Midway Blowout EarthCache
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A mysterious volcano-like crater in the midst of flat farmland.
Looking to the South as you drive Highway 181 between Gregory-Portland and Taft, you may notice an enormous mound of dirt off in the distance. Viewing the mound from above, you would be tempted to think a small volcano had erupted at the location or that the area had been struck by a meteorite. Neither scenario is correct.
So how did a large crater appear in the midst of miles of flat terrain?
The rich black farmlands surrounding the site are known geologicaly as the Victoria Clay,* a soil type that extends along the coast to Nueces County. The rich soil is commonly referred to as "black land" or "hog wallow" owing to the dark color and numerous depressions dotting the surface.
The soil is a mixture of sticky clay, silt, and humus with small amount of sand. The high clay content causes the land to swell when wet, then crack as it dries. The cracks can extend many feet below the surface intersecting with each other. Surface material then falls into the cracks, creating the the soil's characteristic "hog wallow" depressions. Walking through "black land" after a rain, the soil will clump to your boots until you can barely lift your feet.
The Victoria Clay is one of the richest soils in the country as evidenced by the expansive fields of cotton and grain stretching as far as the eye can see. The clay was formed from the underlying calcium carbonate-rich clay of the Pleistocene age. Prior to its agricultural use, the Victoria Clay was open prairie covered with native grasses.
So what does all of this have to do with a crater in a farmer's field?
Well, it turns out that deep beneath the "black land" was another highly sought after resource - "black gold."
From the Handbook of Texas Online: "The Midway Oilfield was developed in 1937 by the Phillips Petroleum Company. On July 28, 1938, one of the nine producing wells blew out, caught fire, and burned for several weeks before being extinguished. The crater formed by the explosion is still visible today."
Blowouts are the result of a rapid and explosive buildup of gases which can travel up the drill hole at near the speed of sound. Modern drilling techniques successfully prevent most blowouts, historically referred to as "gushers." Blowouts are extremely dangerous, often igniting into a fireball that burns for weeks or months. Bringing a blowout under control sometimes requires drilling of "relief wells" nearby to intersect the original drill hole.
To log this find:
1. Estimate the size of the crater.
2. Describe the soil characteristics that might contribute to the longevity and other features of the crater walls.
Email the results to: ckpetrus@mac.com
*Reconnoissance Soil Survey of South Texas, by George N. Coffey and Party, USDA Field Operations of the Bureau of Soils, 1909.
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