Bedrock

Posted on February 18, 2012 by Erin Parker
Erin Parker

Bedrock (noun): 1) Solid rock underlying loose deposits such as soil or alluvium

2) The fundamental principles on which something is based

It is the third week of the semester, and one of my unruliest classes of high school students is struggling with geologic time. It’s immense and intense and I dared ask them to do some calculations along with the vocabulary. They’ve already worked their way through a version of Carl Sagan’s Cosmic Calendar activity, where they’ve crunched all of time from the Big Bang to the present day into one year.

Today, I’ve handed out props with rough dates attached, and asked the class to physically arrange themselves in order of appearance in the fossil record- a stuffed black plague microbe stands in for the first life-forms; a plastic Buzz Lightyear represents modern humans. After I separate the monkey (representing first mammals) from the dinosaur (representing dinosaurs, but intent upon the destruction of everything in his path; note to self, next semester, hand the dinosaur to a quiet, calm student), the kids arrange themselves in a straight line, equally spaced from one end of the chalkboard to the other. Here is where it gets tough, when I ask the remaining kids to “fix” the line.

“Amphibians came before reptiles!” shouts one student, and the classmate holding the tree frog’s terrarium obligingly switches places in line. A few more shuffles, and the sequence of fossil emergence is in rough time order. The kids are still in an equally spaced line, however, and I’m still waiting for someone to realize that the formation of the Earth and the accumulation of oxygen in the atmosphere shouldn’t be able to hold hands.

Welcome to the world of high school earth science- I teach 10th -12th grade students, and it’s a diverse bunch. Strangely, the vast majority of students that are enrolled in my geology class are not excited to be there on the first day. They whine and complain about being forced to learn about rocks. By the time they leave, I like to think that the same majority have both come to some scientific and geologic understandings, and enjoyed themselves along the way.

Along with the typical struggles of public education, high school geology is routinely treated as a dumping grounds by school counseling staff and, to a lesser extent, colleagues, for students who desperately need science credit and are seen as being problematic, lacking in foundation skills, and have been generally unsuccessful in science in the past. This makes the teaching of earth science particularly difficult- how do you manage disengaged students with challenging behaviors and inspire them to connect with geology content? How do you keep the subject matter relevant, rigorous, and robust while working within the reality that many of my students can’t read at grade level and need not just foundational science skills, but foundational life skills?

I don’t know the answers, but I am certainly trying to make geology and oceanography come alive for my kids. My contributions to Earth Science Erratics will focus on my challenges and successes connecting students to earth science, and my own occasional sojourns into the realm of field geology.

Oh, and the geologic timeline? A student finally recognized that by placing themselves in front of the chalkboard in such an evenly-spaced line, they were throwing off the scale of both geologic and biological events. Everyone grudgingly squashed together towards the classroom door marked ‘present day’ and we re-emphasized the immensity of the time that had occurred since the formation of the earth to the first appearance of well, Buzz Lightyear.

I like to set the stage during the first week of geology by opening with really big questions about how the Earth formed and what it took before we could be sitting here in fifth hour, pondering our place in time. Geologic time and Earth’s fossil history form the bedrock of the course, placed firmly beneath our metaphorical feet, allowing students to have a frame of reference for everything else we cover. Now, if only I could keep the dinosaur and the monkey apart from one another…

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    WEFTEC 2011 – Day 3: the beginning?

    Posted on November 20, 2011 by Will Dalen Rice
    Will Dalen Rice

    The third in a series reporting on the Water Environment Federation’s annual technology conference. Part 1 here. Part 2 here.

    Monday was, for many people, the first day of the conference. That being the case, the first agenda item of the day was the opening general session. This was held in one of the largest halls at the facility in LA. I was sitting so far back, I was having trouble seeing the giant screen, which was projecting what was happening on stage, which was basically in a different zip code. Regardless of that issue, the audio reached me and got me excited about water.

    The initial welcome was put forth by LA mayor Antonio Villaraigosa. He talked a little about how LA was innovatively tackling the issues of so many people in such a small space with water being a strained resource. He talked about the massive amount of water being treated, wastewater being moved and cleaned, and the stormwater also coupled into the cycle. The first motto of the conference was “we believe in clean water.”

    Next, Jeanette Brown (immediate past president) came out on-stage to recognize everyone involved in WEF, the WEFTEC organizers and board members, as well as various prize winners in the water-based arena. She then introduced Jeff Eger, the new president. One of his first acts was to present the “Water’s Worth It” Campaign. This is the new initiative by which everyone in the water industry can unify and reaffirm the importance of what is done. It’s a WEF logo and slogan, but more important, it is meant to be a unifying, identifiable symbol that everyone can get behind to place more value in what is really the most valuable resource we have.

