October 17 – Play Ball!

Today’s factismal: The first earthquake to be shown live on television happened in 1989.

You may have heard that there is a 72% chance that there will be a large earthquake near San Francisco sometime in the next thirty years. And that there is an  85% chance of a large earthquake on the San Andreas fault sometime in the next ten years. Experts think that it could cause as many as 1,800 deaths and as much as $200 billion in damage. But how can we know how much damage an earthquake will do? Simple – we know because we saw one happen, live on TV.

It was a balmy October evening in San Francisco. The Giants were competing with the Oakland A’s for the pennant, and the two teams were warming up in preparation for game three. As the television sports casters searched for something to add a little local color to the broadcast, they were given the greatest exclusive in history: an earthquake struck the area. And not some piddly little 4.0; this was a 6.9 Mb earthquake! As the anchors tried to describe what was happening, the world saw buildings shake, highways fall, and homes crumble into rubble.

A section of the collapsed highway (Image courtesy USGS)

A section of the collapsed highway
(Image courtesy USGS)

Amazingly, there were only 63 people killed in the earthquake (the 1905 temblor was about 30 times stronger and killed 3,000 people). Most of these happened in Oakland where a double-decker highway collapsed on itself. Interestingly, many credit the baseball game for the low fatality count. Because many people had left work early in order to watch the game, the highways were relatively uncrowded which meant that fewer people were hurt.

California is almost certain to have another large earthquake in the next three decades (Image courtesy SCEC)

California is almost certain to have another large earthquake in the next three decades
(Image courtesy SCEC)

But what is even more amazing is that the danger isn’t over. There is a 99.7% chance that some part of California will have another earthquake at least as powerful as this one in the next thirty years. So we know when the next big on will happen (soon); what we don’t know is where. And that’s where you can help. The USGS and Stanford University are developing a new type of distributed seismometer that uses the accelerometers in tablets, smartphones, and computers to provide more complete coverage of earthquakes; the data that this Quake Catcher Network gathers will then help them to narrow down when we can expect the next big one. If you’d like to take part, head over to:
http://qcn.stanford.edu/

October 17 – Live! On TV!

Today’s factismal: The first earthquake to be shown live on television happened in 1989.

It was a balmy October evening in San Francisco. The Giants were competing with the Oakland A’s for the pennant, and the two teams were warming up in preparation for game three. As the television sports casters searched for something to add a little local color to the broadcast, they were given the greatest exclusive in history: an earthquake struck the area. And not some piddly little 4.0; this was a 6.9 Mb earthquake! As the anchors tried to describe what was happening, the world saw buildings shake, highways fall, and homes crumble into rubble.

A section of the collapsed highway (Image courtesy USGS)

A section of the collapsed highway
(Image courtesy USGS)

Amazingly, there were only 63 people killed in the earthquake (the 1905 temblor was about 30 times stronger and killed 3,000 people). Most of these happened in Oakland where a double-decker highway collapsed on itself. Interestingly, many credit the baseball game for the low fatality count. Because many people had left work early in order to watch the game, the highways were relatively uncrowded which meant that fewer people were hurt.

California is almost certain to have another large earthquake in the next three decades (Image courtesy SCEC)

California is almost certain to have another large earthquake in the next three decades
(Image courtesy SCEC)

But what is even more amazing is that the danger isn’t over. There is a 99.7% chance that California will have another earthquake at least as powerful as this one in the next thirty years. So we know when the next big on will happen (soon); what we don’t know is where. And that’s where you can help. The USGS and Stanford University are developing a new type of distributed seismometer that uses the accelerometers in tablets, smartphones, and computers to provide more complete coverage of earthquakes; the data that this Quake Catcher Network gathers will then help them to narrow down when we can expect the next big one. If you’d like to take part, head over to:
http://qcn.stanford.edu/

August 23 – Bardarbing, Bardarbang, Bardarbunga!

Today’s factismal: The Bardarbunga volcano in Iceland has begun to erupt!

