 For the scene with Scorponok bursting out from the sand and  attacking the soldiers, the effect was achieved by detonating primer  cord under the sand. The explosions would be in close proximity and  very dangerous to the actors in the scene so before the scene was  filmed, Michael Bay told the actors to run and keep running no  matter what happens or else they could seriously be injured or even  worse, killed. As a result, the look of panic on the actors faces  as they flee from Scorponok in this scene is 100% genuine.