page_title: Project Gnome
section_title: Gnome shot and aftereffects
hierarchical_section_title: Project Gnome / Gnome shot and aftereffects
context_page_description: Project Gnome was the first nuclear test of Project Plowshare and was the first continental nuclear weapon test since Trinity to be conducted outside of the Nevada Test Site. It was tested in southeastern New Mexico, approximately 40 km southeast of Carlsbad, New Mexico.
context_section_description: Gnome was placed 361 m (1,184 ft) underground at the end of a 340 m (1,115 ft) tunnel that was supposed to be self-sealing upon detonation. Gnome was detonated on 10 December 1961, with a yield of 3.1 kilotons. Even though the Gnome shot was supposed to seal itself, the plan did not quite work. Two to three minutes after detonation, smoke and steam began to rise from the shaft. Consequently, some radiation was released and detected off-site, but it quickly decayed. The cavity volume was calculated to be 28,000 ± 2,800 cubic metres (989,000 ± 99,000 cu ft) with an average radius of 17.4 m (57 ft) in the lower portion measured.
  The Gnome detonation created a cavity about 170 ft (52 m) wide and almost 90 ft (27 m) high with a floor of melted rock and salt. A new shaft was drilled near the original and, on 17 May 1962, crews entered the Gnome Cavity. Even though almost six months had passed since the detonation, the temperature inside the cavity was still around 140 °F (60 °C). Inside, they found stalactites made of melted salt, as well as the walls of the cavity covered in salt.
  The intense radiation of the detonation colored the salt multiple shades of blue, green, and violet.  Nonetheless, the explorers encountered only five milliroentgen, and it was considered safe for them to enter the cavern and cross its central rubble pile.  While the three-kiloton explosion had melted 2400 tons of salt, the explosion had caused the collapse of the sides and top of the chamber, adding 28,000 tons of rubble that mixed with the molten salt and rapidly reduced its temperature.  This was the reason the drilling program had originally been unsuccessful, finding temperatures of only 200 °F (93 °C), without high pressure steam, though the boreholes had encountered occasional pockets of molten salt at up to 1,450 °F (790 °C) deeper amid the rubble.
  As of 2008, all that existed on the surface to show what occurred below was a small concrete monument with two weathered and slightly vandalized plaques.
caption: Geological section at the Gnome site.