mpollock July 17th, 2010
Guest Blogger: Becky Alcorn
Yesterday we spent the day in Undirhlithar mapping the quarry wall that will be the focus of my IS. We climbed the majority of the wall with the exception of a few unstable places and collected a hearty 25 samples (some from places that I’m still not quite sure how we managed to reach). We finished up in Undirhlithar today and traveled farther south to another quarry, Vatnskarth. Here we could see were the lava met the glacial deposit, which was awesome! We collected samples for Meagen and then came back home so I could get to the nitty gritty of labeling my pictures. I spent many hours today sorting through my pictures and labeling where I collected each sample, which is much more tedious and time consuming than it sounds. Tomorrow we’re heading east for two days to camp and see Eyjafjallajokull! We’ll be sure to post when we return, so if you don’t hear from us in a few days we were probably swallowed up by the volcano.
mpollock July 15th, 2010
Guest blogger: Becky Alcorn
Today was our first day of field work in Undirlithar quarry. Although a lot of the quarry has been filled in in the last year, we had a very successful day and found three dikes that can be used in my IS. We began mapping the south wall that will be the focus of my IS and collected several samples for future analysis when we return to Wooster. We’re even returning to the quarry later tonight to continue our work since the sun never sets and we never sleep.
mpollock July 14th, 2010
Guest Blogger: Becky Alcorn
Today we took the Golden Circle tour in Iceland. I think I saw more amazing geologic sites on this one tour than I’ve ever seen before. Our tour began at Thingvellir in the rift valley where we hiked along the Mid-Atlantic Ridge and spent a good deal of time trying to calculate the spreading rate. We then drove to Geysir where I saw my first geyser! (and enjoyed the wonderful smell of sulfur). I also got to enjoy my first taste of hamburger sauce at the visitor center there. Our tour ended with a stop at Gullfoss, an incredible waterfall with only a small rope in some places to prevent you from falling in (take your kids at your own risk, I guess).
mpollock July 13th, 2010
Guest Blogger: Becky Alcorn
Meagen og ég kynntist í Boston í gær og hafði tiltölulega viðburðasnauður flug til Íslands. Við komum á hostelið okkar í kringum miðnætti og komst hversu frábær hún var sannarlega. Ekki aðeins var flugvellinum skutla strætó þeirra brotinn niður, en svo var internetið, lykill á herbergi, og hitari í herbergið okkar. Til allrar hamingju þeir gáfu okkur í næsta herbergi sem var ekki heitt. Því miður en ekki var fortjaldið í herbergið okkar og það er aldrei raunverulega gets myrkur. Óþarfur að segja, að leita okkur að öðrum húsnæði í dag. Eftir að við að finna nýjan stað til að vera, tók við ferð upp til Reykjavíkur til að kanna borgina, sem var falleg … og fengum dýrindis Taílenska matur!
(As you can see, in the short time that I’ve been here, I’ve become fluent in Icelandic. See below for the English version.)
Meagen and I met in Boston yesterday afternoon and had a relatively uneventful flight to Iceland. We arrived at our hostel around midnight and discovered how fantastic it truly was. Not only was their airport shuttle bus broken down, but so was the internet, key to our room, and the heater in our room. Luckily they gave us the next room that wasn’t sweltering hot. Unfortunately though there was no curtain in our room and it never really gets dark. Needless to say, we searched for other accommodations today. After we found a new place to stay, we took a trip up to Reykjavik to explore the city, which was beautiful…and we got delicious Thai food!
mpollock February 22nd, 2010
I received a letter today from Leo, a middle school student in Berkeley, California. He and his classmates are studying plate tectonics, and Leo is doing a research project on Iceland. He writes:
You said on the College of Wooster website that the Icelandic flexure zones are dipping to a magmatic chamber. Is that chamber what fuels Iceland’s volcanoes? Do these flexure zones make fissures? And it seems that these huge folds have to disturb the rocks, so why are there so few earthquakes in Iceland? You also say that we can use this to learn how oceanic crust is formed? Don’t we already know how? Isn’t the sea-floor spreading how the crust is formed? Or are you trying to figure out how the ORIGINAL crust formed? Because figuring out the ORIGINAL crust sounds like it would be really fun. Last question: Can you monitor the flexure zone’s movement? And if you can, can you use that data to predict volcanic eruptions, if the flexure zones and volcanoes are somehow related?
I’ll do my best to answer all of your questions, Leo, but first, let’s chat for a bit about the geology of Iceland. Iceland is unique because it is a hotspot (an area of very high volcanic activity) that straddles the Mid-Atlantic Ridge (a divergent plate boundary).
The rift wasn’t always in this location, though. The picture below shows the rift today (1n and 1v), the future rift (4), and the rifts that used to be located in the western part of the island (2 and 3).
Flexure zones, which develop as a result of seafloor spreading, are one of the reasons that scientists know the position of the ancient rifts. As you already know, Leo, the plates diverge at mid-ocean ridges, and the underlying mantle ascends, melts, and transforms into magma. The magma either cools slowly (creating a rock called gabbro, which makes up the thickest and deepest part of the ocean crust) or rises up to the surface (through conduits called dikes) and erupts on the seafloor as mid-ocean ridge basalt (MORB).
As you can imagine, a lot of MORB lava is erupted right at the mid-ocean ridge axis. So, early lava flows tend to be buried by later lava flows. As the lavas are buried, they tilt toward the ridge axis, creating a flexure zone. The picture below shows a side-view of a flexure zone. The mid-ocean ridge axis is in the middle of the pink lavas, which have buried the gray lavas, which have buried the green lavas, which have buried the blue lavas.
