Showing posts with label eruption. Show all posts
Showing posts with label eruption. Show all posts

June 6 - Eruption of the Century!

  Posted on June 6, 2022     


This is an update of my post published on June 6, 2011:


The largest volcanic eruption in the 1900s happened very early in the century - on this date in 1912 -

- but (thankfully) far from large cities and population centers.


Novarupta (which means “new eruption”) is located at the base of the Alaska Peninsula. It is almost 300 miles from Anchorage (Alaska's largest city) and about 750 miles to Juneau (Alaska's capital city). When it began to erupt on this day in 1912, nobody knew it for a while. Alaska was not yet a U.S. state, population density was even lower then than it is now, few scientists were studying volcanoes, and there was not yet a worldwide seismic network in place. People as far away as Juneau did hear the sound of later blasts.

For the next sixty hours, Novarupta continued to erupt, shooting gas, rocks, and ash high into the air. Compared to other famous volcanoes, Novarupta emitted 30 times more “ejecta” than did the 1980 eruption of Mount St Helens. Yet the latter volcano, even with modern monitoring and plenty of warning, killed 57 people. There were NO human deaths attributed to Novarupta! (Unfortunately, many, many plants and animals died.)


Novarupta now

(Sadly, the largest volcanoes in the 1800s were super deadly. In 1815 Tambora killed many thousands of Indonesians directly and was the cause of even more deaths because so many crops and so much forest was destroyed, and in 1883 Krakatoa killed from 36 to 120 thousand Indonesians. Obviously, these volcanic eruptions were in more densely populated areas, although they were more powerful, as well.)



Nowadays we can photograph eruptions from space!

Also on this date:






 
























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May 30 - Mount Lassen Awakens After 27,000 Years!

 Posted on May 30, 2021

This is an update of my post published on May 30, 2010:




A volcanic peak in Northern California, Lassen Peak, formed about 27,000 years ago, but for thousands of years it just sat there looking pretty as Maidu and other American Indian groups hunted and gathered in its shadow
, and as European Americans such as Peter Lassen and William Nobles led groups of settlers past as they traveled to the Sacramento Valley.



Some people visited the area and climbed the peak, but few people lived near there. (As it turns out, that was probably a lucky thing!)

On this day in 1914, a steam explosion shook the mountain. This announced to the world that Lassen was active again after all those thousands of years of being “dormant” (which basically means “sleeping”).



Humans could say, “Thanks for the warning!” Actually, the mountain gave a series of warnings—more than 180 steam explosions occurred over the course of a year. Finally, after all those warnings, in May of 1915 larger eruptions shook the area, with hot, glowing blocks of lava spewing out of the mountain, an avalanche of snow and volcanic rock roaring down one flank, and mudflows pouring down another. The “Great Explosion” of 1915 shot pumice and other rocks high into the air, and a cloud of ash and gas rose more than 30,000 feet up. People who lived more than 200 miles away could see the eruption!



And nobody died!

This huge rock flew through the air,
landed with a mighty thunk,
and stayed hot for months!

It's still called "Hot Rock"!

Steam explosions continued to occur for two more years, but then Mount Lassen began to settle down again. There are geothermal areas in the park – hot springs, mudpots, and steaming fumeroles – but there haven't been eruptions or explosions for many decades now. Scientists and governmental agencies continue to monitor the volcanic areas, and every year thousands of visitors safely visit the hot spots and climb the volcano.



One active area near Lassen Peak
is called Bumpass Hell


What causes volcanoes?


Volcanoes are openings in the Earth's crust that allows molten rock, ash, and gases to escape from underneath.

There are two main reasons for volcanoes: the actions of tectonic plates, and “hot spots” caused by mantle plumes.


The rocky crust of the Earth is not one whole sphere of rock, but is instead eight giant plates and many smaller plates of rock.


These plates move about on the hotter upper mantle, sometimes spreading apart and letting molten rock come up through the resulting crack, sometimes running into each other and pushing up mountains, and sometimes with one plate pushing down underneath another. The areas where plates pull apart or run into each other are often edged with volcanoes and feature earthquakes.

The diagram above shows how Lassen Peak and other 
Cascade volcanoes were formed, as the Pacific Plate
ran into and then pushed underneath the continental plate.

The diagram below shows how the Hawaiian Islands
were formed in the middle of the Pacific Ocean.


Hot spots are quite different. They are probably caused by mantle plumes, areas in which hotter columns of molten rock rise through the mantle and cause volcanic eruptions in the crust. They can be far from the edge of the tectonic plates, but as a plate slowly glides over a hot spot, a chain of volcanic islands can form. The Hawaiian Islands are a famous example of a chain of “hot spot” volcanic islands.


Mount Lassen is an example of a tectonic-plate volcano, and it other nearby volcanic mountains make up the Cascade Range. Mount St. Helens in Washington, which exploded in a deadly and economically destructive eruption in 1980; Crater Lake in Oregon, which is the remnant of Mount Mazama; and Mount Shasta in Northern California are other volcanoes in the Cascades.