    With the official-type business out of the way, the two keynote speakers began. First, there was Dr. Rita Colwell. She has spent significant parts of her life studying water, child mortality, and Cholera. She found a strong correlation between copepod presence and Cholera bacteria presence. The zooplankton (copepods) are often carriers of the Cholera bacteria, and provide a sort of host for the Cholera bacteria to thrive and spread. Since the zooplankton is related to the phytoplankton population (food source), and phytoplankton population is related to rainfall and measurable by chlorophyll quantitative analysis, Cholera could be correlated with weather phenomena and further predicted via weather models. Dr. Colwell’s computer models ended up being very effective in predicating Cholera behavior given a specific location and weather analysis. Academically, her work was done at this point. She went beyond this though, asking “What can be done now that we know where and when it is going to happen?” Focusing on a region of Bangladesh, she experimented with filtration for water sources. In this highly populated, very wet region of the world, water sources often double as sanitation transport, and vice versa. Water quality is very low, especially with a large population of impoverished people. Luckily, the copepods are very large organisms, and through crude filtration, they can be eliminated. Sari cloth ended up being the local, most easily attainable option for copepod filtration. With minor training and experimentation, they found that their “Sari Filter” experimental group had reduced instances of cholera by 50%. The filtration aspects of a piece of old Sari folded 4 or more times was all that was needed. They believed the percent of success may have been even larger, but was skewed lower due to mixing of control and filter test groups. Subsequently, returning many years later to the test area, they found the practice had been adopted further, and even more people were benefitting from this research. This is the kind of story that really creates excitement about getting out there and tinkering to solve our large scale problems. Science can lead to great things. But then again, great things can happen without science too.

    Enter Doc Hendley, former bartender and musician, and current water non-profit champion. Doc came on stage after a great show of research and benefit from Dr. Colwell to tell us a more personal story. One day he woke up and decided that being a bartender and musician was no longer his road in life. He found out about the many people in this world who didn’t have clean water, and it surprised and shocked him. He didn’t know much about his own water much less water for the rest of the world and he had never questioned that the rest of the world wasn’t as fortunate as him. Like most of the public, he basically thought water was free and everywhere. Finding out that wasn’t true compelled him. So, he hosted a gathering and served wine to all his friends, attempting to raise money to help get water for people. He ended up raising more money than he had ever planned. Then, he was ready to hand that money over to Samaritan’s Purse so they could drill wells or whatever, but something strange happened. They said no. They told him to keep his money. They instead trained him in everything they knew about providing water, and sent him out into the world to spend the money on his own. This is where the story of Doc Hendley and Wine to Water began. Today they are working with locals all over the world, providing lower tech, hyper-local solutions to getting water. Whether its filtration, locally rigged machinery, or other simple and easy methods, Doc and his organization are filling in the gap between high-tech, expensive water exploration/ development and the absence of water altogether. He admitted that his engineering abilities were indeed non-existent and he implored the crowd to stop looking so hard, and to just start doing. Solutions exist and the need has never been greater. After hearing this guy speak, its hard not to quit my job and show up on his doorstep telling him I will follow wherever the water leads him.

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      Categories: Environment, Water

      WEFTEC 2011 – Day 2

      Posted on November 13, 2011 by Will Dalen Rice
      Will Dalen Rice

      The second in a series reporting on the Water Environment Federation’s annual technology conference. Part 1 here.

      Day 2:

      The second day of technical sessions started with lingering memories of the Hampton Road Sanitation District presentation. They do a lot of innovative stuff at HRSD and their progress in nutrient removal and use is cutting edge. Specifically, their pilot studies on source separation and collecting it were quite intriguing. In terms of treating wastewater, there are very different chemical and biological processes needed to treat “Number 1” which is entirely different than “Number 2.” During collection, they mix and can inhibit the breakdown and processing of each other, but in-system separation is not feasible. Source separation, on the other hand, means they leave your bathroom in separate pipes. In terms of urine, this can mean a rather simple set of steps to recover the Nitrogen, Phosphorous, and other salts. So that left the simple task of figuring out a way to separate the waste streams leaving the restroom and getting adoption by people. The guy speaking joked at how people originally looked at him as if he had two heads when he originally proposed the idea. It worked though. Now, they are collecting separated waste streams and creating separated quantities enough for doing further research on the nutrient removal and usage. He presented a really good story of questioning, innovating, and overcoming all kinds of obstacles for the sake of progress.

      213: WEF/ WERF Hands on selection of the Best Combined Heat and Power System for your plant
      Combined heat and power in the wastewater industry is the general presmise by which you use anerobic digesters to create methane (and break down organics). This methane is then used in some form to generate power. There are a few different ways to do this and depending on where you sit will determine what system you choose to use. The variables include: current pirce you pay for power, cleanliness of your gas stream, quantitiy of your gas, plans for utilization of power (how much waste heat do you need for plant use?), and how much extra resource do you have for running and mainteing a generation source. This workshop had plenty of attendees getting walked through this process. This was one of the most encouraging things to see. Although CHP is not a new concept, the newer technology and better understanding of it is making it more viable to a wider range of treatment plants, meaning less waste gas flairs and more renewable energy production. While the details are all a little technical, everyone can see the benefit of truly creating energy from what was thought to have previously no value.

      209: Green Infrastructure: Beyond the Hype
      This was another session where I had visions in my head that didn’t really come to fruition. In hindsight though, this session topic was exactly correct per the headline. The topic was actually stormwater. In terms of water, stormwater is something most people don’t think about until their house is flooding or they have driven their cars into a puddle they cant get out of. Like water treatment and wastewater, stormwater infrastructure is “out of sight, out of mind,” and only becomes noticed when it doesn’t work. The old imperative was to transport any precipitation off the land and away as fast as possible. The new paradigm, the “green” methodology, says maybe faster isn’t better. Maybe getting the water back into the ground or storing the water somewhere is better than runoff. This session gave a more practical and reality based approach to determining how green infrastructure works, how to maintain it, and presented equally the up and downsides of managing water instead of just trying to get rid of it. There was lots of talk about rain gardens. There was lots of talk about public perception, education, and interaction. Overall, there was a positive feel to the situation and it seems that progress is moving at the pace typical of massive infrastructure re-thinking. It won’t be done tomorrow, but its moving forward.

