The Night The World Exploded (1957)

Dr. Conway has perfected a machine which he believes will predict earthquakes, and has determined that one will strike California within 24 hours. He and his patron, Dr. Morton, attempt to convince the Governor but he cannot bring himself to declare an emergency when there is no proof the machine works - which, within 24 hours, it is proven to do. More significantly, Conway is getting readings which indicate a series of additional, pending quakes around the world, which also begin to occur; and more still seem to be on the way. With his assistant "Hutch", to whose love for him he seems oblivious, Conway takes his equipment to the deepest point of Carlsbad Caverns, in hopes that being closer to the center of the earth will help discern the cause of the earthquake epidemic. It does, when they inadvertently discover a new element which lies dormant in watery pools deep within the earth but, when in contact with air, becomes violently explosive. Forces unknown appear to be pushing this element surface-ward around the globe, and a computer analysis determines that enough will be exposed to explode the entire world within a little more than 28 days...