Interesting story about a dying scientist who plans to tap the geothermal energy beneath the Earth's crust, with dire consequences. Andrews, Scott and Moore, as well as Alexander Knox, all give excellent performances. Special effects are superb and very believable. I remember seeing this on TV when I was little, and it scared me to DEATH. Seeing it again as an adult, it is not quite as scary, but is still fast-paced and entertaining.
While the science is now dated, thanks to the discovery of plate tectonics (the Earth's crust is divided into may separate "plates", and therefore already has many "cracks"), the story is still entertaining. The interaction between Dr. Sorenson (Andrews), an aging scientist trying for one last victory; his young wife Maggie (Scott), a scientist in her own right; and Dr. Rampion (Moore), the project's geologist and an old flame of Maggie's to boot; works very well, even if it is a bit formulaic.
All in all it is a fun movie, and definitely worth the time to see it. Especially now that it is finally being released on DVD in its original 1.85:1 widescreen format. A worthy addition to any classic sci-fi film collection.
(PS: *I* wrote that summary listed on the back cover when I was in college! They just added a few extra words. Don't believe me? Look it up on IMDB!!)