Crater Lake ne of the most dramatic Ofeatures of Crater Lake is its blue Lake Facts Blue Through Time color; in fact early explorers called the lake “Deep Blue.” When sunlight Deepest lake in the United Blue is the color of constancy, hence the penetrates into the lake, the red through States and seventh deepest in term true blue. The unearthly blueness of the green portions of the light are the world Crater Lake reflects its pristine character preferentially absorbed by water and and gives scientists a focal point for suspended particles. The blue light, which Maximum diameter of caldera studying human impacts on aquatic penetrates more deeply, is eventually at the rim environments over long periods of time. scattered by water molecules and returns 6 miles (9.7 km) to the lake surface and our eyes. Average height from Crater Scientists with the U.S. Geological Survey Concentrations of nutrients such as Lake’s surface (USGS), National Park Service, and nitrogen and phosphorus are low in the to caldera rim Oregon State University have lake, which explains why growth of About 1,000 feet (305 m) systematically studied the lake for the last microscopic plants (called algae) is low. two decades. Long-term monitoring of this The blueness of water is greatest when Lake surface area 2 lake is a priority of Crater Lake National densities of particles and algae are low. 21 square miles (54.4 km ) Park and will continue far into the future. Maximum depth 1,949 feet (594 m)

Maximum surface temperature 64°F (18 °C)

Plankton Free-floating microscopic algae (163 kinds) and animals (11 species)

Fish Kokanee salmon and rainbow trout, both introduced

eologists have determined that Mt. Mazama in southwestern GOregon erupted and collapsed 7,700 years ago, leaving a deep- sided hole called a caldera. The hole filled approximately half way with water over a period of several hundred years to create Crater Lake. Native Americans tell a parallel story of lake creation. Llao of the Below World lived in Mt. Mazama. Skell of the Above World descended to Mt. Shasta, to the south of Mt. Mazama, to do battle with Llao on behalf of an Indian chief’s daughter. Skell collapsed the top of Mount Mazama to imprison Llao forever beneath the world. Skell wanted peace and tranquility to cover up this dark pit, so he filled it with beautiful blue water.

U.S. Geological Survey and the National Park Service U.S. Department of the Interior USGS FS-018-03 U.S. Geological Survey Partnership in Monitoring March 2003 Early Scientific Exploration In the late 1800s, William and piano wire, they measured the depth disappeared from sight. Since then, a Gladstone Steel recognized the of the lake. Their maximum measured black and white disk, known as a importance of Crater Lake for depth was only 47 feet (14.3 m) more Secchi disk, has been used to measure scientific understanding. He funded than sonar measurements made in 2000. the lake’s clarity. Clarity in August scientific surveys of the lake, which averages 98 feet (30 m), but values as encouraged President Roosevelt to sign In 1896 an adventurous science crew high as 142 feet (43 m) have been a bill in 1902 giving Crater Lake national rowed out across the lake. One member recorded in the last two decades. park status. had a white dinner plate in his pack. His Changes in clarity are related to the objective was not lunch but rather the amount of algae in the lake and the In 1886 a USGS crew carried a half-ton first record of lake clarity, which he transport of sediment into the lake. boat up the slopes of the mountain and measured by lowering the plate into the Crater lake is the clearest measured then lowered it to the lake. Using a pipe lake on a rope and recording when it natural body of water in the world.

Biological Characteristics Diving into the of species but the lake’s biological Examples of Plankton Nitschia gracilis abundance of any single mysteries is the Distribution in Summer Daphnia pulicaria species tends to be Stephanodiscus hantzschii job of federal scientists like 30 sparse. Furthermore, Gary Larson and Mark different forms of Buktenica. They and their 25 plankton, both plant and university partners study a animal, live at different host of lake characteristics. 20 depths, down to about For example, they teamed 15 600 feet (200 m). up with university professor C. David McIntire to 10 The animal life includes

determine that plant relative abundance small and large forms of 5 plankton occurs at invertebrates as well as unusually deep depths in 0 fish. Eleven kinds of Crater Lake, which is 0 20 40 60 80 100 120 140 160 180 200 zooplankton inhabit Depth in meters partly a result of great light Crater Lake: nine penetration in the lake’s microscopic rotifers and clear water. The plant plankton uses this sunlight to two crustacean zooplankton. Rainbow trout and kokanee produce oxygen through the process of photosynthesis. salmon inhabit Crater Lake, both introduced by people Because of the extreme clarity of the lake, the maximum decades ago. The trout tend to frequent the shoreline, and amount of photosynthesis occurs between 131 and 262 the kokanee salmon live mostly in the open water down to feet (40-80 m). Plant plankton in the lake is rich in number a depth of about 450 feet (150 m).

A Barometer for Change For more information Crater lake is a world-class laboratory because it is pristine except for Information and Outreach the consequences of fish introduction. As a national park it has a high USGS Forest and Rangeland degree of protection from human activities. Long-term monitoring of Ecosystem Science Center 777 NW 9th St., Suite 400 Crater Lake is providing a baseline of information about the natural dynamics Corvallis, Oregon 97330 of the lake. This baseline serves as a reference when researching changes in Phone: 541-750-1048, Crater Lake itself and in other lakes around the world. Research at Crater email: [email protected] Lake continues as a collaborative effort of the USGS, National Park Service, http://fresc.usgs.gov Oregon State University, and others. As research continues, we learn more Crater Lake National Park about the lake and monitor our success at managing it so that future PO Box 7 generations also can marvel at this deep blue wonder. Crater Lake, OR 97604 541-594-3100 Fact sheet written by: Gary Larson, USGS Forest and Rangeland Ecosystem Science Center, [email protected] Mark Buktenica, Crater Lake National Park, and Robert Collier, Oregon State University http://www.nps.gov/crla Fact sheet designed by: John Ledges