When a volcano erupts, you have a lot more to worry about than just the lava. The lava will do a lot of damage, but so can the ash and the gas that comes along with it. Sometimes, the ash and the gas is the most dangerous part.
When all of the emissions of an erupting volcano come together, they're called a pyroclastic flow. This is a pyroclastic flow enveloping Mt. Pinatubo in the Philippines after an eruption in 1991. If you see one of these headed in your direction, run away.