Google Earth Images - the neighborhood

These 2 images show the small-scale elevation changes left by the wide braided river system I blogged about yesterday.  The snow accentuates the relief: in some places, deeper snow fills channels and they show up as brighter white traces.  In other places, the channels are darker - probably because on warmer days, they hold moisture that melts the snow.
Both are screenshots from Google Earth.  If you want to explore the area, search either for Randolph MN or Stanton MN.

Puddles, Gravels, Pebbles, Cobbles, and Knowing Too Much

 

We had a couple of warm days this week, and three big liquid pools appeared in the ice.  Three of them, just offshore of the back yard.  None of the neighbors has these windows to lake; in fact, the guy two doors down was still driving his pickup out to his ice fishing house the day the pools in the ice appeared.

At first I figured they were probably just puddles on top of the ice.  But they got bigger and bigger, and bluer, and then there were four of them.  On a warm afternoon this week, I walked out onto the dock to see them better.  Of course the dock is pulled up onshore in the back yard, the end of it resting on the sandy strip we’ll call the beach this summer, but it’s a good six feet off the ground right now,  so it’s a better vantage point for viewing the pools in the ice.  Even from there I couldn’t quite tell.  So I  climbed down to get some pebbles. Or maybe they were cobbles.  Pebbles, cobbles whatever.  Stones, for the purpose of throwing.  One missed the mark, and stopped on top of the ice just before it hit the water.  I threw the next one harder and sure enough, it disappeared with an extremely satisfied ka-gloop, sending wide ripples out to the edges of the pool.  Definitely not just a puddle, a gen-yoo-ine hole in the ice.  That meant the end of walking the dog on the lake, as far as I’m concerned, though he hasn’t quite agreed with me yet and keeps wanting to head in that direction on our daily walk.   But the next morning, the dozen or so ice fishing houses we could see from here were gone, and the collective human wisdom will prevail.  After all, we are taller and can throw rocks and therefore see better the distinction between puddle and open water.

So I’m thinking probably have some springs in our 150-ft slice of lake, pumping warmer groundwater upward under the ice.  If I am right, it is a wonderful stroke of luck, that just offshore of our backyard some springwater will be flowing upward, keeping our stretch a little cooler and a little cleaner than it would otherwise be this July. 

If I’m not right, and instead what’s seeping up under the ice is leakage from our septic system, then something very different will be going on out there in July. Probably something very different, and unpleasantly green and soupy, will be happening by April.   

This is science at its best:  you see how I did that? I created multiple working hypotheses.  Testable in a few short months.  Clear water or green soup.  The trick will be to remain objective if one of the testable hypotheses turns into stinky and expensive  disaster.

Today is bright and cold and back down to the 20’s and a few ice fishermen are out again, but without their houses.  They walked out, and they’re just sitting on buckets on the ice.   The pools are shrinking today, and may ice up again before tonight’s storm hits.

I don’t know what will stand out for my readers in the preceding story (probably the stinky and expensive green soup), but for me what sticks is my inability to just call the stones I threw in the puddle “stones.”  I’ll tell you, there are some very wonderful things about knowing a thing or two or three about geology, but there are some irritations too and one of them is that I have to force myself to use the word “stones.” 

The things I picked up off the ground to toss into the pools of water are, technically speaking, pebbles, but big ones, almost big enough to be cobbles.  In the world of geology, and particularly in the world of sedimentology (the specialization of my training), the distinction lies at 64 mm.  Or if you prefer, 2.5 inches. Or, if you are reading this because you are one of the extra-lucky few people who know about Krumbein’s Phi Scale (maybe even because I taught it to you), right around φ = -6.[1]  The stone still sitting on the ice out back looks to be just about exactly that, as was the one that is now at the bottom of the lake.  So, you see, I am stuck not knowing quite what to call them.  Pebbles or Cobbles. 

