Iron Stained Walls

landfill-Fe-4053 — The limestone walls of the quarry were stained red with iron precipitate.

The cliffs of the quarry were stained red. Blood, seeping out from between the bedding planes between layers of rocks, might have left similar traces down the sides of the near-vertical cliffs’ faces. But these stains are actually made of iron.

Rain falling on the land above the quarry, seeps into the ground. There it moves downward through the soil, leaching out some of the minerals there, but going ever downward. Downward until it meets a layer of soil or rock that it can’t get through. Clay layers are pretty impermeable, though in this case it’s a layer of coal. The water can’t move through the near-horizontal coal seam very fast, so instead it moves sideways across, and eventually seeps out onto the cliff face.

rust-diagram — The red on the walls of the cliffs are an oxidised iron precipitate (rust). The iron most likely was dissolved out of the pyrite in the coal seams.

The seeping water still has those minerals it dissolved in the soil. It also has more dissolved minerals from the coal it encountered too. Coal forms in swamps when trees and other plants fall into the waters and are buried before they can completely decompose. Decomposition is slow in stagnant swampy waters because most of the insects and microorganisms that do the decomposing usually need oxygen to help them with their work. Stagnant water does not circulate air very well and what little oxygen gets to the bottom of the swamp-water is used up pretty fast. You could say that conditions at the bottom of the swamp are anoxic (without oxygen), or reducing.

COALFORMATION — Coal formation. Image from the National Energy Education Development Project.

pockelrg — A shiny pyrite crystal in a lump of coal (happy holidays). Image via USGS.

Iron in air will rust as it reacts with water and oxygen — rust is the red mineral hematite (Fe₂O₃) that you see on the walls of the quarry. Iron in a reducing environment, on the other hand, will form minerals like pyrite (FeS₂). According to our guide, the thin coal seam in the quarry has a fair bit of pyrite. In fact, because of the pyrite, the coal has too much sulfur for it to be economical to burn. Like the landfill gas, hydrogen sulfide, burned sulfur turns into sulfur dioxide, which reacts with water droplets in the air to create acid rain so sulfur emissions are regulated.

The water that seeps along and through the coal seam will dissolve some of the pyrite, putting iron into solution. However, the iron will only stay dissolved as long as the water remains anoxic. As soon as the high-iron water is exposed to air, the iron will react with oxygen to create rust. Thus the long stains of rust on the cliff walls show where the water emerges from underground and drips down the cliff face.

landfill-Fe-4053a — Diagram showing the coal seam, and the seeping water that creates the iron (rust) staining.

Iron precipitate in other environments

nt-red-ppt-0459 — On our Natchez Trace hike we found it quite easy to stick fingers into the red precipitate at the bottom of the stream.

We’ve seen the precipitation of iron (rust) as a result of changes in redox (oxidizing vs reducing) conditions before: on the sandbar on Deer Island in the Gulf of Mexico; in the slow streams along the Natchez Trace Park‘s hiking trails in Tennessee. Iron precipitation is an extremely common process in natural environments, and it’s easily noticeable. Just look for the red.

sc-deer-barrier-1873 — The rich black of decaying organic matter, sits just beneath the rusty-orange surface sediment. The red is from hematite (rust) and shows that the surface is oxidizing, while the black shows that just a few centimeters beneath the surface, there is no oxygen to decompose the organic matter (a reducing environment). This image was taken on Deer Island on the Gulf Coast.

Laumeier Sculpture Park

Laumeier-3773 — At Laumeier Sculpture Park.

“It’s one of the places I’m most proud to bring people when they visit St. Louis,” commented (more or less) one of the other faculty on our field trip to the Laumeier Sculpture Park. My hope was that this trip, combined with our visit to the Leonardo Da Vinci Exhibition, would be a nice way to demonstrate that the distance between art and science isn’t so large after all.

Laumeier-3737-s — I believe this sculpture is called, "Balance".

I required all of my students (physics and middle school science) to identify their favorite piece and sketch it. We’ll be covering forces, balance and mechanics in the coming quarter, making this part of the spark-the-imagination part of the lesson.

Also, detailed sketches are not easy. An accurate drawing requires a lot more careful observation than even taking a picture. By trying it themselves they’d get a much greater appreciation of Da Vinci.

The large pieces are quite impressive. The brightly painted metal tank combination at the top of this post just towers over everything. However, one of the neatest was carved out of one enormous piece of wood. It’s made to emulate the distinctive, ridged bark of the cottonwood tree. The artist accentuates the ridges and valleys quite elegantly, making a wonderfully warm and organic abstraction.

