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article imageMassive fissure two miles long has opened up in Arizona desert

By Karen Graham     Jan 30, 2017 in Environment
Tucson - The Arizona Geological Survey (AZGS) is monitoring a massive 2.0-mile (3.2 kilometers) long fissure that has opened up in the desert in Pinal County, between Casa Grande and Tucson, Arizona.
The AZGS first became aware of the fissure in 2014 while doing a review of Google Earth images, looking for abnormalities in the terrain. This finding prompted the AZGS to visit the site and take measurements of its length, width, and depth reports Forbes.
"When I went out to map the fissure, I realized the fissure was much longer than what was apparent in the Google imagery, almost 2 miles [3 kilometers] long in total," Joseph Cook, a geologist with the AZGS told Live Science in an email. The scientists have since used a drone to get closer images of the crack that seems to continue growing and getting wider and longer.
The crack  discovered in 2014  has continued to grow both in length and width in Pinal County  to th...
The crack, discovered in 2014, has continued to grow both in length and width in Pinal County, to the southeast of Phoenix.
Arizona Geological Survey
More recently, heavy rains locally have caused the crack to widen with increased erosion and collapse of the overlying sediment, revealing the underground fissure. The drone footage shows just how massive the crack really is, dwarfing people walking along its edges in the video.
Cook says the fissure is expected to widen and get deeper. Right now, it is estimated to be some 9 meters (30 feet) deep in some areas. "I am sure the length of this fissure will increase over time, we are only seeing the surface crack of what collapsed, the underlying fissure is longer," he said.
Earth fissure near Picacho  Arizona.
Earth fissure near Picacho, Arizona.
S.R. Anderson/USGS
What has caused the massive crack?
First of all, the Earth is not splitting apart, so this isn't a scenario out of a Sci/Fi movie. But it is worrisome, to some extent. Actually, the crack is caused by groundwater use, primarily for agriculture. As groundwater is pulled up, it leaves a void or cavity, and the ground above it sinks, or subsides. This is called land subsidence.
Human exploitation of our groundwater is the reason land subsidence has become a global problem. In the United States, more than 17,000 square miles in 45 States, an area about the size of New Hampshire and Vermont combined, is impacted by land subsidence. The continued exploitation of water resources and land development will only exacerbate the problems and create new ones.
Approximate location of maximum subsidence in the United States identified by research efforts of Dr...
Approximate location of maximum subsidence in the United States identified by research efforts of Dr. Joseph F. Poland (pictured). Signs on pole show approximate altitude of land surface in 1925, 1955, and 1977. The site is in the San Joaquin Valley southwest of Mendota, California.
Dick Ireland/USGS
Cook explains that Arizona is full of cracks. "We see earth fissures forming around the margins of these subsidence areas and along mountain fronts within the subsidence areas," says Cook.
And the crack is worrisome, says Cook. Because the fissure is so large and still growing, he is afraid that someone might ride their off-road vehicle out to get a closer look at the crack. If someone were to get off their vehicle and walk too close to the edge, they could easily fall in and get stuck or even buried.
More about fissure, groundwater use, subsidence, Geological survey, human exploitation