Yellowstone

Monitoring Deformation in Yellowstone National Park

Movement of the ground in Yellowstone can tell scientists a lot about what’s happening below the surface. In order to monitor subtle “deformation” of the ground, YVO relies most heavily on Global Positioning System (GPS) stations, strainmeters, and tiltmeters, with instruments that are maintained by UNAVCO.

GPS receiver sitting on hill above lake with trees.

GPS monitoring station P709 is located on The Promontory between the South Arm and Southeast Arm of Yellowstone Lake. It was installed in 2005 as part of the Yellowstone component of the National Science Foundation's Plate Boundary Observatory (PBO) under permit YELL-SCI-5546. (Public domain.)

Within Yellowstone National Park, UNAVCO operates more than a dozen continuous Global Positioning System (GPS) stations, five borehole strainmeter and tiltmeter stations, and a lake level monitoring system on Yellowstone Lake. The greater number of GPS stations, coupled with the comparatively poor performance of tiltmeter and strainmeter data over time periods longer than several days due to instrument drift, make GPS the most important ground-based deformation monitoring method at Yellowstone.

GPS is the backbone of deformation monitoring at Yellowstone

Continuous and semipermanent GPS receivers at Yellowstone precisely record the positions (horizontal and vertical coordinates) of points on the Earth’s surface. By measuring the movement of these locations over days, months, and years, scientists are able to track the rate and direction of ground motion. Mathematical models of this movement through time can help scientists decipher the volcanic and earthquake processes occurring beneath the surface. GPS measurements help answer questions such as: Is material moving in the subsurface? If so, how much material is there, and where is it located?  What is the material made of (e.g. magma, water, or gases)? Is the material moving toward the surface? 

Data from the GPS stations in Yellowstone National Park are transmitted via radio and satellite links to UNAVCO for archiving, and then on to various groups around the world via publically available links for detailed analysis. The net result of this effort is a stream of high-precision and real-time data on how the surface of the Yellowstone region is deforming—critical monitoring data for the Yellowstone Volcano Observatory.

InSAR image of Yellowstone spanning 2004-2006

Color bands in this radar interferogram depict the pattern of surface deformation at the Yellowstone caldera from September 22, 2004, to August 23, 2006. The southwest and northeast parts of the caldera floor rose about 11 cm (4.3 inches) and 15 cm (5.9 inches), respectively, while the north caldera rim near Norris Geyser Basin subsided about 7 cm (2.8 inches). (Credit: Charles Wicks. Public domain.)

InSAR provides large-scale images of ground movement

InSAR (Interferometric Synthetic Aperture Radar) is a technique for mapping ground deformation using radar images of the Earth's surface that are collected from orbiting satellites. Unlike visible or infrared light, radar waves penetrate clouds and are equally effective in day and night.

Two radar images of the same area that were collected at different times from similar vantage points can be compared against each other. Any movement of the ground surface toward or away from the satellite can be measured and portrayed as a "picture" – not of the surface itself but of how much the surface moved (deformed) during the time between images. These “pictures” are called interferograms and are used by deformation specialists at YVO to measure ground movement over very large areas, such as the entire Yellowstone caldera. Unfortunately, InSAR is not effective when the ground is covered in snow, or in areas of particularly heavy vegetation. This means that only data collected in the summer can be used, and some areas of Yellowstone are “hidden” from the radar signal beneath dense tree cover.

Leveling preceded GPS and InSAR

Prior to GPS and InSAR, scientists used classical land surveying techniques to map surface deformation at Yellowstone. Leveling is a surveying technique used to measure vertical deformation – surface uplift or subsidence. It's decidedly low-tech compared to GPS or InSAR, but it played a pivotal role in our understanding of Yellowstone. Read more about Leveling surveys and the discovery of uplift at Yellowstone.