      204: Wastewater Microbiology
      The microscope people were still here on day 2. This was one of the only sessions that was repeated. I once again was unable to resist looking into a microscope to see the living world present in a single drop of water. Protists are cool, so don’t let anyone else tell you any different.

      Next: Day 3. The conference really begins.

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        Categories: Environment, Water

        The Charlevoix impact crater

        Posted on November 10, 2011 by Tim Sherry
        Tim Sherry

        Figure 1: Aerial radar of Charlevoix impact crater.

        Special thanks to field trip leaders Alain Tremblay and Francine Robert

        Last month the Canadian Tectonics Group (CTG) held their annual meeting at Charlevoix, Quebec, the site of a Devonian [Lemiux et al. 2003] impact structure. The field trip portion of the meeting centered around learning about and seeing impact structures in outcrop.

        This post feature some impact structures we observed while cutting a transect (Figure 2) from the center of the impact crater (mylolisthenite) to the crater rim (normal fault with backthrusting).

        Figure 2: Locations of impact structures. White dots outline approximate crater rim.

        Setting and background

        The impact structure, 54Km in diameter ["Charlevoix"], is approximately half-exposed. The other half is under the St. Laurent River (Figure 1,2,3). The crater straddles the cystalline Grenville province, the Cambrian-Ordovician sediments, and accreted Appalachian Orogen. Supra-crustal faults make up the impact cratering. Major fault systems trend Northwest and Northeast, consisting largely of normal faults. Polymictic breccias provide the best evidence form impact, though other impact related rock types are present (cataclastic gouge, pseudotachylite, shatter cones) [Lemiux et al. 2003].

        Figure 3: Digital Elecation Model with epicenters Lamontagne et al. (2000)

        The St. Laurence fault trends Northeast and is associated with Late Proterozoic early Paleozoic Lapetus Ocean rifting. The fault is relatively undeflected within the impact structure, suggesting post impact reactivation [Lemiux et al. 2003].

        Impact Rocks

        Shattercones. 19T 408942.00 m E, 5263137.00 m N

        Figure 4: Shatter Cone. Lineaments point in the direction of impact.

        At this stop we observed shattercones on many scales in limestone and mudstone. The lineations on a shatter cone point in the direction of impact. Basically a shock wave travels through the rock, creating a network of fine fractures, often arranged in a conical shape (Figure 4).

        Along the railroad tracks, heading back to the parking lot, shattercones could be observed in coarser grained crystalline rock. This was a great opportunity to show how much better formed shattercones are in fine grained rock vs. coarse grained.

        Mylolisthenite. 19T 407510.00 m E, 5260539.00 m N

        Figure 5: Injecting mylolisthenite

        What, you’ve never heard of mylolisthenite? The term mylolisthenite is used to distinguish a specific type of breccia. It is pale grey to green (Figure 5), fine grained, breccia contained various clasts within the non-fused matrix (differentiating it from pseudotachylite), even though melt fragments can be found within the rock [Rondot, 1989].

        Here we are in the inner ring of the crater, beside the center peak. Our location during impact is within what is known as the transient bowl, just below the impact surface.

        Soft-Sediment Deformation. 19T 409437.00 m E, 5267768.00 m N

        Figure 6: Refolded sheath fold?

        Here we saw some crazy sediment deformation on various scales (Figures 6, 7). This outcrop was previously interpreted as an undersea debris flow. I don’t think the group came to a consensus on whether this was from gravity slope slumping or a result of impact. We did agree that the formation was VERY wet during deformation.

        Figure 7: Soft sediment deformation

        Breccia. 19T 410858.00 m E, 5271299.00 m N

        Figure 8: Breccia in crystalline basement.

        This area is near a large open fold, presumably related to impact. This breccia could be of tectonic (St. Laurent fault) or impact origin (Figure 8).

        Normal fault with backthrusting. 19T 414296.00 m E, 5275355.00 m N

        Okay, I know that sounds crazy… but hear me out. First off, I tried to stitch together a panorama of this whole outcrop that I could annotate, but Photoshop was giving me trouble stitching it together. So instead he’s some pictures.

        Figure 9: Drag folds, apparent normal motion

        … and a bit to the right, along this outcrop…

        Figure 10: Backthrust fault

        … and just a bit further along the outcrop (please forgive the distortion)…

        Figure 11: Backthrust (far-left side, behind bush) and open folds.

        Two hypothesis were presented for this outcrop. The first being that these quartzite beds were thrust up onto the crystalline basement. The second being that these are drag folds (Figure 9) associated with normal motion of the crater collapse. I support the normal fault hypothesis, here’s why.

        When a crater impacts, a transient bowl is created. This bowl then relaxes, collapsing downward, creating normal faults along the crater rim.

        What about the backthrusting and folding? Typically when normal faults are observed, they are associated with an extensional stress regime, and are the result of accommodating this extension. Here though, we have a semi-sphere bounded area. Extension isn’t being accommodated, collapse is. So even though we have normal motion at our crater margins, there is local shortening as this material collapses into the crater (Figure 12), giving rise to the backthrust and open folds (Figures 9, 10, 11) observed at this outcrop.

