volcanology basics

Continuing my series where I try to define words of volcanic interest, the new Eruptions Word of the Day is a favorite of mine, mostly because my undergraduate thesis on Vinalhaven Island in Maine ended up dealing with a lot of these types of deposits ... so, without further ado, the word is peperite! Now, what exactly is a "peperite"? Well, a picture is worth 1,000 words, right (so that will save me some time): Peperite in the Vinalhaven Diabase, Vinalhaven Island, Maine. Image by Erik Klemetti. Click on the image to see a larger version. Let's make some observations: The rock is full of…

Lava flows from Kilauea in Hawai`i move towards a home in Kalapana. Whenever I think about the hazards posed by most lava flows, I tend to think about the opening scene in the Hitchhiker's Guide to the Galaxy. Developers are planning to knock our hero Arthur Dent's house down and as a last ditch effort to stop its destruction, Arthur lies down in front of the bulldozer. The demolition supervisor, a certain Mr. Prosser, at one point asks Arthur if he knows how much damage the bulldozer might suffer if he just lets it roll over poor Mr. Dent. Arthur says he doesn't know and Mr. Prosser replies…

The northern Chilean and southern Peruvian Andes are full of volcanoes that look stunning - I mean, jaw-dropping details of volcanism litter the landscape. The reason for this is two fold: (1) there is an awful lot of volcanism in the northern Chilean/southern Peruvian Andes (as known as the Central Volcanic Zone) - and has been that way for over 10 million years and (2) it has also been very, very dry in the area (most of which is known as the Altiplano-Puna Plateau) for at least a few millions years as well - it is the home of the Atacama Desert! So, this means you get lots of volcanic…

Tourists hiking next to an active lava flow on Pacaya in Guatemala in 2006. I'm flying back to Ohio today after a successful few weeks of fieldwork/paper writing. Apparently I have a pile of tomatoes waiting in our garden in Granville ... ! On to news: To go with the news that lava flows from Kilauea creep ever closer to structures in Kalapana, the NASA Earth Observatory posts its first volcano image in a bit. The shot shows the steam-and-gas plume from the Halema`uma`u Crater in Kilauea's summit caldera. You can also see some video of the lava flows near Kalapana as they move along the…

Kilauea lavas on the move near Kalapana. Image taken July 17, courtesy of the Hawaiian Volcano Observatory. Some news over the last few days: The lava flows from Kilauea are moving with a vengeance right now, damaging roads and heading for some structures. The lava flows near Kalapana have moved almost 200 meters since Sunday, closing within 100 yards of homes in the area. The lava is moving to the east along Highway 130 and 137 - and tourists are making it difficult to get around as they park to watch the lava - upwards of 2,000 people! A number of people (and dogs) have had to be…

The latest Eruptions Word of the Day is "Tuya". So, what is a tuya? This is a tuya: A tuya! Click on the image to see a larger version. Image by Erik Klemetti. Alright, well, that doesn't entirely help, does it? Lets look at the feature the arrow indicates. Some observations: (1) It is low and broad. (2) It has a relatively flat top. (3) It is steep-sided. (4) If you look real close, you can see crudely columnar jointing in the some of the outcrops near the top. (5) If you had a piece of it in your hand, you'd know it was a volcano rock (andesite, very rarely you can find bits that are quite…

So, I've had requests on the blog to help to do some defining of volcanologic terms on the blog, so I thought I'd try a new column called Eruptions Word of the Day. I'm not sure how often it will run, but let's give it a try. Eruptions Word of the Day for July 5, 2010: Dacite Dacite is a magma type defined by silica (SiO2) content between 63-68 (or 69) weight percent. That is the textbook definition, but some other typical characteristics of dacite lavas (or magmas) is the presence of certain minerals: plagioclase feldspar and hydrous minerals (containing water in their mineral structure)…

Hope no one minds my shameless plug here, but I get a lot of questions about books to read if you're interested in learning about volcanoes. There are an awful lot of good books out there and we can add one more to that list: Volcanoes: Global Perspectives" by Jack Lockwood and Rick Hazlett. I've been able to go through the book and it covers almost everything a volcanophile would want to know about volcanism on Earth and in the solar system - including some information I didn't know (which isn't a big surprise). It is written as a textbook for advanced undergraduates, but as along as you…

The ash plume from Eyjafjallajökull, piercing the cloud deck above the volcano. Image courtesy of the Icelandic Met Office, taken on May 13, 2010. See the latest report on the eruption. With all the rapid fire news on eruptions as of late, combined with my busy schedule during the school year, I haven't been able to post as many articles on some basic aspects of volcanology. I will try to remedy some of this over the summer and the first will look at volcanic ash and specifically the ash from Eyjafjallajökull. I've taken some photomicrographs of the ash from Eyjafjallajökull (sent to me…

The eruption at Eyjafjallajökull-Fimmvörduháls continues on - the explosive spatter and bomb eruptions at the new central vent (on the second fissure) were impressive all night, making the hikers/cars/aircraft look like mites in comparison. This eruption has, so far, followed the pattern of Hawaiian-style volcanism quite well, so I thought it could be a good time to talk about what exactly Hawaiian-style volcanism is. There is a sequence of events that leads up to and follows the start of an Hawaiian-style eruption - although this sequence can stop at any point along the way - but it is…

