Thursday, August 10, 2017

Aden Volcanic Field

Aden Volcanic Field, it was like home for several years, while I worked on my Master's Thesis.  (This aerial photo, taken by Rollag and Associates, shows the northwestern part of the volcanic field.)  Aden Crater, a small shield volcano (approx. 2000 ft. across) is in the center left of the photo.  (The photo is oriented with North at the top.)

The Aden Basalts and associated Afton Basalts are part of the approximate 500 square miles of the Potrillo Volcanic Field, a regional feature related to the Rio Grande Rift.  The area is located in the South-central part of Doña Ana County, New Mexico, about 20 miles Southwest of Las Cruces.
The two irregular craters in the center bottom of the photo were part of my thesis project.  There were three other craters to the Northeast that were also given cursory coverage in the report.  The enigmatic craters, composed of boulder ramparts surrounding a collapsed floor, have been a source of curiosity among UT El Paso geologists since the middle 1960s.  More recent work on these types of craters in Hawaii by Tim R. Orr (USGS) yielded an explanation for their formation and gave them a name "Lava Tube Shatter Rings" (I called them "Explosion-Collapse Craters".)
Above is a photo of Quaternary-age Aden Crater, showing the typical low-profile of a basaltic Shield Volcano.  This photo was taken from one of the Lava Tube Shatter Rings within my field area.  The base of Aden Crater is about 4 miles across.  [The remainder of the photos in this post are mine, except for the aerial photo of the Lava Cone, also by Rollag and Associates.]  

The entirety of the Potrillo Volcanic Field offers a wide range of relatively-young basaltic volcanic features, e.g., Cinder Cones, Maar Volcanoes, Shield Volcanoes, Spatter Vents and Spatter Mounds, "Volcanic Bombs", "aa" and "pahoehoe" textures, Lava Cones, Lava Tubes, Columnar Jointing, Fumeroles, Ash Deposits,...(a few of which are shown here in this post.)

Outside of Aden Crater (a late-stage feature), most of the basalt flows are thought to be the result of "Fissure Eruptions".
Above and below are images of an intact Lava Cone (a miniature Shield Volcano).  The surface vent is about 6 feet across and the empty, roughly circular chamber below is about 30 feet in diameter and perhaps 20 feet deep.  This Lava Cone is unusual in that usually, once eruptions have ceased and remaining lava within have withdrawn and subsided, the cone usually collapses in upon itself. 
Another interesting feature, near the primary Lava Tube Shatter Ring (highlighted by my Thesis), was this tiny Spatter Vent, i.e., a tiny, sputtering volcano.
Within Aden Crater itself, near a subsided vent, was this Spatter Mound, shown below.  [A 5 foot long "Jacob's Staff" shows the scale.]  Usually, spatter activity is within the dying stages of a volcano's life span.

(Below) A few hundred yards East of Aden Crater are these crude Columnar-Jointed, Fissure-erupted Basalts.
[All of these photos were taken during a span of 32 - 28 years ago.  The area was and remains a Federal Wilderness Study Area, so I don't know what the current status is, vis-à-vis visits to the area.  As it is a few miles North of the Mexico Border, there might be some hazards in the area, due to smuggling, etc..  It goes without saying that when traveling in the desert, one should always carry a first aid kit, several gallons of water, local maps, etc..]

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