Mount Vesuvius claimed the towns of Pompeii and Herculaneum in 79 A.D.
The shape of the world has been changing for all of history due to the shifting of tectonic plates. As the plates move along the surface of the planet, they bump into each other, causing massive impacts along fault lines. Sometimes plates slide over each other, while other times they crumple together to form mountain ranges.
Earthquakes
Many residents of the Pacific Rim, a huge area that includes the western United States, eastern Asia and Oceania, have firsthand experience with the devastating power of earthquakes. Earthquakes occur when pressure builds up along a fault line until one edge finally gives in. These events are measured on the Richter magnitude scale, which measures how much energy is released in an earthquake. The energy of an earthquake is released underground, but the shock waves are still felt on the surface, especially in buildings that were not built to withstand crustal movement. The largest earthquake ever measured was a 1960 quake off the coast of Chile in 1960 that measured a 9.5 on the Richter scale.
Tsunamis
Tsunamis are caused by significant displacement of the ocean floor, or large landslides into the sea. Their effects can be much longer lasting than the landfall of a set of waves; they can wipe out entire civilizations and reduce living conditions to the worst-case scenario. In recent history, tsunamis have affected Indonesia and northeast Japan, and the National Oceanic and Atmospheric Administration estimates that tsunamis have claimed more than 420,000 lives since 1850. The worst tsunamis occur when a major earthquake greater than 7.0 on the Richter scale strike in shallow waters close to shore. Forecasting tsunamis is a difficult task since each earthquake is unique, and the variety of shorelines is so great.
Volcanoes
Volcanoes loom over communities below as a constant reminder of nature's destructive force. They seem to congregate around tectonic fault lines, as 60 percent of the world's active volcanoes are situated at tectonic boundaries. Like earthquakes, volcanoes near the shoreline can produce massive landslides that can, in turn, cause tsunamis. Additional dangers of volcanoes include lava flows, pyroclastic flows, and sun-erasing clouds of ash which can significantly alter the world's climate. The cities of Pompeii and Herculaneum were covered in 7 meters of ash in the 79 A.D. eruption of Mount Vesivius, and Mount Krakatoa's 1883 eruption dropped the global temperature by 1.2 degrees Celsius in the following year.
Mitigating Disaster
Tectonic shifting cannot be stopped nor can it be prevented. Studying these events is very difficult, and they are nearly impossible to predict with any reasonable amount of time to warn the populations of surrounding communities. A worldwide tsunami warning system was put in place in 1946, but it has given more false positives than accurate forecasts. You should run through an emergency preparedness exercise on occasion in case disaster strikes your area.
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