So yes, flexure zones dip toward the magma chamber, and yes, magma chambers fuel volcanoes. However, the flexure zone that I’ve worked on is part of the Snaefellsnes-Skagi Rift Zone (#2), which went extinct about 7 million years ago, so its magma chamber is long gone.
Now, let’s move on to your other questions:
Do these flexure zones make fissures?
Not exactly. Fissures typically develop above magma that is moving around in subsurface dikes. Sometimes, the magma reaches the surface and creates a fissure eruption, like the one pictured below.
Can you monitor the flexure zone’s movement? And if you can, can you use that data to predict volcanic eruptions, if the flexure zones and volcanoes are somehow related?
Good question. Geologists definitely monitor ground movements around volcanoes in an effort to understand when they might erupt, although most of the instruments measure changes to the surface of the volcano. You can find more information about volcano monitoring at the USGS website.
And it seems that these huge folds have to disturb the rocks, so why are there so few earthquakes in Iceland?
You might be surprised by the number of earthquakes in Iceland. You can get up-to-the-minute information about Icelandic earthquakes at the website for the Icelandic Meteorological Office. The map below shows all of the earthquakes that occurred in Iceland over the 48 hours before this blog post. You can see that most of the earthquakes are located in the active rift zone or in the South Iceland Seismic Zone.
You also say that we can use this to learn how oceanic crust is formed? Don’t we already know how? Isn’t the sea-floor spreading how the crust is formed?
Yes, the ocean crust is formed through seafloor spreading, but we don’t know all the details about seafloor spreading yet. For example, there are a lot of questions about how the flexure zones form. How quickly are lavas buried? How deeply are lavas buried? How much of the flexure zone forms near the axis? How much forms far away from the axis? Are the lavas slipping on one another (like a deck of cards)? We have ideas about these questions, but we really need to do more research to understand the details.
I hope I answered your questions, Leo. Thanks for the email! Good luck on your research project!
mpollock July 19th, 2009
After a relatively uneventful journey and a short stay in Wooster, we’ve made it to Dickinson College in Carlisle, Pennsylvania. We’re spending the week analyzing our samples on Dickinson’s X-Ray Fluorescence Spectrometer (XRF) and X-Ray Diffractometer (XRD). First, we need to turn our rocks into powder. We typically begin by cutting down the sample on a rock saw.
Then we grind the smaller pieces to get rid of any contamination introduced by the saw.
The samples get cleaned in a sonicator.
And the clean samples get set out to dry.
Finally, the samples can be crushed. We can crush them in a shatterbox or by hand using an agate mortar and pestle.
Voila! We have powder!
mpollock July 14th, 2009
Now that we’re finished with field work, we’re back on the road. First, we stopped at Godafoss, one of Iceland’s beautiful waterfalls (also an excellent location for columnar joints!).
Next, we headed to Krafla, an active volcanic region in northern Iceland. Krafla includes Namafjall, a geothermal field with hot springs, mudpots, and fumaroles. It also encompasses Viti, a famous volcanic crater. The information center was open when we arrived, so we stopped to watch a short movie about Krafla’s eruptive history and how the Icelanders use Krafla’s geothermal energy to generate electricity. We even had a chance to look into the powerplant while it was operating.
Today, we’re back in Reykjavik. We had an opportunity to visit the Culture House, a museum that houses some the medieval sagas. The intricate details preserved in many of the ancient manuscripts were impressive.
After the Culture House, we bumped into some familiar faces…the Hales Fund Iceland Group! Blog worlds collided.
We chatted about rhyolites and glaciers, then headed to Reykjavik’s ultimate bakery. According to Rob, “It was good. Period.”
mpollock July 12th, 2009
Done! Today was our last day in the field. Rob finished hunting for zeolites on Vatnsdalsfjall.
To get to the last field area, we had to cross “the deadly fields of sadness,” hummocky and swampy fields that are treacherous to walk across. One of us (guess who?) wished for a “luck dragon to fly us to the top of the mountain.” Then we had to cross a river. Adam kindly offered piggy-back rides to everyone. Rob took him up on it. Meanwhile, Todd and Meagen took a different approach.
Yesterday, Adam finished his field work, but the day started with a small adventure. On our way to Adam’s last field site, the car somehow found a ditch! Fortunately, a nice elderly Icelandic farmer knows charades, and Meagen was able to ask him for help. He came to the rescue with his dog and his tractor! After that, we hit the rhyolite jackpot and Adam completed all of his I.S. sampling.
Like the Estonia Crew, we’re almost ready to head home, but not before we see Krafla and meet with the Hales Fund Iceland Group.
mpollock July 9th, 2009
Over the past few days, Todd has been helping Yexary map a gabbro body in Skagastrond. They were highly productive and finished mapping today! Meanwhile, Adam, Rob, and Meagen are still on the wild rhyolite chase. Yesterday, we found rhyolite in a stream cut near Skagastrond, just where the map said it would be.
Today, we climbed Langadalsfjall in search for rhyolite that was mapped near the very top. On the way up, we found lots of dikes intruding the sheet flows. The exposures were so great that we couldn’t help but sample.
We finally made it to the spot where the rhyolite should be only to find piles of rhyolite talus, grassy meadows, and white tuff. Despite our disappointment, we sampled the talus and enjoyed the awesome view.
Unfortunately, we have a casualty to report. Rob thinks that Langadalsfjall is only big enough for one, so he tried to kill Adam in a rock avalanche and throw Meagen off a cliff. Thankfully, Adam and Meagen survived to see another day, but Meagen’s boots didn’t.