August 26 – Well, Blow Me Down

Today’s factismal: The “Year Without A Summer” was not caused by the eruption of Krakatoa.

Stop me if you’ve heard this one before – way back when, there was a massive volcanic eruption that was so loud it was heard in Australia and put so much ash into the air that everything froze and we had a year without a summer. Great story, right? The only problem is that it isn’t; instead, it is two great stories.

The eruption of Mt Saint Helens was actually fairly small as such things go (Image courtesy USGS)

The eruption of Mt Saint Helens was actually fairly small as such things go
(Image courtesy USGS)

The first story is actually the last one. Back in 1815, Mount Tambora in Sumbawa exploded in the largest volcanic eruption in recorded history. It turned 24 cubic miles of rock into dust and debris and was loud enough to be heard for 1,200 miles. The eruption alone killed some 11,000 people. Worse, all of that dust in the air dropped the global temperature by a full degree below which was enough to kill crops and cause starvation in many areas; experts estimate that this killed another 60,000 people. (For comparison, the global temperature is now nearly two degrees above average this is not a good thing, either.)

When Pinatubo erupted in 1991, it cooled the planet by about 0.25 °

When Pinatubo erupted in 1991, it cooled the planet by about 0.25°

The second story happened nearly 68 years later at a spot nearly 900 miles away. On August 26, 1883, Mount Krakatoa erupted violently. The eruption wasn’t a surprise as the mountain had been spewing “fire fountains” into the air for months. What was a surprise was the size of the eruption; experts think that the neck of the magma chamber had become plugged with debris. Like holding your thumb over the neck of a soda bottle while shaking it, that allowed the pressure to build until it finally spewed out. That would have been bad enough, but the eruption created a caldera that went down below sea level. As the ocean water rushed in, it created a phreatic (steam) explosion, resulting in a sound so loud it could be heard 2,600 miles away and a tsunami that devastated coastlines across the Pacific and killed some 36,000 people. Because this was a smaller explosion than Tambora, only a few cubic miles of dust were tossed into the stratosphere and the weather was only made chilly instead of cold. As a result, there wasn’t the mass starvation of the previous eruption.

Exciting as the two eruptions were and interesting as the volcanology is, there is another facet to the two events that has a far more practical effect on us today: their effect on the weather. Since modern meteorological systems weren’t in place during the two eruptions (heck, meteorology hadn’t even been invented when Tambora blew!), climatologists must search for clues to their effects using old ship’s logs and diaries. And that’s where you come in. At Old Weather, you can look through the logs of sailing ships to discover what the weather and other things were like. By highlighting those entries, you help the folks who are trying to figure out what our new weather will do next. To learn more, blow on over to:
https://www.oldweather.org/

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