Sometimes the eruption is so loud it sounds like an explosion. Hot magma cools as it rises to the top. Some of it becomes solid on the way up. The solid pieces are blasted out in the eruption. The smaller pieces about the size of marbles are known as volcanic ash and the larger ones are called volcanic bombs .
Volcanic bombs can be as big and as heavy as trucks.
The very small particles are called volcanic dust. Lava flows as long as it is in liquid form and usually flows slowly. The thicker the lava, the slower it moves. Thicker lava does not travel very far and will pile up to make rocks. The hotter the lava, the faster it flows.