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You may not see any active volcanoes in the Reno area today, but this deposit is evidence of volcanic activity here in the past. Geologists believe that it was deposited by a lahar (volcanic mudflow) associated with the ancestral Cascade Range about 12 million years ago.
This cache is part of the 1st Annual International EarthCache Day event, October 8, 2006.
Lahars are mudflows or debris flows composed mostly of volcanic materials that flow down the flanks of a volcano. These flows of mud, rock, and water can rush down valleys and stream channels at speeds of 20 to 40 miles per hour (32 to 64 km per hour) and can travel more than 50 miles (80 km). Some lahars contain so much rock debris (60 to 90 percent by weight) that they look like fast-moving rivers of wet concrete. Close to their source, these flows are powerful enough to rip up and carry trees, houses, and huge boulders miles downstream. Farther downstream they entomb everything in their path in mud. Historically, lahars have been one of the deadliest volcano hazards. They can occur both during a volcanic eruption and when a volcano is quiet. The water that creates lahars can come from melting snow and ice (especially water from a glacier melted by a pyroclastic flow or surge), intense rainfall, or the emptying of a volcanic crater lake. Lahars that interacted with glaciers are cold. However, some lahars are very hot, with their water near boiling, because the recently erupted volcanic rock was very hot. Large lahars are a potential hazard to communities downstream from glacier-clad volcanoes such as Mount Rainier on the outskirts of Seattle, Washington.
The Reno area may not have any active volcanoes today, but this deposit is evidence of volcanic activity in the past. Geologists believe that it was deposited by a lahar from the Kate Peak volcano which was active about 12 million years ago with volcanic vents located throughout the northern Carson Range immediately south of here. A lava flow related to this deposit covers much of what is now the Somersett development north of the Truckee River.
To access this EarthCache site, park at Mayberry Park at the south end of Woodland Street at waymark coordinates:
N 39o 30.204'
W 119o 53.807'
Walk west on the paved trail from the park to the footbridge across the Truckee River located at:
N 39o 30.320'
W 119o 54.065'
Cross the river to the south bank and take the trail east to the EarthCache coordinates given.
To log this visit, e-mail your answer to the following question to the site developer along with the number of people in your group, and if possible, a photo of your group at the Earthcache site.
Looking at the hillside around the lahar exposure in the ditch cut, would you say that the lahar deposit is more resistant to erosion, less resistant to erosion, or about the same as the surrounding rock?
CAUTION IN USING GPS UNITS AND TOPOGRAPHIC MAPS
(Note that GPS coordinates are relative to a particular datum used to describe the nearly spherical shape of the Earth’s surface. Most topographic maps published by the U.S. Geological Survey use the North American Datum of 1927 (NAD 27), but most GPS units are set for either the North American Datum of 1983 (NAD 83) or the World Geodetic System of 1984 (WGS 84). NAD 83 and WGS 84 give nearly identical locations with hand-held GPS instruments, but NAD 27 can be off considerably. In this part of Nevada, there is little change in latitude between the 1927 and 1983 data, but for longitude the datum of 1983 is shifted relative to the datum of 1927, such that, if you use your GPS unit to measure a location using WGS 84, the point will plot on the U.S. Geological Survey topographic map approximately 100 meters farther east than its true location on the map. If your GPS unit is set to NAD 27, you need to look for the WGS 84 waypoint approximately 100 meters farther east from your location.)
BASIC VISITOR-USE AND PUBLIC SAFETY INFORMATION FOR PUBLIC LANDS IN NEVADA:
All visitors need to plan ahead and prepare for outings in Nevada’s public lands by:
• Knowing the regulations and special concerns for the area you are planning to visit (obeying laws that prohibit collection or destruction of artifacts);
• Carrying a map and a GPS unit and/or compass (Maps are available for purchase at all BLM offices and from the Nevada Bureau of Mines and Geology, www.nbmg.unr.edu.);
• Staying on existing roads and trails;
• Staying away from all mine shafts and adits;
• Planning for extreme weather, hazards, and emergencies;
• Carrying a full-size spare tire, extra food, water, and warm clothing;
• Being aware that cell phones DO NOT usually work in the rural areas away from the major highways;
• Leaving your travel plans with a responsible party, including the date and time of your return;
• Linking to “Tread Lightly and Leave No Trace” websites (www.treadlightly.org and www.lnt.org).
Please see www.nbmg.unr.edu/EarthCache.htm for more information about this and other Nevada EarthCache and GeoCache sites of geologic interest. Thank you
U.S. Geological Survey Fact Sheet 0071-00, Landslide Hazards
Christopher Henry, NBMG geologist, 2006, personal communication
Tingley, J.V., Pizarro, K.A., Ross, C., Purkey, B.W., and Garside, L.J., 2005, Geologic and Natural History Tours in the Reno Area, Special Publication 19, expanded edition.
For more details about this book, please visit the following webpage: (visit link)
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Coordinates are in the WGS84 datum