Explore Volcanoes (Virtually Speaking!)

How Volcanoes Work” is an interesting website with lots of diagrams.

Kids' National Geographic has a page about volcanoes.


There are several different kinds of volcanoes
and volcanic eruptions.




There are volcanoes elsewhere in the universe, other than Earth! The largest volcano that we know of is on the planet Mars: Olympic Mons, which is about the size of the state of Arizona.


Here is a website that explains why volcanoes on Mars tend to be bigger than any we have on Earth. 
And here are some new hi-res photos of the Martian volcanoes and other Martian features.



Also on this date:


























 


May 18 - Thar' She Blows Day

Posted on May 18, 2020

Mount Saint Helens, in Washington, "before" pic

The signs were clear:

On March 20, 1980, Mount Saint Helens in Washington state (U.S.) experienced a pretty big earthquake. 

On March 27, 1980, the volcano started venting steam and ash.

On March 29, 1980, a new crater could be seen - and the mountain was topped by a blue flame in both craters!

On March 30, 1980, instruments on Mount Saint Helens measured 93 separate tremors (small earthquakes).

The experts agreed: the volcano was active, and it would soon erupt. Scientists told governmental officials and other policy makers, and the governor of Washington declared a state of emergency on April 3, 1980. He created a "red zone" around the volcano, and anyone caught inside the zone without a pass would receive a fine or a 6-month jail sentence (!). Outside the red zone was a blue zone where workers in mines and lumber were allowed - again, only with special passes.


Some curious people ignored the rules and moved highway barricades so they could get close enough to glimpse the volcano and get a taste of danger. Some people who had cabins in the red zone were bummed that they weren't allowed to go to their own property. 

At the end of April and early May, a bulge grew on northern part the mountain, and the area behind the new bulge started to sink. Even more looky-loos came to watch.

Thank goodness, on May 16, the visible eruptions stopped. So a lot fewer curious types came. Still, the public put so much pressure on officials, asking to go to their cabins and get their stuff out, that on May 17, officials bowed to pressure and allowed 50 cars and trucks of property owners into the red zone. They grabbed whatever property they could carry out.

Another property-owners trip was scheduled for 10 a.m. the next day...

But at 8:32 a.m., on May 18, a 5.1 earthquake hit the volcano, and a huge landslide (the largest in recorded history) began, moving across a lake and through a river valley. The landslide caused a giant wave of displaced lake water - about 600 feet (180 m) high - which in turn caused a 295-foot (90 m) avalanche of debris.


A few seconds after the landslide started, gases and partially molten rock exploded sideways, releasing ash and pumice, overtaking the landslide and fanning out into a 23-mile by 19-mile devastation zone. The blast had the force of an atomic bomb; actually, I read that it was the equivalent of 1,500 atomic bombs!

This was the most deadly and economically destructive volcanic eruption in the history of the contiguous United States (the 48 states excluding Alaska and Hawaii). Around 57 people were killed directly by the eruption. 

Only three of the people killed were in the red zone: a scientist, a photojournalist, and a man who refused to leave his home. The first two were dedicated professionals who were on the job.

David A. Johnson
 The scientist, David A. Johnston, is credited with saving a lot of lives, as he had publicly insisted that the eruption would be very dangerous. The last anyone heard from Johnston was his radio report - the FIRST report anyone heard of the eruption - "Vancouver! Vancouver! This is it!" Even though he was six miles from Mt. St. Helens, in what he hoped was a safe place, the side-blow of the volcano rather than the expected "blowing its top" almost instantly killed Johnston.

The third man who died in the red zone, the man who refused to leave his home despite warnings and urgings from officials, was quite old, and he wanted to live and die on the mountain. So he got his wish.

Three of the 57 people who died in the eruption were miners carrying permits to work in the "blue zone." Luckily the volcano's big eruption was on a Sunday, because around 300 lumberjacks were NOT working in the blue zone.

The rest of the 51 people who died in the eruption were all in areas deemed safe. But the thing is, scientists and experts know a lot, but there are so many unknowns in the universe, especially when it comes to volcanoes; who could have guessed that the volcano would start to bulge in one direction and then "blow its side" instead of its top? And who can know exactly where landslides and avalanches and streams of lava and other pyroclastic flows (hot gas and other volcanic material) are going to go? And who can guess at just how big an eruption is going to be?

I read about a family of four who took a drive hoping to see an eruption, and about a couple who went camping on a bluff. All of these people stayed in what had been thought to be a safe area. A relative of one person who died said that the state owed her and other loved ones an apology.

And yet: When experts and officials are telling you that a volcano is going to erupt soon, you maybe want to stay WAAAYYY farther away than just 4 miles into the "safe" zone. You maybe don't want to go to that particular mountain region for camping or hiking or picnicking or fishing, or "just a drive," even if it takes months for the expected eruption to occur or for scientists to give the "all clear" signal.


Although volcanic ash from the Mount Saint Helens eruption ended
up traveling around the world (It took two weeks), the amount
of ash in nearby towns was very unhealthy!


Mount Saint Helens, in Washington, "after" pic