I discovered yesterday, that for some reason or the other, a number of my posts’ comments sections were closed. I’ve re-opened them all again, but I’m still not sure why they closed themselves.
Also, as I mentioned before, if you try to post a comment and it does not show up it was probably caught up in my spam-filter. I’ve caught a few like that, but it’s impossible to check them all. A direct email should suffice to solve that problem if it occurs (see contact me). I appreciate all the feedback.
The cold front of this mid latitude cyclone spawned several fatal tornados on April 28, 2011. The cold front is the blue line with triangles pointing toward the east. Image via NOAA HPC.
The cold fronts of mid-latitude cyclones bring thunderstorms, rain and spawn tornadoes like the ones we’ve seen over the last few days. In the spring and fall, these cyclones just sweep across the southern U.S. again and again. The line of their passage sort-of marks the northward migration of the sub-polar low in picture of the global atmospheric circulation system.
The circulation cells of the global atmospheric circulation system migrate north and south with the seasons. Image links to larger version (1 Mb).
Each individual front, with its storms, is a feature of the weather. Climate, on the other hand, is the result of the average position over time: the series of fronts which make the southern U.S. wet in the spring and fall.
The sub-polar low is not the only feature that brings lots of seasonal rain. The ITCZ does also, and the rains that the ITCZ’s movement north and south of the equator bring, are what we call the monsoons. The yellow star on the animation, just to the north of the equator, sees monsoonal rains in the summer. Since the ITCZ follows the sun with the seasons, the monsoons always come in the summer; even in the southern hemisphere.
As climate changes, biomes move, and the range of the brown recluse spider migrates north and east (blue area) from its current location (red dashed line). Image adapted from Saupe et al. (2011).
Just in time for us to learn about global change, this interesting study on the expanding range of brown recluse spiders came out. Once restricted to the southern U.S. and the midwest, future climate change will allow them to expand north to Minnesota and east into Pennsylvania.
The researchers, Saupe et al. (2011), used ecological niche modeling. This method takes known information about where the spiders live, such as climate (e.g. summer temperatures) or topography (e.g. mountains versus plains), to figure out the current extent of their ecological niche. Then they use climate models to figure out where those same conditions will apply in the future. Thus the spiders march north.
A God's Eye View of Moses parting the Red Sea. Image from the Glue Society.
The Glue Society has a most interesting set of satellite images modified to look like major biblical scenes. CreativeReview has more pictures and details, including of the crucifixion and Noah’s Ark.
“We like to disorientate audiences a little with all our work. And with this piece we felt technology now allows events which may or may not have happened to be visualized and made to appear dramatically real,” say The Glue Society’s James Dive. “As a method of representation satellite photography is so trusted, it has been interesting to mess with that trust.”
— CreativeReview (2007): The Bible According To Google Earth
I think this topic came up when we were talking about atmospheric circulation. The question was about if the winds generated descending, diverging air could have parted the Red Sea. The answer was no, because the general atmospheric circulation system is a thing of climate — averages of the weather — while any winds strong enough to part the red sea would be actual weather, like the storms we seem to have been seeing every day for the last few weeks.
Oddly enough, just last year researchers from the University Corporation for Atmospheric Research (UCAR) did a computer model that showed that hurricane force winds from the northwest could have uncovered an underwater reef to allow Moses his passage (the article is Drews and Han, 2010).
However, the scientists found:
[The] reef would have had to be entirely flat for the water to drain off in 12 hours. A more realistic reef with lower and deeper sections would have retained channels that would have been difficult to wade through. In addition, Drews and Han were skeptical that refugees could have crossed during nearly hurricane-force winds.
— NCAR & UCAR News Center (2010): Parting the waters: Computer modeling applies physics to Red Sea escape route.
Global warming over the last 130 years. The graph shows the temperature anomaly, which is the difference in temperature from the average (0 on the graph). The total change from the 1820's is about 0.8 degrees Celsius. Graph from NASA GISS.
IN addition to the global graphs, there are a lot of really neat graphs showing:
separate graphs from the tropics versus the northern hemisphere versus the southern hemisphere (the different latitude bands);
the difference between the northern and southern hemispheres;
the U.S. only;
seasonal changes.
The graphs typically show the temperature anomaly, which is the difference in temperature from the normal. The “normal” is taken to be the average temperature between 1951 and 1980.
