Continuity: The motel clerk is wearing glasses only when shown from behind.
Factual errors: Cascade Range volcanoes do not typically erupt flowing basaltic (free-flowing) lava. They certainly do not simultaneously erupt pyroclastic and basaltic flows as depicted.
Continuity: Harry's truck emerges from the river completely dry.
Continuity: The passenger side window is destroyed when the car hits Harry's truck in the river, yet in all subsequent scenes, it's there.
Continuity: During the credits, Pierce Brosnan's name is misspelled at the line, "Mr. Bronson's Driver"
Continuity: Dante's Peak itself occasionally disappears in some brief shots.
Continuity: When Terry is in the hospital with a broken leg, Greg is doodling on his cast. In a later shot Terry's cast is clean.
Factual errors: The boat engine was water-cooled by taking in water from the lake and running it through the engine. The acid in the lake would have caused the engine to seize very quickly.
Continuity: The helicopter crashes into the ground nose-down and continues moving for several feet after impact, which should indicate that the cabin is being crushed; we also see parts flying off the rotor. But a moment later, it rises again in a manner completely unlike the way the wreckage might bounce, more the way it would if was still under power; and we see that the cabin is still intact.
Revealing mistakes: After the town hall meeting, people are running past the trophy case when the quake starts. Everything is shaking and falling except the trophies which stay perfectly still in the cabinet.
Audio/visual unsynchronized: In the establishing shot of the grandmother's cabin, we hear a chorus of peeping in the sound effects mix. These are small frogs often called "spring peepers" and they will usually only sing after sunset, not in the middle of the day as depicted here.
Revealing mistakes: Tremors strong enough to reduce buildings to rubble hit the town, but the trees lining the sidewalk remain motionless.
Continuity: When the crew is unloading SpiderLegs in the parking lot, Greg has a highly noticeable case of five o'clock shadow. Less than a minute later, when he is inside directing SpiderLegs remotely, he is clean-shaven.
Factual errors: When Harry and Terry are measuring the concentration of sulfur dioxide in the caldera, the instrument probe is protruding out the open cabin door into the helicopter downwash. Sulfur dioxide is more than twice as dense as air; it would be highly unlikely that this technique would provide any meaningful results.
Continuity: In one of the last scenes as Harry is racing the truck down the streets of the deserted town trying to outrun the pyroclastic flow, the streets are obviously covered with at least a foot of ash, and yet the truck leaves no tracks, or stirs up any ash, as it goes by.
Factual errors: In one of the scenes, the pick-up truck was trying to outrun the pyroclastic cloud. A pyroclastic cloud moves at 140kmh and could not possibly be outrun by a truck with no tyres.
Continuity: Cars in front of and behind Harry's truck leading up to the one-lane bridge during the evacuation.
Continuity: The one-lane bridge leading out of town is wide enough to fit two cars side-by-side during the evacuation, yet when the vulcanologists are fleeing in the Humvees and USGS van later, it is barely wide enough for one vehicle.
Revealing mistakes: When part of the freeway collapses, cars on the section still standing do not move, for no reason.
Continuity: The blue pickup is hit twice on the freeway onramp.
Continuity: A red Ford Taurus parked outside the high school is later seen on the freeway onramp before it collapses. As it does, it is suddenly just driving onto the onramp.
Continuity: While driving around the abandoned town shortly before the volcano erupts, Harry's truck passes the same overturned police car four times.
Continuity: A station wagon is clipped by a black Dodge on the freeway onramp, but when the onramp collapses in the next shot, the station wagon has disappeared and other cars that were far behind it are visible.
Continuity: The red van that Paul is driving onto the bridge when they are evacuating the town has no vent windows, yet when Paul is stuck on the bridge, and it begins to overturn, the same van that he was driving can be seen to have vent windows.
Factual errors: When Harry drives the green pick-up truck over the thinly crusted lava flow, the truck comes off the flow with nothing more than four flat tires and a charred bottom. In reality, lava is capable of temperatures as high as 2,000 degrees Fahrenheit, which would have melted the undercarriage and left them trapped.
Continuity: When the couple go into the hot spring, the woman hangs her shorts on the 'sign'. But when Harry, Linda, grandma and the kids come there the shorts are gone.
Factual errors: After the eruption (following the meeting in the school) we see many broken cables flowing around. In reality, that would have short circuited the town's electrical system and the whole town would have gone dark.
Continuity: When the volcano had started erupting, Harry and Rachel rushed back to her place in his truck to get her kids. The both of them run into her house and she found the letter from the kids. They run back out to the truck and the truck's headlights are on. They're standard headlights, which appear yellow in color. They leave and find the bridge is jammed with traffic and Harry decides to cross the river. In the shot of them crossing the road and going down the bank towards the river, not only are all the truck's lights on - not just the headlights - but they're very bright, white, possibly HID headlights until the truck's demise.
Continuity: Just before the freeway collapses we see a window from the city hall shatter, but when the Chevy Blazer falls of the on ramp we see that the window is intact.
Continuity: In one shot we see a realty sign collapse off an office building, however in the previous shot as Harry and Linda are approaching the structure, the sign has already collapsed.
Continuity: Just before the main eruption Harry turns left on what is supposed to be Bank Street. In the shot he is actually turning right on Cedar Street.
Revealing mistakes: When the freeway collapses, all of the vehicles very obviously have no occupants. This is because all the cars are in reality scale models, which are used several times to film stunts without using CGI.
Incorrectly regarded as goofs: When they go to save the grandmother, just before the lava comes bursting through the wall, the grandmother has a garbage bag in her hands. When the lava breaks through, she appears to drop the bag and starts running. Then they show the whole family outside, and the bag is back in the grandmother's hands, with no time for her to have picked it up. In fact it was Mayor Wando who dropped her bag; she was standing in front of the grandmother, making it appear that she dropped hers.
Incorrectly regarded as goofs: The Grandmother is badly burned when she swims across the acidic lake a short distance, although Pierce Brosnan seems unaffected despite rowing with his coat-covered hand for about 5 minutes.
Factual errors: Though, it is true that volcanic activity can turn lakes and other bodies of water around the volcano acidic. But, the acid would not burn through the boat as quickly as depicted in the movie.
Revealing mistakes: In the scene where Harry, Rachel, and the kids are racing from the volcano toward Graham's hideout, a faint face can be seen in the cloud of dust when the camera cuts back toward the erupting volcano.
Factual errors: When Dante's Peak explodes, it generates a pyroclastic flow which Harry barely outruns with a truck with no tires. This would not be possible, as pyroclastic flows are capable of traveling at over 100 MPH, which would overtake them long before they can reach the mines.