How big is Yellowstone Lake?

Yellowstone Lake, the largest high-elevation lake in North America, is one of the crown jewels of Yellowstone National Park. Situated at an elevation of 7,733 feet (2,357 meters) above sea level, this majestic body of water spans approximately 136 square miles (352 square kilometers) in surface area. It is roughly 20 miles (32 kilometers) long from north to south and 14 miles (23 kilometers) across at its widest point from east to west, giving it a shoreline that measures around 141 miles (227 kilometers).

Depth and Volume

Yellowstone Lake has an average depth of about 139 feet (42 meters), but in some places, it plunges to a maximum depth of 430 feet (131 meters). Its total water volume is estimated to be more than 4 trillion gallons, making it a significant aquatic feature not just within Yellowstone National Park but in the entire Rocky Mountain region.

Hydrothermal Influence

One of the unique aspects of Yellowstone Lake is that it sits atop the Yellowstone Caldera, a massive volcanic crater. The lake floor is geothermally active and features underwater geysers, hot springs, and fumaroles. Researchers have even discovered large hydrothermal explosion craters beneath the lake, such as the Mary Bay crater on the northern shore, which formed during a violent eruption thousands of years ago.

This geothermal activity creates unusual conditions under the lake’s surface, including localized areas of warm water and chemical-rich environments that support unique microbial life. The lake occasionally experiences temperature stratification, especially during warmer months, with warmer surface waters sitting atop much colder deep layers.

Seasonal Changes

During winter, Yellowstone Lake typically freezes over from December through May, although geothermal activity can prevent ice from forming in some localized areas. Ice thickness can reach up to two feet in colder years. The thaw begins in late spring, and by early summer, the lake becomes navigable again for research boats, fishing, and recreational use.

Tributaries and Outflow

Several small streams and creeks feed Yellowstone Lake, including the Upper Yellowstone River, which enters the lake from the south. The lake’s only outflow is the Yellowstone River, which exits at the lake’s north end near Fishing Bridge. This river eventually flows north through Hayden Valley and past the Grand Canyon of the Yellowstone, contributing significantly to the region's hydrology.

Ecological and Recreational Importance

Yellowstone Lake plays a vital ecological role in the Greater Yellowstone Ecosystem. It provides habitat for native cutthroat trout, although populations have faced challenges due to the introduction of invasive lake trout. The lake also supports a variety of bird species, such as ospreys, bald eagles, and waterfowl, as well as mammals like river otters and grizzly bears that rely on its resources.

For visitors, Yellowstone Lake offers opportunities for boating, fishing, kayaking, and scenic picnicking, especially near the developed areas like Lake Village and Bridge Bay Marina. However, due to its size and high elevation, the water remains cold year-round, and sudden weather changes can pose risks to inexperienced boaters.

Yellowstone Lake is not just remarkable for its size, but for its geological and ecological complexity. Its high elevation, geothermal setting, and role in the park’s ecosystem make it a truly extraordinary natural feature—one that continues to captivate scientists, naturalists, and millions of visitors each year.