Plate Tectonics and the Earthquake in Japan

The magnitude 8.9 earthquake that devastated coastal areas in Japan shows up very clearly on the United States Geologic Survey’s recent earthquake page.

earthquake-japan — The big red square marks an aftershock of the magnitude 8.9 earthquake off Japan. (Image via USGS). Note that most of the earthquakes occur around the edge of the Pacific Ocean (and the Pacific Plate).

Based on our studies of plate tectonics, we can see why Japan is so prone to earthquakes, and we can also see why the earthquake occurred exactly where it did.

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The obvious trench to the east and the mountains and volcanoes of the Japanese islands indicate that this is a convergent margin. The Pacific plate is moving westward and being subducted beneath the northern part of Japan, which is on the Okhotsk Plate.

japan-plates — The tectonic plates and their boundaries surrounding Japan. The epicenter of the earthquake is along the convergent margin where the Pacific Plate is being subducted beneath the Okhotsk Plate. Image adapted from Wikimedia Commons user Sting.

The epicenter of the earthquake is on the offshore shelf, and not in the trench. Earthquakes are caused by breaking and movement of rocks along the faultline where the two plates collide.

In cross-section the convergent margin would look something like this:

convergence-japan — Diagram showing the tectonic plate movement beneath Japan. Note the location of the earthquake is beneath the offshore shelf and not in the trench.

The shaking of the sea-floor from the earthquake creates the tsunamis.

So where are there similar tectonic environments (convergent margins)? You can use the Google Map above to identify trenches and mountain ranges around the world that indicate converging plates, or Wikimedia Commons user Sting’s very detailed map, which I’ve taken the liberty of highlighting the convergent margins (the blue lines with teeth are standard geologists’ markings for faults and, in this case, show the direction of subduction):

Tectonic_plates_boundaries_detailed-en-conv — Convergent plate boundaries (highlighted blue lines) shown on a world map of tectonic boundaries. The blue lines with teeth are standard geologic symbols for faults, with the teeth showing the direction of the fault underground. Image adapted from Wikimedia Commons user Sting.

The Daily Dish has a good collection of media relating to the effects of the quake, including footage of the tsunami inundating coastal areas.

Cars being washed away along city streets:

Our thoughts remain with the people of Japan.

UPDATES:

1. Alan Taylor has collected some poignant pictures of the flooding and fires caused by the tsunami and earthquake. TotallyCoolPix has two pages dedicated to the tsunami so far (here and here).

2. Emily Rauhala summarizes Japan’s history of preparing for this type of disaster. They’ve done a lot.

3. Mar 12, 2011. 2:10 GMT: I’ve updated the post to add the map of the tectonic plates surrounding Japan.

4. A CNN interview that includes video of the explosion at the Fukushima nuclear power plant (my full post here).

5. NOAA has an amazing image showing the tsunami wave heights.

680_20110311-TsunamiWaveHeight — Tsunami wave heights modeled by NOAA. Note the colors only go up to 2 meters. The maximum wave heights (shown in black in this image), near the earthquake epicenter, were over 6 meters.

They also have an excellent animation showing the tsunami moving across the Pacific Ocean. (My post with more details here).

6. The United States Geological Survey (USGS) put out a podcast on the day of the earthquake that has interviews with two specialists knowledgeable about the earthquake and the subsequent tsunami, respectively. Over 250 kilometers of coastline moved in the earthquake which is why the tsunami was so big. They also have a shakemap, that shows the area affected by the earthquake.

shake-map — USGS ShakeMap for the earthquake. Image via the USGS.

7. ABC News (Australia) and Google have before and after pictures.

8. The University of Hawaii has a page about, Why you can’t surf a tsunami.

9. A detailed article on earthquake warning systems, among which, “Japan’s system is among the most advanced”, was recently posted in Scientific American.

10. Mar 15, 2011. 9:15 GMT: I’ve added a map of tectonic boundaries highlighting convergent margins.

shinmoedake-eruption — Shinmoedake Volcano.

11. The Shinmoedake Volcano erupted two days after the earthquake, but they may be unrelated.

guardian-reactor-status — Fukushima reactor status as of March 16th, 5:00 pm GMT from the Guardian live blog.

12. The Guardian’s live blog has good, up-to-date information on the status of the nuclear reactors at Fukushima.

Human Evolution not Drawn as a Tree?

Razib Kahn has a fascinating interview with Milford Wolpoff, one of the main scientists behind the research that argues that humans are not all part of a single family tree, descended from a single ancestor who moved out of Africa about 200,000 years ago.

This section focuses on the theory, and has a nice explanation of what mitochondrial DNA is (and why it’s important):

It gives an excellent perspective on how science works, and how scientists work (scientists are people too with all the problems that entails).

The entire thing is a bit dense, but it’s one of the better discussions I’ve seen describing the process of science in action, with little hints at all the challenges that arise from personality conflicts and competing theories.

