Discover Top Posts Tagged with #stratovolcanoes

Tancítaro, deemed dormant, unveils its seismic activity through extensive research by Román Álvarez Béjar and team. Seismic swarms and magma

Tancítaro, deemed dormant, unveils its seismic activity through extensive research by Román Álvarez Béjar and team. Seismic swarms and magmatic injections challenge perceptions, emphasizing the need for vigilant monitoring of all Mexican stratovolcanoes.

#Tancítaro #seismic activity #Seismic swarms #magmatic injections #stratovolcanoes #volcano

Mount Fujiyama of America...

Prior to 1980 a well known Cascade peak was often referred to as Mount Fujiyama of America. It’s conical snow capped shape suggested a strong resemblance to it’s cousin the real Mount Fujiyama in Japan. The American peak is Mount Saint Helens. After the major eruption on May 18,1980 the mountain got a natural makeover in the form of blowing off nearly 1,300 feet of its summit. The resemblance to Mount Fujiyama changed in a matter of a few short terrifying moments.

In a series of posts highlighting the notable peaks one sees and may walk near or around on their way north to Canada on the Pacific Crest Trail, we come to Mount Saint Helens. In actuality the PCT doesn't get all that close to St. Helens but on a clear July, August or September day it can’t be missed staring back as a hiker looks to their left. Mount Adams and Mount Saint Helens share nearly the same latitude line. During the time of the pioneers the two would often get confused.

Mount Saint Helens was the first Cascade peak to be climbed strictly for pleasure and not for economic, military or scientific reasons. Thomas Dryer, who founded the Oregonian newspaper in nearby Portland was the first to go to the top in 1853.

The mountain is the youngest of the stratovolcanoes. Scientists have dated its beginning to nearly 40,000 years ago. However the summit that we saw on pre-1980 postcards only went back about 15,000 years. The visible part of the present day volcano only took shape about 2,200 years ago, long after the Ice Age. The mountain’s youthfulness protected it from a lot of erosion so it displayed a very symmetrically pleasing shape.

Prior to 1980 the mountain was the most volcanically active volcano in the lower 48. The local Klickitat tribe referred to it as Tah-one-la-clah or Fire Mountain due to its history of eruptions.

Finally on May 18,1980 the mountain literally blew its top. With an explosion that was the equivalent of 30 million tons of TNT 1300 feet of the top went into the stratosphere. This produced the largest avalanche in recorded history. 57 people lost their lives and destroyed 150 square miles of forestlands. A four mile long lava flow with temperatures between 600 and 1400 degrees Fahrenheit, melted the upper 45 feet of the Mount Saint Helens Glacier. Ash from the eruption flew as far as Montana but remnants of the ash clouds circled the earth and enhanced sunsets for weeks afterwards.

In 1981, my partners, Jim Peacock and Rees Hughes hiked from the Columbia River to Rainy Pass. We had no idea what we would find a year after the eruption. At least six inches of gray ash filled the trail. The landscape east of Saint Helens was gray. Not a lot of plants as they were suffocating under the blanket of ash. Walking along we kicked up dry clouds of ash and gave each other distance so as not to breathe too much of this stuff in.

After the eruption, the volcano shrank from 9,677 feet to its current elevation of 8,364 feet. The drama of the eruption is still evident but as the years go by nature has slowly been reclaiming the landscape. What was an ashen gray stump of its former self still retains some of that color but the forest is re-emerging in places. The area is now managed as the Mount St. Helens National Historic Monument.

Walking north the mountain no longer resembles Mount Fujiyama but is another sentinel leading the way north along the PCT. If the day is clear the view north and slightly west includes the ‘grand master’, Mount Rainier. West is St. Helens, and behind is Mount Adams. This is a landscape of BIG volcanoes that make up the ‘ring of fire’. That ring stretches to Mount Fujiyama.

#Mount Saint Helens #Mount Adams #Mount Rainier #Mount Fujiyama #May 1980 #Stratovolcanoes

Martian stratovolcanoes Zephyria Tholus and Elysium Mons

While stratovolcanoes are common on Earth, they’re extremely rare on other planets of solar system.

on Mars, almost all volcanoes are shield, except few cinder cones and two stratovolcanoes (of those, one is also a shield). on Venus there are no stratovolcanoes at all, but there are pancakes domes, that can’t be found on Earth and Mars. It should be noted, however, that Venus has an atmospheric pressure that is 90 times the one of Earth, so possibly stratovolcanoes might have been squished from the start, developing into shield instead.