Laumeier-3791 — Looking up at the cottonwood tree sculpture.

There’s also an indoor museum (which was closed while we were there), and, apparently, pieces are added and taken away so the park is worth revisiting. The only problem is that you’re not allowed to climb on the sculptures. This is a quite understandable precaution to protect the pieces, but, as some of the students observed, the sculptures “invite” you into and onto them. It’s a stark contrast to the St. Louis City Muesum, which is designed specifically to be played on.

Shades of grey

We’re focusing on the biological sciences in the natural world this year. I’m a great admirer of the sketches and illustrations in the notebooks of the great naturalists so that’s how I plan to integrate art. Our art teacher is a great help, and she started us up with sketching in pencil and our first exercise was to get a feel for the different soft pencils. The little panel we shaded in with B, 2B, 4B and 6B pencils is a nice metaphor for what we’re working on in middle school.

There was a bit of giggling though. Last year one of the poems presented was:

Said Hamlet to Ophelia,
I’ll draw a sketch of thee,
What kind of pencil shall I use?
2B or not 2B?
– Spike Milligan

This was just before we saw Hamlet in St. Louis. Though I don’t know if the poem make the famous line more comprehensible.

shakespeare-01 — Hamlet in the park in St. Louis.

Rafting on the Meramec

After the caves at Meramec Caverns we took a rafting trip down the Meramec with the same company that runs the Caverns. They drove us to a put-in point a couple kilometers upstream in an old yellow schoolbus and left us with two rafts and the full kit and we floated down the stream back to the cavern’s parking lot.

The stream was quiet and it was an easy float, especially with the nice weather. We saw turtles sunning on the logs, a bald eagle flew across of the bows of the leading boat, and we chatted with a few of the other boaters on the river.

Not a bad way to spend an afternoon.

Soulard Coffee Garden

soulard-coffee-shop-02 — Inside the Soulard Coffee Garden.

A great place for a cup of tea or breakfast in the morning, the Soulard Coffee Garden and Cafe is close and comfortable with an extremely friendly staff and clientele. Makes one want to spend more time in St. Louis. It’s a bit small so you might not want to bring the entire class.

St. Louis overview

I had not particularly wanted to go up into the St. Louis Arch myself, but the students really wanted to and we had a little time to spare after the Science Museum. So I grabbed tickets for the last tram to the top, and I’m glad I did. Looking down on the city and river from above you could, in an almost tactile way, reconcile the geographic elements with the history that we’d talked so much about at Anheuser-Busch.

arch-eads — Eads Bridge across the Mississipi River in St. Louis.

Standing in line, waiting for the tram to the top, we were treated to a short documentary on the Eads Bridge, the first across the Mississippi in St. Louis. The video stressed the importance of the bridge in allowing the city to become the gateway for westward expansion.

The tram arrived and small rectangular doors opened up to reveal tiny escape pods fit for a spaceship. Five of us squeezed in, fortunately we were all friendly. The distinct possibility of claustrophobia tinged the air. Three minutes 47 seconds later we reached the top. Forty-five degree rain was pouring down outside. The wind was so strong you could, if you held still and waited for it, feel a slight sway in the Arch itself.

arch-river-traffic — Barges in the distance.

arch-cargill — Grain silos and transhipment docks.

Looking east we saw the mighty Mississippi. Not quite so mighty as it is in Memphis, which is downstream of the confluence with the Ohio River, but enormous nonetheless. On the river, huge barges carried freight cars with unknown cargo south toward New Orleans. Just below, an helicopter sat on an helipad barge waiting for an emergency call. Directly across the water, on the east bank, enormous silos with their own docks waited to load barges with grain collected from across the mid-west.

It was still pouring when we left the Arch, and the rain continued on even during dinner. But leaving the restaurant, heading back to the hotel, the setting sun to the west, refracted through raindrops over the river, created one of nature’s own ephemeral monuments. A poignant reminder that forty-five, or even one hundred and forty-five years are but a moment in the deep span of geologic time.

Segway lessons

From playing with robots we tried an actual application of robotics. We had the Segways 101 course at the St. Louis Science Center.

The lesson itself was fun, with an entertaining video of people falling off Segways. They also had a little obstacle course to let you try doing all of the things the video told you not to do (but most of it was for the more advanced class).

Afterward, we discussed the fact that this too was robotics and a pretty advanced application at that. We did not talk much about how the Segways were supposed to revolutionize urban transportation but students did recognize the fact that aesthetics were a major impediment to their broader adoption.

The price was a bit steep however, and I’m a little conflicted about if it was worth it.