A group of high school students are taken on a field trip by their teacher, to learn about geology. They go way out into the desert and explore a remote cave. One by one they are slain by some type of creature that lives there--and it doesn't help that the teacher is one of the early victims. They get lost and try to survive as they are picked off one by one.
This does not remotely compare to other "horror cave" movies, like THE DESCENT or THE CAVE, as the gore and effects are minimal and the actors among the Z list. However, I did like what the monster turned out to be--it made total sense and is actually plausible.