I am always amazed how much we are still discovering about massive volcanic eruptions that happened as little as a few thousand years ago. Geologically speaking, that is something that happened yesterday, yet even that small slice of time can obscure some giant volcanic events whose effects could have spread across the globe.
Two recent studies have improved our understanding of two truly enormous eruptions that happened in Central and South America. One, only 1,500 years ago, may have produced one of the tallest eruption plumes in the past 10,000 years while the other may have been one of the most voluminous blasts in that same period. In both cases, it took careful geologic field mapping and geochronology (dating) to unravel two events the likes of which we haven’t experienced in centuries.
The Earth has always been in the path of rocks from space. When the solar system was forming, the early Earth was pelted with rocks so frequently that it left the surface molten. In fact, the creation of the Moon was caused by a massive impact of a “rock”, albeit a Mars-sized rock. These days, there are many fewer impacts (thankfully) but the threat still remains that an asteroid we might not even know about yet could strike the planet. This week, as part of the 2019 Planetary Defense Conference, NASA is running a scenario where an asteroid impacts the Earth to contemplate what the results of such an impact might be today.
The Earth has many battle scars from previous impacts. These relicts of asteroids are a reminder that Earth gets hit. Many times, the craters left by an impact is erased by the Earth’s dynamic surface processes: weathering and erosion, eruptions, plate tectonics, oceans. However, some impacts are preserved due in part of their recency, size or the geologic history of the area.
Most people would think that it would be hard to hide the evidence of a massive volcanic eruption. It shouldn’t be hard to track down the source of tens of cubic kilometers of ash and debris because it should just get thicker and thicker until you reach the volcano that disgorged the mess. Yet, somehow, it isn’t that easy. We live on a geologically active planet where all the processes of weather, tectonics, volcanism and more can quickly disassemble the deposits of an eruption — even a giant one — to the point where it might be challenging to pinpoint the source.
One such example is a layer of ash found around the northern coast of the Mediterranean called the Y-3 ash. Some Y-3 ash had been dated to ~28.6 to 29.4 thousand years ago and the ash itself has a chemical composition that is a lot like one of the biggest volcanoes in the Mediterranean basin, the Campi Flegrei. Yet, although this ash can be found for thousands of miles away from the Bay of Naples (home to the Campi Flegrei), geologists had not found any matching volcanic deposits near the caldera volcano itself that could be the match to the Y-3 ash. So, what’s going on?
We know surprisingly little about seismicity (on Earth it would be earthquakes) on other planets. Although we have done a little seismology on the Moon, both “listening” for natural temblors or creating our own, beyond that, we haven’t had much luck. Sure, the 1970s Viking landers had seismometers as part of their array of instruments, but they were sitting on the deck of the landers, not placed on the ground, so almost no useful data was collected.
The newest Mars lander, InSight, is there to remedy this problem. The NASA mission landed on Mars in December 2018 with the goal of learning as much as possible about the Martian interior. Mars doesn’t have anywhere near the geologic activity of Earth. So far, we have never witnessed any volcanic activity on Mars and the most recent volcanism might have been a million years ago or more. There is no obvious flowing water on the surface of the planet save for some evidence of ephemeral springs in craters. The carbon dioxide ices at the poles do change with Martian seasons, as does the frequency and intensity of the massive dust storms — but that activity is restrained to the surface.
There is no evidence of anything like Earth’s plate tectonic system, now or possibly even in the past 3 billion years of Martian history. Evidence for that comes from the massive Martian volcano Olympus Mons, which appears to be the product of a hotspot, much like Hawai’i. However, instead of a chain of volcanoes that formed as the Pacific Plate moved over the Hawaiian hotspot, all the lava erupted from Olympus Mons appears to have piled up in one location, suggesting few moving plates like on Earth (but maybe not a complete lack of tectonics).
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.
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.
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.
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.
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.
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.