonneville. One of the places is Bonneville Salt Flats near the Great Salt Lake. Around this site, one can see the traces of the shorelines that represent different levels of the lake at it receded. They are etched into the mountains surrounding the salt flats.

Wind and water combine to create the flat surface of salt. A shallow layer of water floods the surface of the salt flats every winter. Come spring and summer, the water evaporates and the wind smooths the surfaces into the vast flat plain one sees today.

  • Size: 12 miles long and 5 miles wide (46 sq miles)
  • Location: Western Edge of The Great Salt Lake Basin

Today the Bonneville Salt Flats are managed by the Bureau of Land Management (BLM) and everyone can visit them. No overnight camping is permitted on the flats and vehicles are not permitted when they are wet or flooded.

Related: These Museums Bring N America's Prehistoric Megafauna To Life

Danger Cave Archeological Site

One of the many archeological sites around ancient Lake Bonneville is Danger Cave. It was formed by the waves of Lake Bonneville and was home to Native Americans as far back as 11,000. It is a significant site for its age, preservation, and extremely harsh environment - survival in this region would have been extremely hard.

Excavations at Danger Cave have greatly expanded our understanding of prehistory in the region and so it is considered to be one of the most significant archeological sites in North America. It is also one of the oldest known Native American sites on the continent.

  • Location: North Of Wendover, West Of Bonneville Salt Flats, Utah
  • Designated: National Historic Landmark in 1961 and a state park in 1968
  • Formed: Around 11,000 Years Ago

It is believed to have been inhabited constantly inhabited by different native people consistently after around 11,000 years ago. Excavations have revealed textiles, baskets, pottery, animal bones, plant remains, weapons, chipped stones, and leather scraps that have been well-preserved in the cave's extremely dry environment.

Unfortunately, Danger Cave was looted in 2019.

  • Cave Tour: $15.00

Occasionally State Parks Utah offers a guided tour of the historic site through the cave. Check their website for any upcoming programs.

There are countless other places to see the remnants of this once mighty prehistoric lake.