Monday, December 19, 2016

Spectacular volcano videos: Identifying eruption processes

- Janine

It's the end of the year, it's cold (there is ice covering everything outside as I write this), and it's time to give your brain a bit of a break. That makes it a great time to watch videos of volcanoes. We are lucky that so many people post amazing videos of volcanic eruptions online for all of us to enjoy (see below warning), and we can learn a lot from them too. When I am looking at my satellite images of dome collapse block and ash flow and column collapse pyroclastic flow deposits on Shiveluch and Mount St. Helens volcanoes I have videos of these processes running through my mind. This is a short guide to what you are seeing in these incredible videos.

WARNING: There are very dangerous and life threatening hazards associated with retrieving this footage, and here at In the Company of Volcanoes we strongly discourage anyone from trying to take your own.

---


This video shows the dome at Unzen volcano undergoing a partial collapse in 1991. This shows how a near-solid body of rock rapidly fragments down to smaller pieces of rock and ash, creating a billowing ash plume rising from the block and ash flow (a type of pyroclastic density current that originates from a dome collapse event). This eruption episode was a deadly one, killing 43 people, including 3 volcanologists - Maurice and Katia Krafft, and Harry Glicken, when a collapse larger than the previous activity caused a pyroclastic surge to sweep over where the group was standing. Having watched this video many times, I am still impressed by how rapidly this solid rock reduces to tiny pieces. I believe this footage of the dome collapse is not the one that caused the fatal pyroclastic surge, as the dome was covered in cloud during that eruption.

---


This video, posted by Earth Uncut TV, shows another dome collapse, this one at Sinabung Volcano in Indonesia on 21 January, 2014. This eruption has been ongoing since August 2010 and numerous phases of dome growth/lava effusion and consequent collapse have formed a pyroclastic fan at the base of the volcano. You can see trees that have been killed by pyroclastic flows for scale. This high-quality footage shows the front of the flow racing down the volcano, and the expanding ash cloud above, entraining and heating air to expand and rise upward. You can see older deposits that formed lobes on the pyroclatsic fan ahead of the flow. Watch closely and you can even see a large 'dust devil' formed due to the hot ground.

The video below (by Photovolcanica) shows the Sinabung lava lobe collapsing, in slow motion, to produce a block and ash flow.



---



Speaking of domes - a dome is a solid plug of rock that is extruded at the surface - there was an excellent chance to study how these work at Mount St. Helens volcano in 2004-2008. USGS took this time-lapse footage of a particular dome type - a spine, that you can see moving nearly vertically and crumbling as it goes. The highest recorded temperatures seen in cracks of a spine were over 700 degrees C, and growing at rates up to 25 meters per day. Read more about the Mount St. Helens spine growth and see thermal images here.
---


Mount St. Helens put on a much bigger show on May 18, 1980. This video is made using the photographs taken by Gary Rosenquist, showing the first moments of the eruption. A cryptodome had been growing under the northern flank of the volcano, making the whole side of the volcano unstable. Immediately after a M5.1 earthquake the northern face failed and began to slide northwards as a debris avalanche, which depressurized the cryptodome, sending a lateral blast out from the volcano which you can see overtaking the debris avalanche.
---



Block and ash flows are usually formed when hot dome rock collapses, so why not look at them using a thermal infrared camera. This above video was taken by the Montserrat Volcano Observatory of the Soufriere Hills volcano on Montserrat. You can see the hotter colors (yellow-white) of the base of the block and ash flow racing down the Ganges Fan, where the denser part of the flow is made of hot rock, and the cooler - but still hot, (pink-orange) expanding ash cloud forming overhead.

---


On to a different style of eruption, and one from my home country - New Zealand. In 1995 and 1996 Ruapehu volcano erupted. Ruapehu volcano has a crater lake at the top, and when the magma hits this water we get a phreatomagmatic (magma + water) surtseyan eruption, where jets of water and ash shoot out of the crater and fall back down to the ground. In this video by Geoff Mackley you can see the white steam plume in the background, and the dark ash-rich jets rapidly rising, and pretty quickly falling back down because they are so dense.

