What Is the Most Dangerous Volcanic Hazard?

By Erik Klemetti | April 17, 2019 11:15 am
The 2015 eruption of Calbuco in Chile, with the city of Puerto Montt in the foreground. Wikimedia Commons.

The 2015 eruption of Calbuco in Chile, with the city of Puerto Montt in the foreground. Wikimedia Commons.

Volcanoes can be pretty dangerous. Thankfully, we’ve gotten better over the last half century at getting people out of the way of volcanic hazards. However, many hundreds of millions of people still live close enough to volcanoes to feel the impact of an eruption — especially when the volcano decides to have a spectacular eruption.

There are a lot of misconceptions out there about what the most dangerous aspects of a volcanic eruption might be. I think many people picture lava flows cascading down the sides of a volcano and imagine that the searing rivers of molten rock are what will do you in.

Well, they’re right in one respect: stay in the path of a lava flow and you will likely cease being alive. But luckily, lava flows are actually pretty easy to avoid as they move rather slowly, rarely up to ~30 km/hr (20 mph) but more likely less than 8 km/hr (5 mph). You can probably out-walk most lava flows.

So, what is it that makes volcanoes so deadly if it isn’t the copious volumes of lava they can produce? Here’s a little countdown of what I think are the most dangerous volcanic hazards based on the number of deaths associated with them, the potential for damage to houses and infrastructure, the frequency with which they occur and the difficulty of avoiding them.

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Two Russian Volcanoes Erupting in Tandem

By Erik Klemetti | March 19, 2019 9:27 am
The long ash plume from Bezymianny seen stretching across the Pacific Ocean on March 17 by Terra's MODIS imager. The smaller plume from Sheveluch can be seen just above the darker Bezymianny plume. NASA.

The long ash plume from Bezymianny seen stretching across the Pacific Ocean on March 17, 2019 by Terra’s MODIS imager. The smaller plume from Sheveluch can be seen just above the darker Bezymianny plume. NASA.

The Kamchatka Peninsula in far eastern Russia is one of the most active volcanic areas on Earth. It isn’t surprising to find multiple volcanoes erupting each week and this week is no exception. Two side-by-side volcanoes — Bezymianny and Sheveluch — were simultaneously erupting over the weekend (above). The eruption at Bezymianny was big enough to cause some air travel over the peninsula to divert flight paths to avoid the ash, but that’s business-as-usual in Kamchatka.

Kamchtka is remote and fairly sparsely populated. Only about 1600 people live within 30 kilometers of Sheveluch and only 47 within 30 kilometers of Bezymianny. The monitoring of the volcanoes in Kamchatka is done by KVERT (Kamchatka Volcanic Eruption Response Team) with help from the Alaska Volcano Observatory. The low risk for people on the ground is balanced by a higher risk for people in aircraft that traverse the airspace over and near the peninsula. Flying anywhere through the long plume of ash a volcano emits can cause serious damage to an aircraft.

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Would You Move Back Into a Town Destroyed by a Volcano?

By Erik Klemetti | March 13, 2019 10:26 am
Building buried in ash from the 2008 Chaitén eruption, with the volcano in the background. Taken July 2008, Wikimedia Commons.

Building buried in ash from the 2008 Chaitén eruption, with the volcano in the background. Taken July 2008, Wikimedia Commons.

It has been nearly 11 years since the surprise eruption of Chaitén in Chile, one of the largest explosive eruptions in the 21st century. The volcano remained active for a full 3 years and the volcanic ash and debris would be washed down the river valleys during heavy rains. In the end, parts of the town of Chaitén would need to be abandoned due to the influx of debris from the eruption. Yet, only a decade later, the areas that were abandoned during the eruption are being rebuilt — a decision that shows the tension between human memory and geologic realities.

The 2008 eruption of Chaitén started out big. The initial salvo from the volcano reached over 10-19 kilometers (35,000 to 55,000 feet) into the air and for most people (including volcanologists), it was the first they had heard of the Chilean volcano. At the time, it was thought that Chaitén hadn’t erupted in thousands of years. More recent work done since the 2008 eruption found that the volcano last erupted in ~1640 AD, which goes to show how quickly a volcano can appear to have been quiet for a lot longer than it really has. That eruption in 1640 was about as large as the 2008 eruption — a VEI 4. Looking even further back, Chaitén produced VEI 5 eruptions (so, 10 times larger) ~5,100 and 8,800 years ago. This was a volcano with a nasty history.

Before (left) and after (right) Landsat images of Chaitén. The after image shows the delta of volcanic debris in the bay and the large dome that filled the caldera during the 2008-11 eruptions. USGS.

Before (left) and after (right) Landsat images of Chaitén. The after image shows the delta of volcanic debris in the bay and the large dome that filled the caldera during the 2008-11 eruptions. USGS.

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What Might Happen if Yellowstone Were Really Heading Towards an Eruption?

