Redoubt Erupts

Mt. Redoubt in Alaska erupted overnight, four times. The ash plum has gone nine miles high, but so far there appears to be little ash fallout regionally.

This doesn't appear to be the size volcano to influence global temperatures. Volcanic activity is measured by the Volcanic Explosive Index (VEI), a nonlinear scale that takes into account volume of products, eruption cloud height, and qualitative observations.

• Mt St Helens in 1980 was about 5.

• Pinatubo in 1991 was a high 6. (That one did influence climate for a year or so).

• Tambora in 1815 was a very high 7. (It was the largest eruption in recorded history, and caused "The Year Without a Summer" in northern countries in 1816 -- or, my favorite term for it, "Eighteen hundred and froze to death.")

In 1989 Reboubt exploded with a VEI = 3.

Here's the Twitter page for the volcano, and an updating site from the Alaska Volcano Observatory.