---



Another great video of a phreatomagmatic eruption is from Kuchinoerabujima volcano in Japan, taken by the Japan Meteorological Agency webcam that monitors the volcano. A 9 km ash plume rose from the Shindake crater with material quickly falling back to the ground and producing pyroclastic flows that you can see moving down the slopes.

---


A very significant and deadly hazard at volcanoes are lahars -flows of water, rock, and debris that race down a volcano because of heavy rains, melting ice, or crater lakes. This particular video was taken by volcanologist Sandy Budi Wibowo on 28 February, 2014, and was shown at the recent Cities on Volcanoes 9 conference in Chile. He shows the different stages of a lahar on Merapi volcano in Indonesia. you can see the flow front going through, and the large boulders that are carried by the lahar.

---


A closer view of just how much rock can be carried by a debris flow can be seen in this footage taken in 2003 at Semeru volcano in Indonesia. These flows are highly erosive and can carve out channels and destroy anything that get in their path. They can be triggered by even tiny volcanic events (like the Armero tragedy), or by non-volcanic related rainfall or the collapse of a crater lake wall. Video by Franck Lavigne at the University La Sorbonne. These can travel great distances away from the volcanoes and are a big hazard around volcanoes that house glaciers, like Rainier in the USA.

---


Over to the name that (pretty much) no one outside Iceland can pronounce - Eyjafjallajökull in 2010, posted by Fredrik Holm. This is an incredible video of an ash plume right at the crater. My favorite part of this is the ballistics - the large chunks of rock that you can see being thrown out of the volcano in an arc projectile then hitting the ground nearby. This is something you definitely want to view from a distance.

---


In this footage shot by a very lucky drone (spot the near-misses) you can see molten bombs and gas being ejected from Yasur volcano on Tanna Island, Vanuatu. This strombolian activity occurs when slugs of gas rise through a conduit, bursting at the surface and sending the walls of the molten lava bubble flying through the air. With the drone's very close calls you can see the molten bombs twisting and deforming as they fly through the air.

---



For a much bigger eruption, and one that gave little warning, we go to Chile to see Calbuco volcano erupting on 22-23 April 2015. This beautiful high-resolution footage by Timestorm Films shows the 15 km high ash plume of the first of two large eruptions. This is a sub-Plinian eruption with a vertical ash column and a laterally spreading umbrella cloud at the top as the ash reaches neutral buoyancy with the surrounding atmosphere. More on the Calbuco eruption can be found in an earlier blog post here.

---


This footage of an eruption at Sakurajima volcano in Japan shows the great show of volcanic lightning caused by ash or ice particles interacting within an ash plume, setting of these impressive electrical discharges. New research is being done looking at how tracking lightning strikes can help volcanologists understand large volcanic eruptions from space, so watch this area of research.

---


Another great phenomena that isn't caught on camera as much are shock waves. This above video (by Linda McNamara) is of an eruption on Tavurvur volcano in Papua New Guinea. Just as the eruption starts you can spot a bright arc expanding away from the vent - this is the shock wave. You can see it going downwards across the cone kicking up ash, through the sky, and then hit the people on the boat. Shock waves occur when so much energy is released during an explosion that the wave initially travels faster than the speed of sound.

---


What goes up has to come down, and volcanic ash fall is something that people who live around active volcanoes have to live with. Volcanic ash is not like the soft ash you find after burning wood, it is pulverized rock, glass, and minerals that are very erosive and bad for human health. The above footage is of the Ontake volcano eruption of September 27, 2014. The end of the video shows how quickly ash can block out the sun. You can learn more about volcanic ash, the hazards, health effects, what to do if you are caught in it, and see what it looks like under a microscope here.

---


This footage shows clean up efforts after the Calbuco eruption. You can see how shoveling ash is like shoveling sand, or for those of you not around a beach (like me right now), heavy snow. This can easily collapse roofs, especially if water is added by rainfall, and is a large hazard around volcanoes that produce large ash columns. You can read more about the fate of volcanic ash here.

