Tracking uplift near Three Sisters volcanoes, using semi-permanent GPS instruments
USGS geologist Dan Dzurisin is near Sisters, in Central Oregon, to set up portable GPS monitoring equipment to track something that's been going on for 25 years and still goes on today. It’s uplift, a subtle rise in the ground’s surface, in an area west of South Sister volcano.
Uplift began in the mid-1990’s and was first observed in radar satellite imagery. The USGS, working with the Forest Service, installed permanent monitoring stations to track the rate at which the area was uplifting.
In addition, every summer Dr. Dzurisin sets out GPS stations to collect ground deformation data. While radar satellites provide a picture of the entire area, these temporary GPS stations give very accurate measurements of how individual points have moved. Dr. Dzurisin and summer intern Natalea Cohen show you how they set up the semi-permanent GPS stations and talk about the importance of the work.
One thing that can cause uplift is magma moving around underground, or in particular, magma rising from greater depth in the earth up to a shallower depth, which forces the surface to move upward in a very broad area. Remarkably, this process has caused very few earthquakes. So, if you're not using satellite radar data or some other form of data to look for it, episodes like this may have happened in other places and maybe in Central Oregon as well, and we just didn't know it.
USGS scientist are monitoring this activity as carefully and thoroughly as they can, and will continue to monitoring the area for as long as it goes on, to gain a greater understanding of this process.