Tule Lake. A place of conflict, beauty, contradiction, extraction, preservation, jurisdiction, nurturance, and striking geologic presence. Visiting Petroglyph Point or one of few caves with paintings, both part of the Lava Beds National Monument, is accessible and rewarding. However, if one becomes curious about these places and spaces, the peoples and animals come and gone and come again, the winds of history, prehistory, planning, and accident quickly buffet, even shred, assumptions.
The Rock Art. There are many studies with various facts, beliefs, and conjectures, which may be dated, fragmentary, or not well-grounded. We are reminded all interpretation risks concocting explanations by aligning selective facts or suppositions. What to do? Go out and look around!
Meanwhile, for background study I suggest starting with the informed work of Robert David. His 2012 dissertation offers a fairly comprehensive bibliography related to Klamath Basin rock art with many references directly applicable to the Tule Lake area. Online, open access: The Landscape of Klamath Basin Rock Art (2012).
Further: Julian Steward (1929 & 1937), Robert Heizer & C. William Clewlow Jr (1973), B.K. Swartz Jr. (1978), Helen Crotty (1979 & 1981), Georgia Lee & William Hyder (various 1980s & 1990s), James Keyser et al. (2006). For Fern Cave, internet searches offer a range of information, though many studies are not public.
The Place. Two books to open doors.
Balancing Water: Restoring the Klamath Basin. 2000. Tupper Ansel Blake, Madeleine Graham Blake, and William Kittredge.
Hell with the fire out: a history of the Modoc War. 1997. Arthur Quinn.