Book Excerpt : Yellowstone Lake

No writer has better described Yellowstone Lake than did renowned naturalist John Muir in an Atlantic Monthly article of 1898:

It is about twenty miles and fifteen wide, and lies at a height of nearly 8000 feet above the level of the sea, amid dense black forests and snowy mountains. Around its winding, wavering shores, closely forested and picturesquely varied with promontories and bays, the distance is more than 100 miles. . . .

It is full of trout, and a vast multitude of birds—swans, pelicans, geese, ducks, cranes, herons, curlews, plovers, snipe—feed in it and upon its shores; and many forest animals come out of the woods, and wade a little way in shallow, sandy places to drink and look about them, and cool themselves in the free flowing breezes.

In calm weather it is a magnificent mirror for the woods and mountains and sky, now patterned with hail and rain, now roughened with sudden storms that send waves to fringe the shores and wash its border of gravel and sand. . . .

Yellowstone Lake is North America's largest high altitude lake (7732 ft/2357 m) at about 14 by 20 miles (23 by 32 km) in width and length and with more than 141 miles (227 km) of shoreline. The lake has an average depth of 139 feet (42 m); its deepest spot is 430 feet (131 m) just east of Stevenson Island.

Tributaries

Approximately 125 tributary streams feed into Yellowstone Lake, mostly from the south and east. One of the streams is the Yellowstone River's source, which enters the southeast arm of the lake from the mountains in Bridger-Teton National Forest. Thus, the lake's outlet at Fishing Bridge is not really the headwaters of the Yellowstone River.

Islands

The seven named islands in Yellowstone Lake are, from largest to smallest: Frank, Stevenson, Dot, Peale, Molly (actually two islands named Sandy and Rocky), Carrington, and Pelican Roost. Frank, Peale, and Molly were named by or for members of the 1871 and 1878 Hayden surveys of the Yellowstone area. The names of the other four are explained in the road logs when they come into view.

Winter and the Lake

In winter, ice nearly 3 feet (1 m) deep covers much of the lake, except where shallow water covers hot springs. The lake freezes over by early January, and the ice doesn't break up until late May or early June. Rangers on ski patrol used to shorten their long trek to the southeast area of the park (the Thorofare) by skiing across the ice from Lake Ranger Station to Park Point on the east shore.

Science and the Lake Bottom

In recent years, scientists have explored some of the lake's bottom using a submersible robot called a Remotely Operated Vehicle (ROV). They've learned that Mary Bay at the lake's north end, where temperatures up to 212°F (100°C) have been measured, is a major hydrothermal explosion crater complex that erupted about 13,000 years ago. They've also found deep pits that may be old explosion craters.

At least two other hot areas in the lake are being studied. West Thumb Bay is one of these areas, with huge hot gas eruptions that stir up food for enterprising trout. Another is northeast of Stevenson Island, where the ROV found a deep underwater canyon containing several hydrothermal springs. Five years later, the scientists returned, just after a major earthquake had shaken the area. The canyon had disappeared!

Spires as tall as 26 feet (8 m) grow in clusters on the lake bottom at one lake hot spot, Bridge Bay. These pinnacles are made of the siliceous shells of diatoms, microscopic algae that live and die near the lake bottom. Exactly how these hydrothermal features form is as yet unknown.

Lava flows that are still very hot underlie much of the lake. Thus all the possible thermal features that we see in the rest of the park are here, only modified by having a lake sitting on them. The result is that many explosion craters dot the lake perimeter, and we know from recent research that there are more on the lake floor. There are also dome-like features, some one-third of a mile (0.5 km) in diameter, bulging up perhaps due to steam.

 This is an excerpt from the Yellowstone Treasures guidebook, 3rd edition, pages 143–5.

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