        Figure 12: VERY simplified cartoon (not to scale) demonstrating crater collapse with local shortening as material is transported into the bowl. Cartoon adapted from Figure 5c of Melosh (1999). Dashed line is crater rim prior to collapse. Blue line is final geometry of crater. Red lines and accompanying arrows are faults/material motion.

        References:

        “Charlevoix.” Earth Impact Database. PASSC, n.d. Web. 8 Nov 2011. <http://goo.gl/qT2t3>.

        Melosh, H. J., and B. A. Ivanov. “Impact Crater Collapse.” Annual Review of Earth and Planetary Sciences. 27.1 (1999): 385-415.

        Lemiux, Yvon, Alain Tremblay, and Denis Lavoi. “Structural analysis of supracrustal faults in the Charlevoix area, Quebec: relation to impact cratering and the St-Laurent fault system.” Canadian Journal of Earth Sciences. 40.2 (2003): 221-235.

        Rondot, Jehan. “Pseudotachylite and mylolisthenite.” Meteoritics. 24. (1989): p320.

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          Categories: Rocks & minerals, planets

          WEFTEC 2011

          Posted on November 3, 2011 by Will Dalen Rice
          Will Dalen Rice

          Introduction:

          Everyone has heard of Einstein’s E=MC2.  But what does this matter on a daily basis?  What difference does this make in terms of my power and water?  At WEFTEC in early October, the issues of power and water came together for 3 days of discussion.

          WEFTEC is an annual conference put on by the Water Environment Federation (WEF) as a way to bring water, wastewater, and stormwater providers together to review the latest technology and scientific research in their fields.  With increasing maintenance cost due to aging infrastructure, stricter regulations for treatment requirements, and decreased budgets due to the recession, money has become an even larger concern.  Add that to the fact that most water-providing professionals work in the government non-profit sector, and you get the perfect storm of job difficulty.  Since one of the biggest operating expenses is power, and power costs money, technology that can reduce kilowatt-hour consumption or power demand is rapidly becoming of paramount importance.

          While efficiency and use reduction help, there is nothing new about making better motors and peak shaving.  The really exciting new stuff is the nutrient and energy recovery work being done.  For the most part, water and wastewater treatment are processes designed to remove a mass of solids from water.  If energy and mass are equivalent, then that mass can be turned into energy.  So, in theory, if you get enough mass coming in with your water, you can turn that mass into energy that you can then use to remove the mass and create clean water.  This is the basic premise behind net-zero treatment plants.  It sounds like science fiction, but it is actually happening.  Furthermore, if you can treat drinking water and stormwater using less power as well, then there will be less power needed and less water needed to help make that power.  Welcome to the Energy-Water Nexus.  This is WEFTEC.

          Day 1:

          Before any of the exhibitors have opened their booths and before any keynote speakers have inspired us to care more than we already do, there are the technical sessions.  The first two unofficial days (Saturday and Sunday this year) were reserved for participants who paid extra to get 8-16 hours of specific training to do their work better.  I was able to pop in and out of 3 sessions on the first day.  Here is what I learned:

          112: Wastewater as a Re-N-E-W-able Resource: Nutrients, Energy, and Water

          Public perception is that wastewater is full of bad microorganisms, and once you “filter” them out or otherwise “clean” out all the bacteria, the water is good again.  It’s really much more than that though.  There are a lot of elements and compounds in wastewater than are useful in other settings.  We don’t want to be drinking them or putting them into our streams and lakes, but many of the materials are plenty useful for farmers.  Organic biosolids as well as specific nutrients isolated from treatment steps (such as Nitrogen and Phosphorous) are very good for adding to soil.  Furthermore, often the creation of these accessory products can create fuel substances as well, such as methane.  This can be refined and used in engines to generate power.  And while these aren’t new ideas, the way we are doing these traditional processes is undergoing some change.  New chemistries are being researched to see how the best way to capture this incoming mass, and use it more effectively in conversion to energy.  There were presentations about further accepting other waste products to be used as treatment aids, again creating greater quantity of valuable nutrients outputs while turning waste into energy-producing, in-process products.  The takeaway for this workshop was that we need to learn more chemistry.  The present and the future of nutrient, energy, and water are going to be all about the chemistry.

          103: Wastewater Microbiology

          We need to learn more microbiology too.  What the public doesn’t realize is that we aren’t cleaning the water ourselves.  We are just making the conditions right for tons of tiny “bugs” to clean the water for us.  This workshop was specifically designed for treatment operators, but the presenters did a good job of selling the idea that microbiology is interesting and important for everyone.  There were slide presentations about what the “bugs” looked like, what their presence or absence indicate to us in terms of the processes they were performing, and what they should be doing (mainly they should be eating).  Furthermore, there was hands-on use of microscopes to really see the bugs in action and get a feel for how to observe them.  Every high school guidance counselor should sit through one of these sessions to further plug not only the benefits of microbiology, but also the interesting aspects of what a microbiologist can do.  Ever wanted to lead an army of 1000’s of organisms that can fit under a microscope but yet do the most important work in our modern civilization?

          113: What is Sustainable Design?