If you are a geologist, these are exciting times. Not only do we finally have a theory that explains how mountains and volcanoes form, we’ve got all kinds of instruments that helps us gather the data we need to test the theory and make it better. (That’s what scientists do, you know – we hatch ideas, carefully feed them on data until they become hypotheses, and then test them with yet more data leaving only the strongest behind as theories. And then we start all over again with the ideas that the theory spawns.)  Thanks to the Cold War, we’ve got seismometers located all across the globe; though they were put there to detect atomic bomb tests, they also record earthquakes which helps us learn more about the inside of the Earth. And thanks to the Cold War, we’ve got satellite altimetry across the globe; though it was created to help us detect bomb craters, it also helps us to measure how the Earth’s surface tilts and where things in the upper crust are moving. And thanks to the Cold War, we’ve got satellites that measure the change in gravity; though they were created to help track submarines (and to make our missiles more accurate), they also tell us where materials in the Earth change density. And, thanks to the Cold War (do you detect a theme here?), we’ve got GPS; though it was created to help the military move around, it also helps us track the movement of continents and mountains. And all of that data has lead in turn to a deeper understanding of the Earth.

And though a lot of that understanding is purely academic, such as the discovery that there is the equivalent of three ocean’s worth of water stored in the minerals of the Earth’s mantle, a surprising amount of it is very practical indeed. Understanding how the plates move around on the Earth has led to discovering new deposits of gold, silver, and diamonds (not to mention oil and gas), and to learning which areas are most at risk for earthquakes and volcanoes. Even better, it has helped us learn how to predict volcanic eruptions (we’re still working on predicting the timing of earthquakes). One of our earliest successes was Mt. St Helens; the scientists in the area were able to predict the eruption and save the life of everyone who was willing to evacuate. And today we have another example of that science at work in the eruption of Bárðarbunga (Bardarbunga {bar-dar-BUNG-ah!} to everyone but the Icelandics).

Like Mt. St Helens, Bardarbunga is a stratovolcano. That means that it is a tall, cone-shaped volcano made up of alternating layers of ash and lava fed from a subterranean magma chamber that sometimes erupts explosively (creating the ash) and sometimes erupts more passively (pouring out the lava). These are among the most common volcanoes on Earth and create some of the most spectacular eruptions (e.g., Krakatoa) as well as some of the least interesting ones (e.g., Stromboli, “the lighthouse of the Mediterranean”). Where Bardarbunga and Mt. St Helens differ is that Mt. St Helens is created by plate tectonics and Bardarbunga is created by a mantle plume. (That’s part of the “testing the theory” we discussed.) Where plate tectonic volcanoes are formed when subducting plates release a little water that stimulates magma production which then creates the volcano, mantle plume volcanoes are created by extra-light material coming from deep within the mantle. We’re still arguing over why mantle plumes should exist, as well as how many of them there are; everyone agrees on Iceland (where Bardarbunga is) and Hawai’i, but that’s it.

Location of earthquakes around the Bardarbunga volcano (Image courtesy aaaa)

Location of earthquakes around the Bardarbunga volcano
(Image courtesy Iceland Met Office)

The number of earthquakes per day (Image courtesy Iceland Met Office)

The number of earthquakes per day
(Image courtesy Iceland Met Office)

 

One thing that we’re not arguing over is that Bardarbunga is erupting. Starting about two weeks ago, seismologists noticed that the number of earthquakes, and especially the shallow earthquakes, in the area had taken a steep jump upward. Because adding magma to a region “stretches” the surface material, you always hear creaks and groans in the form of small earthquakes when it happens. In addition, the geophysicists in the area using GPS had noticed that the ground was starting to tilt; that’s another strong hint that there was magma moving into the area. And so Iceland raised the eruption threat to “Orange” (right below “Red” or “Watch out – the lava’s a’coming!”).

