Month: April 2011

Coon Creek Matrix Under the Microscope

Hunting for microscopic fossils at the dinner table. Inside the circle is 100x magnification; outside the circle the magnification is 1.

My students will tell you that I’m never happier than when I have my cup of tea. On the night after our visit to Coon Creek, I put a tiny sample, about the size of a matchstick’s head, of sediment matrix on a microscope slide, and added a drop of water to disperse the grains. Then I sat there, while the chaos of dinner-making swirled around me, and searched for tiny, microscopic fossils of creatures that died long ago. With my cup of hot tea beside me, it was like sitting in the eye of a storm, flaming hamburgers be damned, a modicum of sanity in the asylum.

Quartz grains from Coon Creek Formation sediment seen under the microscope at 100x magnification. Quartz is easy to identify because of the way it breaks with curved fractures.

The first thing I noticed though were the quartz grains. They’re very small, silt-sized, but are the largest grains in the sediment. They’re pretty easy to identify because they break like glass, with curved, conchoidal fractures. They’re also pretty little things under the microscope; little, sharp-peaked, transparent mountains.

Other minerals are visible in the sediments. Though they're relatively large they're still dwarfed by the quartz (100x magnification).

Other minerals are visible in the slides, but they’re dwarfed in size and quantity by the quartz. Yet there is enough of the dark green, glauconite clay to bind the quartz grains together and protect the shells embedded in the sediment from dissolution by the universal solvent, water.

It’s interesting to observe these other minerals, because they take the more classic crystalline shapes and forms. The sharp edges are parallel to one another because of the alignment of the atoms in the mineral crystal.

Snail like shape of what's probably a planktonic (lives in the water) foram. (100x magnification).

Finding the micro-fossils took a little patience. The entire slide had only four obvious specimens. Since they’re so small that meant a lot of going back and forth under the small field of view of the 100 magnification objective lens. They look like foraminfera to me, but it’s been a while since I’ve encountered them. Foraminfera, or forams for short, are tiny organisms that secrete beautiful calcium carbonate shells. They can be found in, or in the sediments beneath, most of the world’s oceans, particularly in the warmer areas.

Finding forams in the Coon Creek Matrix is a nice little exercise. One of my students, seeing what I was doing, wanted to try it too, so she made her own slide and searched until she found her own specimen. It was somewhat inspiring, so I’ve put together a more detailed post about finding microfossils.

We also found a neat little shell that looks like the overlapping scales on a pine cone. We were disconnected from the internet, so I was only able to look it up when I got back to school.

What looks like a type of boliviana foraminfera. It's benthic, which means that it lives in the sediments not in the water.
What looks like a type of bolivina foraminfera. It's benthic, which means that it lives in the sediments not in the water. (100x magnification).

Dr. J Bret Bennington at Hofstra has posted a nice PowerPoint of his introduction to marine microfossils lecture. As a basic introduction, it’s quite comprehensible to middle-school students, or people like myself who did not pay as much attention as they should have during that part of Paleontology. Anyway, based on these notes, the pine-cone-shaped thing is probably a variety of bolivina, a benthic foraminfera. The Foraminifera.eu-Project, is a wonderful, volunteer-produced resource for pictures and identifying forams.

Bolivina are benthic, which means they spend most, if not all of their time in the mud. Planktonic micro-organisms, on the other hand, spend their lives floating around in the water.

Foraminfera have calcium carbonate shells, as do clams and oysters. In the shallow oceans there is a slow rain of them that cover the sea-bed over the millenia. You can end up with thick layers. In fact, the white cliffs of Dover are white because of all the microscopic calcium carbonate shells. In the deeper reaches of the oceans there are much fewer of these shells because they dissolve under high pressure. As a result, down there you tend to find microfossils of diatoms and radiolarians, things with silica shells. Silica is that same material from which glass is made, and is the same material in quartz.

Finding microfossils has actually been quite important for understanding the history of the Earth’s oceans and climate. But that’s another story.

Visiting Abintra Montessori School

Abintra Montessori's Middle School.

On our immersion trip to the Nashville area we visited Abintra Montessori’s Middle School class. They’re an excellent school, about the same size we are with about a dozen students. Yet every time I visit another Montessori school I’m amazed by the subtle differences and remarkable similarities: they read many of the same books; they cover the same topics in social and natural science (as should be expected since we’re in the same state and are at the same academic level); but, most curiously, their students mirror my own pupils in independence, confidence and sociability.

