Posted on May 22, 2019
When we talk about Natural Disasters, we are often talking about terrible weather:
Brutal sandstorms, violent lightning strikes, killer tornadoes, deadly blizzards, destructive hurricanes (or typhoons or cyclones; all three are basically the same thing).
But there are Natural Disasters that are not weather-related. Instead, they have to do with tectonic forces.
Tectonic forces are those that originate below the Earth's surface as a result of the movement of the continental and undersea plates. The two main disasters in the "tectonic" category are volcanoes and earthquakes.
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| The Earth's crust is made up of a lot of different tectonic plates that move around! |
Volcanoes
On this date in 1915, Mount Lassen erupted violently, ejecting rock and pumice, ash and gas. The ash and gas formed a column more than 30,000 feet tall - it could be seen from as far away as 150 miles! A large, deep crater formed at the mountain's summit. Only three square miles of nearby region were devastated, but mudflows and pyroclastic flows of hot ash, pumice, and rock reached many more miles.
Don't worry, Mount Lassen's eruption didn't kill people, although it did cause a few minor injuries among people escaping the mudflows. The thing about volcanoes is that they commonly are rocked by earthquakes before they erupt, and they often vent steam or show other signs of being active before they blow big. Lassen woke up on May 30, 1914, after 27,000 years of being dormant, and there were about 400 eruptions between 1914 and 1921, including the one we commemorate today (the biggest eruption of them all).
Because it was the first U.S. volcano to erupt in the 1900s, Lassen Peak's eruptions and activity were very well photographed and studied.
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| Lassen Volcanic National Park is a lovely place to visit - although of course scientists monitor tectonic activity and earthquakes in case the volcano shows signs of becoming active once again! |
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| When two plates collide, volcanoes can form above the collision zone. |
Earthquakes
The most powerful earthquake ever recorded occurred in Chile on this date in 1960. It ranged from 9.4 to 9.6 on the "moment magnitude scale" (expressed in the terms we are pretty familiar with from the Richter Scale).  |
| Unfortunately, the "Great Chilean Earthquake" and the tsunamis that resulted from the quakes caused a lot of damage and many deaths. |
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| Damage in Hawaii, more than 6,000 miles (10,000 km) away from the earthquake's origin. |
The earthquake set off tsunamis that did more damage, even, than the original 10-minute-long shake. The tsunamis kicked off waves up to 82 feet tall; a tsunami devastated Hilo, Hawaii, several local tsunamis battered the Chilean coast, and high waves affected faraway spots like the Philippines and Japan!
Like the volcano, this powerful earthquake had some warning - but the warning was an earlier almost-as-powerful earthquake! On May 21, 1960, an 8.1 quake rocked Chile. On May 22, 1960, two more strong earthquakes hit in the same locale as the first; fifteen minutes after the third quake, the monster 9.4 quake hit around 280 miles (460 km) away from the first three.
Smaller aftershocks shook Chile until June 6.
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| Just as the collisions of tectonic plates can cause volcanoes, these collisions can also cause earthquakes. |
Tectonic plates cause what has been
called "continental drift" - the slow
changing of the number and position
of the continents.
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