Lava Beds National Monument
November 21, 1925
Lava Beds National Monument, in Siskiyou and
Modoc County,
is the site of the largest concentration of lava tube caves in the
United States. The monument lies on the northeast flank of the Medicine Lake shield volcano,
the largest volcano (total area covered) in the Cascade Range.
The region in and around the monument is unique because it lies on the junction of the
Sierra-Klamath, Cascade, and Great Basin physiographic provinces.
In addition, the monument is geologically outstanding because of its great variety of “textbook”
volcanic formations; i.e., lava tube caves, fumaroles, cinder cones, spatter cones, maar volcanoes,
and lava flows. Over 30 separate lava flows located in the park range in age from 2,000,000 years BP
to 1,110 years BP. Some of the major Lava Flows within Lava Beds National Monument include:
Callahan Flow, Schonchin Flow, Mammoth Crater Flow, Modoc Crater Flow, and
Devils Homestead Flow. Schonchin Butte is an example of a cinder cone.
The high elevation, semi-arid desert environment of Lava Beds receives an
average of 15 inches (381mm) of precipitation annually. The climate is characterized by warm, dry
summers and cold winters. The average annual high temperature is 60 F (16 C) and average annual low
temperature is 35 F (2 C). Temperature extremes range from –18 F ( -28 C) to 102 F (39 C). Average
annual snowfall is 44 inches (1118 mm). The lava tube collapse systems and lava outcrops support a
great diversity of plant life, from an impressive variety of lichens and mosses to plants such
as desert sweet (Chamaebatiaria millefolium) and the aromatic desert (purple) sage
(Salvia dorrii carnosa). An impressive variety of fern species are present in cave entrances including
the spreading wood fern (Dryopteris expansa) and the western swordfern (Polystichum munitum).
These species are well outside of their normal range 90 - 125 miles away on the northern California
coastline.
Volcanic eruptions on the Medicine Lake shield volcano have created an incredibly rugged landscape punctuated by cinder cones, lava flows, spatter cones, lava tube caves and pit craters. During the Modoc War of 1872-1873, the Modoc Indians used these tortuous lava flows to their advantage. Under the leadership of Captain Jack, the Modocs took refuge in "Captain Jack's Stronghold," a natural lava fortress. From this base a group of 53 fighting men and their families held off US Army forces numbering up to ten times their strength for five months. Gen E. R. S. Canby was killed here by Captain Jack at a peace meeting on April 11, 1873.