---



One of the strangest lavas on Earth occurs at Ol Doinyo Lengai volcano in Tanzania. As you can see in the video above (shot by Jeffrey Brown), the lava runs kind of like water, and sort of sounds like it too! This is carbonatite lava - a cooler (500-600 degrees C) carbonate-rich lava that erupts as a black liquid, then cools to a white rock.

---



A more run-of-the-mill (but still awesome!) lava is found on Hawaii - usually what people think of when I say I am a volcanologist (no I haven't been to Hawaii, yet). These lavas are much hotter and erupt at temperatures over 1000 degrees C. The CenterStudyVolcanoes posted this great high-speed footage of a lava flow in Hawaii, showing how the flow moves as breakout lobes, inflating as time passes. You can see the surface folding and breaking apart, giving the beautiful morphologies and textures you can see on many basaltic pahoehoe lavas.

---



Not all lavas behave the same. A more viscous version is a'a lava, like this footage taken at Kilauea volcano on 1 June, 2010 by volcanochaser. Since there is a high glass content due to the rapid cooling (quenching) of the lava you can hear the loud 'clinkery' noise coming from chunks of lava breaking and cascading down the flow front. Lavas produce these a'a textures when the flow becomes more viscous due to lava composition, slope changes, cooling, or the increase in the number of crystals forming in the lava. You can also get 'blocky' lavas, where large chunks of lava ride along the flow surface.

---



If you can't get enough of lava then a hot, churning lava lake is for you. This footage, shot by Geoff Mackley and his team shows the intense Marum volcano lava lake on Ambrym Island, Vanuatu. The hot, very fluid lava is gas-rich, causing the convection or bubbling at the surface of the lava body. Lava lakes are actually pretty rare so this is a chance to see how a large body of hot lava behaves. Note: I would never, ever encourage anyone to attempt to get this kind of footage.

---



Another type of eruption where you can see hot masses of low-viscosity lava is during a fissure eruption, and for this we can go back to Iceland. In August of 2014 the Holuhraun eruption began north of the Bárðarbunga caldera and erupted enough lava over six months to cover an area of 84.5 km2. You can actually see how much of your home town/city would be covered by this amount of lava here. In this drone footage you can see how the eruption has built up it's own walls that hold the lava lake. You can also see the large amount of gas with high amounts of sulfur dioxide that became a hazard for people living downwind of the volcano. Video credit goes to DJI/Eric Cheng.

---


Sometimes underwater eruptions go completely unnoticed, and sometimes the only clues are huge pumice rafts that cover thousands of kilometers and travel with ocean currents for months.This video posted by Stuff.co.nz was taken by a pilot, and shows the pumice raft that originated north of New Zealand round the Tonga-Kermadec trench. If this wasn't seen by a pilot, we might not even know it happened.
---

Aside from being incredible videos to watch, there is so much we can learn from watching footage of volcanic activity. We can calculate eruption rates, timing and sequence of events, volumes, temperatures (with thermal infrared), velocities, and where hazardous rocks tend to fly during an eruption. All of this helps us to understand volcanic processes and hazards, so we can eventually get people out of the way and protect lives.

This, and it provides inspiration at the end of a long day of Ph.D. dissertation writing.




Note: Where credit isn't given to the source, the original source was not listed. Please give full credit to any videos and images you post online.

Tuesday, December 13, 2016

Interpreting historic eruptions with old dusty hidden treasures: Introduction to historical and social volcanology

Guest Blogger Jazmin Scarlett

Follow her on Twitter: @scarlett_jazmin
Jazmin shares more of her adventures on her own blog: Phdvolcanology.wordpress.com


My name is Jazmin Scarlett, I am a PhD student in volcanology and I am not trained in geology, geophysics or geochemistry.

I am trained in understanding hazardous processes and how humans interact with them. I am, therefore, a weird mix of physical and social scientist. I understand the processes behind volcanic activity, but I mainly understand the many characteristics of volcanic hazardous phenomena. I understand how they impact on the natural and built environment and in turn, I understand how humans respond, mitigate and prepare against them. However, the interactions between hazard and person is more often than not more complicated than just hazard + human = impact.

