Medicine Lake Volcano and Lava Beds National Monument, California
Authors: Donnelly-Nolan Julie M. 
Published: November 2007

Medicine Lake Volcano is located in the Modoc Plateau physiographic province in northeastern California, about 30 mi(50 km) northeast of Mt. Shasta. It is a Pleistocene and Holocene shield volcano whose products cover about 900 mi2 (2,500 km2);volume is estimated to be about 130 mi3 (600 km3). Lava Beds National Monument is located on the northern flank of the volcano.The monument encompasses mostly basaltic and some andesiticlavas. Higher on the volcano, basaltic lavas are mostly absent, andesite dominates, and high-silica lavas are present including the spectacular late Holocene rhyolites and dacites of Glass Mountain, Little Glass Mountain, and the Medicine dacite flow (Anderson, 1941). A wide variety of volcanic and tectonic phenomena can be seen at Medicine Lake Volcano. Many features are young and very well exposed, making it an ideal place for a field trip to see the range of volcanic activity from basaltic to rhyolitic (Fig.1).

Medicine Lake sits at an elevation of 6,676 ft (2,005 m) within a 4.5-by 7.5-mi (7- by 12-km) caldera; the highest point on the caldera rim is 7,913 ft (2,398 m), and the plateau surrounding the volcano is at about 4,000 ft (about 1,200 m). The volcano is traversed by numerous roads, and access is good although most roads are unpaved. Four-wheel-drive vehicles are unnecessary for this trip and for access to most of the volcano, but high clearance is recommended. For weather and road conditions, it is wise to call ahead to one or more of the national forests whose lands cover most of the volcano: Modoc National Forest (Doublehead Ranger District, Tulelake, CA) for the eastern half including the caldera and the campgrounds at Medicine Lake;Shasta-Trinity National Forest (headquarters in Redding, CA), the southwestern part; Klamath National Forest(headquarters in Yreka, CA) for the northwestern part.

Campgrounds are also available at Lava Beds National Monument. Be forewarned that campgrounds can fill upon holiday weekends. Depending on the weather and on the depth of winter snowfalls, it may not be possible to drive across the caldera in early summer. It is recommended that this field trip guide be followed betweenthe Fourth of July and early October.Roads may be openand clear in June and into early November, but be sure to contact the local Forest Service or Park Service office to find out. Lava Beds National Monument can bevisited year-round.

The weather is unpredictable from day to day at high elevations.Temperatures commonly drop to freezing even during midsummer nights at Medicine Lake. A typicalsummer day will reach 90°F (32°C) at lower elevations, 70–80°F (2l-27°C) higher on the volcano, with a buildup of clouds in the afternoon perhaps resulting in isolated thunderstorms. Food and gas are not available along the route of the trip; water is available only at Medicine Lake and at the Visitors Center and campground in Lava Beds National Monument.

A few other words of advice. Wear gloves and eye protection when samplingand climbing on young, glassy, high-silica flows. Youwill need lights (and something warm to wear) for stop 8 and any other caves you might visit; flashlights can be borrowed if necessary at the Visitors Center in Lava Beds National Monument. Remember not to collect samples in the monument.Watch out for rattlesnakes at lower elevations, particularly in the monument. And be aware that new roadsare being built all the time and old ones are destroyed. Do obtain the Forest Service and topographic maps for the area (Bartle, Hambone, Medicine Lake, Mt. Dome, and Timber Mountain 15' quadrangles), but remember that the Forest Service maps available as of this writing (early 1985) are only approximations to reality and that the topographic maps are about 30 years old.

I have written this as a one-day trip. It is designed to show a variety or rock types and morphologic features. If each stop takes half an hour, the whole tripshould take about 10 hours. Many other stops are possible, and I have listed a few below if you wish to makeit a multiple-day trip. A few other stops are written up in Donnelly-Nolan and others (1981).The classic geologic reference is Anderson (1941);this paper contains a very useful, although generalized map. Some petrologic references include Condie and Hayslip (1975), Mertzman ( 1977a, 1977b), and Grove and Baker (1984).

The turnoff to Medicine Lake is on Highway 89 about 16.5 mi (26.5 km) east of McCloud and about 20 mi (32 km) east of Interstate Highway 5. Driving east, the turnoff is just past the Bartle store; there should be a small sign on your left. Turn north onto a good paved road that goes through the place called Bartle on the Bartle 15' quadrangle. Continue north about 4 mi (about 6,5 km) to a junction with another paved road on the right; again, there should be a sign pointing toward Medicine Lake. Turn right(note that if you take the left-hand road, it continues north as a good paved road past Little Glass Mountain and across the northwest flank of Medicine Lake Volcano, then turns west and connects with Highway 97 at Macdoel). Trip mileage begins at this intersection.