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U.S. Department of the Interior Scientific Investigations Report 2007-5174-A U.S. Geological Survey Plate 1 HAZARDS ASSESSMENT FOR , NORTHERN CALIFORNIA By Julie M. Donnelly-Nolan, Manuel Nathenson, Duane E. Champion, David W. Ramsey, Jacob B. Lowenstern, and John W. Ewert 2007

121º37’ 30” 121º 30’ Map showing caldera features and Gas hazard zone limit caldera-related hazards at Medicine Phreatomagmatic Hot Lake volcano. Green line (gas hazard hazard zone limit Spot zone limit) indicates elevation contour Volcanic vent that defines the closed basin within the 41º 37’ 30” Seismometer caldera, including Medicine Lake. This Medicine Eruptions Intrusions Events in World History is the area within which volcanic gases Lake Hoffman 0 (Inferred) Glass Flow flows x heavier than air could accumulate and Little Glass Glass Genghis Khan founds Mongol Empire potentially result in asphyxiation for Mountain Westminster Abbey construction begins flows anyone within the zone. Orange KLAMATH 2,000 London founded picnic dashed line (phreatomagmatic hazard NATIONAL area campgrounds FOREST campground zone limit) indicates likely extent of Medicine Tutankhamun reigns in Egypt boat Lake ramp phreatomagmatic deposits of hot private MODOC Little NATIONAL volcanic mud should a volcanic vent 4,000 FOREST Mount private N open under the lake. flows shown Hoffman cabins Stonehenge construction begins CALDERA RIM 97 0 1 mile in red are 5,200 years old and younger. SHASTA- TRINITY 0 2 kilometers Hot Spot (red “x”) is site of the volcano’s o 6,000 NATIONAL pit craters g

49 a FOREST only fumarole. srae

8,000 Mt. Mazama erupts to form Y

10,000 People arrive in Tule Lake basin

12,000

o o 122 7’ 30” 120 52’ 30”

Klamath Falls 14,000 Timing of postglacial eruptions (red lines in first column) and inferred intrusions (gray lines in second column) at Medicine Lake volcano. Intrusive events are inferred from the presence of WAWA quenched magmatic inclusions in erupted or from petrologic studies. Events in world and regional history are shown for comparison. Mount produce phreatomagmatic explosions. The immediate area of the St. Helens About Medicine Lake Volcano Summary of Major Volcano-Related 7’ 30”

o lake, including the campgrounds and cabins, would be blanketed 42 OR Hazards by muddy, possibly hot . Eruptions of lava flows or domes Medicine Lake volcano (MLV) is a very large shield-shaped in or near the caldera would probably be preceded by explosive Newberry VVolcanoolcano KLAMATH volcano located in northern California, where it forms part of the Lava Flows and Domes eruptions that could deposit many meters of pumice near the vents. COUNTY Crater Lake southern of volcanoes. It has erupted hundreds of The most likely future eruption at MLV would be a small Any such flows would advance slowly, but if they reached the lake, Mount McLoughlin times during its half-million-year history, including nine times basaltic lava flow a few kilometers in length on the flank of the local explosive activity might occur. Small pyroclastic flows could during the past 5,200 years, most recently about 950 years ago. volcano, accompanied by local near-vent explosive activity that be generated by the collapse of steep flow fronts. Before Medicine Lake CALIFORNIA 139 volcano This record, which represents one of the highest eruptive would build a or spatter cone. Hazards would include and during magmatic intrusions and eruptions, gases, including 121º 45’ 121º 15’ Tulelake Lower Lower frequencies among , includes a wide variety of violent ejection of hot blocks of lava on ballistic trajectories near carbon dioxide, sulfur dioxide, and hydrogen sulfide, can be Klamath CA Klamath Tule Lake Lake 100 km different types of lava flows and at least two explosive eruptions the vent, as well as intermittent explosive pyroclastic eruptions that transported to the surface. The closed topography formed by the Lake 97 Tule that produced widespread fallout of ash. Compared to those of a could send ash clouds several kilometers into the air and deposit caldera rim around Medicine Lake could allow toxic gases to pond Lake

