Tuesday, May 25, 2010

Posting again soon...

Got caught up in various projects, but I'll be settled down again in a few days (and hopefully back to posting). 

Tuesday, May 18, 2010

Reflecting on risk

I don't have any stories to share with you about the 1980 Mount St. Helens eruption, since I wasn't around then - and the other geobloggers are doing a fine job of collecting reminiscences already.

Volcanologists, like everyone else, sometimes joke about their jobs, but it's anniversaries like today that have prompted me to reflect on it instead. I love the work that I'm doing, and what I'm training to do. It's exciting, and takes me to exotic places, and I get to learn all sorts of fascinating things about how volcanoes work. But whenever I'm near or on an active volcano, there is always an element of danger as well. Because volcanoes are natural systems, they always have some element of unpredictability. It is possible for scientists to forecast what a volcano may or may not do, but it's impossible to predict anything with absolute certainty, so we can't be absolutely sure that any part of a volcano is safe, no longer how long it's been dormant or how mild its activity seems. Not to mention that volcanic settings in general are not safe or nice - there are any number of dangers from unstable or rough terrain, toxic gases, and just the remoteness and inaccessibility of many volcanic areas.

Those are all things I have to consider when I'm doing fieldwork at active volcanoes. In the past year, I've visited Stromboli and Etna and Santiaguito; this summer I'll be traveling to Montserrat, where Soufriere Hills is still erupting. Each time I set foot on a volcano, I acknowledge - consciously or not - that the chance to learn about it overrides the potential hazards of the setting. I don't take unnecessary risks, or make careless or foolhardy decisions if I can avoid it; I'm not going to wander into an exclusion zone or into an active crater just for the sake of samples and photos. But the recent significant eruption at Santiaguito reminded me that even the settings that seem safe at one moment can become deadly in the next, and the lateral blast that occurred at Mount St. Helens thirty years ago today is an excellent example of the same.
Dr. David Johnston was one of the 57 people who lost their lives in the 1980 eruption of Mount St. Helens. He knew the dangers of working on an active volcano, and no one could possibly fault him for being at the Coldwater II observation station when St. Helens erupted; if it hadn't been him there, it would have been someone else. The volcanologists working there at the time hadn't even considered that the volcano might produce a lateral blast, though they - including Dr. Johnston - were certainly uneasy about the setting.  In interviews, his friends, family and colleagues invariably say that Dr. Johnston died doing something that he loved.  As a volcanologist, I am doing something that I love whenever I go to study an active volcano; I can't imagine myself as happy in any other job. But it isn't a safe job. I know it's difficult for my family to think about, and I don't like to bring it up, but there is always a chance that I could be hurt - or worse - working at an active volcano. It's the same risk that many of my friends and professors take. True, all of us take risks every day - driving, flying, playing sports - but volcanology involves unique risks that most people don't have to deal with on a regular basis.

I hate to write such a depressing post about what would otherwise have been an exciting event, but it's what's been on my mind today. Volcanology is an exciting, unique science; volcanic eruptions are fascinating events. But it's always good to remember that this is one of the sciences where the researchers take risks for the sake of their work.

Monday, May 17, 2010

Geo-image Accretionary Wedge

My geo-photo of choice is a bit of interplay between the forces of geology and biology: an ohi'a shoot growing from a crack of a lava flow on the flank of Mauna Ulu, on the Big Island of Hawaii. The photo is significant to me for a number of reasons: This was my second trip to Hawaii, but the first time I'd had a chance to learn the techniques of volcano monitoring; it was also the first time that I'd really begun to understand the workings of an active volcano. This hike, part of a volcanology field course run by UH Hilo, took us up a lava channel to the summit of Mauna Ulu, through more forms of basaltic lava than I'd ever imagined existed. It was fascinating stuff. It was also a surprise to come across little enclaves of plants every so often - the first colonizers of a totally inhospitable environment. The contrast of the green leaves of the ohi'a and ferns against the dark lava flows was striking, and quite beautiful. 

This photo reminds me that even the destruction caused by volcanoes doesn't last forever. Tomorrow's anniversary - that of the May 18, 1980 eruption of Mt. St. Helens - brings to mind the amazing transformation that the blast zone has undergone in the 30 years since the event. The same persistent forces were at work on Mauna Ulu since its eruption ended in 1974, and the patches of life that I saw in a lifeless terrain were a subtle reminder of the processes of change. 

