Halloween Stream Table Run

Today's stream table run was an adventure in basin geometry. I've been wanting to find a way to keep the stream from getting hung up on the sides of the table.



I have a bunch of rubber sheeting left over from a roofing project. Yes, I saved several square feet of sheet rubber. Because I'm an experimentalist. And I used it to created coved corners at the base of the table. I built up curved sides with the plastic media and then draped the plastic over it.


The finished sub-base, prior to filling with additional media.


Here's about a 4-hour time lapse. You can see the stream pull away from the side of the table on a few occasions, but I think I may try and make the angle a little shallower.

A little perspective

Okay, so you want to see something? Come closer. Now click on this link. See that: that's one of the things reminding me to grow my own vegetables. Drink water from the tap instead of bottles. Consume less. Not because I hate all things related to consumer culture. Not because all corporations are evil. But because if everyone of those 7 Billion wants to live/eat/consume like we do in the "Cultural West" something has gotta give. There's no way we can "give the world a Coke" all the time. There's just not enough stuff to do it. We live on a finite world. Resources are not infinite.

Happy Birthday

I like Halloween. Not so much for the costumes and tropes of ghouls and goblins but more for my own personal reasons. Today is my birthday. And today, I get to share this planet with the 7,000,000,000th person. When I was born, there were about 4.1 Billion people. We've added almost 3 billion since I got here. There's a story about exponential growth here somewhere, but it eludes me at the moment.

Doctor Mister Indiana Potato Jones Head

What's cooking for the Accretionary Wedge? So far we've got this:

Mythbusters on Netflix

Mythbusters is a fascinating show in many ways. That most of the episodes are streaming on Netflix is an added bonus. Plus, you can see how the show has changed structurally over the years. Aside from the obvious changes in the appearance of the hosts (aging, pregnancy, hairstyles, etc.) I've noticed three big changes in the general narrative style.

The first is that newer episodes don't go into as much depth in the context of the myth - they don't have the cultural anthropologist explaining some of the social implications of the myth itself. It's a level of detail I think added to the show, but it did slow the pacing down (which brings me to the second item).

The second relates to pacing and speed. The number of seconds spent forming complete sentences appears less. More clever comments from the hosts, shorter explanations from the narrator and more cuts between camera angles. If you look at other shows, they often tighten up their editorial styles over time. And shows from previous decades appear glacial in their pacing compared to shows now. For example, compare "Monty Python" to "A Bit of Fry & Laurie" to "Who's Line is it Anyway?" British version to "Who's Line is it Anyway?" American version to whatever sketch comedy show is being produced now. Some of these are cultural (it seems to me that the Brits are a little less frenetic than us Yanks). Some of this is just cleaning up the story, but some of this is coming at the cost of developing a deeper understanding of the material.

Thirdly, they don't make a distinct break from the more scientific content as they develop the test of a myth. I like that they've dropped that little sign saying "Warning: Science Content!" I think it's counter productive to interrupt the test of a myth by alerting people to some background science information. Science education works best by connecting with everyday phenomena - not by reinforcing fears of science as separate and only for those that can "handle" it. So while the length of the individual ideas is shorter, the actual science content is better integrated (when present).

Oh, and this brings up a fourth change - as their budget has gotten larger, the types of cameras they use has improved. I love high speed camera footage. And remote cameras, HD video, with multiple angles makes the show more interesting visually (although having lots of viewing angles means more editing).

One thing I would like to see - some kind of exciting/interesting set of demonstrations and experiments that you can do at home. The best way to keep kids interested in science is to allow them to learn and discover on their own. "Playing" with science is part of that joyful discovery I've talked about before.

So...

...who's ready for some Calvinball??

Permeability and the Emriver Stream Table

Got the students to do some groundwater stuff in lab today. One of the steps was to estimate the permeability of a column of sand. I used the falling-head permeameter rig that I had videotaped and demo'd earlier.

But instead of a third column of sand, I tossed some of the plastic media that comes with the Emriver setup. If you've seen these stream tables in action, you know that groundwater flow is pretty important in determining bank stability and, ultimately, what the open channel is doing.