I find this last congruence most interesting, because I’ve seen it in other places, too. It reflects a shared culture. One developed despite the fact that neither these students (mostly) nor their teachers had never met or even corresponded before.

There is a theory that Scandinavian countries can be more socialist because they are so culturally uniform and it is easier to connect with, and be emphatic to their fellow citizens. There is probably something similar in the Montessori secondary level in particular. Students are expected to display a large amount of independence in how they work and use their time. It’s why Montessori Middle Schools tend to be cautious about taking in students who do not have some Montessori background. It can often take a lot of time for students more familiar with the rigors of more traditional, command-and-control classrooms, to adapt to, and work effectively in, an environment with so much freedom and dependence on individual responsibility.

The differences between our schools are important, too. I’ve been thinking about Frederic Hess’ argument for more educational diversity in the U.S.. Teachers are different, parents’ philosophies of education are different, and students are different, so we should not expect a one-size-fits-all system of education to be the most effective.

Abintra and Lamplighter share the same philosophy, have students with a shared culture of independence and intellectual freedom, and basically the same curriculum. Yet as small, independent schools the teachers have a lot of freedom to adapt and interpret that curriculum based on their own expertise.

It also means that we have a lot to learn from each other.

Coon Creek Science Center: Collecting Cretaceous Fossils

70 million year old shell and its imprint in a clay matrix, collected at the Coon Creek Science Center.

Collecting the amazingly well-preserved Cretaceous molluscs and arthropods at the Coon Creek Science Center was an excellent way to learn about fossils and the geology of the Mississippi Embayment.

Consider: the actual shell of an actual organism that actually lived 70 million years ago; not the form of the shell, petrified in silica; not the silent imprint of ridges and grooves in the mud of some bivalve’s test, long dissolved by the silent flux of millenia of groundwater flow, although you can find those, too; but to stand in the daylight, on the gravel bar of a creek, and hold the actual shell of an actual marine organism that lived here when it was six meters under water.

When we got to Coon Creek, Pat Broadbent did her typical, excellent presentation, starting with the very basics question of, “What are fossils?” Apart from the aforementioned actual preserved shells, you can also find trace fossils, like, for example, where the imprints of the an organism is left in the mud while the shell itself has long dissolved away. They can be imprints, or molds of the shells. One of my students found the mold of a crab’s claw along the creek bed; the mud filling in the claw had solidified into rock but you could clearly see where the pincer once articulated.

Pat also talked about the Mississippi Embayment, which is the long, broad valley through which the Mississippi River flows.

The breakup of the supercontinent, Pangea. Notice how the North Atlantic Ocean is opening as North America pulls away from Europe and Africa. You can also see the flooded Mississippi Embayment. (Image from Scotese, C.R., 2002, http://www.scotese.com, (PALEOMAP website)).

When the supercontinent Pangea started to break up, North America pulled away from Europe and Africa. This created a rift that eventually became the North Atlantic Ocean. At about the same time, North America tried to split into two as a second rift was created, right where the Mississippi Embayment is today.

How the coastline of North America, has changed over the last 100 million years. The sediments at Coon Creek were deposited in the Cretaceous (black line). The current coastline is shown in blue. (Image from Wikipedia).

But the rift failed (Cox and Van Arsdale, 2007). It did, however, stretch and thin the continental crust enough to create a large inland sea running up the middle of North America. Over the 100 million years since, the rift formed, the Mississippi Embayment has filled in, first with oceanic sediment, but then with terrestrial sands and silts as the mountains to the east and west were eroded away and washed into the inland sea.

The layer of silt and glauconite clay that encases the fossils at Coon Creek is called the Coon Creek Formation. Pat was very clear that we should refer to this material surrounding the fossils as “matrix”. The “d” word was prohibited. These sediments were deposited while the sea still flooded the embayment. They formed a sand bank, several kilometers offshore.

I vaguely remember doing some research on glauconite a long time ago. Glauconite pellets are found in shallow marine waters, usually far enough away from the coastline so that sediment is deposited slowly, and it’s the finer materials, such as silts and clays, that are deposited. The water also needs to be deep enough to protect the fine sediment from the force of the waves. These are ideal conditions for clams, mussels, conchs, and their Cretaceous relatives.

