14 
PROCEEDINGS OF THE CALIFORNIA ACADEMY OF SCIENCES 
Series 4, Volume 64, Supplement 1 
Figure 10. A California sea lion, Zalophus californianus (on rock right of center), watches a kayaker in Painted Cave, 
a sea cave on Santa Cruz Island. Dave Bunnell. 
Cave Region 7 — Mojave Desert 
A limited number of extremely isolated caves are known in the Paleozoic Limestones that crop 
out in the mountains of the Mojave Desert in southern California. Most caves are between 1,000 
and 1,500 m in elevation. The caves are relatively dry due to the regional aridity. We have data on 
207 caves and karst features (59 biological sites), 13 sampled lava tubes, 4 sampled groundwater 
sites, and 90 mines (27 biological sites, Table 1). Pisgah Crater and Amboy Crater contain many 
lava tubes, but biological studies have only recently begun there. Pisgah Crater has perhaps 200 
lava tubes (Harter 1992) with age estimates from 50,000 to 2,000 years, depending on which erup¬ 
tion is dated. Amboy Crater’s age ranges from 100,000 to 18,000 years ± 5,000 years (Wikipedia 
2016c). 
Cave Region 8 — Colorado Desert 
This region is the northwestern subdivision of the much larger Sonoran Desert, and contains 
the valley draining to the Colorado River in southeastern California, sometimes included in the 
Mojave Desert. The majority of the Colorado Desert lies below 300 m, with the lowest point at 
84 m below sea level at the Salton Sea. Although the highest peaks of the Peninsular Range reach 
elevations of nearly 3,000 m, most of the region's mountains do not exceed 900 m. The region 
includes all of Imperial and portions of San Diego, Riverside and San Bernardino counties, includ¬ 
ing a narrow swath along the Colorado River (Fig. 1). More than 1,000 min es and a few caves are 
known in the region. Biological records are available from nine caves, 15 mines, and one well 
(Table 1). Obligate subterranean species are as yet unknown from this region. 