Here's the rig:


Here's a scatter plot of all the measurements made by me and the students. For the most part, my measurements are the series that don't vary too much, while the student measurements are all over the place (well, within about 20% anyway)


This ins't a really good way to display univariate data - it's hard to determine any kind of tendency or something like that. So if I collect all the calculated permeability values and display them in a box plot, you can see that the permeability of the plastic media is about 0.3 cm/sec.


So the permeability of this material is really pretty high. You could decrease permeability a little bit more by compacting the media, but there's typically a lot of water that's flowing through the media as "groundwater." So if you're sketching up a plan for Emriver experiments, accounting for groundwater flow is probably a helpful step - especially if you're trying to produce steep gradients in a stream bed. The extra groundwater flow will tend to encourage movement of the plastic media in directions you may not expect at first.

Thurs-Demo: The one with ping-pong balls

Have some ping pong balls? Have some liquid nitrogen (LN2)? You've got yourself a party! Poke two holes in a ping pong ball - angle the holes so they kind of slant sideways. They should point the same direction relative to some axis (think of a hero engine here). Now, dunk the punctured ball in the LN2. Then remove the ball (with tongs, folks - this is super-cold stuff) and as it warms up, it should start spinning.

I didn't think of this demo - there are some pretty cool videos that demonstrate this elsewhere on the internet. But I'm the only person I know of who put the ping pong under blacklights (long wave UV) and suspended it in a stream of air. Think of it as my "value-added" contribution to edutainment...

Changed Comment Settings

Okay, the wacky spam hasn't shown up as often lately, so I'm backing off on comment moderation (only comments on older posts will be moderated). We'll see how that goes - I've been wondering if the delay on comments has been dissuading people from adding their 2¢.

What's in a number?

They say the world's population is going to reach seven billion on October 31st. That's a lot of people.

Transformative works at the intersection of art and science

Sometimes there comes a product or concept that completely transforms the way you see things. This has happened to me recently when my lab got its Emriver stream table.



Why am I so jazzed about this thing? Well for one, it's a stream table. There's no easier way to teach and learn about stream processes than by watching a stream move sediment around. Secondly, it's the way in which Steve has chosen to implement the concept. By using ground-up melamine plastic, he has managed to address (if not completely solve) the problem of scale. And by using plastic, there isn't nearly the wear and tear on the recirculation pump, hardware, hands, floor, countertops, etc. that mineral sand would have.

In fact, by working with the plastic media, I have a whole set of plans for teaching soil mechanics with this stuff. I've shied away from some lab activities and demonstrations in the past because of the mess that real soil would cause. I've also stopped doing a few of them because the students inevitably scratch up the table tops as they drag sand around. But the ground plastic is easier to clean up, doesn't cause problems for the other folks who will use the lab room later, and by being less dense than mineral sand scales to other activities more readily as well.

This is what I mean by a transformative work. It is something that is immediately recognizable, useable, and the tools/ideas that underly its use are transferable to a wide variety of other activities. It may be a stream table, but it has already given me ideas that I can use in other courses beyond introductory geology. In fact, there is a great deal of potential simply in the aesthetics.



I brought a handheld UV flashlight to the GSA meeting (like you do) and discovered that the standard plastic media fluoresces bright blue under long wave ultraviolet light. So I set up a whole bank of 18" fluorescent UV bulbs (5 of them to start with) and started filming the stream table. Then, of course, I realized that I could place some of the fluorescent plastic BBs that I had been experimenting with earlier into the stream and watch them move down the channel. The long exposure then traces their path. Of course, I had to shoot some video:



And here we have the nub of my gist, as it were. To me, this is art. And it is also science. As an undergraduate, I majored in both Art and Geology. Part of it was my strong interest in Natural History Reconstruction (aka drawing dinosaurs). But part of it was that as a geologist, I spent as much time representing the natural world via abstraction. Most of these abstractions were intended to represent the real world, but they were themselves not the real world. Much of the work I did as an artist was informed by my interest in science. Techniques for making complex color palettes relied as much on color theory and the physics of light as they did on the aesthetics/emotional connotations of what colors I used. Photography is dependent on the optics of the light moving through lenses and the chemistry of the film (this was before cheap digital, of course) as well as the choices of subject matter, position in the frame, object of focus, etc.