By Erik Klemetti | March 6, 2019 12:17 pm
A geyser basin at Yellowstone Caldera. Image by Erik Klemetti

A geyser basin at Yellowstone Caldera. Image by Erik Klemetti

Everyone loves Yellowstone, don’t they? For a volcano that might not have erupted for 10,000 years, it gets a disproportionate amount of media attention. Much of the hype is just because the media (news and entertainment alike) has made Yellowstone seem like something that is bound to erupt in our lifetimes and destroy all civilization. Yet today, there are really no signs that the Yellowstone caldera is heading towards a new eruption anytime in the near future — and that’s geologic “near future”, so decades to centuries … or likely even longer.

So, Yellowstone isn’t heading towards an imminent new blast. However, what would we expect to see if Yellowstone were ramping up towards a new eruption? Much of it would be what we might expect from any volcano that is preparing for a new eruption.

Uplift: Magma takes up space. So do all the gases that molten rock releases as it sits underground. However, there aren’t big open caverns underground for the magma to fill, so it has to shove existing rock out of the way and the easiest direction to do that is up. So, as magma increases underneath Yellowstone (or any volcano), the land surface should rise.

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What Do We Do About the Next Massive Natural Disaster?

By Erik Klemetti | February 25, 2019 9:36 am
Damage from the 2010 earthquake in Haiti, the century's deadliest disaster so far. United Nations/Wikimedia Commons.

Damage from the 2010 earthquake in Haiti, the century’s deadliest disaster so far. United Nations/Wikimedia Commons.

Few things in life are as unpredictable as natural disasters. Many times, they strike with little-to-no warning and even if there is advanced knowledge of an impending disaster, people are rarely fully prepared to deal with the event or potential consequences.

As populations rise and metropolitan areas grow, the risk associated with a massive natural disaster rises with them and that’s something that has investors worried. Last week, Warren Buffett discussed his concerns about how the economies of the world would respond to giant disasters like an earthquake in the Pacific Northwest or a Katrina-scale hurricane in New York City. In 2017, Berkshire Hathaway saw a $3 billion loss due to natural disaster, and needless to say, Buffet’s worried that more natural disasters could cause irreparable harm to the global economy.

All this got me thinking about natural disasters, especially the deadliest among them. Now, trying to compare disasters is tricky as there’s an element of apples to oranges to it. Some disasters are singular points in time (like an earthquake) while others could last for weeks or longer (like floods). Many times, it isn’t the disaster itself that causes the most fatalities but rather the secondary effects like famine, disease and displacement. However, we can make a few general statements.

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Climate Change Could Make Mediterranean Hurricanes More Damaging

By Erik Klemetti | February 5, 2019 10:53 am
Medicane Numa, captured by Aqua's MODIS image on November 18, 2017. NASA.

Medicane Numa, captured by Aqua’s MODIS image on November 18, 2017. NASA.

Trying to model what the cascading impact of anthropogenic climate change might be around the world is challenging to say the least. This isn’t a simple relationship where global average temperature goes up and everything changes in concert. As we’ve seen in the United States with the Polar Vortex, a warmer average global climate can also mean much colder short-term weather as typical patterns are perturbed by the chain of events caused by warming. So, as the dominoes fall in a changing global climate, we need to understand what the long-term impacts of weather phenomena might be as the overall climate heats up over the 21st century.

A recent paper in Geophysical Research Letters tries to model the impact of global climate change on Mediterranean hurricanes (or Medicanes). These are like the hurricanes we get off the Atlantic in the U.S., but instead they gain their structure as cyclones within the Mediterranean Ocean. Today, there might be ~1-2 Medicanes per year, many fewer than we see in the average hurricane or typhoon season in other parts of the globe. However, if climate change causes Medicanes to become more frequent or more powerful, then suddenly they become a much larger hazard for Europe.

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Visit the Early Solar System Today

By Erik Klemetti | February 1, 2019 7:43 am
An equatorial view of Bennu by OSIRIS-REx, taken on December 12, 2018. NASA.

An equatorial view of Bennu by OSIRIS-REx, taken on December 12, 2018. NASA.

The early solar system was a strange place. Instead of all the planets with which we are so familiar, there were likely lots of small proto-planets and moons competing to get larger and larger. That’s because early on, the planets were accreting — that is, they were being built as bits of rock, dust and gas stuck together due to collisions. The larger the object got, the more pieces would be attracted to it thanks to its increasing gravitational pull.

Eventually, these objects would get big enough to attract very large objects and massive collisions could happen, melting parts of these planetesimals. They would also grow massive enough to retain heat and start to melt their interiors, potentially forming a planet like Earth, where we have layers divided up by density: heavy elements at the core, lighter elements at the crust. This process of differentiation is the hallmark of the largest objects (planets, moons and asteroids included) in our solar system.


Read more: The early solar system was a messy place


That’s why the two objects that NASA has just visited are so fascinating! They might give us a look at that early solar system, before the planets took over. The first is in the inner solar system while the second is in its outermost reaches and both capture that primordial state of accretion.

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Could Past Global Climate Have Been Changed by an Eruption … in Scotland?

By Erik Klemetti | January 25, 2019 10:37 am
Sgùrr of Eigg in Scotland, the location of some of the deposits of a massive explosive eruption in Scotland 56 million years ago. Flickr/Kevin Walsh.