Anyone who has spent too much time in school specializing in one thing or another runs into this trouble.  I imagine some astronomers are unable to see constellations as the rest of us can, knowing (as they do) that Alnilam, the center star in Orion’s belt,  is a blue-white supergiant, 1300 light-years away, much farther than Mintaka (900 light years) or Alnitak (800).  And that Alnitak itself is three stars, one of them a blue supergiant.  Already, see, there’s really no possibility of simply seeing these three stars in a straight line in the sky ever again.   You know too much.

My sister the Latin scholar posted on Facebook today something I did not know, but now do:  that the word “science” derives from a word meaning “to know.”  Now that I know that, it’s not too far a stretch to see why for many people the word “scientist” means “know-it-all.”  And not in a good way.

But the rewards of knowing a few things about science are usually worth these minor annoyances, annoyances like not being able to use a perfectly good word like “stone,” or not being able to see Orion’s belt as a two dimensional line ever again. 

In the case of my back yard, the pebbles, or cobbles, are part of a much bigger picture, a wonderful unlikely story.  A really big story actually, about a wide gravelly rush of melted  glacier that came charging through what is now the Cannon River Valley on its way to the Mississippi.  The big river flowed through steep rapids and drops, constantly tumbling and shifting all of this gravel from one side of the valley to the other, keeping any encroaching tundra vegetation to a minimum, and eroding away the edges of the white sandy hills at the valley’s edges. For a few hundred years, this river was probably most dramatic during the summer, when the ice was melting.  Glacial melting would have slowed or even stopped during the cold winter months.

Eventually, though, summer by summer, the glaciers that covered Minnesota with a mile-thick slab of ice finished melting.  Then, the wide, wild river calmed and narrowed to the trickle of its former self we call the Cannon.

How do I know it was fast, and steep, and powerful?  Because slow flat lazy rivers don’t move cobbles.  They move mud and silt, and during spring floods, maybe some sand.  Consider this 1902 photo of a gravel-bedded braided river in Alaska.  Imagine the mountains in the background are huge melting blocks of ice.  Now you're close to the picture I have in my head. 

http://commons.wikimedia.org/wiki/File:Alaska_Floodplain_1902.jpg

 If I can figure out how to post a Google Earth image to this blog, I’ll show you what the ground looks like along the road to our house – it’s a myriad of low ridges and sluiceways, running roughly parallel to the course of the Cannon, that made up the gravel bars and channels of the wide braid plain of the pre-Cannon riverway.

 Now the mile-wide gravel plain underlies the well-tamed towns of Stanton and Randolph, the Stanton airstrip, the Syngenta experimental fields, and the irrigated cornfields of the big farm on the corner by our house.  Irrigated because gravelly soil is well-drained soil -- too well drained to grow corn without extra water. *

So this is what science does, at least for me.  It takes me from the pebble I tossed off the dock to this image of an Alaskan river, and puts it right in my back yard, with a brief detail to Krumbeins logarithmic phi scale.  Not bad for an afternoon of blogging.  

It's a good thing, this knowing.  

---

[1]Okay, if you truly want to know:   use this formula,

D = D₀2 ^{− φ}
where D is the diameter of the particle in question and D_o is a reference diameter of 1 mm. 

The value on the phi scale is the exponent of 2 that gets you to the diameter of interest times (-1).Why the multiplication by (-1)? It’s a convenience invented for the majority of sedimentologists, who deal more often with particles smaller than 1mm.  The gravel and conglomerate aficionados, like me, just put up with negative phi values, happy to know we are in the minority, and no one is trying to hone in on our macroscopic turf.  

*Also just a little too well drained for me to ignore the possibility that my septic drainfield may seeping warm water below the house’s foundation and out to springs under the lake. I'll keep you posted.  Check back at Stork Raving in three or four months. 

Ephemeral Winged

An adult mayfly.  Image Source.

 

A student in one of my classes rafted down the Mississippi River last summer, and made a movie about it.   I don’t know much about the journey, and the film isn’t done yet, but as you might imagine, this is a student whose mental wheels are always in motion.  In class last night, during a lecture-turned-conversation about population biology, she asked if I knew anything about the millions of insects that rose from the river, clouded the air for a few days, then disappeared.  Mayflies, I said.

