Monday, February 25, 2008

Geohmms (Accretionary Wedge 6)

Welcome to the 6th thrust-repeated section of the Accretionary Wedge. The theme this time was “Hmm.” Things about our planet that intrigue y’all. Geologists have a tendency to work on all sorts of scales, and this is reflected in this month’s entries. Sadly, though, the smaller scales were conspicuously underrepresented. Nobody is dying to know about crystal defects, space groups, or microinclusions. We are, apparently, macroscale thinkers or larger.

In fact, the smallest scale object that interesting people this month was a word. A recent GSA Today article made a new case for the Anthropocene, and the digital cuttlefish, not merely satisfied with a hmm, wrote an entire poem.

Despite the lack of comments there, the rest of the GBS had plenty to say, and none of it was hmm.
Callan offered a detailed explanation of the paper. BrianS calls it “more of a PR stunt than a rigorous scientific idea.” Andrew quotes Walt Whitman. Greg Laden says no. Chris gives some background and perspective on subdividing geologic time before suggesting that renaming might be premature. Maria calls the Anthropocene unbearably narcissistic, shortly before claiming to be partial to the term. BrianR expressed exasperation that semantics can get everyone is such a tiff. And Tom simply notes the news without comment. Note that Apparent Dip and I, both isotope geochemists, made no comment. After all, ages are properly measured in numbers, not names.

For all the hubbub, you’d think it was a four letter word, not a four syllable one.

Moving on, we scale up from the word to the student. Sciencewoman wonders- and expresses concern (more of a HMm that a hmMm) about the lack of racial diversity in her upper level classes.

Looking at the population as a whole rather than in his class, MJC Rocks wonders why people in general are not fascinated by geology. His post in accompanied by a classic field photo.

And that is it for the language/ people / culture scale hmms. From here, we step back down to the mineral.

Silver Fox wonders about some blue quartz that she remembers from her youth. Unfortunately, her favorite outcrop seems to have been covered by a leach pit.

On the laboratory scale, Maria is curious what, if anything, a neutral buoyancy experiment tells her about real systems.

Now, step up to the outcrop.

Sandstone, Interrupted! has Hypocentre puzzled by the discontinuity of his favorite bed.

Ron is wondering if his fault might swing both ways, but only preserve the medial sandstone on one side.

And the bigger faults are also intriguing. Harmonic Tremors is interested in the pre-periodic period of the Parkwood section of the San Andreas fault. He’s even lucky enough to have gotten a reference in the comments.

On the volcano scale, Chris wonders why Mt. Taranaki is so far west, relative to the rest of New Zealand’s volcanoes. I’ve only seen Taranaki from the plane, and my reaction was more of an Oooo than a Hmm, but I see his point, and suggest that he read up on Japanese volcano locations, as I seem to recall northern Honshu has two rows of volcanoes, and many run-on sentences. While the distance from the subduction zone will in part explain the increased alkalinity (deeper melting zone), it doesn’t explain why there is only one such volcano, nor why it is so pretty.

But I’m not the only one to look out a plane window. Mel said hmm all the way to her ski holiday, while traversing the snow-covered NW United States and SW Canada.

And anonymous Chris wondered about “rivers of stone” reported by Darwin in the Falklands.

Moving up to the plateau scale, Andrew presents new research on the Colorado River prior to the grand canyon formation.

And Chris Rowan wonders about the crinkly microplate style tectonics that happens where plated are grinding past or under each other.

On the hemispherical climate scale, Kim wants to know why an excessively sinuous jet stream is bringing her so much snow, while Callan wonders about global climactic and chemical implications of the hypothetical snowball Earth.

Dropping back down in size by a factor of 2 to a smaller planet, Jeannette is curious about magnetic anomalies on Mars, and what the tectonic implications are. Luckily for her, Chris Rowan blogged about this very topic, back before hmm was a fashionable thing to say.

Finally, on the galactic* scale, I’m curious about what makes our home planet the way it is. And how different planetary formation can be before it produces something completely unrecognizable.

So, there’s the list. Several people have already been lucky enough to get replies in their blogs. So if you are also intrigued by any of these things, wander on over, and see if you can help out a fellow geoblogospheroid.

I think the next installment of this carnival is Geology in the Movies by Magma cum Laude, but we should probably get her to confirm that before we bury her in rants.

[edit: two new late entries added]

*e.g. data-poor.


Garry Hayes said...

Great job, great topic! Thanks for hosting this month.

Ron Schott said...
This comment has been removed by the author.
Ron Schott said...

Great job, Chuck. Just one thing... you can add my name as a geochronologist/isotope geochemist who has nothing to say about the Anthropocene. I did a fair amount of U/Pb zircon dating and isotope geochemistry on conglomerate clasts for my Ph.D. thesis.

Kim said...

After all, ages are properly measured in numbers, not names.

Hear, hear!

(That would be the reason why I wasn't aware that the Tertiary was officially gone.)

I can see a geochronology vs stratigraphy duel in the geoblogosphere's future. (I wonder what weapons each side would pick? Isotopes vs mud? Though I guess Brian R would have to pass on it, since he has worked with both.)

(Nice job, Chuck.)

C W Magee said...

Can I just add "et al."?

Jessica Ball said...

I confirm Geology/ists in the Movies for next month. I'm setting the due date as Easter Sunday (the 23rd), so I can post on John Wesley Powell's birthday. I'll put up a post later today so people can link or email their submissions.

Jessica Ball said...
This comment has been removed by the author.
Jessica Ball said...

Whoops...let's try this again. Here is the next call for posts.

Andrew Alden, Oakland Geology blog said...

Since is shutting down my blog, I've put my entry into a new page here.

Unknown said...

Chris, there is something that REALLY makes me go hmmm... it is the nature of the Canadian kimberlites. A kimberlitic explosion is violent enough to send something into orbit, according to many reports. And we don't have such volcanos any more. And they tend to occur in pipes of a couple acres, when they do occur.

But the kimberlites of Canada occur in dikes, in a giant circle around the Hudson Bay, 850 mi in radius. Moreover, that circle is broken where its edge intersects the edge of Canada, where Greenland left. But if you look over at Greenland, you'll find that Greenland also has kimberlites, and they continue the giant circle.

The structure looks to me like a giant shatter ring, like if you google-images 'bullet through glass', and the shatter ring appears to align in the Permian.

But the Ca