WELCOME TO HOLTVILLE HOT SPRINGS
By definition, a hot spring is a spring that discharges water that is warmer than typical human body temperature. Hot springs can generally be found all around the world, including very cold areas, and are most prevalent in regions that have or have had geothermal activity.
Water for hot springs can stem from varying sources. Typically, surface water escapes underground and returns to the earth’s surface after being heated by a magmatic heat source deep within the earth. In the case of the Holtville Hot Springs, the heat source is approximately 2000-2500 feet below the ground. The geology of the Imperial Valley is such that the very low elevation and relatively thin crust of the earth allows for geothermal activity used for leisure, such as these hot springs, and for more practical purposes, such as the geothermal power plant found to the northeast of this location.
At the site of the springs, one might notice a strong smell akin to rotten eggs. At times, this smell is not present, but at other times it is noticeable. This smell is the result of hydrogen sulfide (H2S) formed from anaerobic bacteria living within the Earth’s crust. The anaerobic bacteria convert the dissolved sulfur in the water to H2S. The presence of H2S is a sign that the water resource is at great depth. The fact that a visitor to this site can smell the H2S is an indication that the concentration of H2S in the air is likely in the range of 0.01-3 ppm. Above 3 ppm, the smell becomes more sickeningly sweet. Above 5 ppm, the H2S present in the air can affect a subject physiologically, including symptoms of nausea, headaches, and insomnia. At 100 ppm and above, the H2S can inhibit the subject’s olfactory sensors; prolonged exposure at this level is often fatal. In other words, if one smells rotten eggs in an area in which geothermal activity is present and suddenly the subject can no longer smell the rotten eggs smell or anything else, the subject should evacuate the area immediately to get to fresh air.
To log this Earthcache, please email the following logging requirement to the cache owner:
1) Based on the strength of the rotten eggs smell at the listed coordinates (if there is a smell), estimate the approximate concentration (in ppm) of hydrogen sulfide in the air. (If there is no smell, state that the estimated concentration of hydrogen sulfide is 0 ppm.)
Land Manager Contact:
Bureau of Land Management - El Centro Field Office
1661 S 4th St El Centro, CA 92243
(760) 337-4400
Bureau of Land Management Policy Regarding Geocaching Activity Can Be Found Here
Sources:
http://science.howstuffworks.com/dictionary/geology-terms/hot-spring-info.htm
http://www.mountainnature.com/geology/HotSprings.htm
http://www.glennmosier.com/2011/10/geothermal-is-the-energizer-bunny-of-the-imperial-valley-2/
https://www.osha.gov/SLTC/hydrogensulfide/hazards.html