Dallol is effectively a volcanic explosion crater. It was formed when basaltic magma intruded in to salt deposits and water. This subsequently caused a huge phreatic eruption. The rising magma made contact with the ground water. As magma is so extremely hot the water evaporated immediately. The result was a huge explosion of rock, ash, water and steam – not to mention volcanic bombs (molten rock which cools and solidifies before it hits the ground).