Continuity mistake: When they are driving up the mountain to get to her kids, they cross a river and they get hit on the passenger side of the truck shattering the window, but later when they show them going up the mountain there is a new window there.
Factual error: After the volcanic eruption, there's a scene where we see our heroes going across a lake, which has been turned to acid by the lava. If this acid is strong enough to corrode the propeller, then surely the fumes would be destroying their lungs, in which case they should be dead, or close to it.
Revealing mistake: After Dante's Peak explodes for the final time, the pyroclastic cloud rolls down the mountain toward the town. Harry shouts "Don't look back, kids, don't look back." and then we are shown a wide shot of the truck zooming down the ash-choked streets. Unfortunately, it's painfully obvious that this is either a miniature or CGI shot, because the truck isn't leaving any tracks behind it or trailing any clouds of ash despite its high speed. (01:28:19)
Factual error: The scene in which the main characters are in the ranger station truck and are driving across the lava flow, you see the tire getting absolutely covered in lava, flinging it inside the wheel well, plus the bottom of the truck is basically only an inch or two above it. How did the gas tank and the fuel lines survive that miraculously without melting or bursting? The heat would literally boil the fuel inside the lines and the truck would no longer be able to run.
Factual error: In the scene where Pierce Brosnan hot wires the pickup truck, it is clear the truck has a locking steering wheel and gearshift. Even if he connected the correct wires to start the truck, he wouldn't be able to move or steer it.
Factual error: In the scene where Paul and the National Guardsman are leaving the motel for the final time after packing up, Paul follows the two Humvee's out of town. Being a Guardsman myself, I know for a fact that all civilians would be in front and Humvees would be following them. It is standard operational procedure.
Other mistake: The first time Rachel brings the team coffee, she has six coffees on a tray. There's five cappuccinos and one regular coffee for Harry. On the tray there is five coffees on one side and one coffee at the other side, obviously being Harry's regular coffee, so that Rachel would be able to tell the them apart. But when she gives Harry a coffee, she gives him one of the five standing together, so he obviously got one of the cappuccinos.
Continuity mistake: Mr. Custer has an on and off problem with his glasses when registering Harry Dalton. When seen full face, his glasses are in his shirt pocket--yet, when seen from the back, he has his glasses on!
Revealing mistake: In the scene where the van is about to be flipped over on the washed out bridge, wires can be seen on the hood of the miniature that pulled it across.
Revealing mistake: When the volcano begins to erupt, cars are seen driving out of the city. When the motorway collapses, and the cars go with it, in the close up shots, there are no drivers inside them.
Continuity mistake: Just after the helicopter crashes, check out the two full-view shots of the vehicle that show the top running lights. Of the three that are left, the middle one has been knocked crooked. After these two shots, the lights are all perfectly aligned again.
Continuity mistake: Near the start of the movie, during the violent eruption when the major characters have quickly loaded their gear into the truck and are trying to escape, the shot changes back and forth from looking into the cabin of the truck from the front and then looking forward out through the windscreen. The windscreen wipers are running at very different speeds. From inside, they run very fast (probably so you can see out through the mud) and very slowly from outside (probably to accentuate the mud etc).
Deliberate mistake: Geologically, the type of volcano in the movie shouldn't erupt so much low-viscous magma; but due to make the volcano exciting to the audience, the movie makers probably deliberately ignored this mistake.
Factual error: That truck they're driving had better be fitted with a couple of powerful rocket motors, because they outdrive a pyroclastic explosion, which would be moving at about 300kmh, and the wide shots show it's moving much faster than vehicle speed. We see the pyroclastic cloud just metres behind the truck - it would overtake them in seconds.
Suggested correction: A pyroclastic flow can have a speed of up to 400km/h. The key word here is "up to" and in reality they are usually much slower than this with the average speed being around 100km/h. Scientists believe the flow that followed the eruption of Saint Helens in 1980 had a maximum speed of just 72km/h.
Read the posting again, watch the film again. " the wide shots show it's moving much faster than vehicle speed." The pyroclastic flow at Mt St Helens may have been slow enough to outrun, but the one at Dante's Peak wasn't. This also makes this a continuity mistake as the sped of the flow varies drastically from shot to shot.
Deliberate mistake: In the shot right after Harry successfully maneuvers out of the river, the truck he's driving should still have water pouring out of it. When he was initially pulling out, the water in the truck was still up to the bottom of the steering wheel, and we can see it draining out, but it would take much longer than a second or two for the water to fully drain out- the truck's completely dry and not leaking at all. (01:03:40)
Revealing mistake: During the pyroclastic flow scene, the flow sweeps a tractor trailer off an overpass, which blows off some of the side panels in the back. Watch the back of the truck before the flow hits it, the panels that come out are already popped out and ready to blow off.
Revealing mistake: When the group is first leaving shore in the boat in the acid lake with the cabin behind them on fire, the angle of the river behind them compared to the shore line doesn't match and moves independently showing how they matted the two different scenes together.
Continuity mistake: When Harry, Rachel, and the kids drive into the mine at the end of the movie, there are already tire tracks there before them, despite plenty of ash having fallen to cover tracks made earlier. Who would have been going in or out of the mine before that?
Revealing mistake: When the lava comes through Ruth's house you can see that it's done with CG. The reddish "streaks" look like from a sci-fi movie. The shapes of the lights and streaks are unnatural.
Continuity mistake: When Harry and Rachel are making their way back to Rachel's house after the volcano's initial explosion we see them go down an alley to avoid all the traffic. As they move down the alley we see a pile of bricks fall from a roof and hit the front of the truck and window which causes large cracks in the glass on the passenger side. However, immediately after this we see the car and in all shots from the outside of the vehicle the cracks are no longer visible.
Suggested correction: Or the white coffee cup was for the guy that's obsessed with her coffee. Considering that it's a little bit bigger than the others and that I'm sure she wrote what each one was on the cups before handing them out, then it's very likely that the one she gave Harry was still a regular. The Grant Heskov-apologies if misspelled-also has the white cup with him, so it is possible that she gave everyone the right one.