The supervolcanoes that we looked at last week were impressive, but Earth is capable of much more.
How to supersize a supereruption
Ordinary volcanoes form as eruptions happen over and over again. The erupted material builds up into such things as cones or mountains. This is true whether each individual eruption lasts for a few hours, days, weeks, months, or a few years. All you need is enough geologic time.
Now imagine a supereruption, one that has much more volume than anything witnessed during recorded human history. Have it go on for millions of years, with pulses of extra-high volume that last a few million years each.
About 16 million years ago, in what’s now the Pacific Northwest, this happened. Over and over again, vast quantities of basaltic lava surged out of the Earth, rolling on as steadily and relentlessly over the land as a modern train now travels the Pasco, Washington/Portland, Oregon route through the geologic wonder left after those lava layers froze into place.
That’s a lot of material. Today we call it the Columbia River basalts. The lava just kept piling up, even after burial of the vents (which were probably fissures). It’s a continental flood basalt, but some geologists have come up with a new name for such a formation – large igneous province (LIP).
At over 170,000 km3, the Columbia River flood basalts are huge compared to Yellowstone’s biggest supereruption – the 2450-km3 Huckleberry Ridge event – but they are on the small end of the LIP scale. The biggest known LIP has a volume of anywhere from 36,400,000 to 76,000,000 km3. Scientists aren’t sure because: (a) it sits at the bottom of the Pacific Ocean; and (b) they don’t know how thick it is.
Most of the Columbia River basalt erupted over 1.5 million years. That span of time is over four times longer than there have been humans on Earth, but in geologic terms, it’s the blink of an eye. That’s another feature of LIPs – a tremendous volume of molten rock is erupted very quickly, at least on the planetary time scale.
A word about terms
Technically speaking, “large igneous province” is informal, like the word “supervolcano.” As scientists learn more about these massive volcanic structures, they will eventually come up with a formal naming system that most earth scientists can agree on.
In the meantime, it’s not incorrect for laypeople like us to call them large igneous provinces (LIPs). That’s how they were originally defined (as far as I can tell) in two scientific papers:
- Large Igneous Provinces: Crustal Structure, Dimensions, and External Consequences (PDF). Millard Coffin and Olav Eldholm. 1994
- Silicic Large Igneous Provinces (PDF). Scott Bryan. 2007 (Note: There are earlier papers by Bryan; this one was most accessible to me)
The mafic LIPs described by Coffin and Eldholm were discovered before Bryan’s silicic ones…wait. What do “mafic” and “silicic” mean?
Runny LIPs and explosive LIPs
LIPs come in two basic types, based on their lava:
- “Red” lava is mafic. That’s a made-up word from chemistry abbreviations Ma (magnesium) and Fe (iron) – the two most common “red” lava ingredients.
This type is sometimes called “red” because mafic eruptions are runny flows of incandescent molten basalt. It can be very beautiful, like these spectacular but harmless lava fountains and flows on Italy’s Mount Etna that volcanologist Boris
BehnkeBehncke filmed in January 2011 (sorry for spelling error!).
Mafic LIPs like the Columbia River basalts are super-sized red-lava eruptions, with fountaining and flowing red lava, that go on for millions years. When they were active, the Columbia River basalts must have been beautiful to watch from space. On Earth…not so much.
Molten basalt contains some nasty things, like carbon dioxide, fluorine, and sulfur dioxide, that can be lethal and/or dramatically change Earth’s atmosphere and its water. Because of their size, mafic LIPs release enormous amounts of these materials into the planet’s environment. On the sea floor, their hydrothermal effects can change ocean temperature and chemical balance, while their massive bulk may interfere with the flow of deep ocean currents that keep the seas oxygenated.
For reasons like these, large igneous provinces have sometimes been associated, as we will see, with mass extinctions.
- “Gray” lava is silicic. It has a a lot more silica in it than magnesium or iron. Silica makes the lava so sticky, it squeezes out of the vent like dried-out toothpaste. If it can’t come out and instead clogs up the volcano’s “throat,” enough pressure may build up for the mountain to explode, as Mount Pinatubo did in 1991. If it does ooze out, it crumbles easily and pyroclastic flows result.
The volcano enthusiasts at PhotoVolcanica have gotten some nice close-ups of a 2014 silicic lava flow at Mount Sinabung in Indonesia, with resulting pyroclastic flows.
Silicic magma has more dissolved water in it than mafic magma does. Water lowers the melting point and also makes the silica that’s in there very sticky. Both water and silica are available near subduction zones, and that’s where you usually find gray lava.
The term “silicic large igneous provinces” is fairly new. There still seems to be a lot of debate (PDF) about it. Just to make things clear here, something like Yellowstone is a supervolcano. We’re calling something like this…
…a silicic LIP, because Bryan does in his paper. (I told you the Columbia River basalts were small.)
The Sierra Madre Occidental, by the way, was the November 2008 LIP of the month. Geologists are different from you and me
There really is treasure in the Sierra Madre. Silicic LIPs tend to bring a variety of economically valuable materials to the surface, in amounts that are large enough to be profitably mined.