The first thing you notice is a small, rickety bridge whose main job is to keep your feet dry as you cross a very small stream. The stream is on its delta, so the ground is very soggy, and the channel is just about start its many bifurcations into distributaries that fan out and create the characteristic deltaic shape.
Delta and estuary of the small stream near the villas.
There’s a bright orange flocculate on the quieter parts of the stream bed. It’s the color of fresh rust, which leads me to suspect it’s some sort of iron precipitate.
It is quite easy to stick your finger into the red precipitate at the bottom of the stream.
Iron minerals in the sediments and bedrock of the watershed are dissolved by groundwater, but when that water discharges into the stream it becomes oxygenated as air mixes in. The dissolved iron reacts with the oxygen to create the fine orange precipitate. Sometimes, the chemical reaction is abiotic, other times it’s aided by bacteria (Kadlec and Wallace, 2009).
The bark has been chewed off the top half of this stick. The tooth marks are characteristic of beavers.
Past the small delta, the trail follows the lake as it curves around into another, much bigger estuary (see map above). We found much evidence of flora and fauna, including signs of beavers.
We even took the time to toss some sticks into the water to watch the waves. With a single stick, you can see the wave dissipate as it expands, much like I tried to model for the height of a tsunami. We also threw in multiple sticks to create interference patterns.
Observing interference patterns in waves.
The Oak Ridge Trail, which we followed, diverges from the somewhat longer Pin Oak Trail at the large estuary (which is marked on the map). The Pin Oak Trail takes you through some beautiful stands of conifers, offering the chance to talk about different ecological communities, but we did not have the time to see both trails.
Instead, we followed the Oak Ridge Trail up the ridge (through one small stand of pines) until it met the road. The road is on the other side of the watershed divide. I emphasized the concept by having my students stand in a line across the divide and point in the direction of that a drop of water, rolling across the ground, would flow.
At the watershed divide.
Then I told them that we’d get back by following our fictitious water droplet off the ridge into the valley. And we did, traipsing through the leaf-carpeted woods.
Students imitating water droplets find a dry gully.
Of course there were no water droplets flowing across the surface. Unless its actively raining, water tends to sink down into the soil and flow through the ground until it gets to the bottom of the valley, where it emerges as springs. Even before you see the first spring, though, you can see the gullies carved by overland flow during storms.
Spring.
Following the small stream was quite enjoyable. It was small enough to jump across, and there were some places where the stream had bored short sections of tunnels beneath its bed.
The stream pipes beneath its bed. Jumping up and down over the pipe caused sediment to be expelled at the mouth of the tunnel.
I took the time to observe the beautiful moss that maintained the banks of the stream. Students took the time to observe the environment.
Taking a break at the confluence of two streams.
Downstream the valley got wider and wider, and the stream cut deeper and deeper into the valley floor, but even the small stream sought to meander back and forth, creating beautiful little point bars and cut-banks.
A small, meandering channel. Note the sandy point bars on the inside of the bend, and the overhanging cut-banks on the outside of the curve.
As the stream approached its estuary it would stagnate in places. There, buried leaves and organic matter would decay under the sediment and water in anoxic conditions, rendering their oils and producing natural gas. We’re going to be talking about global warming and the carbon cycle next week so I was quite enthused when students pointed out the sheen of oils glistening on isolated pools of stagnant water.
The breakdown of buried organic matter produces gas and oils that are less dense than water.
Finally, we returned to the estuary. It’s much larger than the first one we saw, and it’s flat, swampy with lots of distributaries, and chock full of the sediment and debris of the watershed above it.
View of the lake from the estuary. The red iron floc in the stream made for a beautiful contrast with the black of the decaying leaves. There is so much red precipitate that it is visible on the satellite image.
This less than three kilometer hike took the best part of two hours. But that’s pretty fast if you value your dawdling.
Salt and sugar crystals have wonderfully distinctive crystal forms. They might well be good subjects for introducing minerals, crystals and some of the more complex geometric solids.
Cube shaped salt crystals under 40x magnification.
The salt crystals are clearly cubic, even though some of the grains seem to be made up of overlapping cubes.
The atoms that make up salt's atomic lattice are arranged in a cubic shape, which results in the shape of the salt crystals. The smaller grey atoms are sodium (Na), and the larger green ones are chlorine (Cl).