As well as understanding the volcano and its hazards, what is around the volcano is just as important. Infrastructure, settlements, topography, climate and so on. Humans are far more complex, so responses, mitigation and preparedness goes beyond what is visible (e.g. running away, building a wall, evacuation drills), it involves understanding what makes us tick when it comes to confronting hazards and risk. This has led me to learning about theories and concepts with sociology, psychology and anthropology.


The village of Byera, located in the high risk volcanic hazard zone.


My approach to ‘social’ volcanology has been a mixture of volcanology, socio-psychology and disaster management. This all started with my masters dissertation into volcanic risk perceptions on the island of St Vincent in the East Caribbean. In order for people to do questionnaires and a semi-structured interview, I first had to learn about the volcano in question, La Soufrière and, its volcanic hazardous phenomena. After that, I had to understand the society, its common problems and other hazardous events (hurricanes, agricultural pests, crime and so on), culture and the country’s take on disaster management and relation to its volcano. After that, it was the matter of being a non-biased and open researcher to get the most representative results as possible.


A street leading to the village of Bellevue in the medium risk volcanic hazard zone.


I learnt so much from the project: about myself, about the island my family is from, about the volcano and importantly, about social volcanology. The sub-discipline itself is quite young, so at the time I felt I got an equal amount of questions and answers! I learnt that the ‘social’ aspect of volcanology involves the need for the researcher to really strip back and understand the society and its connection to its volcano(es) and to be patient with participants. I spoke only to the lay-public, so despite keeping everything as jargon free as possible, there were still things I had to take the time to explain. I was going into the project using human geography techniques…but came out learning about socio-psychology and a bit of anthropology!


The beginning of the Windward volcano trail.

I took all the questions and answers from that project into my current PhD which is still looking at St Vincent. The initial innocent question was: “how did people respond in the past?” and it has now got me using historical geography understanding. My current project is investigating three historical eruptions of La Soufrière impacts on the society, alongside how the society developed with the volcano. This has involved all aspects of social volcanology (perceptions, development, awareness and so on) within the historical context. I have to understand factors such as the economy, colonial relations with the British Empire, the societal hierarchy, the slave plantation system, emancipation and the significance of gaining independence. It is split up into three parts: reconstruction of the eruptions using archive sources (across six different archives in three different countries), impacts on the agriculture sector (sugar, cotton, arrowroot, banana and others) as well as certain parameters of the society (responses, recovery, disaster relief, resilience) that may have influenced the ‘co-volcanic society’ today. ‘Co-volcanic society’ is a new term being created between myself and my supervisors about the reciprocal relationships between volcano and society.



A pile of archive documents related to the 1902 eruption of La Soufrière. These documents belong to The National Document and Archive Service of St Vincent and the Grenadines.

A Barbadian newspaper article with a strong religious reaction to ash fall from the 1902 eruption. Barbados always experiences ashfall from St Vincent due to the dominant Easterly winds.

Part of my historical hazard mapping experience. These are datapoints with descriptive observations of pyroclastic density currents for the 1812 eruption, often referred to as “lava” during this time. They are mapped onto a 1796 map.


On the main Leeward road in the southeast of St Vincent.

School children learning about volcanoes during volcano awareness week 2016 on St Vincent.

Governmental correspondence for Barbados during 1902. Book is within The National Archives in London, UK.

One of my interviewees in the town of Chateaubelair. He shared his experiences of the last eruption in 1979. He moved his family to a safer location south of the island then returned to volunteer helping sick people evacuate.

Being a historical and social volcanologist requires me understanding the volcano and the exposed population within the historical context. It is a unique approach to volcanology and one I am proud to follow. There are many ways to understanding volcanoes, mine is just one of them.

Photograph taken by volcanologist Dr Tempest Anderson at the Orange Hill Estate house after a pyroclastic density current on the 7th May 1902. Photographs held at the Yorkshire Museum, UK.

Diary entries from American barrister Hugh Keane, who observed the 1812 eruption. Diary held at the Virginia Historical Society, Richmond, VA


La Soufrière crater in April 2016.



