Saturday, February 11, 2017

Does Kamchatka belong to North America?

On this traditional map of tectonic plates, Kamchatka belongs to North America
This past week has been a week of science -- Wednesday was "Day of Science" in Russia.  Russia has "Days of" many things, there is a Geologists Day, a Day of Volcanology, a day of the city of Petropavlovsk-Kamchatksiy, a Day of Fishermen,... and TODAY--Sunday 12 February--is a national day for healthy life, with skiing, Tanya says over 1.5 million people nationwide have registered for (cross-country) skiing events.  Avoiding the crowds, we went yesterday, when they were still setting trail and putting up bleachers at the ski center outside the city.

And I have learned that yesterday (11 February--ok, that's actually "today" at this point in the Americas) was/is International Day of Women and Girls in Science, declared by the United Nations. UN on women and girls in science.  I've blogged in the past about this topic.  For example Russian Women Geoscientists and from Hokkaido University, Girls be Ambitious!

For Science Day at the Institute of Volcanology and Seismology, which is part of the Far East Division of the Russian Academy of Science (FED RAS), the director, Akademik E.I. Gordeev gave an introduction, which Tanya partially translated for me; I can understand words and sometimes gist, but commonly lose track and give up.... He talked about the state of the Institute and read the names of those receiving special commendation this year; he announced that everyone would be getting a 5000-ruble bonus, which caused a happy rustle in the auditorium.  Then the owner of the Shamsa supermarkets (I call him "Mr. Shamsa") pronounced some congratulations and presented us with a huge basket of fruit.

There were then three scientific talks, the first by a close colleague, Andrey Kozhurin, on tectonic geomorphology; I could understand much of it and discussed it with him later. The second talk was about HSE elements in Kamchatka petrology (I asked Tanya what were HSE, she didn't know, I just now looked it up on Google--highly siderophile elements).  He also used PGE, which I did figure out as platinum group elements.  I didn't understand much at all of that talk, but perked up when a map of the Kamchatskiy Peninsula was shown--one of our major stomping grounds.  The third talk was about seismic monitoring, with some details on recent Zhupanovsky volcanic activity and on the remarkably deep 2013 Sea of Okhotsk earthquake (Mw 8.3).  Then there was an archival movie about "volcanoes and life" -- it was quite romantic; I think it focused on 1970s Tolbachik eruptions; there was poetry composed and recited by one of the narrators, an Akademik volcanologist whose name I forget -- lots of facial hair.

9 Feb 2017 meeting at IVS with some young scientists;
more about them individually, later
On Thursday I met for the second time with our "young scientists" group (I have defined "young" as younger than I am 👵).  I gave a presentation entitled, "Does Kamchatka belong to North America?" -- an important plate tectonic question addressed by some of our group's research and publications.  When we submitted a manuscript to Geology with a long, convoluted title -- about an extruding Okhotsk block and coastal neotectonics -- the editors asked for a catchier title, and I came up with "Does Kamchatka belong to North America?", which, when the paper came out in 2006, gave us headlines around the world.  Here is just one example.  You can Google for more, and find a pdf of the article on Tanya's IVS site.  
Jody's photo.  Upper left to lower right:  Slava Sokolovsky,
Katya Kravshunovskaya (RIP), Vitya Morozov, Sasha
Storcheus (RIP), Kevin Pedoja, Viviana Alvarez, Tanya
Pinegina, Vanya Storcheus, Misha Egorov.

The first author of the paper is Kevin Pedoja, now a professor in Normandy, France.  This photo is from our Ozernoi field season, which was a classic in many ways, not least of which were the gourmet meals we had from fresh salmon, caviar, shellfish, wild fowl, mushrooms, berries, ... kak zhizn! (what a life!).  While Tanya's and my paleotsuanami group spent our time on low beach ridges, Kevin and Vitya (Morozov) would run up to the high terraces to get elevations and make observations.  This involved challenging bushwacking and not-uncommon bear encounters.  Then Kevin would become our "French chef" in the evening.

Here is the basic puzzle:  
The plate boundary between North America and Eurasia is well defined in the Atlantic (white line in picture to left); the mid-Atlantic ridge marks where the two plates move away from each other.  That ridge continues up into the Arctic, but loses character off Siberia.  There is not another distinct plate boundary between that endpoint and the boundary of the Pacific oceanic plate, which is subducting beneath the Aleutians and along the Japan-Kuril-Kamchatka (JKK) trench.

Our basic null hypothesis was that if Kamchatka belongs to the North American plate, then there should not be tectonic activity north of where the Aleutian chain collides with Kamchatka, which is also where the JKK subduction zone ends (the corner in the red line, above).  We have subsequently published two longer articles about this collision zone. By the way, Hokkaido and northern Honshu would also be part of the North America plate in this traditional model (see map at top of blog).  In recent years, other plates have been proposed in this area, including the Okhotsk plate, which has been relatively well accepted by now, and the Bering plate, which is not as well accepted.
In the 3-plate, older model, North America
encompasses Kamchatka, the Sea of Okhotsk,
and northern Japan.  We can call this our
"null hypothesis."
In the newer, 4- or 5-plate model, the Okhotsk plate
is being squeezed where Europe and North America come
together, pushing it (and thus Kamchatka)
 toward the east/southeast.

Much of our Kamchatka field work has focused on the area at and north of the Pacific "corner"  There have been some large historic earthquakes along this border, some tsunamigenic, which tends to support a 4- or 5-plate model.  As paleoseismologists, we have found a relatively high frequency of tsunami deposits in this region, comparable to or higher than some other subduction zones.  And as neotectonicists, we have found uplifted marine terraces that show significant rates of uplift indicative not of the tectonic quiescence one would expect in the three-plate model, our null hypothesis.  So, if you ask us, "Does Kamchatka belong to North America?" our answer would be NO.
Photo by Kevin Pedoja of (labeled) uplifted terraces north of the terminus of the Kuril-Kamchatka subduction zone.

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