Yesterday, I showed you these photos...



...and asked you to guess what they reminded me of.

Man, there were some great ideas people pitched forward! I was really impressed. One person even came up with the same idea that occurred to me!

Okay, so clearly what we've got here is a puddle that's drying up right? Some leaves and other botanical debris fell into the puddle and has thus become concentrated in this spot.

The pattern I noticed was a linear pile of debris [consisting mainly of the woody little "petals" of the tulip tree (Liriodendron tulipifera) "flower"] as well as a dark color due to being damp. The edge of the damp patch parallels the edge of the linear tulip tree debris field. I think the way this formed was that in the puddle's earlier (larger) state, it was deep enough for the tulip tree "petals" to float, and wind pushed them all over to the same side of the puddle (the southern edge). As the puddle dried out, this stranded flotsam preserves either an earlier "shoreline" or an offshore parallel to the shoreline. (The second possibility would apply if the "petals" were too big to get pushed all the way to the actual shoreline: they may run aground some distance "offshore.")

This brought to mind the relationship between a continental ice sheet and the end moraine it leaves* behind. Glaciers expanded outward, reach their maximum size, stay there for some amount of time, flowing along and depositing a scum of debris all along their edges. Later, they melt back, or possibly melt away entirely. However, the debris belt marks how far out they once reached. Here's a geological equivalent, in a map** showing end moraines (green) in Minnesota, Iowa, and South Dakota:


As the moraine marks the former extent of the glacier, so too does the stranded line of tulip tree flotsam mark the former extent of the puddle. Fresh from my lectures on glaciation and the Ice Ages, I got the sense I was looking from west to east across North America, seeing Canada recently scraped clean (wet areas) and the far-right ("south") accumulation of tulip tree petals morphed in my mind into a terminal moraine complex.

The main problem with this analogy: puddles are standing water, not flowing ice. Still, I can't help but see a similarity in process, regardless of the huge differences in scale and materials. I see the world through geology-colored glasses.
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* no pun intended
** From the U.S.G.S.'s "Glacial map of the U.S. east of the Rockies, west half" (1959)," via here

Labels: analogies, contest, glacial landforms, glaciation, iowa, minnesota, nova, plants, south dakota

Nevada's Yucca Mountain site for a proposed nuclear waste repository has lost much of its funding in President Obama's proposed budget. Personally, I think this is a good call - I never thought that the Yucca Mountain site seemed viable for the geological long-term. For a facility being designed to outlast human civilization (warning signs are not written in English, but in sign language that's predicted to still be useful when potential meddlers show up 10,000 years from now), Yucca Mountain is located in too tectonically-active an area for my liking. Basin and Range extension, with associated earthquakes and volcanism, imperils the facility's security over the long-term.

But then where do we put this nuclear waste? We've got more and more of it every day. I'm a fan of nuclear energy because I feel that in spite of the risks associated with radioactive leaks, it's a proven technology that looks better all the time because it produces no carbon emissions. To me, the relatively short-term (local) risk of radiation leaks is outweighed by CO2's long-term (global) risk of climate change. Provided sufficient security, I think it's a great "halfway house" between fossil fuels and 'alternative' energies like solar, wind, and geothermal.

Yucca Mountain has several advantages in terms of its location: it's dry, and it's not in someone's backyard (far from large populations -- though Los Vegas residents might quibble with the definition of "far"). But Nevada's regular seismic shaking (3rd in rank among the U.S. states, after California and Alaska) and the proximity of some young volcanic extrusions make me think it's not so great a spot if you want the waste to stay put. I'm thinking that the best place for nuclear waste would be in the craton, the stable interior of the continent. I'm thinking: Canadian Shield, maybe in Minnesota or Michigan or Wisconsin. The issue there is water: you would be trading tectonic stability for saturation and precipitation.

I'll readily admit I'm not an expert here -- just a geologist speculating on an issue that's more complex than mere geology. What do you think? Where's the best place to store nuclear waste until radioactive decay makes it reasonably safe? Use 10,000 years as your hypothetical timeline, bearing in mind how different the world is today than it was 10,000 years ago.

Labels: CO2, earthquakes, energy, environmental, michigan, minnesota, nevada, volcano, wisconsin