To me, art and science are inextricably linked. They aren't so much two sides of the same coin, because you can deal with them at the same time. In my mind, science and art are part of the same lens. You can't use one without the other, but you can emphasize one or both. It's kind of like the whole process of learning. You can learn by having the information formally presented to you in some fashion, or you can learn by discovery. You can do both at the same time, or have one emphasized over the other.

This brings me back to the stream table. You can teach formally with this thing. You can allow people to discover and learn completely on their own. It may seem like I'm just "playing" with the Emriver system right now. But what I am doing is more complex than that. I am testing the setup. How do I need to adjust stream flow in order to achieve the best (quickest and most obvious) meandering behavior? How big an impact does a small or large adjustment in the standpipe (base level) have on the stream? How easy would it be for a small group of undergraduates to manipulate the variables or make observations about a stream system? What other activities can I do with my students using the Em2?

This isn't just "play," but joyful discovery: seeing new possibilities and creating new syntheses where none existed. Ideally, students who don't have the background I do will make their own discoveries - learning what I want but also something new. Generating a sense of excitement and accomplishment through discovery is one of my favorite parts of teaching.

Oh, and the stream table can be more than just a teaching tool. I've already got some ideas for research. Particularly as regards fossils in river deposits. For example, snail shells have a much larger hydrodynamic cross section than the sediments in the stream. These BBs are similar in that they are much easier to move despite being bigger. Where do the BBs tend to "pile up?" Are there relationships between the "facies" of plastic media (fine/course/mixed, etc) and where the BBs pile up - is this related to the fluid dynamics of the stream alone, or is it a combination of stream power and the surrounding sediment? In the field, there is a distinct connection between sedimentary facies and where we find particular fossils (or how well-preserved these fossils are). We can infer a fluvial process, but with the stream table, we can see it happen. I'm very excited about where this can go.

Do I recommend you get one? Well, if you have the funds and the space I absolutely do. But these things aren't cheap. And they do take up some space (although their storage footprint fits on a standard 4'x4' shipping pallet). But if you're limited in funds, or already have a stream table, you can still learn from the research and design done by the Emriver folks. In fact, you might be able to get parts and supplies to outfit your own system. If nothing else, go and play in a sandbox - you never know what you'll discover by playing around.

A longer run, with a little funk

I let the stream table run for over 2 hours straight yesterday. I would have an even longer video, but the flash card on my camera filled up. I really like how you can see small perturbations cancel each other out in some places and become amplified in others. In the words of Spock, "Fascinating."

Thurs-Demo:The first one with the stream table

There's a new addition to the Dirt Lab's inventory. We're the proud owners of a shiny Em2 stream table, manufactured by the folks at Little River Research & Design. Overall, I'm more than thrilled with the design and performance. I've spent the past week putting it through its paces and testing out some ideas for labs/demos for teaching and some research possibilities. I'll be adding more to this over time - the other bloggers who also have stream tables are invited to share ideas and perhaps we can have some kind of "users group" dedicated to extracting the most from these things. Maybe that's something that Google+ may actually be good for? Or perhaps with their redesigned site, perhaps the LRRD folks can provide a type of forum for these discussions.



Without much description, here are a few time lapse movies I shot over the last week. Each "run" was probably 1-2 hrs. The less "jumpy" ones were shot at 15 sec/frame while the others were made at 30 sec/frame. I shared a few previews on G+ last night and Steve Gough (LRRD's Prime Kahuna) mentioned a top-bottom view works better. Fortunately, iMovie lets me rotate the movie. So here's the adjusted film.

Cutting off the meanders

I ended up experimenting with making meanders today. I found that if you add just a little bit of extra "sand" to the lateral accretion areas (e.g. point bars) you end up producing very strong meanders. Particularly if you reduce the slope of the table.


Here's a shot of a few oxbow lakes being formed mid-run.


Here's a quick time-lapse video that demonstrates how adding extra material to the point bars rapidly increases the sinuosity of the stream. Keep in mind that the only thing I did here was to add sediment to areas of accretion. I didn't dig any channels or remove any material. I did have to add sediment along the floodplain in a few places to compensate for the change in gradient as the sinuosity increased.

