Long Valley Hydrologic Advisory Committee takes geo data seriously
Never heard of the Long Valley Hydrologic Advisory Committee? You wouldn’t be alone. Most folks aren’t aware the HAC even exists.
In an informational public meeting Tuesday evening, HAC members from the U.S. Geological Survey (USGS), the Bureau of Land Management (BLM), Ormat and the U.S. Forest Service describe what the role of the committee is and how its members contribute to its work in Mono County and surrounding areas.
As Mono County Economic Development Director Dan Lyster explained, the LVHAC was formed in 1985 as the LV Technical Advisory Committee, but changed its name and indeed its focus a year later. Originally set up to have input on development of geothermal resources, its scope has expanded to include monitoring and safeguarding of resources considered geologically important, such as area fish hatcheries, springs, and sites of geothermal interest, such as Hot Creek and Casa Diablo.
During the past 25 years, data collection has improved dramatically since the LVHAC formed a partnership with the USGS, which does monitoring via its Volcanic Hazards Program under the auspices of a cooperative agreement with Mono County.
The USGS, however, does not interpret data gathered from monitoring of groundwater, thermal pools, gas from fumaroles and snowpack, among other items. HAC members do that, and use their findings to inform and advise public agencies, such as the BLM and Mono County for everything from permitting of new geothermal wells to disaster preparedness.
The LVHAC made it clear that it is not a legislative or regulatory body, and has no such authority.
Water covers 70% of the Earth’s surface, and by definition, hydrology means the study of the movement, distribution and quality of that water. But in our area, it’s not water above ground that concerns the USGS. Volcanic Observatory Scientist Maggie Mangan monitors our volcanic activity and its impact on below ground geothermal water sources with great interest.
Hot Creek, for example, a notable part of the Long Valley Caldera, is the exit point for more than 70% of the Caldera’s hot water that makes its way to the surface. That water is heated by volcanic activity situated directly below the caldera, which is bordered on the southwest by Mammoth Mountain Ski Area and Mammoth Lakes, the northeast by the Glass Mountains, and the south and southeast by Convict Lake, Crowley Lake and Casa Diablo.
Volcanoes don’t have to be shaped like the classic cone structures seen in the movies. Indeed the Eastern Sierra is part of a small number of “super volcanoes” that can be found in continental North America. While the Long Valley Caldera generally resembles more of a sagging roof, geologically speaking, near the center is what Mangan called a “resurgent dome area,” which has seen uplift of about 1 meter between 1980 and 2000. Molten lava, which is lighter than solid rock, rises, and cracks and displaces other rock, causing earthquake swarms and gas emissions, and lead to domes that form over a period of years, such as the caldera’s resurgent dome.
The last eruption in our area was 300 years ago in the middle of Mono Lake, but we could always be on the verge of another. From her post at the San Jose/San Francisco CalVO (California Volcanic Observatory), Mangan also monitors potential volcanic eruptions in California and parts of Nevada, per Congressional directive, “to assess hazards and inform crisis management in various localities.”
“Most folks know California has earthquakes, but most don’t know we even have volcanoes,” Mangan said. Scattered throughout the state, she said most are fairly “young,” with molten rock “in their guts” that can pose a risk of unrest and eruption. Several eastern ranges benefit from geothermal capability, including the Lassen range and Casa Diablo locally.
Hydrology, it turns out, has its antecedents in other areas of volcanic study, particularly mudflows, concrete-like rivers made up of heated water, rock, ash, dirt and other debris, and CO2 emissions. She cited Horseshoe Lake as an example, which has experienced leakage that has killed numerous trees in that area and occasionally poses health hazards to humans and animals.
“Tracking water temperature changes helps illustrate the effects of shallow hydrological shifts from magma movement,” Mangan explained. And she went on to point out that the network of remote stations used to take hydrologic, seismic and volcanic-related readings in the Eastern Sierra is among the most state-of-the-art worldwide. In fact, she posited that the only one similar in scope and technology is situated in a similar locale of interest in Italy.
“Data comes in to Mammoth Community Water District [also a LVHAC member] 24/7/365,” Mangan said. As to any threat levels, nothing is raising any major flags thus far. “The southern part of the caldera is a ‘zone of interest,’ which has had some fairly consistent earthquake activity, until about 2006. Since then it’s been relatively quiet,” she concluded.
And if you’re wondering whether geothermal drilling has anything to do with those series of quake swarms, Mangan insisted the answer is no. Quakes were being logged in the area prior to geothermal utilization and have been ruled out as a cause. In any case, if an event were to become imminent, we’d likely know it was coming weeks or months before anything happened. Volcanoes differ from other natural events in that, while they have a long duration once they’ve occurred, they have a longer advance timeline as well.
Home on the Paleozoic range
Hydrologic study can also involve ancient Earth history. Did you know, for example, that the mountains we now know as the Mammoth Crest/Bloody Mountain/Mt. Morrison range are actually the most complete record of what California looked like during the Paleozoic era from 250 million to 550 million years ago?
“It’s the rosetta stone of geology for this part of the country,” noted Gene Suemnicht of EGS, a geologic consulting firm for many government agencies and industries. Even though the rocks have changed over time, and the terrain isn’t as easy to explore as the Grand Canyon with its layer cake exposures all laid out in one vertical display, numerous important geologic discoveries in the last century or so have their origins in our nearby mountains.
Approximately 760,000 years ago is when the last major change was experienced, when a volcanic eruption blasted 150 cubic miles of ash as high as 60,000 feet into the atmosphere, according to calculations. “That wasn’t a good day to be fishing,” he quipped. Suemnicht said the resulting cataclysm is estimated to be 600 times larger than the one that racked Mount St. Helens in Washington State in the 1980s.
Hot ash fused into hot rock and rained down on what is now Bishop and points nearby, forming the Bishop Tuff, a tuff being a rock formation made up of consolidated volcanic ash. Some of the ash known to have been part of the blast has been found as far away as Kansas, and along the Gulf Coast. And a major section of the mountain range subsided and essentially sank into the Bishop Tuff section of the caldera, a chunk so big that drilling down thousands of feet has so far failed to find the bottom of the slide.
What does all that have to do with hydrology? Plenty, Suemnicht thinks. “If the present is the key to the past, then the reverse is also true,” he posits. “We can learn a lot about our geothermal systems by understanding what happened ‘down under’ millions of years ago.”
Following the forming of the caldera as we see it today, fumaroles formed mostly on the westernmost side, and hot springs mostly on the east. Decades of wells, both experimental and for development helped yield a lot of information as to the area’s geothermal viability. Water, a permeable surface and a major heat source are the three essential items, and Mono County has them in abundance.
Hot Creek, Suemnicht said, has actually been made up of two geothermal systems, once from about 300,000 years ago, which has since faded, and the current one, which dates back about 40,000 years.
In closing, BLM Geologist Collin Reinhardt briefed the audience on the BLM’s permitting and inspection of many of the leases and construction on government land, which it conducts in association with the Forest Service. Reinhardt said 25% of BLM lease royalties go to Mono County (the rest are divided up between federal and state taxes).
And Charlene Wardlow from Ormat said that the planned upgrade of the old G-1 Casa Diablo power plant to the new, more efficient M-1 plant won’t mean any changes to the existing wells there. She also touted some of the benefits of the new CD-4 plant near Shady Rest, which, when built, would mean property taxes and BLM royalties to Mono County, as well as sales taxes and some job creation.