Salt is an ionic compound, made of sodium and chloride atoms (NaCl). When a number of these molecules get together to form a crystal, they tend to arrange themselves in a cubic pattern. As a result, the salt crystals are also cubic. In fact, if you break a salt crystal, it will tend to break along the planes that are at the surfaces of the planes of the atomic lattice to create a nice, shiny crystal faces. Gem cutters use this fact to great effect when they shape diamonds and other precious stones.
Of course different crystals have different atomic arrangements. The difference is clear when you compare salt to sugar.
A single sugar crystal looks a bit like a fallen column.
Sugar crystals look a bit like hexagonal pillars that have fallen over. According to the Beet-sugar handbook (Asadi, 2007), sugar crystals actually have a monoclinic form, which could end up as asymmetric hexagonal pillars. Salt crystals, on the other hand, have the habit of forming cubes.
Proper respect for other living things requires us to minimize the waste we produce, and learn from the creatures we eat.
First off, three cheers for Viet Hoa, the Vietnamese food market on Cleveland Ave in Memphis. I’ve been searching for a source of fresh, uneviscerated, marine fish in this mid-continental city for quite a while, and I’ve finally found them. The market was the source of the subjects of an excellent anatomy lesson, and a delicious dinner.
I’d grabbed three fish, and a few goodies, and packed them on ice on the day before our trip. The large red snapper was a little pricey because it was fairly big, but I knew it would be quite tasty and I was hoping the internal organs would be big and clearly visible. The milk fish was an unknown, but it was big and cheap so worth experimenting on. The last fish was the smallest, and I’m not quite sure what kind it is, except that it’s marine. I’d tried one at home the previous week and found that while it had an excellent taste, the internal bits were on the small side.
Red Snapper
On the first night of the immersion I started with the biggest fish, the red snapper, with everyone around the table. I’m happy to say that all my students were there for the lesson, facing the table, even the more vegetarian minded. I’ve always believed that there is a certain, necessary, ethic to knowing where your food comes from, and what went into preparing it for you. If you’re going to eat meat, you should be able to spare a moment to think about the animal.
Small intestines are very long (and stretchy).
The digestive system was the easiest to identify and trace. The mouth and anus are pretty obvious on the outside. After cutting through the skin of the belly, you can follow the intestines from the anus all the way to the stomach. The intestines are quite long.
Shrimp-like stomach contents.
We found two partially digested, shrimp-like creatures in the stomach of the red snapper.
From the other end of the digestive system, once you get all the contents out of the body cavity, you can stick a probe through the mouth (watch out for sharp teeth) down through the esophagus to the stomach.
Pulling back the gills, you can see all the way through to the mouth. One student noticed how bright red the gills were, so we talked about oxygenation of blood and compared the fish’s gills to the human respiratory system.
Finally, I laid the fish on a bed of thinly sliced onions, surrounded it with wedges of tomato (seeded), covered it with lemon slices, dribbled a tablespoon of olive oil on top, and forgot to add the cup of white wine (which we did not seem to have on hand for some reason) and the bay leaf. It was a big fish so we ended up baking it for about 40 minutes at 400 degrees Fahrenheit.
Then we ate it. I say we, but it really was just a couple of students and myself who did most of the eating, although I believe I convinced everyone to at least try it. Of the more serious students of anatomy, the eyeballs were highly prized; with only three fish we did not have enough to go around.
Dinner is served.
By the time we were done with dinner the skeletal system was very nicely exposed.
The Other Fish
Opening the body cavity of the Milk fish.
A couple of my students did the honors of cleaning the other two fish. With its large organs, the milk fish was an excellent subject for dissection, but it was not particularly palatable. We did however find the gall bladder.
The breached gall bladder is on the lower right of the picture.
Even the smallest fish proved a worthwhile subject for the more patient student.
Up to the knuckles in fish.
Instead of eating the rather unappetizing, baked milk fish I combined it in a soup with some clams I’d picked up from Viet Hoa. I’d grabbed the clams so we compare modern bivalve shells to the cretaceous ones we’d find at Coon Creek. A bit of boiling with a few herbs, made for an excellent broth the following night.
In Summary
Cleaning fish for an anatomy lesson worked very well. As we excavated each internal organ, we could talk about what it did, why the fish needed it, and what was its analogue in humans. And, in the end, they made for a couple excellent meals.
P.S. – From the Gulf Coast Research Lab’s Marine Education Center, here’s a reference image for a perch dissection.