Emriver setup

Before and after shots of the new stream table that arrived this week. If you look at the clock in the background, you can see that it only took me about an hour to set up. I'll have to provide more detail about setup and running the stream table.

IT'S ALIVE!!!

Yay of yays. The stream table has arrived.Oh the things you can think when you've got a new piece of equipment. I'm going to be shooing my colleagues out of my lab on a daily basis now...

Thurs-Demo: The extra one from LRRD

While at GSA in Minneapolis, the Little River Research & Design folks had a capacity crowd for the duration of the exhibitor hall hours. One of their demo runs included a lovely demonstration of levee failure:

Thurs-Demo: The one that never ends

I'm helping with a field trip today, so I'm posting this to (hopefully) automatically appear in about 12 hours...

The other week, I mentioned the interesting behavior of the flume/pump system I had set up. Changes in one direction did not follow the same pattern as changes in the other direction. I stated (and still think this may be the case) that this could be an example of hysteresis.

Happy Fossil Day!!!

Here's a little Dikelocephalus cephalon (trilobite head & "nose") for your viewing pleasure.

Stream Table Fascination

While I was at GSA, the most popular booth appeared to be Steve Gough and the folks at Little River Research & Design. Their stream table setups were among the busiest spots on the entire floor of the exhibitor hall. Steve posted a short time lapse video of the crowds (you may recognize some of the people in the film...)

Hopefully I'll get around to a more thorough recap - including meeting the faces behind some of my favorite geology blogs.

Back from GSA (for now)

Back from GSA. Or rather, I'm done going to the conference - I've got students to teach today. But I'm going to be talking about some geology tomorrow and Saturday for the field trip associated with the session at GSA. For those of you that were at the meeting, what did you think of the escalator setup?

I, for one, got stuck in a recursive loop for a time:

Friday Flume Fun

Earlier I posted about some interesting data that I got from setting up a simple flume/channel. At first I was rather excited - maybe there was some aspect of fluid dynamics that I was seeing (flow separation, turbulence, etc.). But this is SCIENCE!, so I have to be able to do a few more things before I can do anything more than speculate.

I hooked up another accelerometer to the pump's outlet (just above the water line) and was confronted with something I expected:


The blue line represents the accelerometer attached near the pump, and the red line is the accelerometer attached to the rain gutter flume. At first glance, it appears that the variation is all due to the pump. Changes in the blue line correspond quite directly with changes in the blue line (though smaller). As one goes up, so does the other. At this point, I was pretty convinced that the only thing I was observing in the first test was some behavior of the pump. But, correlation is not causation, so I looked at the data a little more closely:


Well, nothing really new, but the shapes of each "sine wave" is not quite symmetric. So what about just one wave?



Hmm... so, if each accelerometer changes in an identical way, I should expect that values of one curve will vary the same way as the other curve. If I plot values of one accelerometer against the values of the other accelerometer (at the same time interval) I should see a nice correlation - as one value increases, the other value will also increase (and decrease as the other decreases). So I plotted the values off the accelerometer attached to the pump versus the values off the accelerometer attached to the flume.


Okay, now we've got something a little more interesting than just wobbles produced by a water pump. There is clearly something more complex than a simple "change in one variable producing a change in another." You can see what look like two "clusters" of points. Changes in one variable correspond with two possible changes in another. The blue points are values from one accelerometer versus another as the values "fall" to more negative values, while the red points are values from when the values were increasing. Grabbing about 300 seconds worth of data makes this pattern even easier to see:



So, instead of just being some simple "noise" produced by the water pump, I've stumbled upon something a little more complex. In fact, this isn't a bad example of what's called a "non-linear" system. Specifically, I think this system is displaying "hysteresis." Where there are two possible values of a dependent variable, given one value of another. A change in the system (the water pump) causes another change (on the flume channel), but increasing changes behave differently than decreasing changes. There is complexity in the system, but it's not a complex setup. Two accelerometers dumping data to a computer, a pump, some water and a four-foot length of rain gutter is all you need.

