Three things that were scientifically accurate:
1. The water became filled with sulfur dioxide before the volcano erupted
2. There were earthquakes leading up to the eruption
3. The big eruption came a little while after the ash
The things that were scientifically incorrect:
1. The lava should have burned them when they drove over it
2. The lava flow would have reached them in the grandma's house
3. The grandma was in the acid lake long enough for it to burn her skin off
