Post by syzygy on Feb 1, 2017 12:20:32 GMT
Quoted from an arizonageology.blogspot blog entry by Lee Allison:
Not even a mile long, visible section on GE imagery marked with red line (figure 1):
New earth fissure - line.kmz (2.41 KB)
Zoom in, turn off line and check the crack!
Monday, January 23, 2017
New two-mile-long earth fissure discovered in southern Pinal County
A fresh, ~ 2-mile long earth fissure occurs 10 miles south-southwest of Picacho Peak State Park on Arizona Trust Land in southern Pinal County (Figure 1a & b.). This new fissure, which is oriented roughly north-south, parallels other fissures in the Tator Hills Earth Fissure Study area. Fissures at Tator Hills were first observed in 1977, and by 2009 over 11 miles of fissures were mapped there.
Figure 1. Appearance of Tator Hill fissures in December 2014 Google Earth imagery. Red arrows point to the new fissure; blue to an older, previously mapped fissure. Note sharp, unvegetated appearance of new earth fissure compared to old fissure. (Photo by B. Gootee)
The width and depth of the new fissure varies dramatically along its length; from a narrow, inch-wide crack to a shallow crevice up to 10 feet wide and 25- to 30-feet deep. At 1.8 mile in length, this newest fissure is more than a ½-mile longer than other area fissure. Unlike older fissures in the Tator Hills, this fissure is free of vegetation, commensurate with having formed over just the past several years.
Comparing dated Google Earth imagery, AZGS Earth Fissure program manager, Joe Cook, determined the fissure began to form between Mar. 2013 and Dec. 2014. The onset of fissuring began in the north before extending southward and may have coincided with heavy rains in fall 2014. The southern portion of the fissure postdates the Dec. 2014 imagery.
Fissure Drone Video. On 19 Jan. 2017, AZGS’ Brian Gootee and Joe Cook, along with Arizona Dept. of Water Resources’ Brian Conway, captured the first drone video of a fresh earth fissure in Arizona (Figure 2, VIDEOS URL). The two videos illustrate the variable geometry (width and depth) and overall fresh appearance of the fissure.
Figure 2. New earth fissure trending north-south in the center of the frame. The sharp contrast in fissure geometry, from open, with a width and depth of 10s of feet, to a closed, crack-like feature, is apparent. (Photo by B. Gootee).
Fissures videos at AZGSweb Youtube channel:
vid#1 (2.75 minutes)
vid#2 (1.75 minutes)
Geohazard! In urban areas earth fissures pose a substantial threat to infrastructure – homes, building, roads and bridges. In rural areas, fissures threaten roaming livestock and individuals recreating in off-road and 4-wheel drive vehicles. Fissure sidewalls are precipitous, unstable, and prone to sudden collapse that could snare an unwary observer standing on the collapsing edge (Figure 3).
Origin of Earth Fissures in Arizona. Earth fissures result from basin subsidence
that accompanies extensive ground water withdrawal in the Sonoran Desert. In Arizona, fissures first appeared near Eloy in 1929 and are now identified and mapped in basins in Cochise, La Paz, Maricopa, Pima and Pinal Counties...
for more, visit sourcepage on arizonageology.blogspot
New two-mile-long earth fissure discovered in southern Pinal County
A fresh, ~ 2-mile long earth fissure occurs 10 miles south-southwest of Picacho Peak State Park on Arizona Trust Land in southern Pinal County (Figure 1a & b.). This new fissure, which is oriented roughly north-south, parallels other fissures in the Tator Hills Earth Fissure Study area. Fissures at Tator Hills were first observed in 1977, and by 2009 over 11 miles of fissures were mapped there.
Figure 1. Appearance of Tator Hill fissures in December 2014 Google Earth imagery. Red arrows point to the new fissure; blue to an older, previously mapped fissure. Note sharp, unvegetated appearance of new earth fissure compared to old fissure. (Photo by B. Gootee)
The width and depth of the new fissure varies dramatically along its length; from a narrow, inch-wide crack to a shallow crevice up to 10 feet wide and 25- to 30-feet deep. At 1.8 mile in length, this newest fissure is more than a ½-mile longer than other area fissure. Unlike older fissures in the Tator Hills, this fissure is free of vegetation, commensurate with having formed over just the past several years.
Comparing dated Google Earth imagery, AZGS Earth Fissure program manager, Joe Cook, determined the fissure began to form between Mar. 2013 and Dec. 2014. The onset of fissuring began in the north before extending southward and may have coincided with heavy rains in fall 2014. The southern portion of the fissure postdates the Dec. 2014 imagery.
Fissure Drone Video. On 19 Jan. 2017, AZGS’ Brian Gootee and Joe Cook, along with Arizona Dept. of Water Resources’ Brian Conway, captured the first drone video of a fresh earth fissure in Arizona (Figure 2, VIDEOS URL). The two videos illustrate the variable geometry (width and depth) and overall fresh appearance of the fissure.
Figure 2. New earth fissure trending north-south in the center of the frame. The sharp contrast in fissure geometry, from open, with a width and depth of 10s of feet, to a closed, crack-like feature, is apparent. (Photo by B. Gootee).
Fissures videos at AZGSweb Youtube channel:
vid#1 (2.75 minutes)
vid#2 (1.75 minutes)
Geohazard! In urban areas earth fissures pose a substantial threat to infrastructure – homes, building, roads and bridges. In rural areas, fissures threaten roaming livestock and individuals recreating in off-road and 4-wheel drive vehicles. Fissure sidewalls are precipitous, unstable, and prone to sudden collapse that could snare an unwary observer standing on the collapsing edge (Figure 3).
Origin of Earth Fissures in Arizona. Earth fissures result from basin subsidence
that accompanies extensive ground water withdrawal in the Sonoran Desert. In Arizona, fissures first appeared near Eloy in 1929 and are now identified and mapped in basins in Cochise, La Paz, Maricopa, Pima and Pinal Counties...
for more, visit sourcepage on arizonageology.blogspot
New earth fissure - line.kmz (2.41 KB)
Zoom in, turn off line and check the crack!