          The third session I was sampling was all about what it means to be sustainable.  I interpreted it as a session where I would see all the cool new technology in the sustainability fight.  In actuality, it was a session about how to show and determine true measures of sustainability.  There were charts, data sets, and excel-based “tools” used to illustrate what a real “sustainable design” was.  It was the least sexy session I had been too, but even with my short in-and-out presence I could see that it was one of the most important.  Its importance lies in the fact that I previously stated:  money is one of the key drivers of the non-profit water service industry.  Innovation has to pan out on paper, and this session was about how to gather data, research, and information before and after a project to show that it meets or exceeds both financial requirements and physical performance goals.

          Part 2 is here.
          Part 3 is here.

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            Categories: Energy, Environment, Water

            The Iron Ore of Bell Island, Conception Bay, Newfoundland

            Posted on October 17, 2011 by Tim Sherry
            Tim Sherry

            Figure 1: Fossil Hunting on Bell Island, Conception Bay, Newfoundland.

            The most memorable stop (for me) on a recent McGill grad student trip that took us around the whole of Newfoundland was Bell Island, in Conception Bay. The discovery of iron ore in the late 1800s led to the an industry boom on the island that lasted until 1966 (Bell Island Mining History). We were fortunate enough to tour the Number 2 Mine (now a museum) and learn about the island’s history and geology. The thing that stuck with me the most was that the story of Bell Island’s mining history was one of pride and more or less, a happy story. This seemed unusual as most stories about mines in the news seem to usually involve accidents, death, or oppression of the mine workers. Our tour guide’s father, grandfather, and great grandfather all worked in the mine. Her tour was filled with pride and a conveyed the bravery of the miners.

            Figure 2: Photo courtesy of VirtualMuseum.ca

            The iron ore is found in a gently dipping Ordovician (Bhattacharrya and Kakimoto, 1982) sedimentary bed in the Wabana Fm. This bed was mined out floor to ceiling leaving 40% in the form of large support columns. This ore was mined across the island, following the bed down-dip until the miners hit the cliffs on the north side of the island. Then the miners did something remarkable. They mined vertically down, and then out and, following the bed beneath the bay for miles. Now that the mine was submarine, the ratio of ore mined to support columns was changed to 40% mined, 60% support.

            Figure 3: Iron ore daylighting in the cliffs on the coast. Debris on the right of the photo is shales that were used to close up the mine shafts after the mine was decommissioned.

            Figure 4: Iron ore bed daylighting.

            Being geologists, we were all asking questions about the nature of the ore. Hand lens examination showed that the ore was made of iron-oxide ooids. This presented an interesting conundrum of imagining the paleoenvironment with conditions allowing the precipitation of iron around siliciclastic sand grains.

            Figure 5: "Oolitic Hematite" ore from the Number 2 Mine. Card has chemical analysis. Iron 51.26% , Silica 11.46%, Phosphorus 0.88%, Sulphur 0.04%, Lime 3.13%, Alumma 4.93%, Manganese Oxide 0.17%, Magnesia 0.61%, Titanic Acid 0.37%, Carbon Dioxide 2.13%, Combinded water 2.52

            We were all curious about how iron ore of this nature could form (especially on this scale). The papers we had on hand offered little explanation for the formation conditions. To add to the riddle I found a piece of ore down by the cliffs containing a shell fossil (Figure 6). Could this creature have been precipitating CaCO3 in an environment that was actively precipitating hematite?

            Figure 6: Oolitic Hematite with fossilized shell.

            There is little consensus about the formation of ironstone ooids. Explanations include crystalization-precipitation, a process not unlike modern day calcitic oods, and subaqueous diagenisis of Al-Si hydroxygel precipitates from detrital clay-Fe hydoxide colloid coagulates (Bhattacharrya and Kakimoto, 1982).

            Bhattacharyya and Kakimoto [1982] conducted an SEM study of the fabric of ironstone ooids and concluded that the ooids formed from a dissolution and re-precipitation connected with mechanical accretion of suspended particles around a nucleus grain. Replacement of CaCO3 has also been proposed. Nothing I found was very conclusive.

            Figure 6: Inside the mine.

            The mine closed in 1966 when it could not economically compete with other iron mines whose ore was easier to process. The population of the island quickly shrunk from ~12,000 to less than 4,000 (Bell Island Mining History). The residents that remain on the island are some of the friendliest people we’ve ever met. For instance, we were camping on someone’s property and they drove up late at night. We thought they were going to kick us off. Instead they warned us to move one of our tents off of an ATV track, and then offered us wood. Bell Island has an amazing history, geology, and people. Our tour guide said that a little piece of Bell Island stays with everyone. She’s right. I can’t wait for the next time I can visit Bell Island.

            Figure 7: Looking out over Conception Bay from our camp site.

            References:

            “Bell Island Mining History.” Virtual Museum of Canada. Virtual Museum, n.d. Web. 9 Oct 2011. <http://goo.gl/ahSpk>.

            Bhattacharyya, Deba P., and Paula K. Kakimoto. “Origin of Ferriferous Ooids: an SEM study of ironstone ooids and bauxite pisoids.” Journal of Sedimentary Petrology. 52.3 (1982): 0849-0857. Print.

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              Categories: Ore geology

              From Erratics to an erratic

              Posted on August 30, 2011 by Metageologist
              Metageologist

              Having found my feet here, Chris @highlyallochthonous has kindly given me a space of my own on all-geo.org. I’ve a stack of posts ready to go, so posting will be less erratic. Hop on over and have a look.

              At the time of writing the latest post is, aptly, about a glacial erratic and its place in Earth and human history.

