- 1 Geology of Crater Lake National Park
- 2 How was Crater Lake formed?
- 3 Introduction
- 4 Geology 101 – Geological Processes at work in Crater Lake National Park
- 5 Books about the Geology of Crater Lake
- 6 Articles about the Geology of Crater Lake
- 7 A Detailed Guide to Geologic Features
- 8 A Geologic History of the Park 1912 by J.S. Diller, USGS
- 9 More Geology Pages in the Library
- 10 Crater Lake Geology in the News
Geology of Crater Lake National Park
Crater Lake is a geological laboratory par excellence, for here we find an immense mountain (the hypothetical Mount Mazama) dissected for us, and its core displayed.
How was Crater Lake formed?
The phrase “GREW, BLEW, FELL, and FILL” describes the process that created Crater Lake.
Grew – Mount Mazama was a large composite volcano that was built during the past 400,000 years by hundreds of smaller eruptions of lava flows. Mount Mazama rose to an approximate height of 3,700 m (12,000 ft) above sea level.
BLEW – About 7,700 years ago, Mount Mazama erupted catastrophically, blowing out about 50 km3 (12 mi3) of magma in a few days. The volcanic ash covered parts of the northwestern states, spreading as far as central Canada. Rare particles of Mazama ash have even been found in ancient ice from Greenland. The airfall pumice and ash covered a total surface area of more than 2,600,000 km2 (1,000,000 mi2) at least 1 mm thick. A volume of 42-54 km3 (10-13 mi3) of the mountaintop had disappeared. Where had all this mass gone? Did Mount Mazama blow its top off?
FELL – Mount Mazama did not blow its top off; it collapsed in on itself. As this enormous volume of magma was rapidly removed from the chamber to feed the climactic eruption, it created a huge void underneath the mountain. Leaving no support for this massive dome, the roof of the magma chamber collapsed, forming the bowl-shape depression known as a caldera.
FILL – About 5,000 to 6,000 years ago, the accumulation of rain and snow filled the caldera. It took perhaps 250 years for the caldera to fill to its present-day lake level, which is maintained by a balance between precipitation and evaporation plus seepage.
Here we have revealed to us all the evidence necessary to reconstruct the processes which formed Mount Mazama, and the clues to the activity of vulcanism and glaciation.
As the Grand Canyon gives an unequalled calendar to the entire history of sedimentary processes upon the North American continent, so Crater Lake Rim exposes the history of the more recent volcanic forces, which so appreciably altered the topography of the Northwest.[Crater Lake National Park as a Field for Scientific Research, Nature Notes From Crater Lake, Vol. 23, 1992]
A Geologic History of the Park 1912 by J.S. Diller, USGS
More Geology Pages in the Library
- 1997 Map of Earthquake Locations – Crater Lake Region, 1920-1925, United States Geological Survey
- 1892 Crater Lake National Park Model, U.S. Geological Survey
- 1997 Geologic Map of the Crater Lake Caldera Floor, United States Geological Survey
- Shaded-Relief Bathymetry Image of Crater Lake, Oregon
- 1908 Crater Lake, Oregon, Map, United States Geological Survey, Professional Paper No. 60, The Interpretation of Topographic Maps
- 1911 Crater Lake National Park Administrative Topographic Map, Dept. of the Interior, U.S. Geological Survey
- Reprinted 1925 Dept. of Interior, U.S. Geological Society, Crater Lake National Park Topographic Map
Crater Lake Geology in the News
- New USGS Geologic Map of Mount Mazama and Crater Lake Caldera – Nov. 24, 2008
- Rainier third most dangerous U.S. volcano – February 28, 2007
- Roving the Floor of Crater Lake – August 21, 2006
- Rockin’ in the Klamath Basin – September 26, 2005
- Seismic monitoring stations wanted at Crater Lake – September 17, 2005
- Geologist’s talk rebuilds mountain: Charles Bacon explains how eruption created Crater Lake -Aug. 25, 2004
- Sinnott Memorial Overlook: new exhibit provides answers – September 02, 2003
- Geologist honored for Crater Lake work – August 19, 2003
- Geologist receives research award – July 22, 2003
- Crater Lake symposium broad as well as deep – October 07, 2002
- New Maps/Report by USGS Scientists show underwater features of Crater Lake in unprecedented detail – June 1, 2001
- Scientists finish mapping floor of Crater Lake – August 2000
- Getting to the bottom of things at Crater Lake – July 21, 2000
- Federal Geologists Say Volcano Is Officially Extinct – March 12, 1946
- Smoking Waters of Crater Lake a Great Mystery – December 21, 1945
- Oregon’s famous Crater Lake not 1,000 years old – December 29, 1934
- A Volcano That Became a Lake – June 5, 1911
- Crater Lake National Park – May 11, 1911
- Government Surveyor Says That Crater Lake has Remarkable Beauty – June 28, 1903
- Deep Water – September 9, 1886
- Examination of Crater Lake – September 4, 1886