The only pure stratovolcano on Mars is named Zephyria Tholus.

https://onehundredmountains.blogspot.com/2011/05/meizan-from-outer-space.html

Meizan from outer spaceA new candidate for the “Mt Fuji of Mars” is proposed. And why stop there… ? Sumimasen: a few posts ago, I did something ill-considered. It was reckless to designate Mons Olympus, the largest volcano on the Red Planet, as "the Mt Fuji of Mars" (火星富士). For even the briefest glance shows that the Martian mountain (below) looks nothing like Mt Fuji. It isn’t even the same kind of volcano.

And, if you do seek a Mars-Fuji, there are better choices. Take Zephyria Tholus, for instance, an “unusually symmetrical cone located in the Aeolis region of Mars … with a flat-floored summit crater”. As you’d expect from this description, Zephyria is likely to be a stratovolcano. That is certainly the conclusion of Emily Lewis and James Head, two savants from Brown University who analysed the radar data from NASA’s Mars Orbiter.

Just like the real Mt Fuji, the Martian cone (above) has slightly concave upper slopes and its edifice is “dissected” by two huge erosion gullies. Even the height is Fuji-like: about 3,000 metres today and perhaps as tall as 3,900 metres in the past. Like Fuji’s, the summit crater plunges about 200 metres deep. However – and this is where the comparison does get a bit stretched – Zephyria’s cauldron is about eight or nine times wider than the Japanese one. Also, its summit slopes are only about half as steep as Fuji’s. All in all, Zephyria would look squatter than Fuji. That, say Lewis and Head, is only to be expected of Martian volcanoes – the low gravity and thin atmosphere allow eruptive debris to fly further, resulting in a more spread-out edifice. You see, Mars is a foreign planet; they do things differently there.

Yet proposing Zephyria as Mars-Fuji shouldn’t be too controversial. It only extends the Japanese custom of awarding the “Fuji” suffix to any mountain that looks remotely conical. Thus, there is hardly a Japanese prefecture without its own Fuji, from one end of the archipelago to the other: Rishiri-Fuji, Ezo-Fuji, Tsugaru-Fuji … The point about all these honorary Mt Fujis is that they share the elegance of their original. In short they are “Meizan”. The word is Japanese, but it can apply to any mountain of note, anywhere. When they relabelled Mt Rainier (below) as “Tacoma-Fuji”, homesick émigrés from Japan implicitly recognised that.

So did Fukada Kyūya, the maven of Meizan. Encouraged by the success of his One Hundred Mountains in Japan (Nihon Hyakumeizan), he was busy compiling a Sekai no Hyakumeizan (One Hundred Mountains of the World) when he died in 1971. But why stop with the world? As Lewis and Head show, other planets have Meizan too. Indeed, there should be more than enough for a One Hundred Mountains of the Solar System (太陽系の百名山). Now which would they be, I wonder.... ?

The other stratovolcano (though is an half shield), Elysium Mons, might have characteristics similar to Mount Etna, a large shield base with a tiny stratocone on the top (though Etna has FOUR tiny stratocone on the top of a still active large shield)

From wikipedia: https://repress.alummah.news/browses.php?q=https%253A%252F%252Fen.wikipedia.org%252Fwiki%252FVolcanology_of_Mars

Elysium volcanic province

A smaller volcanic center lies several thousand kilometers west of Tharsis in Elysium. The Elysium volcanic complex is about 2,000 kilometers in diameter and consists of three main volcanoes, Elysium Mons, Hecates Tholus, and Albor Tholus. The northwestern edge of the province is characterized by large channels (Granicus and Tinjar Valles) that emerge from several grabens on the flanks of Elysium Mons. The grabens may have formed from subsurface dikes. The dikes may have fractured the cryosphere, releasing large volumes of ground water to form the channels. Associated with the channels are widespread sedimentary deposits that may have formed from mudflows or lahars.[37] The Elysium group of volcanoes is thought to be somewhat different from the Tharsis Montes, in that development of the former involved both lavas and pyroclastics.[38]

Elysium Mons is the largest volcanic edifice in the province. It is 375 km across (depending on how one defines the base) and 14 km high. It has single, simple caldera at its summit that measures 14 km wide and 100 m deep. The volcano is distinctly conical in profile, leading some to call it a stratocone;[39] however, given the predominantly low slopes, it is probably a shield. Elysium Mons is only about one-fifth the volume of Arsia Mons.[37]

Hecates Tholus is 180 km across and 4.8 km high. The slopes of the volcano are heavily dissected with channels, suggesting that the volcano is composed of easily erodible material such as volcanic ash. The origin of the channels is unknown; they have been atrributed to lava, ash flows, or even water from snow or rainfall.[40] Albor Tholus, the southernmost of the Elysium volcanoes, is 150 km in diameter and 4.1 km high. Its slopes are smoother and less heavily cratered than the slopes of the other Elysium volcanoes.[41]

#stratovolcanoes #alien #mars #zephyria tholus #Elysium mons