Today, the eruption threat was raised to Red as a small plume of ash and smoke was seen coming from the ice covering Bardarbunga. And that is the second important way that Bardarbunga differs from Mt. St Helens. Where Mt. St Helens had a light dusting of snow on its top, not more than a hundred feet thick, Bardarbunga is buried beneath a glacier; this is even more impressive when you realize that the volcano’s top lies 6,600 ft above sea level. The Vatnajökull (vat-na-JOKE-ull) glacier covering the volcano averages 1,300 ft thick and so forms a most excellent plug over the volcano. And that means that we may get an great view of a subglacial eruption!

Satellite image of Iceland; Bardarbunga is in the middle of the large chunk of ice (Image courtesy NASA)

Satellite image of Iceland; Bardarbunga is in the middle of the large chunk of ice
(Image courtesy NASA)

When hot lava meets cold ice, several things, all of which are fascinating, happen. The heat from the lava can melt the ice, forming a subglacial lake that eventually breaks through and rushes downhill like a crazed wet, weasel; this “jökulhlaup” (“glacier run” {yokel-oop}) can carve valleys and denude meadows faster than a politician can pocket a bribe. If there is enough ash mixed in the water, it forms a lahar which is basically a mud flood moving sixty miles an hour and not stopping for directions;in 1985, a lahar killed 23,000 people in Columbia. If the lava is erupted more quickly than the water can drain, then the heat may cause the water to turn into steam creating a steam explosion. This can then fling pieces of lava as large as a house for miles around.

Even if none of these things happen, the volcano will still put out ash and carbon dioxide and other particulates. The ash can make flying hazardous as the sharp edges eat away at jet turbine blades and propellers and literally sand-blast windshields into opacity. It is for this reason that planes are directed to fly well away from any erupting volcano. The carbon dioxide may seem like a lot, but it is actually relatively little. If this is a typical volcanic eruption, then it will put out about 500,000 m3 of lava and will eject about 8,300 tons of CO2 into the atmosphere, along with 2,000 tons of SO2 and 6,300 tons of H2O. In comparison, a car emits about 5.5 tons of CO2 per year, so Bardarbunga will add less CO2 than the amount generated by Houston traffic over the length of the eruption. But the SO2 is particularly interesting. As Franklin suggested back in 1784, volcanoes can cool the planet. We are still arguing about how they do so, but we know that the SO2 plays a key part. It acts to reflect sunlight back into space, helping to cool the planet. But such effects are short-lived; when Pinatubo erupted in 1991, it cooled the Earth by nearly 0.7°F but temperatures were back to normal by 1993.

So right now we’ve got an erupting volcano with lots of potentially interesting effects. Grab the popcorn and stay tuned!

August 29 Update: The eruption has subsided and Iceland has reduced the threat level to “orange” (possibly dangerous but not certain).

March 27 – Whole Lotta Shakin’ Going On

Today’s Factismal: The strongest earthquake in North American history took place in Alaska on March 27, 1964.

When it comes to earthquakes, California gets all of the press (and the bad movies). Part of that is because California was home to the 1906 San Francisco earthquake, which helped to spur modern scientific research. Part of that is because California is a heavily populated state that is destined to have another large earthquake sometime in the next thirty years. And part of that is because California is the only state to have televised an earthquake live on national television.

Thirty days worth of earthquakes (image courtesy USGS)

Thirty days worth of earthquakes (image courtesy USGS)

But California isn’t the only place in North America that has earthquakes. All along the Pacific Coast, from Baja California to Oregon to Washington state to the Aleutian islands, earthquakes happen every day. Most of them are very small and do very little damage. But about once a century a “great earthquake” (that is, an earthquake stronger than magnitude 8) happens. And on March 27, 1964, it was Alaska’s turn.