What I knew last night about mayflies will fill this short paragraph.  They hatch all at once, they live as adults for a day or two, they mate, they lay eggs, they die.  All of them at once.

After I described what I know about the life cycle of  mayflies, another student asked the obvious:  “What’s the point?”

If I were an ecologist, or an evolutionary biologist, or had just about any different credentials for teaching about populations and ecosystems than the ones I have, I might have had an easier answer, which might have involved an explanation of the genetic drive to pro-create.  And if I were a little more new-agey in my professor persona, I might have appealed to an explanation about the nature of the life-force, the chi of the mayfly.  But my intellectual training didn’t feed me either of these lines of argument.  I scanned my brain for anything else I might possibly know about the Mayfly.  I came up with this extra data:

They’re a bit bigger and bulkier than a dragon fly, but not pretty, brown with long transparent wings. I have an image from my childhood of a small clear lake in Michigan’s Upper Peninsula, its clean sandy bottom littered with millions of dead mayflies. That’s it.

Nope, I said, as far as I could tell, no point at all.  A younger, more idealistic group of students might have been dismayed, even horrified, by this answer, and I might have spent the rest of the semester back-pedaling, apologetically trying to work the philosophy of It all in to the rest of the course, trying to demonstrate that the world isn’t a harsh careless no-point-at-all kind of place.  But my students now are hard working-night-school-attending adults, and not afraid of harsh real-world answers.  “nope, no point at all” was a perfectly satisfactory answer for most of them, and instead of dismay or despair on their faces I saw chuckles, sighs, acceptance.  One student helpfully suggested: well I suppose they feed the fish and birds while they’re at it.  I agreed. 

But this morning I am left with the feeling of a good question not fully answered.  So I Googled:  Mayflies, meaning of life.

Image Source

I was surprised, as I often am by Google, at how many hits this query produced. A fellow blogger finds the meaning of Mayfly life in getting them to transfer from a tree to himself.¹ 




But I had to keep looking. 

And I have learned a lot in the past hour.  It all fills the next long paragraph.

The mayfly is not a single species, but an entire taxonomic Order called Ephemeroptera.  Ephemeral, winged.  Those taxonomists who came up with the name for this Order knew how to get to the heart of things.  But mayflies actually go through multiple life stages, and only the final stage is ephemeral, and winged.  The eggs hatch into nymphs, and some species go through as many as 28 separate nymphal stages. The nymphal stages can last up to four years. This starts to look like a pretty rich life.  As nymphs, they can eat, swim, and be eaten. Some species burrow, others live under rocks. Doubtless if they wanted to, these nymphs could form meaningful bonds with other nymphs, could appreciate the beauty and peril and joys of their nymph-ness, looking forward to future life stages, including contemplating their species’ imperatives to swim or burrow or live under rocks, harboring envy or hatred or unrequited love for other species of nymphs.  But it’s doubtful that they would want to.  Another Google search -- Mayfly consciousness – does yield some interesting links to the possibility that honeybees have enough neural networks to be able to count ².  Not quite the level of self-awareness we have in mind if we want the Mayflies to find meaning in their lives.  But certainly their brains are big enough for mayfly purposes.  Importantly, their brains are sufficiently large and sophisticated that they can sense the perfect conditions for moving into the next phase of life, a collective urge strong enough to bring their selves to the water’s surface en masse, to become full-fledged full-winged adult mayflies, hungry for survival of the species.

I admit, I am a little less dismayed or horrified (idealistic youngster that I am) by the brevity and singularity of purpose of their short adult lives.  Even though it is unlikely, these nymphal stages comfort that part of my imagination that wants there to be more to it .  If the Mayfly’s life has any meaning for us, it may be simply that while the end goal is vitally important for survival, the rich, multi-phased nymphal processes of getting there are where it’s at. 

¹http://www.blogsmonroe.com/nature/2010/06/they%E2%80%99re-baaack/

² http://www.dailymail.co.uk/sciencetech/article-1228661/Insects-consciousness-able-count-claim-experts.html