A simple smear of the sediment across a microscope slide is enough to show that the matrix is has a lot of quartz. You need a microscope because the mineral grains are tiny, silt sized or smaller.

But the best part of looking at the slides is finding the microscopic fossils. They’re not as ubiquitous as you might think, but they’re there if you look. I found a couple of forams, a snail-like one and another that looks like a bolivina species.

What looks like a type of boliviana foraminfera. It's benthic, which means that it lives in the sediments not in the water.
What looks like a type of bolivina foraminfera. It's benthic, which means that it lives in the sediments not in the water. It is surrounded by silt-sized grains of quartz.

However, the smear slides came later. After Pat’s talk, she took us out to a small mound of matrix that had been excavated for sampling. Everyone grabbed chunks of matrix and pared away at them until they found something promising. These promising samples were wrapped in aluminum foil so we could clean them up under more controlled conditions.

Cleaning samples.

Cleaning takes time and patience, so Pat showed us how to do it, and each student worked on a single sample. The main idea is to create a display of the fossil using the matrix as a base. The general procedure is to:

  • Use a small pick, paintbrush and spray-bottle of water, to wash and wipe away the matrix from the fossil.
  • Let it dry out well, which usually takes about five days.
  • Paint the entire thing with a 50-50 mix of acrylic floor wax and water. Pat recommends Future Floor Wax, but that seems to have been rebranded out of existance.
  • Repeat that last step three times (let it dry for about 15 minutes inbetween) to get a well preserved, robust sample.

After the instructions on cleaning, we broke for lunch. For most of us lunch could not have come early enough, not because we were particularly hungry, but because it was quite cold outside. Just the week before the temperature had been above 20 °C, t-shirt weather. Now students were clustering around a couple space heaters trying to ward off frostbite (or at least that’s what they claimed). I did offer that they could stay inside after lunch while the rest of the class walked along the creek, but no-one took me up on it. I don’t know if it’s specific to this group or just to adolescents in general, but if there a chance to walk through water, and get dirty and wet, they’ll take it no matter what the consequence.

Students looking for fossils in gravel bar.

Walking the creek, pulling shells and molds out of the gravel bars, was the best part of the visit.

Students standing in the creek, testing their rubber boots.

The water was shallow, not getting up above the shins, despite the rain showers of the preceding days. A few students borrowed rubber boots, which half of them proceeded to fill with water.

There were quite a lot of fossils. Some of the bivalves have really thick strong shells that not only survived the 70 million years since the Cretaceous, but being washed out of the matrix and tumbled down a stream bed with all sorts of sand and gravel. Some of the casts, like the aforementioned arthropod claw, are also pretty robust.

Snail shell that's been in the ground for millions of years and then got washed out into a gravel bar.

A couple of the more interesting finds are the rather elongate tube like structures that are believed to be either fossilized burrows, or fish feces (coporolite). The material in the coporolite has been replaced by minerals, which is why it survived, but it still retains a little of the ick factor.

There’s an awful lot to learn at Coon Creek. I did not even mention the mesosaur skeletons that have been found there, but there is a nice IMAX movie, Sea Monsters, that’s a nice complement to the field trip because it’s set at the same time, and in the same marine environment as the Coon Creek Formation.

Cool and Wet, but Quiet

Early morning rain drops fall on the lake at Natchez Trace.

It’s dawn, but the sun has not yet come up. Even when it does it won’t be able to break through the solid, low sheet of stratus clouds. Make that nimbostratus clouds, ’cause it’s raining. The light, forever-drizzle as the spring warm fronts push slowly, persistently, against the winter.

Male cardinal getting ready to protect his territory.

It’s cold, but the birds are out, and so am I. Impervious to the weather, two bright males compete for the attention of a female. She stands apart, as patient as the rain. The males chase each each other from tree to tree. Their intentions are overt, their challenges obvious; yet there is so much less tension than when primates interact.

Studied indifference.

I appreciate their lack of subtlety.

I like rainy days. They bring back memories: of hard, tropical rain beating a pulsing, bass, asyncopation on a galvanized steel roof; of goalkeeping on a flooding field, where you could not even see the half-line, much less the other goal; of hiking the calmed streets of New York, dry and warm with the hood up on a bright orange raincoat.

The rain isolates and quiets the world. Though I enjoy our immersion trips, and really believe they are one of the best mediums for learning, I savor those few minutes of solitude each morning. Before the cacophony to come.

