Lava Beds National Monument is located in northeastern California, in Siskiyou and Modoc counties. The monument lies on the northeastern flank of Medicine Lake Volcano and has the largest total area covered by a volcano in the Cascade Range.

The region in and around Lava Beds National Monument lies at the junction of the Sierra-Klamath, Cascade, and Great Basin physiographic provinces. Th... Wikipedia

Pluto's Cave (or Pluto Cave) is a partially collapsed lava tube on the northern outskirts of Mount Shasta in the Klamath National Forest. Its main entrance is located close to the 99-97 Cutoff c. 12 miles (19 km) North-east of Weed and c. 14 miles (23 km) East-southeast of Grenada. The tube is roughly 190,000 years old, which is quite old for a lava tube, as they normally collapse quickly (in geol... Wikipedia