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.
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.
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.
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 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.
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.
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.
It’s that time, once again, to give out the Pliny. Since 2009, my readers have voted on what they think was the most significant volcanic event of the year. Sometimes the vote is very close and sometimes, well, you can guess what the outcome will be before the envelope is opened. Let’s start off with some honorable mentions that garnered votes from some of you:
Sierra Negra: Back in June of 2018, Sierra Negra in the Galápagos erupted for the first time since 2005. Lava flows poured down the flanks of the volcano, prompting some evacuations but this eruption was overshadowed by events that will come later in the countdown.
Kadovar: At the very start of the year, Kadovar in Papua New Guinea, produced the first major eruption of 2018. This was a big surprise as no known historical eruption had occurred at Kadovar. Residents had to be evacuated from the island and the volcano went on to have explosions for much of the rest of the year.
2018 was quite a year across the geosciences … which is hardly shocking considering we live on the most geologically active planet in the solar system. Some of the events were tragic, because when it comes to headlines, that is what gets the most attention. Others were warnings of things that could be headed our way and others were, thankfully, downright exciting and uplifting. Here’s my quick takes on some of the big geoscience events from the year that was:
Lower East Rift Zone Eruption at Kīlauea
I suppose for a volcanologist like me, it would be hard to top the largest eruption in the United States since 1980. Not only that, the surprising eruption of Kīlauea from its Lower East Rift Zone (top) — the first in half a century — dumped over 1 cubic kilometer of lava out and collapsed the summit of the Hawaiian volcano. Thankfully the eruption was free of fatalities and only had a few minor injuries. Unfortunately, many people in the lower East Rift Zone communities of Lelani Estates and Vacationland Hawaii lost the homes and livelihoods.
Indonesia was struck but multiple tsunamis in 2018, neither of which were caused by the same mechanisms that generated the 2004 Boxing Day tsunami. In September, a tsunami swept through parts of Sulawesi. This tsunami was likely caused by a submarine landslide triggered by an earthquake. The combined impact was over 2,200 deaths and tens of thousands of people made homeless, especially in the city of Palu.
Just this month, a collapse of part of Anak Krakatau during an eruption triggered a tsunami in the Sunda Strait. Almost half of the volcano that grew inside the caldera formed by the massive 1883 eruption of Krakatau fell into the sea and the resulting tsunami has killed over 225 people so far. Since the collapse, the volcano has been producing explosive volcanic eruptions caused by magma interacting with seawater — something called Surtseyan-style eruptions.
A new vent opened today on Etna in Sicily with lava flows and an ash plume from the new vent near the Southeast Crater. The eruption started after over 100 earthquakes up to M4 rattled the volcano on December 24. People (mostly skiers) on the volcano were evacuated as the eruption began. The ash plume from the eruption prompted the airspace around Catania to close as well. From the look of the ash plume, some is being produced by the eruption but part of the plume may be coming from the interaction of lava and snow on the slopes of the volcano.
? Joseph Nasi pic.twitter.com/cMmCN3mlkX
— EtnaLive (@EtnaLive) December 24, 2018
— eSPAINews (@eSPAINews) December 24, 2018
Today’s pass by NASA’s Aqua satellite got a shot of the ash plume from the eruption drifting to the southeast:
For the second time this year, an unexpected tsunami hit the coast of Indonesia resulting in hundreds of deaths. This tsunami may have been generated by an eruption of Anak Krakatau in the Sunda Strait, with Indonesian officials speculating that an eruption that occurred late last night may have triggered undersea landslides. So far, at least 220 people are known to have died , over 800 were injured and multitudes are missing. Many of the deaths were in Pandelang, located at the end of bays that could have amplified the height of the waves. The tsunami waves were as high as 3 meters. You can see some of the destruction from these waves in the video and images below. UPDATE: The death toll is now over 400 and local authorities are asking people to stay off the beaches until midweek.
