Anyway, yes. Pyroclastic flows are the classic PDCs. Traveling at speeds of 80 kilometers (50 miles) per hour – and often far faster – they form when an entire, or part of, an eruption column collapses, usually when the violent depressurization of the magma source dies down, or when the column cools enough to become somewhat dense.
Sometimes, you get weird flows that move as slow as 18 kilometers (11 miles) per hour, but these are incredibly rare – and the one in the trailer clearly is moving far quicker. So let’s discount these ones.
Within them, mixtures of ash, lava blebs, and superheated gas can reach temperatures of up to 1,000°C (1,832°F), and even the air around them can be pushed up to several hundreds of degrees.
Forget the average; the top human running speed is 45 kilometers (about 30 miles) per hour. Grady is not Usain Bolt, so it’s unsurprising he gets caught up in the movie’s pyroclastic flow. His skin would boil and rupture, his muscles would violently contract, he'd quickly asphyxiate and, as occurs in some instances, his brain would boil and his skull would explode.
Grady doesn’t die though, which suggests to Phoenix it’s “a pyroclastic surge”, a PDC where the ratio of gas to debris is far higher. These are sometimes so “light” that they’ve been seen flowing up hills and across water. They’re often cooler than flows, but she points out that “it would still be anywhere from 200°C to upwards of 982°C (390°F to 1,800°F)” on the inside.
“Doesn't seem likely that he'd be able to outrun a flow even in the best of circumstances,” Phoenix concludes.
Crispy Chris Pratt it is, then. What about those dinosaurs? Franzi Sattler, a palaeontologist and evolutionary biologist at the Free University of Berlin, has some thoughts.
“There are definite constraints when it comes to what determines how fast an animal, in this case, a dinosaur, can walk or run,” Sattler tells IFLScience.
“It depends on how big it is, and there is no way a 30-tonne sauropod can run with its entire, massive body weight. So you can bet that a large animal, running at a max speed of a few tens of kilometers per hour, couldn't survive this.”
There are a few smaller, sprightlier animals in the trailer though, and they appear to stand a better chance of outrunning the pyroclastic flow.