HOW TO FAKE A VOLCANIC ERUPTION

JURASSIC WORLD: FALLEN KINGDOM

THE PLOT

After a volcano destroys their island, the dinosaurs are brought to a sanctuary in the US, where, instead of being protected, they are sold off to the highest bidders. The bad guys then genetically modify an even more ferocious dinosaur. It escapes.

THE SCENE

As the characters run from a volcanic eruption, blobs of lava slam into the ground around them, throwing up dirt and setting fires.

ALL THE LAVA and debris flying through the air was CGI, but the visual-effects people needed a practical effect when it came to the blobs splattering when they hit the ground. Wherever the lava interacted with the terrain, they also needed us to create ribbon fires that would be shown burning the vegetation, with smoke rising off of them.

For the lava bombs, all our charges were made of something called detonating cord, a small-diameter cord filled with explosive powder. We spool out the length we need and wrap it into a flat disc we call a Frisbee. That goes into a heavy steel tray that we can set on the ground and conceal. We put material in the tray that will blow into the air and look like whatever the indigenous dirt is. The goal here was to create a simulation of these hard chunks of lava hitting the ground and kicking up dirt. We wanted it to look like the dirt was being thrown out to the sides, as if some object was splashing into a mud puddle. So we put it

on top in the middle, then covered that with a layer of mulch, thicker around the edges. Then, when the charge blows, since the sand particles are small and light in colour, you don’t really see them, and they hold down the explosive energy in the middle, forcing the mulch out the sides.

To create the fire lines that the burning blobs of lava left behind, we used LP gas. The gas runs up through a hose that goes to a pipe that has slots cut into it, just like a burner on your stove. Probably 1 km of slotted pipe for the burners, 1 km of pipe to get the gas up to the burners, and then 300 m of 5 cm hose that connects the gas to the burner system. We cut it, threaded it, and slotted it. It took us weeks and weeks and weeks. And the logistics of getting some of it up into those jungle roads was quite a challenge. We usually used cans of chafing-dish fuel as pilot lights, but we also had a mixture of biofuel and sawdust that doesn’t contaminate the soil, and burns away clean.

Then there’s the small matter of safety. We put additional pilot lights on the downhill side of the whole system. LP gas is heavier than air, and the crew is all at the bottom of the hill. So if we had a leak, and the leak didn’t get ignited and started rushing down the hill, you could have a giant cloud of gas enveloping the crew and finding a source of ignition. And that would be a disaster.