spectacular glowing orange and purple sunsets. Whereʻd they come from?
Once
again, this pulse of superb sunsets is thanks to atmospheric pollution from a volcano.
High altitude
balloon measurements just found sulfur density 20 times normal in the stratosphere. The
story was reported in last weekʻs issue of the journal Science.
There were
some great sunsets in 2008, that time due to the ash-filled eruption of the
Alaskan volcano Kasatochi. It exploded in August of that year.
And there were
years of great sunsets in the 1990s from the Philippine volcano Pinatubo, which
erupted in June 1991.
(In the NASA
images from space at left, the upper shot is before Pinatubo. In the lower image, the layers of aerosols from 1991ʻs eruption of Pinatubo are visible in the
atmosphere.)
The latest
bit of atmospheric pyrotechnics is thanks to Raikoke or Raykoke, a Russian volcano
that dominates an island in the Kuril chain of the Northwest Pacific. The June
22 eruption ejected a plume of sulfur dioxide and particulate matter 50,000
feet into the atmosphere.
The Raikoke
event may be helped a little by another eruption in the first week of August,
this one from the volcano Ulawun in Papua New Guinea. Its plume is believed to
have reached 63,000 feet.
But while those
are impressive events, the volume is not believed to be sufficient to alter
climate. Pinatubo was identified responsible for a two-year period of global
cooling that temporarily halted the planetʻs pattern of warming.
Pinatubo lifted 15 million tons of sulfur dioxide into the atmosphere, where it formed a layer
of sulfuric acid droplets that both blocked sunlight and made great sunsets.
© Jan TenBruggencate 2019
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