Impact events
The largest natural disaster that can befall the Earth and the only thing that can cause a total environmental cataclysm is an impact event with a large extraterrestrial body. A solid object from space needs to be of a certain size to cause a crater on Earth. Lesser objects burn up when they enter the protective atmosphere of Earth, we see them as shooting stars, but our planet is constantly struck by space dust, tiny rock particles that can barely be seen with the naked eye. Water covers a little more than 70% of Earth’s surface, and these tiny space particles, known as tektites, are preserved in the ocean floor sediment. Concentrations of tektites can also be found on certain parts of the contintents. This includes parts of Indonesia, Laos and Cambodia.
In between space dust and large meteorites are the rocks that have killed only a handful of people during a few thousand years and so far have caused very limited damage to human buildings. In 1908 a bolide, a mixture of debris and ice, exploded about a kilometer above ground in Tunguska, Siberia. It was only 10–15 m in diameter but the shock wave from the explosion felled trees in a 20,000 km2 area.
If an extraterrestrial body that struck Earth was 100–200 m in diameter, a great portion of the continent it struck would become uninhabitable. If it landed in the ocean it would cause tsunami waves more than a hundred meters high. Such a scenario could happen but impacts of this size are so rare that worrying about them does not make sense. It can be expected that the media will try to convince you that the end of the world will arrive through a large impact event, but the likelihood is ten to a hundred times greater that you will experience a volcanic eruption of the highest magnitude, VEI:8, than the impact of a meteorite a hundred meters across.
The TRITON database contains information on all known volcanic eruptions of all sizes and meteorite-bolide collisions in the past 10,000 years.