Taken by J.D. Briggs at Kilauea Volcano
Hawaiian eruptions are one of the most spectacular natural events that the Earth produces. But how do they occur? Again it is all down to gas and what it is doing beneath the surface and in the conduit. Firstly these eruptions get their name from the Hawaiian island chain where they are most commonly seen, however, the recent Eyjafjallajokull eruption and activity at Mount Etna are also good examples.
The basic definition is that these eruptions are continuous and related to a constant 'jet' of gas and magma clots from the vent. This definition is important as it is possible to get very rapid pulsing which should and is usually termed as strombolian. The exact mechanism for Hawaiian eruptions is debated. It is important to think about where gas exsolves from the magma (where it transitions from being dissolved in the magma to a separate gas bubble in the magma). CO2 exsolves at the greatest depth several kilometres below a summit, SO2 is next to exsolve and H2O (the most abundant)
within several hundred metres of the surface vent. All this is dependent on amounts of gas present as well. There are two main theories:1) Hawaiian eruptions occur when magma rise speed at depth is greater than bubble rise speed, this allows the growth of bubbles in the magma. As the magma rises (and the pressure exerted on it decreases) the gas will take up a higher percentage of space (fragmentation) and will also speed up. This will cause the jets of magma which are seen at the surface.2) This theory depends on a magma foam (magma and gas mixture) accumulating in a magma chamber or shallow storage zone
at an area where gas can exsolve (as discussed earlier). This foam region then collapses and feeds into the conduit to rise to the surface where the combined gas/melt mixture is enough to produce fountaining at the surface.Some Hawaiian eruptions are so voluminous in nature that the ejection of magma clots can land and form lava flows of their own as the majority of magma mass erupted doesn't have time to cool. These lava flows are termed 'rootless'.
I won't go into landforms any further here, thats a whole separate post involving scoria cones, spatter ramparts. etc Please don't look at the wikipedia page on Hawaiian eruptions it is very disorganised and is not helpful! If you have access to scientific papers, the paper by Parfitt, 2004 called: "A discussion of the mechanisms of explosive baslatic eruptions" is definitely one of the best I have read.On a side note the
eruption of Tolbachik is in the midst of a spectacular eruption, involving a mixture of strombolian and hawaiian activity which is producing some lengthy lava flows. There are some excellent photos here taken by Gorshkov Sergey
and a discussion on eruptions blog here on the features presented by lava flows
From the GVP website, the Tongariro complex is at the front.
is a volcanic complex, which is shown in the picture to the right in the foreground, with Ruapehu behind. On the 20th November it had its second significant explosion
of 2012 from the Te Maari crater (video below).
Historically Tongariro (from current centre of activity Ngauruhoe) and the nearby Ruapehu are the most active in New Zealand. Tongariro last erupted in 1977 in a very small eruption classified as VEI 1 and generally throughout history it has experienced little strong activity above VEI 3, an exception being a VEI 5 event a few thousand years ago. It is highly likely therefore that the current period of inactivity will follow the same trend.
After finding the below video from the recent Eruptions blog post
, I thought it would be a nice idea to discuss briefly what is potentially occurring in the conduit for the duration of this video. It is not often that you have videos as good as this (click the read more button on the right!).
Taken by Oleg Volynets, eruption in 1975.
After the eruption of Plosky Tolbachik for the first time in 36 years, I thought it might be useful to have a quick background look at the volcano. When looking at the previous eruption history eruptions were spaced more closely together prior to 1975 and were generally smaller in nature than the VEI 4 category of the 1975 eruption (pictured to the right). It certainly has a rich amount of activity stretching back several thousand years.As ever eruptions blog has provided information
and will likely give regular updates on the eruption. I highly recommend taking a look at the Russian website for Kamchatkan activity (KVERT) where there is a nice overview of various volcanoes not just Plosky Tolbachik (here I link to Plosky Tolbachik
). By looking at the following link on the same website
, you can see images of the summit area taken at different times over the past few years. The most recent was taken during August 2012 and I note the visible absence of steam from the volcano. Suggesting (tentatively) that at this stage there may have been no evidence of a reawakening at the summit.
Furthermore, when looking at the seismic activity this seemed only to increase a few days prior to the eruption, as detailed on Volcano Discovery
. All this illustrates that there can be a minimum amount of activity detected prior to the eruption of a volcano! Personally I find the volcanoes of Kamchatka fascinating and it will be thoroughly interesting to see how this eruption develops over the coming months and potentially longer.
In the evening I occasionally like to watch a documentary (and have talked about their importance
) or two and yesterday evening was no different. I am used to the cheesy nature of National Geographic and Eden type programmes but have never physically burst out laughing as much as I did during this one! The culprit - Amazing Planet: Born of Fire on Eden in the UK at the moment.