Damage from the 1964 Alaskan earthquake (Image courtesy USGS)

Damage from the 1964 Alaskan earthquake (Image courtesy Alaskan Earthquake Information Center)

For four minutes, the ground shook from the release of a magnitude 9.2 earthquake. Centered near Anchorage, it devastated the area, turning the soil into quicksand and the sea into a raging tsunami that swept far inland and headed out to California, Hawai’i and Japan. Over the next year, more than ten thousand smaller aftershocks would rock the Alaskan coast. Luckily, because Alaska is only sparsely populated, the death toll was low. But over $310 million in damage (more than $2,000 million in 2012 dollars) was done.

Buildings that sank into the ground during the earthquake (Image courtesy USGS)

Buildings that sank into the ground during the earthquake (Image courtesy USGS)

The scariest thing about the Alaskan earthquake is that the same conditions that caused it are also seen in Puget Sound, near Seattle, and along the Oregon coast. In order to understand the dangers of these mega-events and to help predict when they may happen, seismologists need your help. Consider hosting a Quake Catcher Network seismometer at your home, and help them record earthquakes from around the world!
http://qcn.stanford.edu/about-qcn/about-network

February 7 – The Earth Moves

Today’s Factismal: The fourth and final large earthquake in three months hit New Madrid in 1812.

Ask most people where earthquakes happen and odds are they’ll say “California”. And that is right; California happens to sit along a plate boundary. Part of California sits on the North American plate and another part sits on the Pacific plate, which is moving to the northwest at about two inches per year. This means that everything that stretches across the boundary slowly stretches until it snaps, creating an earthquake.

One year of earthquakes across the world. (Image courtesy the USGS)

One year of earthquakes across the world. (Image courtesy the USGS)

But California isn’t the only part of the world with earthquakes. They happen where the Pacific plate dives under the North American plate in Alaska. They happen where the Pacific plate goes under the Eurasian plate in Japan. They happen where the Indian plate goes under the Eurasian plate in Sumatra. And they happen where the Nazca plate goes under the South American plate in Chile. What all of these earthquakes have in common is that they happen where two plates meet.

But not all earthquakes happen at plate boundaries. About 20% of the earthquakes happen in the middle of a plate (what we call “intraplate”). Because they break the rules, those earthquakes are among the most interesting. And if you ask any seismologist what was the most interesting intraplate earthquake, odds are the answer will be “New Madrid”.

The New Madrid earthquake series started on December 16, 1811, with an earthquake that shook buildings for miles around and sent a small wave upstream on the Mississippi.That was followed six hours later by another earthquake of about the same strength. The area had a series of small aftershocks that had mostly died away by the time of the next major earthquake on January 23, 1812. That event caused widespread minor damage, mostly by jiggling the ground so hard that the soil turned to quicksand, tilting buildings and collapsing chimneys. But the worst was yet to come. On February 7, 1812, the last major earthquake hit the area. It completely destroyed the town of New Madrid and caused the Mississippi to run backward for a few hours. The earthquake was strong enough to ring the Liberty Bell in Philadelphia, over 900 miles away.

Because the seismometer hadn’t been invented yet, seismologists have to estimate the strength of the event based on eyewitness reports. They believe that the earthquakes had an energy between magnitude 7 and 8. That means that they were around sixteen times more powerful than the Loma Prieta earthquake in 1989.

The New Madrid Seismic Zone (Image courtesy USGS)

The New Madrid Seismic Zone (Image courtesy USGS)

The area remains seismically active today. Though most of the events are magnitude 3 to 4 (about 1/1,000,000th as strong as the 1812 events), there is concern that another large event could happen. As a result, the area is monitored by seismometers and has been investigated by many seismologists from around the world.

You can help seismologists learn more about earthquakes in New Madrid and elsewhere. You can find earthquakes using the Rapid Earthquake Viewer or the USGS Earthquake Monitor. And please contribute to science by telling the USGS if you felt the earth move!
http://earthquake.usgs.gov/earthquakes/dyfi/

January 14 – Did you feel it?

Today’s Factismal: There were nearly 4,000 earthquakes today.

