PrintRing of Fire
Did you catch all of that? Review the chapter with another Johnny Cash tune not sung by Johnny Cash, "Ring of Fire.", Mt. St. Helens by the subduction zone—it really is a burning thing!
DR. RICHARD B. ALLEY: Hi. I'm not Johnny Cash. But I have been in a ring of fire.
[MUSIC- JOHNNY CASH, "RING OF FIRE]
(SINGING) Subduction is a burning thing. It feeds a fiery ring. Cold, dense ocean floor will soon retire down through the mantle for a ring of fire.
Subduction scrapes off mud 'round a burning ring of fire. Takes water down, drives the volcanoes higher. Makes light andesite from a ring of fire. A ring of fire. Basalt is born calm and dark at a spreading ridge or Hawaii's hot-spot park. Dangerous stratovolcanoes fountain higher when fed by subduction and a ring of fire. Subduction scrapes off mud 'round a burning ring of fire. Takes water down, drives the volcanoes higher. Makes light andesite and a ring of fire. A ring of fire.
Great earthquakes from the moving load, stick, slip, and plates just might implode.
Eruptions, landslides-- we require Tsunami warnings from the Ring of Fire.
Subduction scrapes off mud 'round a burning ring of fire. Takes water down, drives the volcanoes higher. Makes light andesite from the Ring of Fire. The Ring of Fire. St. Helen's blew high, others blow higher. Go in awe and fear to the Ring of Fire. The Ring of Fire. The Ring of Fire.
Enrichment: The Biggest Eruption in the Whole USA
The eruption from Mt. St. Helens in 1980 was not especially big—each of the main Yellowstone eruptions moved about 1000 times more material, for example. But, the Mt. St. Helens eruption killed more people (57; before that only 2 deaths in the US were blamed on volcanic eruptions, with none since), and did more property damage (almost $1 billion), than any other eruption in the United States since the country was formed. Novarupta, in Alaska in 1912, blasted more material than the Mt. St. Helens eruption, but was so far from most people that no one died and damages were small; also, Alaska, at that time, was a territory of the US but not yet a state.
The 1980 Mt. St. Helens eruption probably involved the largest landslide ever observed by humans, in the US or anywhere else, at least since we started writing down what we saw. So, by many measures, in 1980, Mt. St. Helens gave us "The Biggest Eruption in the Whole USA." Here's a Rock-Video parody to show you what happened. If an eruption this big happened from Mt. Rainier, which is close to many more people, the damages would be far, far greater. And, Rainier might just do it some day...
[MUSIC PLAYING] PRESENTER (SINGING): Good morning, Mountain. Hello, crater. Lava dome raising its head. Cracks in their showing the molten rock glowing so hot it's orange and red. Behind the new dome, there's a glacier, fed by the massive snowfall. Fire and ice may make you think twice, either can make you feel small.
May on the mountain, 1980, the magma was coming full bore. The poison gas rising, the earthquake surprising, the north slope was bulging out more. Scientists worried, authorities hurried to save everyone if they could. Those few felt the power, but in the last hour, those few feared that everyone would.
The forces of nature dwarf us here as they shape the mighty land. But as we wonder, as we fear, we can understand. But there once was a time when we could not imagine just what it would mean to say, "We saw the biggest eruption in the whole USA."
Morning the 18th came the earthquake, the north slope went sliding to ground, uncorking the bottle that went off full-throttle. "This is it!" the most memorable sound. Almost as fast as sound came fury. 700 degrees in the blast. The forest was leveled, the landscape was beveled, 57 had breathed in their last.
Now we and the mountain live together. We both have a place on this sphere. It gives us new land, and the scenery grand, new soil for the trees and the deer. But bigger ones happened before cameras. Yellowstone was 1,000 times more. And Crater Lake's blast, not that far in the past, sent ash up to Greenland and o'er.
The forces of nature dwarf us here as they shape the mighty land. But as we wonder, as we fear, we can understand. And that helps us prepare for a bigger one coming. But until then we can say, "We saw the biggest eruption in the whole USA!"
St. Helen's will reach you, St. Helen's will teach you, and stay with you when you say, "I saw the biggest eruption in the whole USA!"
Good morning, Mountain.
Enrichment: Just for Fun—Rockin' Around the Silicates
We've seen that most of the Earth's crust is made of minerals with silica (silicon and oxygen) in them. Melting these minerals feeds volcanoes, and freezing the melt clogs volcanoes and makes new minerals in new rocks. When we get to the Redwoods and the Badlands in a couple of weeks, you'll see how the weather attacks the new minerals, and you'll meet a few of the minerals being attacked. Here, just for fun, you can see some truly beautiful minerals, and learn a bit about the wonderful ways they are put together—Lego blocks and erector sets have nothing on nature! Meet the main minerals of the crust, in a parody of Bill Haley and the Comets' Rock around the Clock. This Rock Video has a bit more detail than we'd ever ask in this class, so don't worry about actually learning the difference between nesosilicates and inosilicates unless you're really interested.
[MUSIC PLAYING] PRESENTER: (SINGING) Definite chemical composition. Repeating order, each in position, controls the growth of the faces crystalline. Minerals, silicates are commonest here. Silicon plus 4 has a friendly face, gets 4 oxygens to share its space. Then little silicon is really hid in a tetradedral pyramid, SiO4 -4 won't balance out. So put a silicon on the other side, of an O -2 that's nice and wide. Then one extra O electron counts each way, with the O in two tetradedra to stay, sometimes it pays to share, there is no doubt.
But shared oxygen's not the only way to balance out the charge today. Put a +2 ion in between two oxygens from the pyramid scene. Give iron or magnesium a shout. Share all four oxygens, that's great. You've made a tectosilicate. And half of four with each Si makes SiO2 coming by. That's quartz, but crystals don't work at the bar.
But there's lots of aluminum plus 3 that needs a space where it can be. Take four SiO2 then place one Al in an Si space. K or Na plus balance alkali feldspar. Or kick out Si for two Al that happen by, and balance with Ca +2, Na to Ca solid solution, and then that is plagioclase feldspar.
But if your tetradedra just won't share, a nesosilicate is there. When each tetradedron can be found with iron or magnesium all around. SiO4, it's olivine you'll see. Share some oxygens but not each one, so many ways to mineral fun. Share 3 in sheets, the phyllosilicate way, Si2O5s in mica, serpentine, clay, with some other things, gives cleavage that's flaky.
Share one O, tetradedra form a pair. Si2O7 in the equation somewhere. Sorosilicate, epidote, you know, but we've still a little way to go 'cause some other tetradedra want to join up, you'll will see.
Share 2 in a ring, Si6O18, cyclosilicates beryl and tourmaline. SiO3 sharing two in a line, or Si2O6, tha'ts also fine. Pyroxene, single-chain inosilicate, baby. Join two ions sie by side, is it rings or chains? Si8O22 gives you amphibole grains. It's a double-chain inoslicate. Learn the hornblende formula, just can't wait. Half the tetradedra share 2 Os half share three. Neso, soro, ino, cyclo, phyllo, tecto, silicates-o, tetrahedral Si and O form the minerals commonest below with Al, Fe, Ca, Na, K, Mg.