It is evidently an American made documentary with a female speaker and if you watch it you will understand when I say that I have never heard someone make volcanoes sound so much like moody teenagers and the sexual connotations were everywhere!
The script writers certainly need to look at what they have written...here are some examples:
- "Why is it some volcanoes go BOOM
instead of BLOOP
?" - I don't know....she never really got round to telling me and have you ever heard a volcano go BLOOP?!
- "Pyroclastic flows are hotter than your oven." - Brilliant thanks for that incite!
- "The mantle is like glowing taffy" - First of all what is taffy and what the hell does it look like when its glowing!
- "Plates perform their catastrophic mating dance" - Talking about subduction - WOW - also used the terms - plunging, ramming and thrusting a lot when talking about ridges - not really sure there is much of that going on at volcanoes love!
- "The Earth is like something Dr Frankenstein put together"- Really, are you sure? I think its quite beautiful myself...
- How did the Himalayas form? Like this apparently - "Then 50 million years ago, BOOM
" - BRILLIANT!
- "For a glimpse of what could be giving the globe major indigestion-go to Hawaii" - Why? Is the Earth ill? Should I be concerned at all? Should I call a Doctor?
- "The Earth, spits and vomits and generally has a bad case of indigestion" - Poor Kilauea its going through a tough time it would seem...
- "Earth soup performing its acrobatics" - more an Hawaiian eruptions.
And finally: "Montserrat is totally repressed" - have no idea where she was going with this one...should I be offering counselling to the lava dome? Is it going through a difficult time?
Anyhow, if you get chance to watch it, I highly recommend it, very amusing!
There has been a lot banded round in the press recently about the L'Aquila trial and the manslaughter charges of 6 years which have been passed on to the scientists involved:
Gian Michele Calvi
Bernado De Bernardinis
I am not going to go into the in's and out's of the trials, good summaries can be had on the BBC website
and from other sources. I am not a lawyer or judge, but a scientist, therefore my knowledge of the law and how it works is very sketchy.
I want to say a couple of things about the possible global implications of this decision. Lets take a hypothetical example from the UK, perhaps the Environmental Agency 'falsely reassures' a neighbourhood about the risk of a flood and the flood actually ends up occurring or a tv meteorologist plays down the effects of a blizzard. From the events in Italy, someone could now say, well, they were prosecuted and imprisoned in Italy, why not here?
Will this mean in the future, any event such as this will be met with a more severe warning? What if nothing happens? What if there are several warnings and nothing happens? People will start to get complacent and the job of scientists will get more difficult.
Science is based upon the interpretation of data or information that they believe to be correct and on theories that are currently believed to be the best available. Scientists on the whole, will act to the best of their ability to try and prevent any harm coming to a population. Lets take another example: Mt. Vesuvius, a dormant volcano with the large population of Naples nearby. Volcanologists think that it may erupt so they issue advice to the authorities to evacuate. The evacuation turns out to be unnecessary, can the authorities prosecute volcanologists for damages or even imprison due to inaccurate information?
As you can see, this trial throws up several scientific dilemmas, which need to be addressed or we will see more controversial decisions such as this. Could this lead to less talented scientists in important decision making roles, or a reluctance to make a decision in fear of imprisonment?
To finish if any appeal is thrown out (or even if they are freed) the results of this trial will surely be felt globally throughout the scientific community and threatens the progress of science, particularly with respects to hazard prediction.
I would like to finish with this message; free the seven, liberen a los siete, rilasciare il sette.
If you feel strongly that the seven should not be charged with manslaughter please sign this petition
I am now a few weeks into my PhD and am enoying it tremendously, it's certainly great enjoying what you do! As my PhD is based around gases and their importance in volcanic systems worldwide, I thought I would produce a series of posts on why they are important in specific volcanic eruption types and touch upon what they can tell us outside of eruptions.
Firstly, a brief discussion on Strombolian eruptions.
The classic example of the Strombolian eruption is from the Island of Stromboli, Italy and I am sure if you search google images you will find many wonderful images of the result of a Strombolian eruption, however, what causes these eruptions?
The cause of a Strombolian eruption is generally accepted to be the result of the movement of a large gas bubble (or slug as it is sometimes called) up a volcanic conduit and subsequently bursting at the surface, hence throwing the hot material out in a spectacular fashion. There is some debate about the origin of these bubbles, whether they are the result of the coalescence of bubbles (the merging of bubbles) as they rise up the conduit from depth or whether they are the result of a collection of gases which create a foam (high proportion of gas to magma) at a point at depth beneath where the surface where this could occur.
