A Pentagon test at a Nevada site this June will likely create the first mushroom cloud seen in the state since the United States ceased above-ground nuclear testing in 1963. Mushroom clouds are commonly associated with nuclear blasts, but this cloud will come from the detonation of a 700-ton explosive charge designed to test new bunker-busting technologies. Most Nevada residents, however, will never see the cloud because the test will take place in the desert -- far away from population centers. The closest city, Las Vegas, is about 90 miles away from test site. Regardless, the military will put out the word to Las Vegas residents that they shouldn't be alarmed in the unlikely chance that they see a mushroom cloud on the horizon. Mountains surround the flat Nevada site where the test will be conducted. The Defense Threat Reduction Agency hopes the test -- called Divine Strake -- will help with the effort to develop weapons that can destroy deep underground bunkers storing nuclear, chemical or biological weapons. The yet-to-be built Robust Nuclear Earth Penetrator has raised opposition from some members of Congress who worry the technology will open the door to a new generation of nuclear weapons.