Blog Post Linda Coutant Nov 29, 2023

A Volcanic Blue Abyss

Crater Lake holds about 4.9 trillion gallons of water and ranks among the world’s deepest lakes. Learn how it formed and what scientists have found in its depths.  

In 1886, a party from the U.S. Geological Survey dropped a lead pipe attached to a piano wire into Crater Lake at more than a hundred different locations. Their goal? To measure the deepest part of this clear, blue water that sits atop the Cascade Mountain Range in Oregon about 100 miles inland from the Pacific Ocean.

The depth obtained through their method — 1,996 feet — wasn’t far off from the 1,943 feet a sonar scan determined in 2000. This namesake feature of Crater Lake National Park, established in 1902, is the deepest lake in the United States and ninth deepest in the world.

Known for its clear blue water, Crater Lake holds about 4.9 trillion gallons. According to the National Park Service, the lake at its deepest point could contain the Statue of Liberty stacked on top of the Eiffel Tower and the Washington Monument — with 100 feet of water still covering Lady Liberty’s torch!

No rivers or streams flow in or out of Crater Lake. Unlike most lakes, it is fed only by rain and snow.

Crater Lake formed when the 12,000-foot Mount Mazama erupted about 7,700 years ago and collapsed on itself. The violence created a caldera 5 miles wide and more than half a mile deep.

Continued eruptions built the base of Wizard Island, which can be seen in the middle of Crater Lake. Over hundreds of years, rain and snow partially filled the caldera. Wizard Island continued growing as three other volcanoes formed underwater, with its east flank developing during the most recent eruption 4,800 years ago.

The Park Service says Native Americans likely witnessed the explosion, given archaeological evidence of their presence in the area. This includes sandals and other artifacts buried under layers of ash, dust and pumice. In the 1930s, the federal Works Progress Administration commissioned artist Paul Rockwood to depict Mount Mazama and its eruption and collapse in a series of paintings. The originals are kept in the Crater Lake National Park Museum and Archives Collections.

What gives the lake its deep blue color? Scientists say it’s a combination of the lake’s depth, purity of water, 100-foot clarity and water molecules’ interaction with sunlight. The hue can vary each day depending on wind, cloud cover and the angle of the sun.

Crater Lake’s aquatic life includes rainbow trout and kokanee salmon, the only fish to survive after seven species were introduced between 1886 and 1941, as well as the native Mazama newt and other amphibians. Many types of phytoplankton and zooplankton form the bottom rungs of the food chain. Moss hangs like icicles on the near-vertical walls of the lake’s rim between 100 and 400 feet deep.

Crayfish, which were introduced in 1915 as fish food, have spread significantly along the shoreline, threatening the Mazama newt. The crayfish are also linked to increased algae along the shoreline, although scientists are still studying why.

Through deep dives, scientists have found at the very bottom colonies of yellow-gold bacteria growing in vast, puffy mats, and a variety of worms, insects and tiny crustaceans able to withstand the intense water pressure.

At the lake’s surface, a mystery resident captures the attention of the public and scientists alike. Known as the “Old Man,” a 30-foot mountain hemlock log carbon dated at more than 450 years old floats around the lake, with 3 feet exposed above water.

Magazine Article

The Old Man of the Lake

How has a giant hemlock managed to float upright in Crater Lake for more than a hundred years?

See more ›

First sighted in 1896, the log gained the attention of officials in Washington, D.C., who commissioned a study of its travels within the lake in 1938. The Old Man floated 62 miles between July and October — with a per-day average of .67 miles and a maximum daily distance of 3.8 miles.

In winter, the lake rarely freezes, although Crater Lake National Park gets an average of 42 feet of snow. The Park Service closes the park’s East Rim Drive and West Rim Drive to vehicular traffic, opening the awe-inspiring landscape to cross-country and downhill skiing, snowshoeing, snowboarding, sledding and snowmobiling. Ranger-guided snowshoe walks are typically offered each winter. Backcountry camping is also available.

At its deepest point, Crater Lake could contain the Statue of Liberty stacked on top of the Eiffel Tower and the Washington Monument — with 100 feet of water still covering Lady Liberty’s torch!

Wintertime visitors can find towering conifers and snow-covered meadows at Rim Village, which overlooks Crater Lake — a perfect spot for taking photos, playing in the snow or shopping at the gift store. You can take a look at the lake anytime using the park’s webcam.

Climate change, however, is affecting the lake and the park. Monitoring by the Park Service and its research partners over many decades indicates a steady downward trend of snowfall and upward trends of air and water temperatures. This can disrupt the lake’s circulation of water within its depths, called “deep-water mixing,” which impacts the distribution of oxygen and presence of nutrients, therefore affecting the lake’s ecology.

Modeling for the next 100 years shows this circulation could be greatly reduced or even eliminated depending on how quickly air temperatures rise.

The changing climate affects plants and animals, too. Whitebark pine trees growing along the lake’s rim, for example, have been harmed by the mountain pine beetle as it survives milder winters, and pika populations have declined as the mammals cannot tolerate temperatures even at 78 degrees Fahrenheit.

Just as eruptions thousands of years ago formed what we see today, this protected area continues to evolve. What will visitors enjoy in the next century? Climate and geography may change, and likely, too, will be the technology people use to study them.

Want to visit?

Crater Lake National Park is located off major highways about 2½ hours southeast of Eugene, Oregon or 2 hours southwest of Bend, Oregon. There is an entrance fee. Crater Lake sits in the middle of the park, which has north, south and west entrances. Be sure to plan carefully when visiting the park in winter.

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About the author

  • Linda Coutant Staff Writer

    As staff writer on the Communications team, Linda Coutant manages the Park Advocate blog and coordinates the monthly Park Notes e-newsletter distributed to NPCA’s members and supporters.