You may not expect NASA's Astronomy Picture of the Day to include terrestrial volcanoes, but it frequently does! And if you're looking for fantastic beauty, you utterly cannot go wrong with these images. Click the links and prepare to be amazed. Each APOD image includes a link to the photographer, so if an image particularly captivates you, or seems perfectly suited for a loved one, see if a print's available.
As most of these beauties are copyrighted, I won't be reproducing them here. But I will tell you a bit more about the geology involved. Let's visit some fire mountains under the Stars!
Sometimes it's hard to decide which is more impressive -- the land or the sky. On the land of the featured image, for example, the Volcano of Fire (Volcán de Fuego) is seen erupting topped by red-hot, wind-blown ash and with streams of glowing lava running down its side. Lights from neighboring towns are seen through a thin haze below. In the sky, though, the central plane of our Milky Way Galaxy runs diagonally from the upper left, with a fleeting meteor just below, and the trail of a satellite to the upper right. The planet Jupiter also appears toward the upper left, with the bright star Antares just to its right.
Volcán de Fuego has erupted more times in recorded history than any other Central American volcano. It's part of the Central American arc, a line of volcanoes caused by the subduction of the Cocos Plate beneath the Caribbean Plate. It's a stratovolcano, and still quite explosive even though its lavas have become more mafic (basaltic) over time. It's quieter but still occasionally vigorous twin, Acatenango (from which the APOD photo was taken), is mostly andesitic.
It's beautiful, but dangerous: its June 3, 2018 eruption killed hundreds and displaced entire villages. Many of its victims, with nowhere safe to go in their own country, are trying to make new lives in the United States. You can help them by donating to organizations like the International Rescue Commitee or RAICES. You can find a list of other organations helping refugees here.
Pictured earlier this month in a two-image composite, lightning stems from communication antennas near the top of Volcán de Agua (Volcano of Water) in Guatemala.
Standing opposite the twins Acatenango and Volcán de Fuego in the Central American Arc, Volcán de Agua dominates the local landscape. It's a stratovolcano that erupted more andesitic lavas than Fuego. It hasn't had an eruption since the Pleistocene, but that doesn't mean it's a tame volcano.
Indigenous folks in the area named it Hunapú, "Place of Flowers," and the Spanish colonizers who sited their capital, Santiago de los Caballeros de Guatemala, on its slopes were happy to call it that until September 10th, 1541. On that day, heavy rainfall caused a massive lahar and flood to pour down the volcano's flanks, destroying Santiago and killing a good number of citizens, including Governor Beatriz de la Cueva. After that, the Spaniards began calling it the Volcano of Water and moved their capital posthaste.
The volcano wasn't done destroying the capital: in August-October 1717, eruptive and seismic activity from Fuego messed with the hydrothermal plumbing and slope stability of Agua, causing more mudflows. Between those and the earthquakes, residents decided to petition the Spanish government to let them relocate the capital again. The crown said no, but another devastating series of earthquakes in 1773 forced the issue, and the capital moved in 1776.
Even sleeping volcanoes can be as dangerous as they are beautiful!
The surreal scene was captured by chance late last month when the astrophotographer went to Mount Etna, a UNESCO World Heritage Site in Sicily, Italy, to photograph the conjunction between the Moon and the star Aldebaran. The Moon appears in a bright crescent phase, illuminating an edge of the lower lenticular cloud. Red hot lava flows on the right.
Mount Etna, locally known as Mongibello, is both a Decade Volcano and a UNESCO World Heritage Site. Nearly continuously erupting, it's one of the world's most active volcanoes. It's a stratovolcano, but one more given to Strombolian activity and massive lava flows than huge blowouts like Mount St. Helens. And technically, it's not one volcano: it's "a series of nested stratovolcanoes with four distinct summit craters." Complicated!
The plate tectonics giving rise to Etna are also complicated. It's located where the African Plate is subducting under the Eurasian Plate, but it's not in the expected volcanic arc - it's on an active fault between the African Plate and the lonian microplate, which head towards the subduction zone together. Either because of this, or possibly a hotspot, the lavas Etna erupts resemble the upwelling mantle material you'd expect more from midocean volcanoes than the crustal melts more typical of subduction zone arcs.
Humans have been documenting Etna's eruptions for over 2,500 years, longer than any other volcano in the world.
What's happened to the Moon? Nothing, but something has happened to the image of the Moon. The heat from a volcanic lava fountain in the foreground has warmed and made turbulent the air nearby, causing passing light to refract differently than usual. The result is a lava plume that appears to be melting the Moon. The featured picture was taken as the full Sturgeon Moon was setting behind Mt. Etna as it erupted in Italy about one week ago.
This marvelous photo shows the searing heat of a lava fountain during an eruption of Etna. Basalt erupts at around 1,100-1,250 degrees Celsius, and the air temperature is rapidly raised.
Just enough details of the eruption were given for me to track down which of Etna's many eruptive episodes this was. It took place from August 20-26th. Strombolian activity and a couple of small lava flows occurred. I don't know the exact date of this photo, but it's very possible it was on the night of August 23-24, when a vent at the New Southeast Crater put on quite a show.
There are many more astonishingly beautiful images that combine astronomy with the earth sciences. We'll be exploring them soon.