But don’t worry. There were that many earthquakes yesterday, too. And there will be that many tomorrow as well. The fact is that every year, there are nearly one and a half million earthquakes across the globe.

One year of earthquakes across the world. (Image courtesy the USGS)

One year of earthquakes across the world. (Image courtesy the USGS)

These earthquakes happen because the Earth is very slowly cooling down. Radioactive decay in the mantle (the thick solid section between the liquid outer core and the crust) and solidification of the outer core create heat inside the Earth. That heat, plus a little “fossil heat” from the Earth’s formation, creates convection in the mantle. And the motion of the mantle drives motion of the Earth’s crust, breaking it into large rigid sections called plates. As the plates collide to form mountain ranges or scrape alongside in transform zones, they release energy as earthquakes.

The different layers of the Earth. Only the outer core is molten; everything else s solid!

The different layers of the Earth. Only the outer core is molten; everything else s solid!

And what a lot of energy they release! A magnitude 2.5 earthquake will give off enough energy to power a home for 14 hours, and there are nearly 1,300,000 earthquakes that large every year. Even better, the energy goes up much faster than the magnitude. A magnitude 4 earthquake gives off enough energy to power a home for 1.6 years. Fortunately, the number of earthquakes also decreases faster than the magnitude; there are only about 13,000 magnitude 4 earthquakes every year.

There are a lot more small earthquakes, but the big ones release a lot more energy!

There are a lot more small earthquakes, but the big ones release a lot more energy!

And that relationship between energy and magnitude is why we can’t prevent a large earthquake by triggering a lot of small ones. It takes about 33 magnitude 7 earthquakes to release the same energy as one magnitude 8. So let’s suppose that you live in a place where you get a magnitude 8 about once every hundred years. You’d need to have a magnitude 7 every three years to release the strain. Or you could do it with a magnitude 6 every month. Or a magnitude 5 every day. Or a magnitude 4 every 45 minutes. Or a magnitude 3 every minute. Obviously, this is not a good idea.

What is a good idea is keeping up with the most recent earthquakes using either the Rapid Earthquake Viewer or the USGS Earthquake Monitor. And please contribute to science by telling the USGS if you felt the earth move!
http://earthquake.usgs.gov/earthquakes/dyfi/

October 17 – Live! On TV!

Today’s factismal: The first earthquake to be shown live on television happened in 1989.

It was a balmy October evening in San Francisco. The Giants were competing with the Oakland A’s for the pennant, and the two teams were warming up in preparation for game three. As the television sports casters searched for something to add a little local color to the broadcast, they were given the greatest exclusive in history: an earthquake struck the area. And not some piddly little 4.0; this was a 6.9 Mb earthquake! As the anchors tried to describe what was happening, the world saw buildings shake, highways fall, and homes crumble into rubble.

A section of the collapsed highway (Image courtesy USGS)

A section of the collapsed highway
(Image courtesy USGS)

Amazingly, there were only 63 people killed in the earthquake (the 1905 temblor was about 30 times stronger and killed 3,000 people). Most of these happened in Oakland where a double-decker highway collapsed on itself. Interestingly, many credit the baseball game for the low fatality count. Because many people had left work early in order to watch the game, the highways were relatively uncrowded which meant that fewer people were hurt.

California is almost certain to have another large earthquake in the next three decades (Image courtesy SCEC)

California is almost certain to have another large earthquake in the next three decades
(Image courtesy SCEC)

But what is even more amazing is that the danger isn’t over. There is a 99.7% chance that California will have another earthquake at least as powerful as this one in the next thirty years. So we know when the next big on will happen (soon); what we don’t know is where. And that’s where you can help. The USGS and Stanford University are developing a new type of distributed seismometer that uses the accelerometers in tablets, smartphones, and computers to provide more complete coverage of earthquakes; the data that this Quake Catcher Network gathers will then help them to narrow down when we can expect the next big one. If you’d like to take part, head over to:
http://qcn.stanford.edu/