Keep in mind, I have only begun what we could call "hypothesizing" here. I am not at a point where I could definitively point to a specific process or mechanism (beyond some kind of "change" in the water pump). Nor is this concept at the point where it goes beyond simply "explaining" a process to constructing a hypothesis that both explains observed behavior and predicts future behavior. In order to be true science, these criteria MUST be fulfilled. But I have preliminary data and observations. I have a few ideas of what might be going on.

Those of you following along at home might be aware that my treatment of the data (and hypothetical mechanisms) has been very shallow. I have not begun to really describe WHAT the accelerometers are measuring. Is it simply a subtle tilting to or away from vertical (thus increasing or decreasing the influence of gravitational acceleration)? Or is some of the acceleration coming from tiny impacts of flowing water or vibrations from the pump? And, of course, what is causing the apparent hysteresis? Is it some difference between increasing/decreasing flow and shear resistance from the water? I'm not sure, but as you can see, this stage of the study is generating lots of questions. That's good. The more questions that fall out now, the easier it will be to pull the system apart (literally and figuratively) to see what's going on. And then, perhaps, I can start to make explanations about what I'm seeing and make predictions about what I will see when I start to make additional changes. Changes like adding sediment.

Whew! That's a lot of thinking. And we haven't even begun to watch sediment transported as bedload yet. But, if you start diving into current research into papers like the one Brian Romans described, you can see what kinds of questions the researchers had to answer before they could even begin to try and account for sediment transport in streams.

So, what would you do next? Scale things up? Reduce complexity in the setup? Eliminate the pump? Why not all of them? And, of course, lets dump some sand in there, too. Keep in mind, this is "science" and if we are to truly understand this system, we must be able to both EXPLAIN what we observe, and PREDICT how the system will behave under different circumstances. Ideally, we'll be able to apply this idea to other systems (like real rivers). Or, at least, gain a better appreciation for complex behaviors.

Who's up for a little chaos theory?

Thurs-demo: The one that tried to listen to rivers

Brian Romans had a really neat post about "listening" to rivers a few weeks ago.




I had set up a demo to show some possible ways that we could "listen" to streams and arrive at some method of estimating bedload transport in streams. My set up was very simple. I had a short length of rain gutter stretched between two bins (one for water to flow into), an aquarium type pump, and some tubing to recycle the flow to the top of the rain gutter.

To "listen" to the river, I attached a microphone and an accelerometer from Vernier, hooked up to their Logger Pro software interface. The microphone was just a simple audio mic and it's range of frequency response was probably too fast (20 Hz) for a really good analysis (something around 1 - 10 Hz would be better, I think). The accelerometer was a simple, one-direction low-g unit. It's one of those that's sensitive enough that it will register a constant 9.8 m/s² acceleration due to gravity if oriented vertically. Here's a sketch of the setup:



I intended to run the setup once without any sediment in the channel to provide a "baseline" of what the system would look like without a load. Then I was going to run the system with a bunch of coarse sand in the channel to observe the difference in the "noise" produced by bedload. Well, my experiment didn't get that far. The "noise" that I recorded for just the flowing water produced a very regular sine wave:




So, being the curious sort that I am, I began to wonder what could cause this pattern in the acceleration (as measured by the small accelerometer mounted on the rain gutter). First, you can tell the accelerometer wasn't mounted perfectly vertical, since the initial (and post-water movement) measurements are only around 8.6 (it should read 9.8). But then there are times it goes up (acceleration increases) and times it goes down (acceleration decreases). The total length of the test was 60 seconds - if you carry out the sine wave a little further, you can fit about 6 "wavelengths" in that time frame. That means there was something changing with a frequency of about 10 hertz. Was it something in the sinuosity of the flow? Was the stream meandering across the channel enough to make the channel wobble and register on the accelerometer?



The graph above is the result of four tests. In order to find out what is going on, the easiest thing to do is manipulate a variable or two, and see how the system responds. The variables I could easily change were: pump output (High/Low) and incline of channel (gentle/steep). That gives me four different tests. Low+Gentle (dark green), Low+Steep (light green), High+Gentle (dark blue), High+Steep (light blue). So, what explanations can you think of? Is there a consistent pattern in the data? Is there a fundamental flaw in my setup? I'm not sure - but it sure is interesting.