At depth, however these bubbles are formed, the size is constrained by the pressure they are under. As the bubble rises, faster than the magma which it is in, it begins to grow in size and accelerate as a result, allowing a high enough velocity to eject material at the surface.Evidently a gas bubble of insufficient size will not result in a Strombolian eruption but can still burst at the surface and contribute to a phenomenon known as passive degassing (which I will refer to in a later pos)t.
Strombolian eruptions can occur on timescales of seconds to minutes to hours or more and are generally associated with less viscous (more runny) basaltic magamas at high temperatures of around or more than 1100 degrees celsius. I hope you have enjoyed my very brief overview of Strombolian eruptions, any questions please post and I will try to answer!
Me, in the cold, summit of Etna in the background.
Apologies for the tardy/lack of posting recently, I promise to get back to regular posting from now on! I have now left my old job and have taken up a PhD position at the University of Sheffield, which will free up a little time during the day for me to post. The basic target of my future research is Sulphur Dioxide released by open conduit basaltic volcanoes.
I have already had the chance to do some fieldwork at the summit of Mt Etna, some of the photos/videos are available via the above links. Until my next post enjoy the photos of me and the subject of my most recent field trip the plume visible in the background of each photo.
The plume from the North East crater of Mt Etna from the Observatory.
Strombolian Activity on 27/07/12
On a recent trip to Etna, I was lucky enough to capture some Strombolian activity on the 27th July 2012 in action in Bocca Nuova at the summit of Mt. Etna (as per picture on the right). On a previous trip to the summit two days prior to this the magma column was low and was producing minor ash explosions (all pictures available here
). On this particular day the magma column had risen high enough to produce regular strombolian explosions which occured from seconds to minutes apart. There was also evidence of a small outpouring of lava from the vent, although this was only visible using a heat camera.
There are also a couple of videos of these events in the videos section
. Apologies for the poor quality, down to a mixture of shaky camera work and strong wind!
After writing about my fortuitous find at the Langdale Pikes
, it brought back memories of several trips to the Haystacks. Of which many were performed in the howling wind and rain, not uncommon for the Lake District. On one very memorable day I was helping a friend with his dissertation fieldwork and the wind was so strong that at one point he actually had to catch me to stop me blowing away! Suffice to say we didnt spend too much more time on the hill.
Anyhow, the Haystacks (pictured below) are another part of the Borrowdale volcanics and make for a very interesting walk (on a good day you can see Scafell Pike and Great Gable for example). In the area are a number of volcanic features including pyroclastic tuff deposits at an area called little round how (if I remember correctly) and the site of a pepperitic contact (something I shall discuss in a later post). One of the most intriguing deposits is littered across the summit of the haystacks itself and can be described as a series of andesitic folds which are thought to have been part of a doming formation. Although detailed research has yet to be completed, to my knowledge anyway. These folds are pictured in the image above where the banding of the folds can be clearly seen.
From wikipedia. The Haystacks are the prominent rock outcrop in the background.
On a nice sunny weekend in England (which doesn't happen a lot!) its always good to get out and about and living so close to the Lake District is always a bonus! There was also an added treat at the top, for the geeky volcanologist in me, where we stumbled across a large amount of obvious volcanic deposits! Now this isn't my particular area of expertise and the deposits were very weathered and quite old, but they looked like a volcanic tuff/pyroclastics with some large clasts (large rocks essentially) entrained inside the ashy deposit. The picture to the right shows one of these clasts very clearly.
The Lake District is geologically very old and these deposits are no different having formed around 470 million years ago in fact, something I found out after bumping into a handy information spot by an excellent pub at the bottom.
A view of one of the many outcrops.
Delving a bit further in to the root cause of these eruptions, it was mostly likely related to volcanism with the closing of the Iapetus ocean, which involved the eventual collision of England and Wales with the Scotland we see today. There are other volcanological spots in the Lake District and the UK and not all of these are as old as the Langdale formations, with the majority of them in stunning locations, especially some which are located in Scotland (Isle of Skye/Mull but to name a few!) and of course not forgetting the lovely Lake District itself. Alfred Wainwright, the man who will never be forgotten for his indispensible guide books and love of the Lakes, stated that one of his favourite spots was the volcanic area of Haystacks and as a result had his ashes scattered near the summit on Innominate tarn.
If you would like to find the Langdale deposits for yourselves, the deposits are most obvious near Harrison Stickle and Pavey Ark (in the Langdale Pikes area) in grid location NY275075 using an OS map (I hope i remembered my map reading skills) and are part of the Borrowdale Volcanics.