Interning at the Muddle

One of my students, Ms. Piper Ziebarth, had the audacity to agree with me, enthusiastically, when I mentioned that my writing could do with a little editing. She also had the temerity to call one of my more artistically designed paragraphs, “boring.”

So I offered her the chance to intern at the Muddle as an editor and reviewer.

This week, most of my students are off seeing a little of what it’s like to have a real job. Apart from getting them out of my hair for a week, the internships are intended to allow them to build some self-esteem by contributing to society (internships must be unpaid), practice speaking and acting in formal situations, and exercise the most interesting and challenging aspect of learning by applying their knowledge in new areas.

Piper's hand at the wheel.

I offered Piper the chance to work with me because she’s a gifted writer, from whom I would do well to learn. Unlike my own, her writing is clear and concise, with strong emotional subtexts that draw the reader in. She’s also internalized the lesson that the revision process is essential, so her work benefits from a strong, critical eye.

Piper’s also one of my more prolific student bloggers.

I’ve not worked at a newspaper or magazine, so I’m only vaguely familiar with their traditional editing process. I have seen both sides of the scientific peer-review process, but there, the focus is more on making sure the end result is scientifically accurate. There, the use of scientific jargon is essential for clarity when communicating among scientists working in a specialized field. While I greatly enjoy the freedom of blogging, I often find myself being pulled into that careful style of scientific writing.

Hopefully, Ms. Ziebarth can help pull me out of it.

Over the next week, my challenge will be to not mention schoolwork, and all the other things we have going on in the classroom, and let Ms. Ziebarth focus on editing and revising.

Ultimately, what shows up on the blog is my responsibility, and I can be quite stubborn. But, hopefully, I’m old enough to learn how to use a good editor and reviewer well.

And Poetry Soothes the Savage Beast

Poetry can be disjointed, illogical and irrational. Sam Tanenhaus argues that that is why poetry helps us make sense of catastrophes and disasters.

One of the enduring paradoxes of great apocalyptic writing is that it consoles even as it alarms.

This has been, in fact, one of the enduring “social” functions of literature — specifically, of poetry. Narrative prose is less well suited to the task. This isn’t surprising: narrative implies continuity and order — events that flow forth in comprehensible sequence, driven by motive forces of cause and effect. …

But catastrophe defies logic. It faces us with disruption and discontinuity, with the breakdown of order. The same can often be said of poetry itself. It operates outside the realm of “logic.” Rather, it obeys the logic of dreams, of the unconscious. This is especially the case with lyric poetry, with its suggestion of vision and prophecy.

— Tanenhaus (2011): The Poetry of Catastrophe, on the New York Times’ Arts Beat Blog.

Andrew Sullivan, on the Daily Dish, highlights W. B. Yeat’s “The Second Coming,” as being quite apt to the topic. It was written just after World War I (Poem of the Week).

Turning and turning in the widening gyre
The falcon cannot hear the falconer;
Things fall apart; the centre cannot hold;
Mere anarchy is loosed upon the world,
The blood-dimmed tide is loosed, and everywhere
The ceremony of innocence is drowned;
The best lack all conviction, while the worst
Are full of passionate intensity.

Surely some revelation is at hand;
Surely the Second Coming is at hand.
The Second Coming! Hardly are those words out
When a vast image out of Spiritus Mundi
Troubles my sight: somewhere in sands of the desert
A shape with lion body and the head of a man,
A gaze blank and pitiless as the sun,
Is moving its slow thighs, while all about it
Reel shadows of the indignant desert birds.
The darkness drops again; but now I know
That twenty centuries of stony sleep
Were vexed to nightmare by a rocking cradle,
And what rough beast, its hour come round at last,
Slouches towards Bethlehem to be born?

— Yeats (1919): The Second Coming, (via Poets.org).

Drilling Through to the Mantle

Between 6 and 25 km thick, the Earth’s crust is an excruciatingly thin skin on a 6400 km globe. Yet even drilling to the bottom of the crust would require a remarkable feat of engineering. Some geologists want to try.

NPR’s Science Friday interviews Damon Teagle, one of the architects of the project. They want to drill in the ocean because oceanic crust is thinner than continental crust (on the other hand, it’s denser too, which is why it subducts).

Using different types of chocolate covered candy, they also have this wonderful video of the basalts, sheeted dykes and gabbros that make up the crust.