Monday, December 5, 2016

The trees of Calbuco

-Alison
Most of my research can be described as looking at rocks to figure out what happened in the past.  There are many deposits from volcanic eruptions that don't just contain rocks. As volcanic soils are very fertile, many volcanoes are forested which means that falling ash or debris flows interact with trees and other plants. The way trees are damaged by the eruption can tell us a lot about what happened. The trees in the blast zone of Mount St. Helens are a dramatic example.
Trees blown down by the 1980 later blast at Mt St Helens (image from 2015).
I was recently lucky enough to visit Calbuco Volcano in the lake region of Chile. You may remember the impressive pictures of Calbuco erupting at sunset on April 22, 2015.  This heavily forested stratovolcano produced a large plume (which dropped tephra, coarse scoria on the slopes of the volcano and ash all over eastern Chile and Argentina), pyroclastic flows, and lahars (debris flows) from melting glaciers and later rain. Janine did a post right after the eruption that contains lots of amazing videos and photographs of the impacts of the ash on people who live near the volcano.

The deposits from this eruption provide ample chances to see how falling and flowing rock interacted with trees. The different types of damaged to the trees helps us figure out more about what happened on the volcano and in what order. The falling scoria buried trees and fences on the slopes of the volcano. This knocked branches and leaves off of many trees and killed many pine trees, but many trees continued to grow! We know the scoria fell mostly straight down, or there would have been more damage to these threes.
These trees were twice as tall before being covered by 60 cm (or roughly 2 feet) of tephra (scoria, cooled gassy magma). The tree is still growing a year and half later.

Pyroclastic density currents are both fast and hot. These currents form when the column of hot rock and gas collapses and instead of gently raining rocks down like the tephra, they form currents of debris that travel down the volcanic slopes. They snap trees in half and burn healthy wood to charcoal as they pass. To scorch wood the flows are typically expected to be 300 C (572 F) or more. For older volcanic deposits this charcoal is very useful to date the eruption, as well as confirm it was hot.
Burnt wood carried by a pyroclastic flow is now part of the deposit. This log is 60 cm or almost 2 feet long.This tree was knocked over and broken by the flow, so we know the flow was hot and fairly dense.

This tree was burnt and broken, but still standing after the 2015 Calbuco eruption.This means the tree was damaged by hot pyroclastic density currents, but they may not have been dense enough or carrying large enough clasts to knock the tree completely over.

This tree was buried by hot pyroclastic debris, but it didn't fall over until after the base had been completely burnt. This helps us reconstruct the timing of the eruption and how powerful the flows were.
These trees were killed by the pyroclastic flow that burnt the lower part of the trunks and singed the tops, but were later exposed when rainfall eroded the debris without knocking them over.

We also saw trees that had been damaged by passing lahars (debris flows). These are slurries of debris and water formed when the hot pyroclastic flows melted glaciers and mixed with water. These flows may be hot near the source, but cool down as they travel and incorporate more water. Lahars also formed after the eruption ended with heavy rains mixed with all the loose debris of the pyroclastic flows. These mixtures can look like fast moving cement and carry a mixture of sand up to big boulders. These flows knock things down, erode deep channels, and abrade things in their path.

The upstream part of this tree had its bark removed up 2 m above the top of the deposit (more than 6 ft). This also helps us know what direction the main flow was headed.
This large boulder became lodged against this tree trunk at the side of the river valley. You can also see how high the bark was scraped off the tree.
Looking closely at these trees you can spot smaller pebbles embedded in the wood.

This log is part of a root that had grown into previous rocky deposits and been ripped up by a lahar in 2015. The ruler is 20 cm long, or about 8 inches. Logs like this really show how powerful the lahars are to rip up trees with such large roots!

The abrasion of a passing flow can sand a tree down from a circular trunk to one like this. The bark and shape are preserved on the underside of this log, while the top half is almost gone!

The logs then become part of the deposit and stick out of the ground at all sorts of weird angles.

The water from the lahars and later rain storms move the loosest rocks and trees leaving propped logs balancing in their wake.

These trees are a good example as to why geology can be compared to forensics. We can look at lots of different types of evidence after an event to reconstruct what happened and when. Documenting fresh deposits like these also help us do a better job of reconstructing older events so we have a better idea of what volcanoes can and have done in the past, so that we know how to better prepare for future eruptions.