Plants of the Lava Beds National Monument, California

Abstract

The total area covers approximately 46,000 acres, roughly a rectangular tract 8 by 9 miles in extent. In elevation it ranges from about 4,000 feet on the north, along the shore of Tule Lake, up to about 5,700 feet in the southwest corner, where, outside the monument, the ascent continues mnore abruptly for a distance of about 6 miles, culminating in the crater-like escarpment surrounding Medicine Lake, the highest points of which are around 8,000 feet above sea level. Geologically the entire area (Fig. 1) is the result of comparatively recent volcanic activity, covering the surface with successive lava flows, coming largely from the Medicine Lake region just mentioned. The ends of the flows are often marked by walls of varying heights which break the more even ascent from north to south; while long sinuous interrupted depressions with an opposite trend indicate the partially broken-down roofs of lava tubes along the line of flow. The undisturbed portions, remaining as bridges, often leave exposed ends of galleries which are known as caves. Most of the area is covered by a varying depth of pumice sand and gravel, providing the most important soil element.