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Roger Weller, geology instructor

Crater Lake, Oregon
by Rebekah Devine
Physical Geology
Spring 2001

Crater Lake

Photograph by Daniel Devine

            Crater Lake is a site to see! It is a caldera lake located in Oregon. A caldera is a depression in the ground created by the collapse of land after a volcanic eruption. It is said that Crater Lake was formed 7,700 years ago when Mount Mazama collapsed after an eruption.

Right before the Eruption of Mount Mazama

Photograph by George Grant, National Park Service


            Mount Mazama is one of the many volcanoes along the Cascade Range. The Crater Lake is located inside the top of Mount Mazama. Mount Mazama is a volcano that is classified as dormant volcano. A dormant volcano is one that rarely erupts currently but has in the past. In the past this volcano had massive eruptions. Eventually after all the eruptions the build of ash, pumice, and cinders created 12,000-foot mountain. The Parasitic cones on Mount Mazama made Mount Scott the highest point in the park. A Parasitic cone is small volcano cone on top of a larger volcano.  


Right after the Eruption

Photograph by George Grant, National Park Service


            The lake extends about five miles. Crater Lake is 1,943 feet deep at its deepest point. It is the deepest lake in the United States and the seventh deepest in the world. Its clarity is also the reason itís a famous lake. You can see down the lake about 134 feet. Surrounding the lake is steep rock that goes up about 2,000 feet. Itís also covered with evergreen forest. The highest point in the park is Mount Scott and it is 8,929 feet. The lowest point is the Red Blanket Canyon at 3,977 feet.


            The lake is fed mostly by snowfall and the level of the lake varies year to year. Its highest level recorded was 6,179 feet above sea level in 1975.  Crater Lake was filled mostly by snow it is one of the clearest lakes in the world. The average snowfall is about 533 inches. Although the lake stays pretty cold year round the surface rarely freezes. The last significant freeze was in 1949. The lake was frozen for about three months. 


Photograph by U.S. National Park Service

            In the middle of the lake is a volcanic cinder cone, which forms an island, called Wizard Island. Cinder cones are formed by volcanic ash building up around explosive vents. There are many small cinder cones in the caldera but Wizard Island is the only one above the surface. The cone rises about 763 feet. Itís made entirely by andesite rock. Andesite rock is an extrusive igneous rock. Extrusive igneous rock is formed when molten rock erupts and flows above the surface as lava and when it is cooled it forms an extrusive igneous rock. Wizard Island is covered by trees and has a small caldera on top. The caldera is 500 feet wide and 100 feet deep; it is sometimes referred to as the Witches Cauldron.

Wizard Island

Photograph by Roger Weller


            The weather for Crater Lake varies on the year and what time of year. In October to about June it is covered in snow. During the months of November to April there isnít much to see because of the snow but itís a great time for skiing. The most snow they have had in a season and still holds the record is 879 inches. It holds the state record of 903 inches in a year. The most snow to hit the ground was 21 feet.


Crater Lake, Winter

Photograph by Marc Adamus


          Summer weather can also vary just like every other place. In May and June it could be sunny one day and snowy the next. July, August, and September are the drier and warmer times to see the lake. It is said that July is one of the best times to see Crater Lake.


Crater Lake, Summer

Photograph by U.S. National Park Service


            Whatís next for Crater Lake? The biggest threat with calderas is the possibility of volcanic activity. However, an eruption as big as the one that created the caldera in the first place is not likely. There has been no activity in this area in 5,000 years. Studies have shown no evidence of magma movement or earthquakes associated with volcanic activity.

            According to geologist there isnít a reason not to expect some possibility of an eruption. If there were an eruption in the caldera it would be an underwater eruption. The mix of water, magma, and hot rock would increase the power of the eruption. The eruption could also produce flooding if the caldera walls were to fall. However, Crater Lake doesnít show a sign of the walls failing.


Photographs by Daniel Devine


            On a personal note, Crater Lake has to be one of the most beautiful sites I have ever seen. The water is such a deep shade of blue and itís so still. When you look out as youíre sitting on the steep rock surrounding this lake it doesnít even look real. It looks like a picture. But there really is no picture or description that could give this place justice.  It is well worth a plane or car ride!


Works Cited

"Andesite: Igneous Rock - Pictures, Definition & More." - Earth Science News, Maps, Dictionary, Articles, Jobs. Web. 25 Apr. 2011.


Cain, Fraser. "Dormant Volcanoes." Universe Today. 09 Apr. 2009. Web. 23 Apr. 2011.


"Cinder Cones." Oracle ThinkQuest. Web. 24 Apr. 2011.


"Parasitic Cone." Parasitic Cone. Web. 24 Apr. 2011.


"Types of Volcanoes - Cinder Cone or Scoria Cone, Hawaii." About Geology - The Complete Guide to Earth Science and Geology. Web. 22 Apr. 2011.


Uhler, John W. "Facts and Figures about Crater Lake National Park." U.S. National Park Service - Experience Your America. Web. 23 Apr. 2011.


US National Park Service. "Facts and Figures about Crater Lake National Park."
U.S. National Park Service - Experience Your America. Nov. 2001. Web. 22 Apr. 2011.


US National Park Service. "Geology of Crater Lake National Park." U.S. National Park Service - Experience Your America. Sept. 2009. Web. 26 Apr. 2011.


US National Park Service. "NPS: Nature & ScienceĽ Geology Resources Division." Ľ Explore Nature. Web. 24 Apr. 2011.