At its peak, ancient Lake Bonneville was basically the Midwest of the Ice Age West - nearly as large as Lake Michigan, sprawling across much of western Utah and parts of Nevada and Idaho. When it finally decided to leave, it didn't just pack up and go; it left behind flat, bright playas and salt flats rich with minerals. Those flats would later serve as a backdrop for engineering feats, technological wizardry, and a few cautionary tales involving stuck wagons.
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 kept the lake in check. Then, about 18,000 years ago, the dam gave way, unleashing a torrent that joined the Columbia River system. Over six weeks, amid one of North America's largest floods, lake levels plummeted by more than 350 feet (105 meters). As the climate warmed and dried, the lake shrank dramatically, leaving behind today's Great Salt Lake, Utah Lake, and Sevier Lake.
Lake Bonneville may be gone, but its ghostly imprint remains - even in satellite imagery. The OLI (Operational Land Imager) on the NASA-USGS Landsat 8 satellite captured bathtub-like rings and wave-cut terraces tracing former shorelines. The dried lakebed - where fine-grained clay, marl, and sandy sediment settled - appears pale against the darker, rockier, more vegetated surroundings.
In the basin's deeper parts, where runoff and groundwater still pool, bright deposits of evaporite minerals coat the land, forming salt flats. These remarkably flat surfaces are the product of water evaporating and concentrating minerals into brines and hard crusts, typically including halite and gypsum, along with potassium- and magnesium-bearing salts. Brines and deposits like these - particularly potash, used as fertilizer - have long made the playa a mining target, as seen in the rectangular evaporation ponds.
In contrast, the darker, more rugged terrain - including the Silver Island Mountains, the Newfoundland Mountains, and the Pilot Range - rises above the playas, built from layers of erosion-resistant sedimentary and metasedimentary bedrock hundreds of millions of years old. These mountains also contain younger igneous and metamorphic rocks 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 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 atmospheric chemistry, and explore a world in unprecedented detail.
During 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 descending toward the surface. Using only the images acquired by DAVINCI's camera systems, the team made three-dimensional maps consistent with existing geologic maps, giving scientists confidence they'll be able to map the geology of an analogous mountainous region on Venus - called Alpha Regio - that DAVINCI will study.
Other epic adventures have played out on and around Lake Bonneville's playas. 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, temporarily earning 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.