typical Cascade , eruptive vents at MLV are widely local accumulations of ash. Also possible, but much less likely, during extended periods of calm wind conditions, potentially 41º 52’ 30” Clear MODOC Lake distributed, extending 55 km north-south and 40 km east-west. would be eruption of fluid basalt flows that extend tens of resulting in asphyxiation. NATIONAL Reservoir 2 FOREST The total area covered by MLV lavas is >2,000 km , about 10 kilometers from the vent area, cover as much as a few hundred times the area of Mount St. Helens, Washington. Judging from its square kilometers, and could continue for decades. Eruption of Airborne Ash LAVA BEDS long eruptive history and its frequent eruptions in recent geologic silicic lavas, including rhyolite and , would likely be Although only a few tephra layers are recorded among the NATIONAL Ross Chimneys MONUMENT 139 time, MLV will erupt again. Although the probability of an confined to the upper parts of the volcano. Such events probably documented products of MLV eruptions, two rhyolite eruptions Black 10 eruption is very small in the next year (one chance in 3,600), the would begin with explosive eruptions sending tephra many that took place about 1,000 years ago generated significant Crater LBNM Devils Valentine consequences of some types of possible eruptions could be severe. kilometers into the atmosphere, as well as generating local that extended tens of kilometers from the vents and likely were Homestead Cave Visitor flow Center flow Visitor Furthermore, the documented episodic behavior of the volcano pyroclastic flows and surges. Growing lava domes could collapse blown high into the atmosphere to levels that today could affect air Center KLAMATH indicates that, once it becomes active, the volcano could continue to form local avalanches of hot rock, although silicic domes and travel. A similar eruption in the future could potentially affect the NATIONAL Callahan FOREST 10 to erupt for decades, or even erupt intermittently for centuries, and lava flows themselves are not likely to extend more than a few largest nearby city, Klamath Falls, Oregon, if winds were from the Flow tree very likely from multiple vents scattered across the edifice. kilometers from their vents. south. Smaller ash eruptions accompanying the construction of molds flow Medicine Hoffman CALDE Owing to its frequent eruptions, explosive nature, and cinder cones would affect much smaller near-vent areas, but these Lake RA 97 flows R Glass Flow IM proximity to regional infrastructure, MLV has been designated a Caldera-Related Hazards also could interfere with low-flying aircraft. Volcanic ash and 15 Little Glass Medicine “high threat volcano” by the U.S. Geological Survey (USGS) Five of the nine eruptions of MLV in the past 5,200 years coarser debris also can induce respiratory problems, cause Mountain Lake flows Glass National Volcano Early Warning System assessment. Volcanic have taken place within or at the margin of the summit caldera. hazardous driving conditions, interfere with communications, Mountain Medicine Lake MODOC eruptions are typically preceded by seismic activity, but with only Located at the center of the volcano, the 7x12-km caldera contains short out power lines, contaminate feed for livestock, and damage CALDERA RIM NATIONAL two seismometers located high on the volcano and no other USGS the namesake Medicine Lake, a 1x2-km body of water bordered by any electronic or motorized equipment. Once dry, volcanic ash pit craters SHASTA- FOREST Grasshopper TRINITY monitoring equipment in place, MLV is at present among the most campgrounds and private cabins. In the unlikely event of an deposits can be remobilized by wind and remain troublesome long Flat flow ribbon flows NATIONAL Paint Pot FOREST poorly monitored Cascade volcanoes. eruption through the lake, the mixing of water and magma could after an eruption ceases. Crater flow 49 MODOC Burnt COUNTY Lava Flow SISKIYOU COUNTY Mount Shasta

HAZARD ZONES 89 View of Medicine Lake This seismometer installa- volcano from the north- tion on the upper west side Giant Proximal pyroclastic flow Crater flow hazard zone limit east. Numerous cinder of Medicine Lake volcano Lava flow hazard zone limit SHASTA LASSEN cones are scattered at Little Mount Hoffman is COUNTY COUNTY across its surface. Lava one of only two seismic INFRASTRUCTURE Postglacial lavas 7’ 30”

Beds National Monument instruments that are o Power line Pipeline 41 is located on the lower located on the volcano. ~12,500 Road Railroad northern flank of the View is southwest across years old County line N N volcano. the Little Glass Mountain Less than 5,200 years old National Monument and flow that erupted about National Forest boundaries 0 5 miles Volcanic vent 0 5 miles 1,000 years ago. Mount 0 10 kilometers Shasta is on the horizon. 0 10 kilometers 41º 7’ 30” Hazard zonation map of Medicine Lake volcano, showing county and land-management boundaries and infrastructure, including major power lines that carry electric power between the and California and the major pipeline that carries natural gas from Canada to California. Inset map shows major Cascade Range Postglacial lava flows of Medicine Lake volcano (MLV) listed in table 1. Faults are shown as volcanoes (red triangles). thin black lines. LBNM is Lava Beds National Monument. Outline of MLV is shown in red.

Background image: Aerial view looking west across Medicine Lake caldera. Medicine Lake is near the center of the visible image. Mount Shasta is on the left horizon. Edited by Taryn A. Lindquist; digital cartography by David W. Ramsey and Judy Weathers The gray, treeless rhyolite dome of Glass Mountain, the most recently erupted lava at Medicine Lake volcano (at about 950 years), is in the foreground.

Donnelly-Nolan, J.M., Nathenson, Manuel, Champion, D.E., Ramsey, D.W., Lowenstern, J.B., and Ewert, J.W., 2007, Volcano hazards assessment for Medicine Lake volcano, northern California: U.S. Geological Survey Scientific Investigations Report 2007-5174-A. Any use of trade, product, or firm names in this publication is for descriptive purposes only and does not imply endorsement by the U.S. Government. For sale by U.S. Geological Survey, Information Services, Box 25286, Federal Center, CO 80225, 1–888–ASK–USGS Printed on recycled paper Digital files available at http://pubs.usgs.gov/sir/2007/5174/a/