A geologic and topographic map of New Mexico, showing the ages of the rocks that make up the state: yellow and orange rocks come from the Tertiary Period and are 40 to 6o million years old, while blue colors indicate Permian-era rocks that can be as much as 250 million years old. (USGS)
Like a waistband after Thanksgiving dinner, New Mexico's borders are gradually gaining girth, according to the Albuquerque Journal.
It’s not much, and it’s not happening very fast -- the state is getting about an inch wider every 40 years -- but the state is unquestionably expanding, according to University of Colorado geophysicist Henry Berglund and his colleagues.
Using a collection of 25 extra-precise GPS receivers planted across New Mexico and Colorado, Berglund determined that the cities of Albuquerque and Santa Fe are creeping away from each other. The rate of change seems ever so slow to the untrained ear, described as approximately 1.2 “nanostrains” per year.
Anne Sheehan, who was Berglund’s faculty adviser and a member of the research team, told the Journal the phenomenon was actually surprising and widespread.
“We didn’t expect it to be so spread out,” Sheehan said.
The stretching of the surface of the Earth is commonly documented at the edge of continental plates, where the jigsaw puzzle pieces that make up the surface of the planet jostle and collide, forming mountains, or move under or over each other. In places like California, the effect can be easy to see, the Journal said.
But the effect in continental interiors -- on states not near the edge of those plates -- was a new one, the scientists said. Whether an upwelling in the gooey mantle that lies beneath the crust or a sag in the plates themselves, what exactly drives the growth remains a mystery.
The findings were documented in the January issue of Geology Magazine.
For more on New Mexico’s strange stretching, see the Albuquerque Journal.
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