National Park Service US Department of the Interior Natural Resource Stewardship and Science Lava Beds National Monument Geologic Resources Inventory Report Natural Resource Report NPS/NRSS/GRD/NRR—2014/804 ON THE COVER Gillem Bluff rises from the plain in northwestern Lava Beds National Monument. A fault runs along the base of the bluff and bounds the western side of the Tule Lake basin. Displacement along the fault uplifted Gillem Bluff. The fault projects south, where it is buried by lavas of Medicine Lake Volcano. The basalts of Mammoth Crater (tan, covered in aeolian deposits of dust and sand) and Devils Homestead (black) flowed against the base of the bluff about 35,000 and 12,300 years ago, respectively. US Geological Survey photograph by Tanya Blacic. THIS PAGE Crystal Ice Cave contains some of the most spectacular ice formations in Lava Beds National Monument, which is known for these features. Over the past two decades, researchers and monument staff have observed the loss of year-round ice within the ice caves at the monument. Because of the sensitive nature of ice formations and cold environments within these caves, Crystal Ice Cave is open to visitors only on ranger-led tours during the winter months. Exploring Crystal Ice Cave is a remarkable way to experience the monument’s volcanic geology while surrounded by stunning ice formations. Photograph by Kenneth Ingham (copyright 2011, used by permission). Lava Beds National Monument Geologic Resources Inventory Report Natural Resource Report NPS/NRSS/GRD/NRR—2014/804 Katie KellerLynn Colorado State University Research Associate National Park Service Geologic Resources Division Geologic Resources Inventory PO Box 25287 Denver, CO 80225 April 2014 US Department of the Interior National Park Service Natural Resource Stewardship and Science Fort Collins, Colorado The National Park Service, Natural Resource Stewardship and Science office in Fort Collins, Colorado, publishes a range of reports that address natural resource topics These reports are of interest and applicability to a broad audience in the National Park Service and others in natural resource management, including scientists, conservation and environmental constituencies, and the public. The Natural Resource Report Series is used to disseminate high-priority, current natural resource management information with managerial application. The series targets a general, diverse audience, and may contain NPS policy considerations or address sensitive issues of management applicability. All manuscripts in the series receive the appropriate level of peer review to ensure that the information is scientifically credible, technically accurate, appropriately written for the intended audience, and designed and published in a professional manner. This report received informal peer review by subject-matter experts who were not directly involved in the collection, analysis, or reporting of the data. Views, statements, findings, conclusions, recommendations, and data in this report do not necessarily reflect views and policies of the National Park Service, US Department of the Interior. Mention of trade names or commercial products does not constitute endorsement or recommendation for use by the US Government. Printed copies of this report are produced in a limited quantity and they are only available as long as the supply lasts. This report is available from the Geologic Resources Inventory website (http://www.nature.nps.gov/geology/inventory/gre_publications.cfm) and the Natural Resource Publications Management website (http://www.nature.nps.gov/publications/nrpm/). To receive this report in a format optimized for screen readers, please email [email protected]. Please cite this publication as: KellerLynn, K. 2014. Lava Beds National Monument: geologic resources inventory report. Natural Resource Report NPS/NRSS/GRD/NRR—2014/804. National Park Service, Fort Collins, Colorado. NPS 147/124460, April 2014 ii NPS Geologic Resources Division Contents List of Figures ................................................................................................................. v List of Tables ................................................................................................................. vi Executive Summary ..................................................................................................... vii Products and Acknowledgements ............................................................................... xi Geologic Setting and Significance ................................................................................ 1 Geologic Features and Processes .................................................................................. 9 Medicine Lake Volcano ................................................................................................................................................ 9 Volcanic Features in Lava Beds National Monument ................................................................................................... 10 Lava Tubes ................................................................................................................................................................. 15 Tectonic Features ....................................................................................................................................................... 20 Paleontological Resources .......................................................................................................................................... 22 Lake Deposits ............................................................................................................................................................ 25 Glacial Outwash ........................................................................................................................................................ 25 Geologic Features with Cultural Significance .............................................................................................................. 26 Geologic Resource Management Issues ..................................................................... 33 Cave Management .................................................................................................................................................... 33 Recreational Impacts on Geologic Features ................................................................................................................. 35 Wind Erosion at Petroglyph Point ............................................................................................................................... 36 Abandoned Mineral Lands ......................................................................................................................................... 37 Rockfall and Roof Collapse ......................................................................................................................................... 37 Earthquakes ............................................................................................................................................................... 38 Volcano Hazards ........................................................................................................................................................ 39 Geothermal Features and Development...................................................................................................................... 41 Geologic History .......................................................................................................... 43 Pre–Medicine Lake Volcano History ............................................................................................................................ 43 Lake History ............................................................................................................................................................... 43 Medicine Lake Volcano History ................................................................................................................................... 43 Glacial History ............................................................................................................................................................ 46 Holocene Epoch: Geology and Culture ....................................................................................................................... 46 Geologic Map Data ...................................................................................................... 47 Geologic Maps .......................................................................................................................................................... 47 Source Maps .............................................................................................................................................................. 47 Geologic GIS Data ..................................................................................................................................................... 47 Map Unit Properties Table .......................................................................................................................................... 48 Geologic Map Graphic ............................................................................................................................................... 48 Use Constraints .........................................................................................................................................................