As a volcanologist, I am partial to impressive lava flows, especially in volcanoes that erupt material that you'd think wouldn't produce big flows. For example, there are quite a few volcanoes in the Chilean Andes that erupt dacite lavas, which are relatively viscous (sticky), so you might expect it to erupt explosively. However, you can get large dacitic to rhyolitic lava flows, quite commonly, and these large flows are called coulées (a "volcanic dome flow"). Lllullaillaco volcano on the Chile/Argentina border. Note the very prominent coulée with flow levees. Click on the image to see a…

The fissure vent eruption near Eyjafjallajokull in Iceland. Image by Ãorsteinn Gunnarsson, March 22, 2010. It has been hard to keep up with the flood of news from the Eyjafjallajokull eruption in Iceland. Eruptions readers have done a good job with getting new images, videos and info up as they happen, so you might want to peruse the comments for those sorts of tidbits (along with discussion of what might be happening). Here is the latest: The eruption at Fimmvörduháls (considering the eruption is actually occurring between the ice caps) could last weeks to months, which isn't too…

Did I mention its a busy week? The lava lake at Erta'Ale in 2008. Image courtesy of Stromboli Online. Our Icelandic saga continues, with more earthquakes and more speculation/information on the parts of Eruptions readers. Keep up the discussion - I'll be fascinated to see who turns out to get closest to what actually happens, prediction-wise. The seismicity has quieted somewhat again in the last 12 hours, so we wait eagerly to see what comes next. Remember, Iceland is the land where volcanoes helped change history, so it is always fun to talk Icelandic volcanism. The NASA Earth Observatory…

We've been discussing calderas recently on Eruptions (I wonder why) and the Laacher See in Germany came up. I've actually been to the Laacher See on a field trip lead by one of the world's experts on the caldera, Dr. Gerhard Worner. So, I thought I'd post some pictures and talk a little about this feature that up until maybe 5 years ago, I didn't even know existed. Laacher See, Germany The Laacher See is a caldera in the Rhine Valley of Germany (see below). It is only ~30 km south of Bonn and ~60 km south of Koln (Cologne), just to the west of the Rhine River. It is part of the East Eiffel…

With all the talk of the current Yellowstone earthquake swarm, I thought it would worth it to write a post on the the structure and caldera - and why we get earthquake swarms that are structurally rather than magmatically-related. First off, lets think about why calderas formed. This is relatively simple - at least superficially. The land (or volcano) above a magmatic system is partially supported by that magma, especially because magma is hot and buoyant. The isostatic support by the magma holds up the land surface or volcanic edifice, so when an eruption expels a large volume of magma, this…

Old Faithful geyser at Yellowstone National Park. A few thoughts about faulting, earthquakes and eruptions: The earthquakes at Yellowstone have been universally attributed to fault movement rather than magmatic activity by the USGS and the researchers at the University of Utah. This is likely based on the moment solutions for the earthquakes (i.e., the sense of motion on the earthquake - side to side, dilation, etc.) and the fact that there are no directly correlative volcanic/magmatic symptoms to go with them (such as pronounced, short-term bulging, excessive hydrothermal venting, etc.) Now…

A pile of news for the new week! The glow of new lava flows from Nyamuragira in the Congo, taken from the Virunga Park Headquarters, January 2, 2010. Mayon PHIVOLCS may lower the alert status at Mayon to Level 2 after almost a week of lower seismicity and no ash explosions since December 29th. Schools that were being used as evacuation centers were also returned to teachers and students for the start of classes after the Christmas holiday. However, the Albay provincial government is now considering a plan to permanently move everyone who lives within the 6-km danger zone around Mayon, even…

It's the last week of classes and it's also AGU (which I will be missing for the first time in 5 years). If you happen to be at the big meeting in SF and hear something you think we'd like to hear, feel free to drop me a line or leave a comment so we can live vicariously through you. Pyroclastic flows at Sourfriere Hills, December 2009. Image courtesy of MVO. Some news: UPDATE 12:40PM 12/14/2009: Just to update the Mayon news from earlier today, PHIVOLC is reporting that lava has been spotting flowing from the main crater on Mayon. Sounds like the eruption we've been waiting for is…

I've gotten a number of questions about volcano books as of late, so I thought I'd write a little post detailing my favorite volcano-related tomes, mostly pitched towards people without a geology-background, but some technical books for those of you who want the gory details (and be sure, they can be very, very gory). Pumice from the Newberry Flow of the Devil's Hills scattered on the soil near South Sister, Oregon. Image by Erik Klemetti, September 2008. Anyway, here we go! General volcanology: - Teach Yourself Volcanoes, Earthquakes and Tsunamis by David Rothery (Teach Yourself Series,…

Chaiten in Chile erupting in January 2009. Even after over a year of activity, Eruptions readers are still captivated by the volcano. Thanks for sending me your questions about volcanoes and volcanism. I'll try to tackle some hear - but as always, keep the questions coming! Send them to For those of you who have submitted a question but don't see the answer here, do not fret. Likely it just means that I needed to do a little more research into the question and will get to it in a later mailbag! So, without further ado ... Mark M.: Here in the Appalachians we have very dense crystalline rock…