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                Categories: Uncategorized

                Accretionary wedge #35 – Porphyroblast

                Posted on June 25, 2011 by Metageologist
                Metageologist

                I like long words (I might even say I was egregiously polysyllabic in my discourse) and when Accretionary Wedge #35 asked me for my favourite geological word I knew it had to be one of those compound names based on dead languages: something like porphyroblast.

                A porphyroblast is a mineral found in a metamorphic rock that has grown larger than the surrounding minerals. As we’ll see later, the growing bit is important.

                Porphyroblasts of many minerals can be found, but the classic mineral that forms them is garnet. It’s always a visual treat; in hand-specimen  it forms handsome red lumps and in thin-section it goes dramatically black under crossed-polars. Yum.

                Garnet is a keen participant in many metamorphic reactions and the mineral chemistry of garnets is such that the relative amounts of Calcium, Iron, Magnesium and Managnese it contains can vary throughout a single grain.  This means that garnet porphyroblasts can be little time-capsules: the way in which their composition varies shows how the conditions under which they formed changed over time. A typical example is where the garnet core formed under conditions of lower temperature and pressure compared with the rim. As the rock was buried and heated as part of, perhaps, an episode of mountain building, the garnet slowly grew, changing in composition over time. Studying the composition  across the grain now allows us to glimpse a part of the rock’s history that is otherwise lost.

                Building mountains involves squashing rocks as well as heating them, which leads to another way in which porphyroblasts can be time-capsules; they can contain fossil fabrics.

                Garnet in Irish schist. Note the early 'vertical' fabric in garnet that is now wrapped by later 'horizontal fabric'. White dot is a reminder that I should buy myself a proper scanner

                The metamorphic reactions that form garnet typically involve the breakdown of minerals like feldspar and mica. As garnet grows at the expense of these minerals, it fills the space they used to fill. Sometimes the garnet grows around minerals that aren’t involved in the metamorphic reaction, such as quartz. The quartz grains end up as inclusions with the garnet. If the rock matrix the garnet grows in has a fabric then this is preserved within the garnet, even if the matrix outside has been destroyed or rotated. Sometimes this ‘fossil fabric’ is folded, or forms beautiful spiral patterns.

                There is a long and sometimes heated scientific controversy about the exact meaning of these inclusion fabrics; some believe that the orientation of these fabrics doesn’t change and that the garnet has stayed fixed while the surrounding fabric has been rotated. Others disagree, but all agree that porphyroblasts provide an important window into the structural history of metamorphic rocks.

                Sometimes porphyroblasts include non-tectonic fabrics, such as below:

                Big staurolite porphyroblast in South African rock (single grain fills image). Rectangular areas are where staurolite fully replaced another mineral. Surrounding areas are a mixture, where the new mineral grew around the quartz

                What a difference a letter makes

                A close runner-up in my favourite geological word stakes is porphyroclast. This is also a mineral found in metamorphic rocks that is larger than the surrounding minerals. Unlike a porphyroblast which grew bigger in absolute terms, a porphyroclast is relatively bigger because all the surrounding grains have been made smaller.

                The best place to find porphyroclasts is in mylonites, which are rocks that have been intensely deformed in a ductile fashion. Mylonites are found in places, like the bottom of thrust sheets, where huge amounts of deformation (aka strain) have taken place. This strain has been accommodated, not by faulting, but my ‘smearing out’ the rocks.  Smearing rocks means smearing individual grains and this process is associated with reduction in grain-size. The processes that allow smearing (various forms of creep) work at the level of the crystal lattice and so are highly dependent on the type of mineral.

                So, if a quartz rich rock is highly deformed the quartz grains may deform relatively easily and end up as a fine-grained matrix. Consider a feldspar grain caught up in a shear-zone. It may be too cold for it to deform internally, in contrast its quartz neighbours. The quartz grains start being smeared out and reduce in size but a feldspar grain doesn’t and so becomes a porphyroclast.

                Note the difference with porphyroblasts which grow bigger than their neighbours, instead porphyroclasts stay big while everything around them gets small, (a bit like Gloria Swanson in Sunset Boulevard).

                Rotated porphyroclast, borrowed from http://shearsensibility.blogspot.com

                Deformation in shear-zones is often asymmetrical (simple rather than pure shear), which means there is an element of rotation to the deformation. Sitting in the middle of this, porphyroclasts sometimes get rotated, which makes them useful shear-sense indicators.

                Phenocryst, porphyroblast or porphyroclast? A case-study from my kitchen

                In my kitchen I have a ‘granite’ worktop which contains large feldspar grains that are generally bigger than the surrounding minerals (not dramatically so, but bear with me). Ask the man who fitted it and he would tell you that he sold me some granite, which means that these large crystals must be phenocrysts, usually minerals that crystallise out from the magma first, making a porphyritic rock. If the phenocrysts clump together then the rock is glomeroporphyritic which is my second favourite geological word. Try saying glomeroporphyritic three times fast: good test of sobriety I reckon, if your tongue can cope with that you are safe to operate heavy machinery.

                'Granite' from my kitchen. Big feldspar grain in centre of picture. Tip of garlic bulb top centre for scale

                This may be granite to an architect but to a geologist it is not. It is not even a granitoid as it is a metamorphic rock, an orthogneiss of some sort. Its full of garnet, both as large grains and as inclusions with the feldspar. In places the feldspar shows evidence of multiple phases of growth. So, are these feldspars porphyroblasts perhaps?

