What Lake Bonneville Left Behind

At its peak, ancient Lake Bonneville would have been a sight to behold. Nearly as large as Lake Michigan, the Ice Age lake spread across much of western Utah and parts of Nevada and Idaho. When it eventually receded, it left behind flat, bright playas and salt flats rich with minerals—a landscape that would later serve as the setting for feats of engineering and technological ingenuity, as well as epic tales of exploration and desperation.

Lake Bonneville began forming about 55,000 years ago during a cool, wet period, when volcanic eruptions in what's now southeastern Idaho diverted the Bear River, causing water to gather in Gem Valley and other basins to the south. For tens of thousands of years, a natural dam at Red Rock Pass helped confine the lake.

Then, about 18,000 years ago, water breached that dam, unleashing a torrent that entered the Columbia River system. Over a six-week period, amid one of North America's largest floods, lake levels plummeted by more than 350 feet (105 meters). As the climate warmed and dried in subsequent millennia, the lake shrank dramatically, leaving remnants that include today's Great Salt Lake, Utah Lake, and Sevier Lake.

Lake Bonneville may be gone, but its imprint on the region's landscape remains—even in satellite imagery. In this image (below) captured by the OLI (Operational Land Imager) on the NASA-USGS Landsat 8 satellite, bathtub-like rings and wave-cut terraces trace the position of former shorelines. The dried lakebed—where fine-grained clay, marl, and sandy sediment settled out of the water—appears pale in comparison to the darker, rockier, more vegetated surroundings.

In deep parts of the basin, where runoff and groundwater still pool, bright deposits of evaporite minerals coat the land surfaces, forming salt flats. These remarkably flat surfaces are the product of water gradually evaporating and concentrating minerals to produce brines and hard mineral crusts, typically including halite and gypsum, along with potassium- and magnesium-bearing salts. Brines and deposits like these—particularly of potash, which is used as a fertilizer—have long made the playa a target for mining, as seen in the rectangular evaporation ponds above and below.

In contrast, the darker, more rugged terrain—including the Silver Island Mountains, the Newfoundland Mountains, and the Pilot Range—that rises above the playas is built from layers of erosion-resistant sedimentary and metasedimentary bedrock that is hundreds of millions of years old. These mountains also contain younger igneous and metamorphic rocks that formed when magma intruded into the ancient sedimentary sequence.

Crater Island, for instance, is composed of sedimentary rocks, including silica-rich sandstones and quartzites that formed as sands accumulated in a shallow ocean, as well as intrusions of quartz monzonite, granites, and other igneous rocks. Periods of crustal stretching later produced the fault-block mountains that define the landscape.

Mapping geological distinctions like this took center stage in June 2026 when NASA scientists and engineers working with the agency's DAVINCI mission came to Crater Island—a place they call "Venus on Earth"—to field-test the design of a set of cameras and a package of instruments that will eventually descend through the thick atmosphere of Venus and photograph mountains at scales finer than these Landsat images. During a 60-minute descent, the pioneering probe will capture near-infrared images, measure the atmospheric chemistry, and explore the environment of a world in unprecedented detail.

During the rehearsals at Crater Island, the camera system took hundreds of images of various rock formations, including iron-rich and silica-rich rock units, while suspended from a helicopter as it descended toward the surface. Using only the images acquired by DAVINCI's camera systems, the team made three-dimensional maps of the area consistent with existing geologic maps, giving the scientists confidence that they will be able to map the geology of an analogous mountainous region on Venus that DAVINCI will study, an area called Alpha Regio.

Other epic adventures have played out on and around Lake Bonneville's playas, as well. The flat, smooth surfaces have often been the setting for new land speed records. In 1960, Mickey Thompson became the first American to break the 400-miles-per-hour (640 kilometers-per-hour) barrier, hitting 406.60 miles per hour (654.36 kilometers per hour) in a streamlined race car on the Bonneville Salt Flats. The feat temporarily earned him the nickname "fastest man on Earth."

More recently, in August 2026, Andy Green, the first person to break the sound barrier on land, set a record for the fastest land speed in a hydrogen-fueled internal-combustion vehicle, reaching 406.320 miles per hour (653.909 kilometers per hour). By burning hydrogen rather than gasoline, the "rocket car" produced no carbon dioxide.

Nearly two centuries earlier, in August 1846, members of the ill-fated Donner-Reed Party also passed along the southern edge of Crater Island. As part of a shortcut toward Pilot Peak, they journeyed from Hastings Pass, past Floating Island, and toward Donner Spring. However, in an ominous sign of challenges to come, their heavy wagons broke through the thin salt crust and became mired in underlying mud, slowing them down and prompting them to abandon several wagons in the desert.

NASA Earth Observatory images by Michala Garrison, using Landsat data from the U.S. Geological Survey. Story by Adam Voiland.

JPEG (14.24 MB)

JPEG (2.87 MB)

Full text from nasa.gov (public domain).