The opinions expressed here are well-reasoned and insightful -- needless to say they are not the opinions of my employers

16 December 2009

Who can believe a scientist?

Dave Petley already wrote about Richard Alley's talk on climate feedbacks; aside from reiterating his call for everyone to go to the archive and watch the webcast, I have nothing to add except that I wish I could tell a story half as well as Richard...

I also attended Leo Hinzman's lecture on arctic hydrology and permafrost response to climate change, and an education session this morning on climate literacy and communication with the public. I think it was Steve Newton from the National Center for Science Education, giving a talk entitled Creationism and Climate Change, that threw me over the edge.

OK, I admit it -- I saw 2012. My story (and I'm sticking to it) is that I had several students in my intro astronomy class (and one or two in my geology classes) ask me the "plausibility" question. I told them that there were several factual elements in the movie: people in the United States do, in fact, speak a form of the english language; there are places in the United States called California and Yellowstone National Park (though they seem to be a lot closer together in the movie than in real life -- I would take all of my classes to Yellowstone if the trip out-and-back were as short as it is for John Cusack and his kids); and geologists are, in fact, heroic figures everyone should look up to.

But, I assure them, everything else you see in this movie is fantasy: the idea that the Mayans predicted the end of the world, that neutrinos could evolve into anything other than different types of neutrinos, that a tsunami generated even by a magnitude 9 earthquake could swamp a ship in the middle of the ocean, or that a tsunami generated by any earthquake could swamp the Himalayan plateau. But now all of that seems incredibly plausible to me compared with the biggest fantasy the movie throws at us: that a single scientist (or a few scientists) could come to the world's leaders with news of an impending environmental disaster and the leaders respond with focus and determination. OK, with focus and determination to save themselves and their rich benefactors, but there was not one call for additional study, or an ad hominem attack on the scientists, or lobbying campaign suggesting that the end of the world was "just a theory," etc...

Roland Emmerich has digitally destroyed cities across America (OK, mostly LA, New York and DC) and the world in Independence Day, The Day After Tomorrow, and 2012. But his greatest CGI sleight of hand is creating worlds where people listen to warnings from scientists...

15 December 2009

Pseudo-plutonic rocks of Moscone South

Granodiorite: low mafics, plagioclase dominant.

Granite: quartz and orthoclase.

Gabbro (?): mafics dominate, apparently as aesthetic choice to include orthoclase.

14 December 2009

AGU, monday night

I attended a session on early solar system dynamics this morning. It included a talk on orbital eccentricity and distance (and how they change as the sun loses mass) in which the author concluded that the Oort cloud cannot exist, but I need to look more closely at his numbers before I comment on any of it. Suffice it to say I'm a fan of the Oort cloud with its long period comets and highly inclined orbits...

One interesting talk was Age of the Solar System Revisited (Wadhwa and Bouvier). Someone once suggested that the age of earth is a function of time. In his Universe Song, Eric Idle quotes some numbers about size, velocity, mass, and sheer number of stars that reflected the knowledge at that time. In a recent interview his co-author, acknowledging that some of the numbers were understood to be different now, offered that "the facts have changed." "No", Idle replied, "the facts haven't changed -- our understanding of the facts has changed."

Our understanding of the age of the earth is based on the age of meteorites. Radiometric dating of meteorites depends on the same key assumptions as dating of other types of rocks, the key assumption being that we're dealing with a system that has been closed since the event we're trying to date.

The formation of planets from smaller planetessimals implies a fair amount of alteration, and at least part of our understanding of earth's composition is based on the existence of meteorites derived from asteroids that went partially down the planet-forming path -- that is, they became large enough and hot enough to differentiate into a core and mantle. So dating any old meteorite fragment won't do.