                Maybe, but rocks are three dimensional and I’ve only shown an image from the top of slab. What about the sides?

                Side of slab showing intense metamorphic fabric with wrapped feldspar grains. Anthropomorphic toy train for scale

                Well that’s a rather different picture. There is a fairly strong gneissic texture within these rocks; so these are porphyroclasts then?

                These feldspars in my work surface, are they phenocrysts, porphyroblasts or porphyroclasts? On balance I think a bit of all three and therefore none of them. It seems likely to me that these were originally large feldspar grains within the original granite and so phenocrysts. There is evidence of recrystallisation which may have made them bigger, but not necessarily much bigger. Looking at the ends of the slab there are feldspar grains wrapped by the fabric so they’ve been deformed like porphyroclasts, but there’s been a some subsequent annealing so there isn’t a particularly dramatic contrast in grain size.

                So try as I might, I can’t accurately use any of these lovely words to describe my work-top, but at least it’s still good to make pastry on.

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                  Categories: Rocks & minerals

                  The Advanced Biofuels Leadership Conference, Day 3: What would you say you do here?

                  Posted on May 31, 2011 by Will Dalen Rice
                  Will Dalen Rice

                  The final part of a 3 part series on advanced biofuels. In the first part, I explained why I was attending a biofuels conference and summarized discussions about interactions between the government and the biofuels industry. In the second part, I explored the issues of funding. Now it’s time to talk about the state of the science and what this all means for the future.

                  The final day of the conference was all about being “feedstock agnostic” in terms of what you give to your genetically engineered, “proprietary organisms.” This was the really cool day where they all talked about what their companies actually did. Some companies were turning biomass into sugars (which I think then gets turned into oils, either by chemical rearrangement or possibly by feeding them to something else). Some companies were growing algae, which can then be turned into biofuel. And still other companies were going straight to oils, using special bacteria that would take a feedstock and secrete oil in response to it. It seemed like they all had bench-top proven technology. The devil was going to be how to make millions of gallons of their product on vastly larger scales. They all had plans and they all had pilot facilities in the making. It was very exciting and the anticipation for what the future will hold was high.

                  Although there is still significant future distance to travel, the technology had come a long way. The leader of the conference made some joking remarks about how the common technological aspects are glossed over as being something simple. “And as you see her on slide 6, we just took the bacteria and rearranged its genes so it would do what we want.” He wasn’t really exaggerating either, as it did seem like all the presentations had some words about genetic modification, but at the same time it was presented as if it was no big deal. Five years ago you wouldn’t have been able to just swap some genes here and there and have it work. The advances in cell-level and genetic modifications have flung open the gate for some enormous opportunity. My favorite presentation was by the group who have moved even further beyond genetic engineering. They had taken to selectively evolving their microbes by applying environmental pressures and then breeding generation upon generations. This blows my mind, and at the same time give me so much hope. Drilling for oil seems so antiquated in terms of what it takes. More difficult oil just takes more risk, more brute force, and more strength in terms of technology to combat the forces of physics. At what point do stop making things stronger and more complex, leading to greater dangers for rig workers? At what point do all the negatives outweigh the positives? After the Gulf oil spill, it seems like there is no limit to peril and damage, but then there was no other option. Now there I another choice, and making the oil ourselves is the new elegant solution, that will lead us into the future.

                  Summary:
                  To wrap everything up, here is what I learned:

                  1. Many advanced biofuels technologies have been proven on a small-scale. Some have been proven on a pilot scale. Full scale production is the next step.
                  2. To get to full scale, further support in legislative policy (ex: RFS, EISA) need to be administered.
                  3. Policy will help support monetary decisions, which require equally monumental financial creativity to get to the current cost-competitive point of oil.
                  4. The policy, supported financial instruments, and technological development timeline need to be decoupled from oil volatility to achieve progress. Otherwise we will continue to pogo stick in place.
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                    Categories: Energy

                    Chalk is weird

                    Posted on May 22, 2011 by Metageologist
                    Metageologist

                    Sometimes you live with something and regard it as normal, dull, quotidian, jejune, blah or maybe just meh. Then one day you suddenly get a moment of clarity and realise that actually, it is really weird. Subtly weird perhaps, but still very odd and mysterious. For me, chalk is like this. I live in Southern England and chalk is all around me, but I only recently got thinking about it properly. Accretionary Wedge #34 and its call for weirdness got me writing about it.

                    Chalk is a weird rock-type

                    Piece of chalk. Weirdly dull and you can't even draw on a board with it . Image courtesy of Geological Society

                    Chalk is a very pure biogenic fine-grained limestone found across much of Western Europe. It is made up of marine dandruff, the hard bits of marine algae (coccolithophores) that have settled to the sea bed. Marine algae is nothing unusual of course, but chalk is made of nothing else. Really nothing, less than 3% of anything else, which makes a piece of chalk one of the dullest rock-types imaginable. No texture, no mineralogical variation, no structure, what a bore; when I moved ‘down South’ and first encountered it I was almost offended by its dullness. I’m a hard-rock man by preference, but even the Carboniferous sediments I grew up with have cross-bedding, variation in colour and other nice things that distract you from the fact that they are only sediments. Chalk is weirdly dull.