They probably have a darker side, too. Such explosive eruptions would shoot solid and gaseous material all the way up into the stratosphere, where it would quickly and easily travel around the world. However, there are a lot of unknowns about silicic LIPs, and possible links between them and mass extinction are still under investigation.
Are LIPs going to erupt in our lifetime?
Geologic processes are very powerful, but they are also very, very slow. We see a volcano erupt at a moment’s notice…
…and we focus on that because we cannot see the hundreds or thousands of years’ worth of slow movements of magma and solid rock that led up to that moment.
It’s especially difficult to imagine a LIP eruption, because it doesn’t happen on the human scale, even though it is sudden in the geological scheme of things.
In fact, no one yet knows much at all about LIPs. The eruptive centers and the basement rocks, that could tell earth scientists about conditions just before the eruption and during its early phases, are deeply buried.
On land these rocks have been exposed to erosion for millions of years. This also makes it difficult for experts to study the original eruption because they don’t know just how much of the initial material that now forms, say, the Sierra Madre Occidental or the Columbia River basalts, is left.
LIPs on the ocean floor are more likely to be intact, but the problem there is access. Because of the great water depth, it’s very time consuming and expensive to study ocean LIPs.
It does seem that some LIPs are associated with plate tectonics and supercontinents like Pangea. However, such a connection isn’t clear for other LIPs (including the Columbia River basalts).
Some experts even suggest extraterrestrial impacts can cause LIPs.
The bottom line is, that until more is known about large igneous provinces, very little can be said about where and when they may happen. It’s certainly worth looking into – some of these supersized supereruptions have devastated life on Earth.
LIPs and mass extinctions
Whether large igneous provinces are caused by plate tectonics, extraterrestrial impact, or some process deep in our planet’s interior, they have been associated with mass extinction. These events have sometimes involved ocean anoxic events (OAE) as well as die-offs of various forms of land and/or marine life.
As of this writing, the connection is best recognized for mafic LIPs because of difficulties inherent in trying to measure the same environmental effects – release of sulfur, for example – in silicic LIP eruptions.
Here is a list of mafic LIPs and associated extinction events from Courtillot and Renn (PDF). It’s 11 years old and may not be up to date, but it is the only one I could find.
|Large igneous province||When it happened||Associated mass extinction|
|Viluy Traps||360 million years ago||end Frasnian?|
|Emeishan Traps||258 million years ago||end Guadalupian|
|Siberian Traps||250 million years ago||end Permian (OAE)|
|Central Atlantic Magmatic Province||200 million years ago||end Triassic (OAE?)|
|Karoo and Ferrar Traps||184 million years ago||end Pliensbachian (OAE)|
|Parana and Etendeka Traps||132 million years ago||end Valanginian?|
|Rajmahal Traps/Kerguelen Plateau||117 million years ago||end early Aptian?|
|Ontong–Java Plateau 1||117 million years ago||end Early Aptian? (OAE)|
|Ontong–Java Plateau 2||93/89 million years ago||end Cenomanian?
|Caribbean Plateau||93/89 million years ago||end Cenomanian?
|Madagascar Traps||93/89 million years ago||end Cenomanian? (OAE)|
|Deccan Traps||65 million years ago||end Cretaceous|
|North Atlantic Tertiary Volcanic Province 1||60 million years ago||end E Paleocene (OAE)|
|North Atlantic Tertiary Volcanic Province 2||55 million years ago||end Paleocene (OAE)|
|Ethiopian and Yemen Traps||30 million years ago||Oi2 event|
|Columbia River Flood Basalts||16 million years ago||end early Miocene?|
When talking about LIPs (or whatever formal name they will eventually be given), we’re on the edge of a wave of research. Scientists have only been studying these supervolcanic granddaddies for a couple of decades, and much more field evidence needs to be collected. This is why I haven’t provided links in that table for you to check out more information. Things change very quickly as more discoveries are made.
I hope this post gives you enough information to get started on your own journey of learning about these fascinating and potentially deadly volcanic events.
Geologists have found LIPs on the Moon and other planets. They were surprised to also find megacalderas like Yellowstone and other terrestrial supervolcanoes up there. Could study of the Solar System’s supervolcanoes help us prepare for the next one here on Earth? Next week we’ll take a look at it.
Update, May 28, 2015: New research has shown that some LIPs in ocean basins are associated with spreading centers like the Mid-Atlantic Ridge and “are less dangerous to life on Earth, as they trickle out in many successive eruptions, not just one giant outpouring of lava, as LIPS on continents.”
Silicic Large Igneous Provinces (PDF). Scott Bryan. 2007
Large Igneous Provinces: Crustal Structure, Dimensions, and External Consequences (PDF). Millard Coffin and Olav Eldholm. 1994
On the ages of flood basalt events (PDF). Vincent E. Courtillot, Paul R. Renn. 2003
Frontiers in Large Igneous Province Research (PDF). Richard E. Ernst, Kenneth L. Buchan, Ian H. Campbell. 2005
Categories: Sunday morning volcano