Let's start with an earthquake fissure overtaking a train. Or the volcano that erupts without precursory activity, or ya know what it's just easier to accept They Just Didn't Care than actually rattle off the voluminous errors in this miniseries.
Immediately following the original airing of 10.5, the news program showed a bunch of real-life geologists watching the movie/miniseries on TV and laughing their heads off.
At the end of the first movie a new seaway opens up from Los Angeles to Barstow. That fine Mojave metropolis is at about 2100 feet above sea level, so you'd expect tall cliffs leading down to the surface of the water below. Instead there's maybe a two-foot difference between the water level and the surrounding land.