The Hot Creek Geologic Area is a very dynamic hydrothermal system. Remain on the marked paths and do not cross fences or barriers. People that have ignored warnings have been severely burned or died.
This creek is within the Long Valley Caldera, a large depression created by an eruption 760,000 years ago. In this eruption, a large volume of magma was ejected from a magma chamber beneath the earth leaving a void. The earth above fell down creating the caldera. The remaining magma has periodically erupted over the past 40,000 years forming the Inyo Craters. The most recent eruption occurred only a few hundred years ago at Panum Crater EarthCache . Even with all these eruptions some magma still remains.
It is this magma combined with the regional water cycle that creates the hydrothermal systems in the area. Snowmelt from the Eastern Sierra infiltrates to depths of between 2 and 3 kilometers where it is heated to 220 degrees C. Due to the pressures at that depth, it does not boil. This super-heated water rises to shallower depths (0.5 to 2 km) along fractures found on the western side of the caldera. Local groundwater flow then moves the hot water eastward. Along the way the hot water mixes with cooler ground water gradually cooling until it comes out of springs located faults that cross Hot Creek at a temperature of 93 degrees C (boiling at this altitude).
On average about 240 liters of water come out of the springs each second. However the flow and temperature are highly variable. The changes are likely the result of subsurface conduits are periodically blocked and unblocked by carbonate deposits and or earthquakes. The amount of water discharged at Hot Creek and the temperature at which it is discharged accounts for 70 percent of the total heat discharged by all the hydrothermal springs in the Long Valley Caldera.
The hydrothermal waters contain a variety of minerals including sodium bicarbonate, arsenic, boron, and fluoride. The concentrations of these minerals exceed safe drinking water standards.
Many of the pools at Hot Creek are amazingly blue. The white precipitates that line the pools, the physical properties of water, and the temperature of the water cause this color. The calcium carbonate dissolved in the hydrothermal water is deposited on the sides of the pools as the temperatures of the water cools reducing its capacity to keep minerals dissolved in it. These deposits are white to very light tan and reflect light very well. When light goes through water, the red is adsorbed and blue is reflected creating the blue we observe. In addition, the bluest pools are generally the hottest since these hot temperatures prevent any biological activity. Once the waters cool to about 70 degrees C, bacteria and algae can grow changing the water’s color to green or brown.
As you walk down to the creek, notice the rocks along the side of the trail. These rocks are hydrothermally altered rhyolite.
Logging questions:
- The text "GC3JMYK Hot Creek Geologic Area – Long Valley Caldera" on the first line.
- The number of people in your group (put in the log as well).
- What temperature do you expect the pool on the north side of the creek to be?
- What evidence did you use to come to that conclusion?
- What distinctive feature can you see in the hydrothermally altered rhyolite at N37 39.673 W118 49.684, N37 39.679 W118 49.678, and/or N37 39.684 W118 49.673?
- According to the sign at the coordinates, how much material was blasted out during the eruption 700,000 years ago?
- How deep is the magma chamber that heats the water? (note that the diagram at the site differs from the one on the cache page.)
The following sources were used to generate this cache.
- Christopher D. Farrar, William C. Evans, Dina Y. Venezky, Shaul Hurwitz, and Lynn K.Oliver, USGS Fact Sheet 2007-3045, Boiling Water at Hot Creek—The Dangerous and Dynamic Thermal Springs in California’s Long Valley Caldera U.S. GEOLOGICAL SURVEY and the U.S. FOREST SERVICE—OUR VOLCANIC PUBLIC LANDS online at http://pubs.usgs.gov/fs/2007/3045