Wow, I am actually lost for words as having watched countless made for TV disaster movies I thought I had seen it all from those which kind of worked to those which were embarrassingly poor but now I will have to redo my scale having sat through "Descent". Right from the word go "Descent" is bad; uninteresting storyline, poor acting, terrible special effects and a disaster idea which uses the same ideas of other disaster movies, it is a new level of laughable. The only excuse to watch this is if you want to inflict torture on someone as it doesn't even reach the mark of being entertainingly bad.
A top secret government science project has gone wrong and is behind the Earth's tectonic plates shifting which in turn is causing a series of catastrophic events. With things out of control a shady official contacts scientist Jake Rollins (Luke Perry - The Fifth Element) to help who along with a team which includes a former girlfriend and a rival set about drilling down to the Earth's core in order to plant a bomb to realign the plates.
Basically every sci-fi disaster movie cliche is present in "Descent" from the government being behind a cataclysmic disaster, the former girlfriend and the rival it has all been used before. And of course for those who know their disaster movies will know that the whole drilling down to the Earth's core to fix things had already been done in "The Core" a couple of years before this was made. I can't even say the acting is okay as whilst Luke Perry brings his brand of charisma to his role as Jake it is a terrible character which ironically is the best one in the movie. And as for those special effects, watching magma cascade over a waterfall early on is fake looking, I mean seriously fake looking.
What this all boils down to is that despite usually enjoying these made for TV disaster movies I found "Descent" bad and not enjoyably bad either. It simply is the bottom of the barrel when it comes to this sort of movie and I can't give you one reason other than to torture someone to recommend it.