                    Flint is weird

                    On an outcrop scale chalk has some interest: it contains flint. Flint is chert that occurs in chalk, that is to say cryptocrystalline silica, black, shiny and with conchoidal fractures. It is extremely common, but no-one really knows how it forms. The silica doesn’t come from sand like in normal sediments, oh no, it is thought to come from sponge spicules, diatoms and other biological sources. It is formed somehow during diagenesis. Often it infills burrows or surrounds fossils, suggesting a role for micro-environments with unusual (weird?) chemistry that allow the silica to precipitate out as a gel. Sometimes soft-sediment deformation is seen to deform flints, so they are soft during early stages of diagenesis. Also flint sometimes infills early faults/fractures to form sheet flints. It can also directly replace chalk, rather than filling cavities. As a resistant erosional product, flint is ubiquitous in Southern England (it forms the gravel drive of my house) yet nobody really knows how it forms.

                    Flint is important in European archaeology. That conchoidal fracture means that hitting flints (knapping if you do it well) gives sharp edges: mammoth-killing sharp. Other rock-types with similar properties have a similar role elsewhere (e.g. obsidian in Central America). Flint tools are very important as they are common and easily preserved and so can be used to trace trade routes. Places such as Grimes Graves in Norfolk show how important they were 5000 years ago. Flint was so important that it was worth digging a 30ft vertical shaft with deer antlers down through the chalk to mine it.

                    Chalk is weirdly English

                    Chalk forms a distinctive landscape called downland that is the quintessential English green rolling landscape. Chalk is very homogeneous and so is a little like a blank slate on which other processes can act. Southern England was never glaciated, but was near the edge of the ice during glacial periods. It is therefore a good place to recognise periglacial landforms. One example is valleys within downland that don’t contain rivers (called ‘bottoms’) which are sometimes asymmetrical, with a shallow side and a steep side. The shallow side is usual the sunny side (South-facing) where more vigorous freeze-thaw broke-up the chalk and flattened the slope compared with the darker side.

                    Chalk Cliffs near Dover

                    During the dark days of World War Two, Britain’s fighting men’s morale was kept up by Dame Vera Lynn, the ‘Force’s sweetheart’, whose most famous song was “The White Cliffs of Dover”. The chalk cliffs of England’s south coast are an English icon. This is a bit odd however as they are at the far end of the country. Go to the wrong bit of Kent (the county Dover is in) and your mobile (cell) phone will pick up French base stations and connect you to a French mobile phone company. If you do actually move over the English Channel to France, what do you see? Large white chalk cliffs, which at the time Dame Vera was singing were covered with Nazis planning invasion. Incidentally, the nicest way to get to France from England is via the Channel Tunnel, which was drilled entirely through the chalk under the sea from England to France.

                    So how did white chalk cliffs become symbolic of England? Well, the song “The White Cliffs of Dover” was actually written by two Americans which might also explain why the song goes on about Bluebirds, which are not native to England.

                    Chalk downland has thin soils. If you strip off this soil you quickly get to chalk, brilliant white against the grass. This can be used to make large pictures on the slopes visible for miles. These images are generally very old and are often of horses but can be, er, other things.

                    White horse of Uffington

                    Cerne Abbas giant, the world's oldest and largest rude chalk drawing?

                    What is the origin or meaning of these figures? Nobody really knows.

                    Chalk is geologically weird

                    Chalk is the dominant rock-type of late Cretaceous Europe. The simple picture is that high sea-levels meant that the Europe was ‘drowned’ meaning that large areas were far from land. No land means no terrestrial sediment (sand or mud) so, debris from marine algae could slowly build up undiluted to great thicknesses (over 1km of chalk in the North Sea). The traditional picture was that chalk was chalk was chalk. Nothing happened, there was nothing to correlate stratigraphically and thicknesses were relatively constant. A recent paper by Rory Mortimore (in Volume 122, Issue 2 of the Proceedings of the Geologists’ Association) gives a good overview of modern knowledge about the Chalk. Detailed correlation across a wide area is now established. A lot is based on bio-stratigraphy and the correlation of volcanic ash-bands (marls, in chalk terminology), which is familiar from many sedimentary sequences. However features such as a flint bands are also useful in correlating different sections. I can understand that the rapid evolution of bivalves or an unusually large eruption might create useful time markers, but why should bands of flint also do so? Weird.

                    The bulk of the paper makes a nice case for the importance of tectonics for controlling sedimentation. Since the rock is very uniform, evidence for this is subtle, but convincing. It is interesting that a rock-type associated with unusual eustatic conditions (an exceptionally high global sea-level during a period of high CO2 (greenhouse conditions)) should show extensive evidence for tectonic control.

                    The final weirdness is the question: why do large deposits of chalk exist only in Europe? To get chalk you need zero terrestrial sediment and a carbonate compensation depth that is not too shallow (or your marine dandruff gets dissolved before reaching the bottom). Terrestrial sediment is not there because of high sea-levels; these are globally high sea-levels, so why is chalk not a global phenomena? In particular why does the North American epicontinental seaway not contain lots of chalk? It was at a similar latitude, so there is unlikely to be any climatic difference to explain the lack of chalk. There is some chalk in Kansas, it seems, but nothing on the same scale as in Europe.  Was there just more mud and sand around, diluting the chalk and turning it into marls, or slightly calcareous sandstone?  I’d love to hear a knowledgeable answer to my question and what would be really weird is if none of you good folks could supply it.

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                      Categories: Rocks & minerals, Uncategorized