People living near the summit of an active volcano, especially those in valley areas, are most likely to be in danger from a pyroclastic flow or lahar. The best course of action for these people to take when a volcano erupts is to evacuate valley areas and head for higher ground away from the volcano. Of course, if the volcano gives ample warning that it is going to erupt, then the best thing to do is evacuate the area and get as far away from the volcano as possible.
Residents in areas that may be affected by volcanic ash during an eruption, need to be prepared. They should stock up on water and food supplies, stay indoors to avoid having clothing burnt or skin irritated by acids carried by volcanic ash, avoid going outside without a wet cloth or some sort of filter over their mouth and nose, stay in areas that are unlikely to receive large amounts of tephra or large sized tephra, avoid staying in buildings that are flat-roofed, and be prepared to be without telephones, electricity, and radio communication. Residents should also be prepared to do a lot of cleanup, and when doing this be careful not to resuspend the ash.
Whilst lahar flows can often be channelled, it is very difficult to stop a lava flow. Different methods have been used including: breaching the sides of a lava tube or channel, diverting the flow, constructing barriers, and bombing the lava flow. Another way to stop a lava flow is to increase the lava flow's viscosity by spraying it with water, increasing the rate at which gas escapes from the flow, stirring the flow, or seeding the flow with foreign nuclei.