Lahars vary in size and speed. Small lahars less than a few metres wide and several centimetres deep may flow a few metres per second. Large lahars hundreds of metres wide and tens of metres deep can flow several tens of metres per second (22 mph or more): much too fast for people to outrun. On steep slopes, lahar speeds can exceed . With the potential to flow distances of more than , a lahar can cause catastrophic destruction in its path.