Bureau of Land Management, New Mexico.
A remnant of an ancient volcanic explosion, Kilbourne Hole was designated a National Natural Landmark in 1975. This crater can be found in a desert basin between the Potrillo Mountains and the Rio Grande in southern Dona Ana County. Kilbourne Hole is roughly elliptical in shape, and is known as a Maar - a pit or depression caused by a volcanic explosion with little material emitted except volcanic gas. The crater is between 24,000 and 100,000 years old, and measures 1.7 miles long by well over a mile across, and is hundreds of feet deep.
Kilbourne Hole has many unique minerals remaining from the eruption. The crusts of the Kilbourne Hole volcanic bombs - objects blown from the volcanic vent in a near plastic state - are dull black or brown, but when broken open they often reveal a brilliant, sparkling yellow and green interior of olivine glass granules.
Directions to Hunt's Hole and the north side of Kilbourne:
Take I-10 to Texas Exit 2, and turn left at Gadsen High School to start on NM-28. Continue on this road for about 4 miles (6.4K). Turn right at Mercantil Ave./NM-182. Continue for about 1 mile. At the first intersection, turn right at Alvarez St. (the Union Mercantile store is one the corner). Continue for about half a mile. Stay left at the fork. Continue on Co. Rd. A020 for about 7.8 miles. Turn right on Co Rd A012. Continue for about 3 miles. Turn left on Co Rd. A011. Continue for about 8 miles. Turn slightly to the left onto Co Rd. A013. Continue for about 3 miles, or until you can see the hole. To get to Kilborne Hole: Make a U-turn and return the way you came on Co. Rd. A013. After about 4.5 miles, you will come to the edge of Kilbourne Hole. You will need to park your car just outside a gate and hike in over the edge.
Directions to the south side of Kilbourne Hole:
Take Interstate 10 exit 155 (Vado Drive). Turn right, or head west to the stop sign at NM Highway 478. Turn left. After approximately 0.2 miles, turn right on NM Highway 189 and travel approximately 1.1 miles. Turn left on NM Highway 28. Continue south for approximately 2 miles. Turn right on W. Afton Road, and drive approximately 11.2 miles. Turn left on Douglas Munro Road, and drive approximately 6.5 miles. Turn left at the "T" in the roadway, drive approximately 0.2 miles, and cross the railroad tracks. Turn left on Co Rd A017, and drive approximately 7.2 miles. Turn right on Co Rd A011. Drive approximately 8.1 miles to the crater.