A significant fraction, perhaps 90%, of interplanetary debris contain chondrules (from the Greek chondros, meaning grain). these tiny particles consist of mostly devitrified silica-glass droplets, and the meteoritic bodies that contain them (called chondrites) have the appearance of sedimentary rocks. The cooling history of the grains supports the idea that chondrites are formed by the agglomeration of smaller solid particles, as the chondrules cannot have been cooled from a melt to form a rounded droplet within the meteoroid. Chondrules, in fact, appear to be among the oldest solid particles within the solar system. I say among the oldest because chondritic meteorites also contain Calcium-Aluminum-rich inclusions (CAIs, which include, but are not limited to, anorthite and pyroxene) that formed at higher temperatures, and pre-date the formation of the chondrules by perhaps 2 million years.

In this talk the authors look at the results from sampling CAIs from several carbonaceous chondrites (these are chondrites that not only contain small amounts of volatiles, but their refractory composition is close to 1:1 with that of the sun). these samples give dates varying from 4.5676 +- 0.001 to 4.5687 +- 0.002 billion years based on Pb-Pb isochrons. the same meteorites yielded more consistent model ages using Al-Mg and Hf-W systematics. The group claims that there is a yet unidentified problem with Pb-Pb system in these meteorites, suggesting that perhaps the problem is that the initial 238U:235U ratios are not as consistent from sample to sample as has been assumed.

AGU, monday morning

I arrived in San Francisco last night at around 5. First let me praise technology -- there was a time when any long drive between population centers meant fumbling with CDs/cassettes/8-tracks (yes, I remember those: I also remember a two-week period when 4-track tapes were going to replace albums altogether, like the big album-sized laser disks, BetaMax, DAT, etc...), or listening to Rush or Dr. Laura for 3-4 hours. Turns out now that, sucky as AT&Ts 3G service is supposed to be, I can pick up internet radio on my iPhone anywhere along I-5, so I just tuned in KCRW and it was like any rainy Sunday afternoon except with people on cell phones driving 80 mph (130 kph) trying to kill me (oh, and the coffee's better at home)...

Stopped in at Moscone to pick up my badge because I knew that this morning would be a complete zoo and as it turns out, I arrive
d just as the ice breaker was starting:

photo of the lines at pre-registration...

photo of the line for beer...

...I remember a time when December meant badgering my parents about all of the stuff I wanted (I'd rant about our consumer culture but I started out the post praising my iPhone), the anticipation of getting up on Christmas morning, the crash in the evening (sugar? tryptophan?).

In my 20s I worked at the Post Office, and Decembers were filled with existential dread: 80+ hour work weeks, made even worse when I went back to school and the Christmas rush coincided with the end of the term.

But for the past 20 years December is the Fall meeting in San Francisco. It's the big one for lots of geoscientists (prediction is up to 16,000 this year), but for students in northern California it is usually where you spent most of finals week, giving your first poster and/or talk, showing up to support your peers even when you only marginally understood their presentation (generally it was either over my head, or they gave a 15-minute talk in 6.5 minutes, or some combination of the two).

My friends from grad school are literally spread around the globe now so part of the meeting is about reconnecting (Santa Cruz reunion at the Thirsty Bear tomorrow night) -- and seeing their students' first posters and talks.

I know that I will hear people complain that the meeting is too big, that it's exhausting to spend the week listening to talk after talk, visiting poster after poster (especially towards the end of the week), but I also know that some people don't get enough and append additional days to the festivities with courses or field trips, or with additional talks (as an undergrad I spent some time as a gopher for the Gilbert Club).

My experience for the past 13-14 years has been teaching mostly intro material, and these meetings give me the chance to reconnect with what attracted me to the geosciences in the first place: being surrounded by people, like me (but way smarter), curious about how the universe works.

Instead of just going to talks related directly to some specific field I'm working in, I plan my week around topics that interest me, whether it's the tectonics of the Himalayas, climate feedbacks, or geologic research in the rest of the solar system. Many of the invited lectures are now webcasts, and most are also recorded and archived on the AGU website. Examples over the first two days are the Whipple lecture this afternoon at 4:00 on Mars exploration, tomorrow's Bjerknes lecture at 1:40 on the history of CO2 and climate and Wednesday's Sagan lecture on the melding of biogeochemical and astrobiological research with environmental science (I would link to the abstracts but I can't quite get it to work). I always go back home energized and ready to teach

More later...

Contact Me

You can send me email at jrepka@saddleback.edu