by John Perry Thursday, January 5, 2012
Over the past 2.1 million years, Yellowstone volcano has had three explosive super-eruptions. During the most recent super-eruption 640,000 years ago, the supervolcano ejected 2,500 times as much ash and lava as the 1980 Mount St. Helens eruption. If such an eruption were to occur today, it would bury the immediate vicinity in ash flows up to 600 meters deep, and would ultimately spread ash across the western half of North America. Meanwhile, sulfur aerosols and ash particles from the volcano would travel the world, lowering temperatures, devastating agriculture and causing alarming water and air quality issues.
The Yellowstone volcano last erupted magma 70,000 years ago, but it is anything but dead. Magma is actively churning beneath the landscape of Yellowstone National Park, and is responsible for the world’s largest and most diverse collection of natural thermal features, including Old Faithful and the spectacular Norris Geyser Basin. The activity also causes periodic swarms of earthquakes.
The volcanism is also responsible for another phenomenon: the multitudes of scientists and instruments that blanket the park at all times, monitoring its constant activity, including the seismic swarms, periodic bursts of gases and fluctuating temperatures beneath the surface. Yet Yellowstone presents unique challenges to volcano monitors. Unlike many other volcanoes, at Yellowstone, the typical precursors to an eruption are not limited to the lead-up to an eruption; such volcanic activity actually occurs on a near-daily basis beneath the park. Yellowstone also differs because it has a near-constant stream of visitors. So researchers monitoring activity at Yellowstone have to look more closely at small changes to know when to issue an alert or close a particular basin to visitors — or, in the worst-case scenario, close the whole park if somehow an eruption seems imminent. Now, researchers have a new tool to help them monitor what goes on beneath the landscape — remotely, constantly and in real time.
Volcanoes don’t erupt without warning. Active volcanoes around the world are fitted with instruments to measure gas fluctuations, seismometers to detect earthquakes and GPS devices to measure ground deformation — uplift and subsidence. These instruments record changes in activity so that researchers can issue warnings if an eruption seems near. Scientists at the Yellowstone Volcano Observatory (YVO) — one of five U.S. Geological Survey (USGS) volcano observatories that monitor volcanoes within the U.S. — closely monitor instruments in the Yellowstone region for volcanic precursors. USGS, U.S. National Park Service (NPS) and University of Utah scientists at YVO rely on multiple arrays of instrumentation to keep tabs on the park.
For instance, seismometers placed at strategic locations record earthquakes. Those earthquakes with magnitudes greater than 1.5 are automatically logged and plotted on a map. Ground deformation measurements are done with ground-based GPS systems that communicate with satellites and satellite-based Interferometric Synthetic Aperture Radar (InSAR) instruments. Networks of GPS continuously measure horizontal and vertical motion at specific locations throughout the park, providing a “moving picture” of these sites. InSAR, meanwhile, measures a large area from space as a snapshot of a single point in time. Because InSAR data take considerable time to acquire and process, these data are collected only once or twice a year. But together, GPS and InSAR allow YVO scientists to monitor ground deformation over time.
Meanwhile, streamflow gauges measure runoff volume from 15 sites in the five major river basins draining Yellowstone National Park. And selected parts of the park, such as Norris Geyser Basin, are also fitted with stream temperature gauges. But many of these gauges are far from the real action where hot waters are emerging from Yellowstone’s geyser basins. Furthermore, the sensors only provide information every 15 minutes.
To augment these existing monitoring and data collection instruments, we built and deployed a new sensor network at the Norris Geyser Basin last June that provides near-real-time updates on temperature variations within 0.2 degree Celsius. Researchers have collected temperature data from the park in the past, but previously, the data were collected manually every month — when it was possible to reach the sensors. Now, the data are collected 24/7 and automatically relayed back to YVO once per day.
The Norris Geyser Basin is the most dynamic thermal area at Yellowstone and displays a variety of transient thermal phenomena — such as constantly active geysers, thermal pools and “mud pots” — that are thought to relate to hydrologic, volcanic and tectonic activity. The sensor network can provide real-time updates on temperature variations due to anomalous hydrothermal discharges or subsurface fluid migration.
The system will allow managers, scientists and the public to keep track of changes to the hydrothermal system, including geyser eruptions, periodic basin-wide disturbances or fluid-release events that may accompany or follow seismic activity. The new system offers several advantages to both YVO and the public. First, data can be viewed within 24 hours of measurement, allowing rapid assessment of changing conditions. Second, equipment malfunctions can be rapidly detected, enabling us to identify and correct any problems. Lastly, if needed, we can ping the equipment to get the most recent data, rather than waiting for it to alert us to any changes.
The system is designed to monitor changes from three different sub-basins at Norris — Gray Lakes, Steamboat-Echinus and Porcelain Basin. It also monitors the main Tantalus Creek drainage and five individual features in the park: Constant, Porkchop, Steamboat and Echinus geysers, and Opalescent Spring. The network starts with 10 radio-equipped high-tech loggers that are distributed throughout the Norris Geyser Basin. They are programmed to measure temperatures within runoff channels from geysers, hot pools, soils and air every two minutes using high-temperature sensors at the end of flexible probes. The loggers communicate with a base station antenna located 10 meters up a tree and camouflaged (so the public can’t see it) near the Norris Geyser Basin Museum.
Because the monitoring system is unique, the project required unique equipment not readily available. The radios have to be small with unobtrusive antennas so that the equipment can be placed beneath boardwalks and within small rock piles — primarily so that it is hidden from the public, per Yellowstone rules, but also so that coyotes and other troublemakers don’t find the equipment and destroy it, as has happened with the old temperature loggers. In addition, the radio signals have to be strong enough so that a day’s worth of temperature data can be sent to a base station almost a kilometer away. And the equipment has to be able to withstand acid waters, steam and subfreezing temperatures during Yellowstone’s notorious winters.
The network, operated by USGS and NPS, began automatically transmitting temperature measurements from geysers and hot springs in the Norris Geyser Basin last August. The data are saved in the loggers each day, and are also transmitted once a day via small radios and the Internet to USGS. During periods of unusual hydrothermal behavior, researchers can request that data be relayed in real time as well. Once USGS has the daily data dump, the data are archived, plotted and distributed to the public on the YVO website. Each day, we then upload and distribute online temperature variations at each logger over 24-hour, seven-day and one-month periods to show changes at each location over time.
The daily temperature data, revealing the recurring activity beneath Yellowstone, resemble a heartbeat readout for the park. Occasionally, there are murmurs: For example, we can see within the data the effects of precipitation from rain and snowmelt as the cold water flows through runoff channels across the geyser basin and then returns to a normal, hotter temperature.
Over the next few years, the information from this network will help us track temperature changes in local streams that might correlate with seismic tremors, and help park officials keep an eye on thermal features for educational and safety purposes. We look forward to learning more as we watch this active system, and explore the hydrological, meteorological and thermal processes at Yellowstone.
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