Wednesday at AGU

A post by Chris RowanChris: Wasn’t it the first of your two invited talks this morning? How did it go?


A post by Anne JeffersonAnne: It went well. Even though I hadn’t managed to run through the presentation out loud beforehand, I hit the final slide with 20 seconds before the light came on, and a couple of people stuck around until after the session to ask questions and give feedback. Plus, the other talks in my session were really cool. I learned about catastrophic ecosystem shifts, landscape controls on net ecosystem productivity, a sedge that behaves like a boulder, and all sorts of neat connections between water, landforms, and life that I hadn’t known much about before.

What did you do this morning?

Chris: Good question. I started off this morning going to a workshop on NSF funding.

Anne: That sounds useful. Any pro tips?

Chris:It was more a good introduction to the complexities of the US funding system, but they did start off by trying to dispel pessimistic rumors about funding levels. The program officers all seem to think it’s a great time to get good geoscience done.

Later in the morning, I sat in a session on the challenges of interpreting rock magnetic records from sediment cores. It’s quite fast and easy to measure things like magnetic mineral concentration and grain size, which can theoretically act as proxies for environmental changes that effect sediment source and supply. Unfortunately, magnetic minerals also tend to be highly sensitive to redox conditions, which means that any environmental signal is convolved with a strong diagenetic filter that can drastically alter the original record. Most of the talks emphasised how difficult it can be to see through the effects of diagnenesis. However, the session ended on a positive note by introducing a potentially cool new source of high resolution magnetic records – from stalagmites in cave systems.

What did you move onto after your talk session concluded?

Anne:In a way I had a nice transition into thinking about my talk for Thursday. I ended up in the poster hall vortex, unexpectedly looking at volcano geomorphology posters. I watched Gordon Grant get very excited about critical flow in molten lava, and I was pleased to see Brian Romans’ fantastic picture of standing waves on the poster. Then I learned what happens when a pyroclastic density current falls off a cliff. After a working lunch, my brain needed a rest and found solace in the geomorphology corner of the exhibit hall, where within the space of a few short meters I found the Emriver stream table, the National Center for Earth Surface Dynamics delta model, and the St. Anthony Falls Lab high-resolution terrain scanner. After that I was ready to head back to talks, and a funny thing happened.

Chris: Oh? What’s that?

Anne: I ran into you.

Chris: Ah, yes. We both decided to attend the Birch Lecture, given by Michael Manga. I believe I was grumbling a bit after sitting through the latest episode of ‘nobody ever believes the paleomagnetists’ in the companion session to my poster session yesterday. Lots of presentations trying to understand the tectonic forces that caused the bend in the Hawaii-Emperor hotspot chain 50 million years ago, when the paleomagnetic data show clearly it’s more to do with the hotspot moving – or ceasing to move – than any change in the motion of the Pacific plate. We’ll convince them eventually – if you can get both of us attending the same talk at AGU, anything can happen.

Fortunately, I soon got into Michael Manga’s very interesting discussion of the hydrological effects of distant earthquakes. It was actually rather impressive seeing how the transient stress produced by the passage of seismic waves could produce large and permanent changes in groundwater flow. It certainly provides some insight into how similar changes, deeper underground, could affect volcanic and earthquake activity.

Anne: [Evil laughter] I knew I’d corrupt you eventually. It’ll be groundwater flow modeling for you next! The earthquake hydrology stuff was quite interesting, but I know the big draw of that talk was Manga’s work on Lusi, the Indonesia mud volcano. Maybe there will be an update on his latest calculations, and what Lusi is doing lately, on this blog at some point?

Chris: I did find it a rather ironic counterpoint that his work on Lusi is all about disproving an earthquake connection – which he did, fairly convincingly. As for an update post, we’ll have to see; he did point to some newly published calculations on the potential longevity of Lusi’s eruption (there’s a 50% chance it will continue for another 50 years) which may be worth looking into.

But first, I have to survive the rest of the conference.

Anne: At least you don’t have to give another talk tomorrow morning.

Chris: True enough. Good luck!

[NB: This is a repost. A server failure at our hosts meant the original was lost.]

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