When you think of volcanoes, what comes to mind first? Ash and rock spewing into the air or lava flows racing down the slopes catching everything in its path on fire? Both of these are common types of hazards from volcanic eruptions, but other hazards such as earthquakes, landslides, toxic gases, climate change, and structural damage are also associated with volcanic activity. Earthquake tremors are sometimes noticed before an eruption as magma starts moving under the surface, or during an eruption as the rock splits open to let lava flow out. Earthquakes related to volcanic activity tend to be smaller and not very dangerous by themselves. For more information on earthquakes and associated dangers refer to Natural Hazards: Earthquakes.
Landslides occur whether or not a volcano is erupting as described in a previous article. But, during an eruption, there can be a special type of destruction known as a pyroclastic flow. A pyroclastic flow is a high speed combination of hot ash, rock, and toxic gases that can move down the sides of a volcano at temperatures of 1,500 degrees Fahrenheit and at 100-150 miles per hour. These tend to follow valleys and are more than capable of knocking down and burning everything in their path. One popular example is the 1980 Mount St. Helens eruption where a pyroclastic flow destroyed an area of 230 square miles. Trees six feet in diameter were knocked over as far as 15 miles from the volcano.
Toxic gases can be emitted from a volcano at any time. These gases can bubble up through volcanic lakes, cracks in the surface, or during eruptions. Even though about 90% of the gas is water vapor, the other 10% can be dangerous, and there are not many ways to tell if the gases are toxic in time to save yourself (unless you are carrying some expensive equipment in with you). Some of the common toxic gases are carbon dioxide, sulfur dioxide, hydrogen sulfide, hydrogen, and fluorine. Carbon dioxide settles in low areas and displaces oxygen, silently killing animals and humans. Sulfur dioxide reacts with moisture in the air to create localized acid rain, which causes corrosion and harms vegetation. Fluorine, which in high concentrations is toxic, can be adsorbed onto volcanic ash particles that later fall to the ground. The fluorine can poison livestock grazing on ash-coated grass and contaminate domestic water supplies.
Toxic gases, ash, and large forest fires associated with lava can combine to change the climate. For example, the 1991 eruption of Mount Pinatubo (Philippines), released large amounts of sulfur dioxide gas that combined with moisture in the air to form a mist of sulfuric acid that cooled the earth by reflecting solar radiation. Many gases as well as ash in the atmosphere can reflect solar radiation. This process can lower the Earth’s average surface temperature for years by several degrees Fahrenheit (°F). If your world is at a climate tipping point, this few degrees difference can start a small ice age, cause glaciers to grow and move, or cause years of bad crops.
Heat from an eruption is an obvious killer, but ash can cause a lot of trouble, especially in modern times. Ash suspended in the air can trigger breathing problems and cause death from asphyxiation. Since ash can be several feet deep in areas near a volcano after an eruption, roofs can fail under the added weight and trees could break and take out overhead lines. Cities would have to remove the ash from streets and railways before transportation by modern means is practical again. Air travel would be stopped until the ash cloud has dissipated. Lack of transportation causes problems with getting food, water, and medical care. As a bonus, central air systems and sensitive electronic systems can fail depending on the amount of ash getting to them. Drinking water in areas where water is obtained from lakes and rivers would be impacted by the ash falling into the water and any bonus chemical reactions.
There are many problems that can stem from volcanic activity, and this article covers a few of the less commonly thought about hazards. Your game can include these as ways to make climatic changes, introduce refugees into the area you are in from survivors closer to a volcano, or add hidden dangers to volcanoes that aren’t visibly active.