Crater Lake, Oregon

 Crater lake from the gift shop parking lot looking southeast. (copyright 2009)

Dead tree stump at the western overlook of Crater Lake (copyright 2009)

Since we are on a volcano kick lets talk about one of the most famous volcanic craters in the United States. No not Yellowstone, Crater Lake, Oregon. You will never see water so blue. It is 1943 ft deep, which makes it the deepest lake in the United States and the 9th deepest in the world. [1] It is so clean and clear you can drink from it. How did this beautiful lake get there? It is a story of fire and ice and water.

The earth’s crust is not stable. It doesn’t sit in one place. It moves on a lake of molten lava and has several tectonic plates. These plates float and move from place to place, albeit, very slowly. The Pacific Ocean plate is pulling apart at the middle creating a rift zone that allows the molten earth beneath to ooze to the top creating volcanic islands like those of Hawaii. These volcanoes are not usually explosive but just pour the lava over the plate creating a “shield” volcano. At the shores of the Pacific the plates that are moving east and west from the rift get subducted beneath the continental plates that are denser than the oceanic plates. At the edges of these subduction zones explosive volcanoes form what is known as the Pacific Ring of Fire. Crater Lake sits in the eastern part subduction zone where the Pacific Plate is being subducted beneath the North American Plate.

The volcano that Crater lake sits in is named Mazama. It’s largest eruption happened at 7700 years ago and was probably the largest in North America for more than half a million years. After minor eruptions and a pause during the ice age that changed the consistency of the gases and molten rock beneath Mazama the Rhyolite in the core of the volcano mixed with water it became an explosive volcano known as a stratovolcano with many parasitic vents on its parameter. It isn’t the only stratovolcano in the area. It is part of a chain of volcanoes that is known as the Cascade Range that streatches from British Columbia to Mt Shasta in California.[2]

Mazama began growing over a half million years ago. At 8000 yag it stood at 12,000 feet. Then it blew with great force 7700 years ago. The ash from this explosion can be found as far away as Wyoming and Alberta Canada. It displaced so much ash from the insides of the volcano that the walls collapsed Mazama lost thousands of feet of mountain top in a span of a few short days. It didn’t stop erupting. Evidence of that is found within the Caldera in the form of Wizard Island and others that are under the water now. [3] Over several hundred years rain and snowmelt gathered in the deep Caldera which has no outlet or intake like many other lakes. Because of its depth and the clarity and cleanness of the water it is a deep azure blue. The water is completely replaced about every 250 years[4] Keeping the water in the lake is not a problem since it is in an area that gets large deep snowfalls. One of the pictures shown was taken in late May of 2011. The snow was so deep you had to stand on it to see the lake and the gift shop was hidden to the middle of the first floor with 4 foot basement walls below it. The heaviest snow fall occurred in 1971 was 37 inches. The average yearly snow fall is 488 inches or almost 41 ft. Per year and like most of Central Oregon you can see snow any time of the year with cold temperatures at night sometimes freezing even in July and August. [5]

Crater Lake in late May 2011 taken standing on about 20 feet of snow above the parking lot.

Can Mazam blow again? It is probable that it will become active as will many of the volcanoes of the Cascade Range since they are relatively young and many like Crater Lake show signs of geothermal activity. A submersible sent down to survey Crater Lake found such activity on the bottom of the lake.[6] It is not expected that it will be as large as the Caldera forming event and it won’t pose danger to areas below because the walls show no signs of collapse. However the mixture of rhyolite and water does make for an explosive combination. Earthquakes are another possibility in the area of up to a magnitude of 7 on the Richter scale.

If you come to Oregon in June, July or August seeing Crater Lake is a must. It is one of those places that qualifies as otherworldly in it beauty and geology. Check ahead for the weather since sometimes the lake is shrouded in fog and you won’t be able to see it if it is. Also if you can, try to get tickets for the boat tour. It will give you a much different view than from the rim. You also will get to visit Wizard Island in the lake. Crater Lake Oregon is truly a sapphire gem surrounded by the green emeralds of ponderosa pines. It is well worth the visit.


[1] http://www.nps.gov/crla/historyculture/index.htm

[2] http://www.nps.gov/crla/planyourvisit/upload/Geology.pdf

[3] http://www.nps.gov/crla/planyourvisit/upload/Geology.pdf

[4] http://en.wikipedia.org/wiki/Crater_Lake

[5] http://en.wikipedia.org/wiki/Crater_Lake

[6] http://travel.nationalgeographic.com/travel/national-parks/crater-lake-national-park/