Pyroclastic flows can wipe out whole cities, and kill thousands of people if the volcano is extremely explosive. For example, the towns of Pompeii and Herculaneum Italy, were totally destroyed by pyroclastic flow in 79 AD, and many lives were lost. Many cases of death are not caused by the lava itself, but is caused by the consequences of the volcanic blast. Suffocation from the gas can be an issue, but landfall, floods, wildfires and earthquakes can also cause major problems. Volcanic ash can be lethal, especially for people who have lung diseases, e.g. asthma. Small particles of ash can also cause erosion of your cornea. .
Subduction not only causes volcanic eruptions, but because of the pushing effect against the sides of each plate, rocks slip and collide releasing energy. The energy is released in waves through the earth's crust and causes the shaking that we feel during an earthquake. Eventually, the two plates builds up too much strain force from all the colliding and shifting, so the two plates suddenly slips past each other, releasing all the energy built up. The energy is released in a form of seismic waves. The location below the earth's surface where the earthquake starts is called the hypocenter, and the location directly above it on the surface of the earth is called the epicenter. Some short-terms effects to a country include destruction and collapse of towns, landslides, tidal waves that cause tsunamis, flooding, broken gas and water pipes and death of citizens. Shops and businesses can also be destroyed, and looting may take place due to the chaos. Some long-term impacts include diseases such as Cholera due to contaminated water and whole towns may have to be rebuilt. The cost of rebuilding whole towns is high, and the economy will break down. Cholera can cause watery diarrhea, nausea, cramp, nosebleed, rapid pulse, vomiting and hypovolemic shock (the loss of body fluids such as blood and sodium), which at some point cause death within 12-18 hours.