Mt. Redoubt bellows steam and ash during it eruption on March 26. For up to date information on the volcano, check out the Alaska Volcano Observatory website. Credit: Al Grillo / AP
Alaska’s 10,000 foot high Mt. Redoubt (READ-out) erupted multiple times last week, sending plumes of volcanic ash and sulfur dioxide up to 65,000 feet high. The volcano is located about 110 miles southwest of Anchorage and its effects are already widespread. Not only has it dumped tons of razor-sharp ash particles across parts of Alaska, but the Global Ozone Monitoring Experiment sensor aboard Europe’s MetOp-A satellite has been tracking the movement of huge ash and gas clouds across Canada, the U.S. and now Europe.
This sunset, featuring the planet Venus, was one of the more colorful from late last summer. Volcanic aerosols from Mt. Kasatochi was largely the reason why. Photo: Bob King
Do you recall the colorful sunsets of last summer? They even hung around into the fall, a gift of another Alaskan volcano named Kasatochi . Eruptions send lots of gases and particles, called aerosols, into the stratosphere, where they scatter the blue portion of sunlight. Blue mixes with the red light from the low sun at sunset and sunrise to create vivid purples. Yellows and oranges are enhanced as well. Mix it all together and the western sky after sundown is transformed into a scene awash in rich color.
Scientists predict similar sunsets from Mt. Redoubt’s eruptions, so be on the lookout this week when another ash-gas cloud is predicted to cross over parts of the U.S.
Not far from the prominent lunar crater Copernicus is a cluster of volcanic domes just north of the 10-mile-diameter crater Hortensius. The domes are about 4-5 miles in diameter and visible in a 6-inch telescope. Moonwatchers can spy them this weekend when the moon is just past first quarter phase. Credit: Consolidated Lunar Atlas
The moon’s been up all week in the evening sky. Although it’s a very quiet place now, the moon was once volcanically active. No tall, conical volcanoes like the iconic ones on Earth are present on the moon, but it does have its share of the blister variety called domes.
Domes are circular in form and typically about 4-8 miles in diameter. Many are topped by a tiny craterlet, which once served as a vent for thick, syrupy lava to pour out onto the moon’s surface. Repeated outflows of lava gradually built up a large, gently-sloped hill of volcanic rock called a shield volcano. Nothing violent here, just a steady and repeated oozing of hot lava. You’ll find many examples of shield volcanoes on Earth — all the Hawaiian islands are shield volcanoes, with Mauna Kea and Mauna Loa as standout examples.
A closeup of Hortensius and the domes, each of which is named after a letter in the Grek alphabet. Notice the summit craterlets. These are the holes where the lava poured out onto the surface over three billion years ago. Credit: NASA
While Hawaii’s volcanoes are still active, those on the moon expired long ago. The great age of lunar volcanism occured 3.8-3.1 billion years ago. This was during a period of intense meteorite bombardment that fractured the crust, allowing lava to well up to the surface. Things have quieted down since then except for the occasional meteorite hit or moonquake. No so with Earth, a planet packed with surprises, where a new eruption could mean a pretty sunset picture for your photo album.