(PS - this is often how science works. Something looks interesting and we start trying to find an explanation. A mechanism or process that explains the observations. Sometimes the initial ideas don't pan out. Sometimes the work takes off in an unintended direction. But that's part of the fun!)

The Wedge: Whaddya Wanna Know?

Anne Jefferson over at Highly Allochthonous (you know you're a geology geek if you can spell their blog correctly on the first try without checking) wants to know about geoscience education and careers. (Updated: thanks to Ron and Matt for pointing out an amusing error)

If you are a professor… what do you wish your students would ask? What do you think they should know, regardless of whether it is formally taught and assessed? Do you think we’re doing a good job preparing our students for think future jobs? What should you and I and other geosciences profs be doing better? Do you want to see more involvement from alumni or others in industry and government?

As an educator and scientist, I really can't bring myself to provide a "final" answer to that series of questions. For me, an answer to a question isn't the end - it's simply a node connected to more questions. It's like a subway. Each station might get you where you want to go, but there's always somewhere else you can go from there. You leave the subway, head up to the surface to go shopping or whatever, and you stop going places.

So my feeling is that, as college professors, we have to teach content. But it's easy to get lost in content. At my university, I don't have true "geology" majors, so I don't have students that will be taking a petrology course of some kind. The content that might be vital for giving students the necessary tools in a petrology course (like identifying a big batch of unknown minerals), isn't going to really be used by my students. But an understanding that rocks are made OF specific types of minerals (and if you really want to know more details, here's where to look) will help them appreciate the world around them and the work that geologists do.

In fact, the only details about minerals I point out as being important are:

• There are lots of different kinds of minerals and we can tell them apart by their physical and chemical characteristics


• Most minerals are "silicates" (contain the elements silicon and oxygen - the two most common elements in the earth's crust)


• Of the silicates some are typically dark in color and more dense (Mafic silicates)


• Other silicates are lighter in color and less dense - plus they are made of much more complex molecules (Felsic silicates)


• Some common minerals dissolve relatively easily in water and weak acids (like Carbonate minerals)


• Some minerals are simply Oxides (a metal like iron or aluminum combined with oxygen) "rust" is an example.


• Other minerals are made of just one element. Since we find these elements all by themselves, we call them "Native" elements (like diamond, graphite, copper, gold and sulfur).


• There are several other groups, some of these contain valuable elements - much of the stuff that makes your cell phone work the way it does depends on these rare elements

From this, my students have enough content to know a few details at the start, but - more importantly - they have a conceptual structure (the "scaffolding" in pedagogy talk) to place additional content. Like why volcanoes with mafic melt sources are fundamentally different than volcanoes with more felsic melt. Or why mafic rocks break down into oxides and simple clay minerals, while felsic rocks break down into quartz and more complex clay minerals. If students take my soils course later on, they have the most important details in-hand and we can talk about more details - like why soils that contain complex clay minerals behave differently than soils with simple clay minerals.

Ultimately, my goal is not to turn students into mini-factbooks, crammed with lots and lots of facts and details. Rather, I want students to appreciate that there are amazing and wonderful stories to be read from the earth. I want them to appreciate that there are important details, but they don't need all the details to begin reading the story. Many of us became geologists because they history of the earth itself was enthralling. We pulled together the important details later, as we dug deeper. The most important part was to be curious. To want to take the time and look in the first place. I certainly see this happening in some fields of geoscience education, but I think we could do more to engage and "hook" the non-geology majors with a desire to be curious.

I know that many undergraduates are coming in to college to learn Skill X to apply to Job Y. This is important, but only "right now." Things will change - so Skill X may be obsolete after a few years (perhaps even by the time you graduate). The Esri blog post about 5 skills every GIS specialist should have applies to many fields, not just careers in GIS.

For students, I want to say that it's okay if they forget the details after they take my course. But don't throw away that scaffolding. And don't stop trying to build onto those scaffolds in the future. To get back to the subway metaphor, you should want to keep going. You should get out at the stops and look around, maybe even buy a newspaper or nutroll or something and hang out. But get back on the train. Go somewhere else. Don't assume for a minute that once the train stops and the doors open that everything stops. Once you have an answer to a question, look at it. What other interesting questions does it generate? Keep asking questions.

Get back on the train.