Friday, May 7, 2010

Volcano Vocab #4: Lahar

As suggested by a commenter on the last Volcano Vocab post, here's a water-and-volcano-related term for you: Lahar ("lah-haar"). 

Lahar is an Indonesian word for a mudflow of volcanic material - that is, a mass movement of volcanic debris that contains some amount of water. (A dry flow of volcanic material would usually just be called a debris flow or debris avalanche.) The key thing that distinguishes a lahar from a "regular" mudflow is the presence of volcanic material in the flow, which can include tephra, ash, hydrothermal alteration products, blocks of lava flows, and other pyroclastic materials. Some descriptions liken this mixture to a flow of cement, and it's capable of moving house-sized boulders huge distances from their source.

Lahar deposits characteristically show poor sorting (lots of different sizes of material, from boulders to sand), multiple rock types, rounded clasts, and muddy matrix supporting the clasts. (Sometimes in deposit matrices you can find rounded voids where bubbles of air were trapped as the deposit hardened around them!) Lahars are most common on stratovolcanoes, but (as we've seen in Iceland), other types of volcanoes can also create the correct conditions to form a lahar. Lahar formation depends on having lots of loose material, and the addition of lots of water over a short period of time (such as from a melting glacier, a hurricane or storm, or a breached crater lake, among other things). They do not require the volcano to be actively erupting, which is one reason why they are so dangerous.

Here's a video of a lahar from Mount Ruapehu in New Zealand (March 2007):

Lahars are an especially dangerous volcanic hazard because they appear and disappear so quickly. Lahar debris that's deposited in a riverbed can easily be eroded by normal river flow, and lahars that have spread beyond valleys and drainages can easily become reclaimed by vegetation. In fact, one of the most devastating lahars to have come from Mount Rainier in Washington State (the Osceola Mudflow)  is now covered with small towns. Because the people in the area are now aware of the danger a repeat lahar would present, they are required to hold evacuation drills. Lahars are somewhat easier to monitor and avoid; acoustic flow monitors (specially calibrated seismometers) can be placed in source zones, and a timely warning can be sent downstream when lahar signals are detected. Sometimes evacuation can be simply a matter of climbing to a higher elevation, although on a floodplain it could be necessary to travel much greater distances to safety, but it does require advance warning.

Armero, Colombia, destroyed by lahar on November 13, 1985. Photo from the USGS CVO website.

Lahar warnings aren't always heeded, however. It's impossible to mention lahars without also mentioning the town of Armero in Columbia. On November 13, 1985, a small eruption of the nearby volcano Nevado del Ruiz melted part of the snow and ice capping the volcano's summit, and produced a lahar. Volcanologists knew that river valleys on the volcano's flanks could channel lahars toward populated areas, and sent warning to towns in the lahar's path; unfortunately, local officials either received incomplete or conflicting information, and/or decided not to listen to the scientists' warnings. As a result, more than 23,000 people were killed in Armero and nearby villagees, when they could have reached safety by climbing only a short distance up the slopes on the sides of their valley. This tragedy drove a USGS scientist to develop the Acoustic Flow Monitors mentioned above, in hopes that more deaths could be avoided; the system is now used at lahar-prone volcanoes worldwide.

Tuesday, May 4, 2010

Where on (Google) Earth #201 - hosted for JimmyJames

Having not posted anything for a while, I was trying to think up something non-taxing to write about (don't want to take on too much on my birthday!) Fortunately, JimmyJames, the last winner of Wo(G)E, made it easy for me - he's ready to reveal the next edition of Where on (Google) Earth! So here it is:

"This is my first win of Where on Google Earth and I'm honoured to be amongst the folks that participate in this contest. I should admit right away that I am not a geologist (nor indeed a blogger) but I have tried to make the WoGE #201 a challenging puzzle.

This edition of WoGE#201 reveals yet another attractive example of folded sedimentary strata.

As ever, to win WoGE find the Longitude and Latitude of the image, identify the country / area and describe the geological significance of the feature, then post this information in the Comments section below. The first one to post the correct information will go on to host the next edition of WoGE.

With respect, I'm invoking the (Ron) Shott rule: "Previous winners must wait at least one hour for each win that they have before posting a solution - other comments would be okay".

Good luck to all of you! And a heartfelt thanks to 'Tuff Cookie' for hosting my post!

To compensate for the low res Google imagery, I have supplemented it with some higher resolution aerial orthophotos for your viewing pleasure."

(Click to see the enlarged versions!)