Jumlah korban dan kerusakan akibat tsunami di Selat Sunda per 23/12/2018 pukul 16.00 WIB tercatat 222 orang meninggal dunia, 843 orang luka-luka & 28 orang hilang. Kerusakan fisik: 556 unit rumah rusak, 9 unit hotel rusak berat, 60 warung kuliner rusak, 350 kapal-perahu rusak. pic.twitter.com/7esz00fnD7
— Sutopo Purwo Nugroho (@Sutopo_PN) December 23, 2018
At least 222 dead people died and another 800 injured on Sumatra and Java islands after a tsunami struck them on Saturday night. It was caused by an undersea landslide resulting from eruption of Anak Krakatau | via https://t.co/rl0mcvAtL8 (Reuter photo) pic.twitter.com/MkNR1VVJbJ
— Palawan Daily News (@palawandaily) December 23, 2018
Whatever happened at Anak Krakatau to cause the tsunami, it appears that the volcano has experienced a major eruption as well. The Darwin VAAC report for the volcano indicate ash reaching as high as 17 kilometers (55,000 feet). The Himawari-8 weather satellite caught the plume from the eruption — you can see it in the false color loop:
— Luca Caricchi (@LucaCaricchi) December 23, 2018
UPDATE: Here’s another GIF showing last night’s eruptive plume from Anak Krakatau:
— Dan Lindsey (@DanLindsey77) December 23, 2018
There are unconfirmed reports that the tsunami was generated by more than half of the existing Anak Krakatau cone collapsing into the sea. No significant earthquakes were recorded in the area last night, so the eruption of Anak Krakatau may be the likeliest source of the tsunami. There are some video that claim to be from after the eruption showing that does look like a dissected cone for the volcano:
Mt. Krakatoa Eruption, one hour ago. Credit to Capt. Mykola from Susi Air#PrayForBanten#prayforanyer#PrayForLampung#PrayForSelatSunda#prayforindonesia#Krakatau#TsunamiSelatSunda#TsunamiAnyer#tsunamibanten#TsunamiLampungpic.twitter.com/xI2TU1ysBv
— Safiro (@hudasafiro) December 23, 2018
UPDATE: Here’s another video from today of Anak Krakatau showing the strong “rooster tail” plumes being produced by magma interacting with seawater. It really does look like the island has changed significantly:
— ??MT???? (@Maulana_Tigor) December 23, 2018
UPDATE: These images from Sentinel-1 show evidence of a collapse of Anak Krakatau along with potential waves generated by the collapse:
GIF comparison between 12/19 – 12/22 pic.twitter.com/nPOdKcZeh3
— R. Natsuaki (@flyingwktk) December 23, 2018
UPDATE: Apparently the current eruption of Anak Krakatau has produced more volcanic lightning than possibly any eruption observed. Over 30,000 strikes since the eruption 2 days ago:
— Chris Vagasky (@COweatherman) December 24, 2018
Sector collapse is one of the major ways that volcanic eruptions can produce tsunamis. An eruption of Unzen in 1792 caused part of the volcano to collapse into the sea, killing over 15,000. Krakatau, the volcano that preceded Anak Krakatau, famously produced a massive eruption and tsunami in 1883. Unlike this event, the 1883 tsunami that killed 36,000 was produced by a caldera collapse, where the entire volcano collapsed into itself forming a bowl that was filled by the sea (below). Anak Krakatau has been built over the past 125 years within that 1883 caldera.
Growth of Anak #Krakatau #volcano since May 2018 from @planetlabs imagery. Fairly rapid recent expansion to the south could possibly have caused some flank instability. Still awaiting post-#tsunami imagery to assess any changes. @Sutopo_PN @vulkanologi_mbg @id_magma pic.twitter.com/ETLqo68Awf
— Simon Carn (@simoncarn) December 23, 2018
As Simon Carn speculates, part of the volcano has grown rapidly over this year and Anak Krakatau has had an active fall, with frequent strombolian eruptions and lava flows – see the images above taken in September. One scenario [SPECULATION] is that a collapse of part of the volcano would allow seawater to interact with the erupting magma, causing the explosive eruption seen last night [SPECULATION] UPDATE: Simon Carn sees characteristics in the eruption that suggest a lot of magma and seawater interaction. Whatever the case, it may be a while before the full reason how the tsunami was generated.
You can watch some of the eruptions going on at Anak Krakatau only a few hours before the tsunami hit, taken by Øystein L. Andersen.
Just completed a hi-speed video of yesterdays (22th December) eruptive activity at #Krakatau volcano. A new lava-flow can be seen descending to left of the island. Filmed 47km away from it, only a few hours prior to the #tsunami hitting the coast of Java. @id_magma@infoBMKGpic.twitter.com/VQaFU7pVvQ
— Øystein L. Andersen (@OysteinLAnderse) December 23, 2018
Øystein and his family escaped the tsunami (just barely) and he’s been updating with images of the aftermath of the tsunami.
I’ll add more information about this tragedy when possible.
It’s that time of year to vote for the 2018 Pliny for Volcanic Event of the Year. We’ve had a lot of volcanic action worldwide this year and you can see some of the highlights in this compilation from the Atlantic or by checking out this year’s Weekly Volcanic Activity Reports from the Global Volcanism Program.
So, as usual, I look to you all to cast a ballot the Pliny. Send me (rockyplanetblog at gmail), tweet me (@eruptionsblog #2018Pliny) or leave a comment with your top 3 volcanic events for the year and I will compile the votes. Look for a post around the end of the year for a countdown of the most exciting and dangerous eruptions from the year that was.
Just to remind everyone, last year’s winner was Agung in Indonesia.
Other winners include
2009: Sarychev Peak, Russia
2010: Eyjafjallajökull, Iceland
2011: Puyehue-Cordón Caulle, Chile/Argentina
2012: Tolbachik, Russia
2013: Etna, Italy
2014: Holuhraun-Barðarbunga, Iceland
2015: Colima, Mexico
2016: Bogoslof, Alaska
Get voting! Ballots are due December 29!
The 2018 eruption at Kīlauea was the largest in the United States since 1980. Between 0.8 and one cubic kilometers of lava poured out onto the surface of the Big Island of Hawai’i over the course of a few months, leading to massive destruction of property and infrastructure, but happily no loss of life. Much of that can be pinned on the excellent work done by the US Geological Survey and the Emergency Management teams in Hawai’i.
Although it has only been a few months since the eruption ceased, a team of USGS and other geologists have released a new paper in Science that discusses the events surround the remarkable eruption. The paper presents a clear description of all the events that happened from March to September, but the real meat of the paper deals with beginning to understand why the eruption happened and what the future might hold.