Sgùrr of Eigg in Scotland, the location of some of the deposits of a massive explosive eruption in Scotland 56 million years ago. Flickr/Kevin Walsh.

We don’t tend to think of the British Isles as a land of volcanoes. However, over geologic timescales, things can be very different. ~50-60 million years ago, the North Atlantic Ocean was opening and the area around the modern North Sea was rife with volcanic activity. Much of these eruptions were lava flows, producing flood basalt provinces similar to the Columbia River Basalt — but now mainly under the waters and ice of the North Atlantic and Greenland. Yet, over in what is called the British Paleogene Igneous Province (BPIP), there may have been massive, explosive eruptions that rivaled the largest eruptions of the past 500 years.

A lot of rock can be lost over ~56 million years. The effects of erosion, especially thanks to multiple pulses of rivers and ice sheets, can erase much of the evidence of even giant geologic events. Such is the case in Scotland, where the remnants of the volcanism are scattered across the landscape. Trying to match up pieces of volcanic material that are tens of kilometers apart can be tricky: do they represent a single, big eruption or many smaller eruptions (or possibly not even an eruption at all, but rather magma cooling underground!) The best ways to match these rocks is to look for clues in the composition and textures of the minerals and rocks.

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The Geologic Nature of Our Borders

By Erik Klemetti | January 22, 2019 10:02 am
The U.S.-Mexico border near San Diego, California. Wikimedia Commons.

The U.S.-Mexico border near San Diego, California. Wikimedia Commons.

The world’s current political climate is one where we are very aware of borders. They divide what we humans decide is one country, one state, one region from another. They can be very clearly defined where everyone would notice the boundary and in other cases, they are merely defined by imaginary lines we’ve projected on our planet. Much of the time, these boundaries are geologic — that is, they use features created by geologic processes to demarcate one nation from another. However, when you look at the geology of the planet, it doesn’t care about nations and these geologic barriers are never forever over geologic timescales.

What got me thinking about geologic boundaries was looking at an area with low stakes: the state line between Arkansas and Mississippi. It is the mighty Mississippi River that is supposedly the boundary between these two states. However, that boundary was set over 150 years ago and rivers meander. That means that the channel of the Mississippi river has moved as the processes of deposition and erosion carve out a new path. This leaves the boundary and the river following different paths:

The Arkansas (left)-Mississippi (right) state line, with the Mississippi River in the middle.

The Arkansas (left)-Mississippi (right) state line, with the Mississippi River in the middle.

The muddy Mississippi no longer follows the same path that defined the state line. You can see where the river was in the landscape, but the twists and turns that existed when the line was marked have now been cut off by the river, so land in Arkansas that was once on the west of the river is now on the east. This will keep on happening and as long as the states don’t mind that there border is not neat and tidy, then the river and the boundary can continue to diverge.

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Volcanic Avalanches Are Pretty Common … and That Might Be a Problem

By Erik Klemetti | January 8, 2019 12:38 pm
The Surtseyan steam-and-ash plume from Anak Krakatau in Indonesia, seen on January 4, 2019 after the collapse. Planet, used by permission.

The Surtseyan steam-and-ash plume from Anak Krakatau in Indonesia, seen on January 4, 2019 after the collapse. Planet, used by permission.

It has been a few weeks since the massive collapse of the Anak Krakatau cone that slid into the sea, generating the deadly tsunami that swept along both sides of the Sunda Strait in Indonesia. We’ve finally been able to see what occurred during that landslide and sure enough, most of the cone that was Anak Krakatau is gone (see below). In its place is, well, not much but open space that has seen seawater fill in. This volatile mix of water and erupting magma has meant that Anak Krakatau has been churning out tall steam-and-ash plumes that, at times, towered >10 kilometers (>30,000 feet) over the volcano. Luckily, the collapse of the cone will temporarily reduce the threat of another tsunami but as the cone builds back up over the years-to-decades, that threat will return because volcanic collapses and landslides are actually fairly common in the geologic record.

Before (left) and after (right) images of Anak Krakatau in Indonesia. Planet, used by permission.

Before (left) and after (right) images of Anak Krakatau in Indonesia. Planet, used by permission.

Here are a few examples of other massive landslides and collapses. Some are the trigger for an eruption, like what occurred at Mount St. Helens in 1980. As magma filled in the volcano prior to May 1980, the slopes were over-steepened and became unstable. When an earthquake struck on the morning of May 20, that over-steepened slope slid away, releasing the pressure on the magma. Much like popping the cork on a bottle of champagne, that magma quickly formed bubbles to make the explosion that happened seconds after the landslide.

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CATEGORIZED UNDER: Rocky Planet, Science, Science Blogs
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Rocky Planet

Rocky Planet covers all the geologic events that made and will continue to shape our planet. From volcanoes to earthquakes to gold to oceans to other solar systems, I discuss what is intriguing and illuminating about the rocks beneath our feet and above our heads. Ever wonder what volcanoes are erupting? How tsunamis form and where? What rocks can tell us about ancient environments? How the Earth might change in the future? You'll find these answers and more on Rocky Planet.
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