Lava Beds National Monument is located in northeastern California, in Siskiyou and Modoc Counties. The Monument lies on the northeastern flank of the Medicine Lake Volcano, with the largest total area covered by a volcano in the Cascade Range. The region in and around Lava Beds Monument is unique because it lies on the junction of the Sierra-Klamath, Cascade, and the Great Basin physiographic provinces. The Monument was established as a United States National Monument on November 21, 1925, including over 46,000 acres (190 sq km).
Lava Beds National Monument has numerous lava tube caves, with twenty five having marked entrances and developed trails for public access and exploration. The monument also offers trails through the high Great Basin xeric shrubland desert landscape and the volcanic fields. The Lava Beds National Monument has 13 hiking trails, all of which cross or enter the backcountry. The most popular trails are short, but lead to a number of historic sites as to several geological areas within the Lava Beds Wilderness. he long trails are mostly in designated wilderness areas.
These trails are primarily associated with park attractions, especially the Lava Beds geological wilderness, and are sometimes out and back Day hikes, and in many cases are improved boardwalks and supported with interpretive signs and exhibits.
Lava Beds National Monument is geologically outstanding because of its great variety of "textbook" volcanic formations including: lava tube caves; fumaroles; cinder cones; spatter cones; pit craters; hornitos; maars; and lava flows and volcanic fields.
Volcanic eruptions on the Medicine Lake Shield volcano have created an incredibly rugged landscape punctuated by these many landforms of volcanism.
Lava Tube Caves:
Lava flows dated to about 30,000-40,000 years ago formed most of the lava tube caves in the monument. As the hot basaltic lava flowed downhill, the top cooled and crusted over, insulating the rest of the lava and forming lava tubes. Lavacicles on the ceiling of a lava tube were left as the level of lava in the tube retreated and the viscous lava on the ceiling dripped as it cooled.
Dripstone was created when lava splashed on the inside walls of the tubes. The leaching of minerals from pumice gravel, soils, and overlying rock provides for deposition of secondary speleothems in lava tubes. Lava Beds National Monument has the largest concentration of lava tube caves in North America. One has electrical lighting, the others are illuminated by ceiling collapse portals or require flashlights, available to loan.