Jurassic Park: Web of Issues

Well we watched Jurassic Park last night and concluded it with a discussion about the issues underlying the movie, the same way we’ve been studying analyzing the issues underlying texts. Discrimination based on race and obesity came up first (the fat guy and the black people “always” die), but I was able to coax a bit of discussion about the role and responsibility of science and scientists. Our discussion is summarized in the graphic organizer above, but there are many more subtexts to the story that we did not have time to explore.

I like both the movie and the book because, like most good science fiction, they explore some interesting issues that relate quite nicely to the curriculum. Jurassic Park has a nice little introduction to DNA and gene sequencing that is tied to some the history of life on Earth. As works of art in their respective fields, however, I prefer the movie. The novel has a lot of wonderful detail, and the scientist in me loves the detail, but the characters are not as well drawn and the story seldom strays from its main thesis, scientific hubris. What it has to say about that issue is well expressed and well researched so it does capture the interest of the reader. (The follow-up book, “The Lost World”, sails adrift of the science, is logically incoherent and has a proportionate deterioration in the quality of the writing.) I do however recommend the original Jurassic Park book to my students as a personal novel.

Steven Spielberg makes a great movie, extracting empathetic performances from the actors. Since the book’s author, Michael Crichton, also wrote the screenplay, the movie stays true to the core issues in the text. I think its a great example of a successful, dare I say synergistic, collaboration.

Tomorrow, instead of retelling around the issues in writing, my students are going to try to do so in a skit. This could get interesting.

Synthesizing the history of life

Sparking curiosity with the Toilet Paper Timeline, then following up with the beautifully drawn Cartoon History of the Universe seemed to work pretty well to keep students interested and engaged in their work. However, in putting it all together in their presentations we needed a simple graphic organizer to point out the highlights.

The History of Life on Earth timeline I put together to start with gives the broad overview, but we need to telescope the Cambrian to observe the really interesting, broad patterns in the evolution of multicellular life.

There are two key ideas I want students to get from these exercises. The first is what the Montessori lessons call the Gifts of the Phylum, which boils down to the fact that different Phyla represent major milestones in evolutionary development. For example, Cnidaria, the phylum of jellyfish, are important evolutionarily because they mark the emergence of organisms with endoderms and exoderms.

The second important concept regards the cycles of extinction and diversification that can be found in the fossil record. Dinosaurs emerge after the Permian-Triassic extinction event and diversify; large and small species, carnivorous and herbivorous, land based and ocean based. Similarly, after the Cretaceous-Tertiary extinction wipes out the dinosaurs, mammals take over and diversify to fill all the empty niches; elephants and mice, tigers and gazelles, rinos and whales.

Toilet Paper Timeline in practice

tp-02 — Who thinks they're at the most important event?

The Toilet Paper Timeline of Earth History worked as well as I’d hoped. The beginning was a bit boring, it was a challenge keeping the kids focused, since nothing much happens for a very long time. It helped that we had to unroll the toilet paper back and forth across the room, so I had a different student take over every time we had to turn around.

That was not quite enough though to keep them from getting distracted, however, so I also assigned people to stand at the location of major events. This worked out nicely in the end because it let me ask them, at the end, whose event was the most important? Most of them made some argument without any prompting; the group is already pretty comfortable with each other and are not afraid of speaking up.

During the unrolling, most events occur in the final two turns. Students did notice this fact, which is the ultimate point of the exercise. Getting them to talk about different events, like the time of the first multicellular organisms or the extinction of the dinosaurs, helped students own the work. All together, it seemed to strike their imaginations.

They also seem to like using Cartoon History of the Universe as their reading assignment.

tp-01 — The Pre-Cambrian. Nothing much happens for a long, long time.

Toilet Paper Timeline of Earth History

Toiletpapier — Image from Wikimedia Commons.

Jennifer Wenner has posted a beautiful demonstration of geologic time using toilet paper for the timeline at SERC. You’ll need a 1000 sheet roll and by the time you’re done there will be toilet paper everywhere.

This is a great demonstration because as you unroll the toilet paper you get a great feel for the long spans of time in the preCambrian when nothing much happens, and then, as you approach the present, events occur faster and faster. There’s 300 million years between the formation of the Moon and the formation of the Earth’s atmosphere. That’s 60 sheets! while modern man only turns up about 10,000 years ago, which is 0.002 sheets; about the width of the line drawn by a pen. Even the dinosaurs went extinct only 14 sheets from the end.

The SERC webpage has a spreadsheet with most of the important dates marked and translated into toilet paper units. The Worsley school in Canada has some nice pictures of the toilet paper being rolled out all the way down the hall.

Earth_timeline — History of life on Earth timeline (from NASA).

Timeline of life

This year the theme is life. My central organizing structure is the timeline of life on Earth. I plan to link all of the discussions of taxonomy, phylogeny and genetics to this timeline over the course of the year.

The timeline above will be the first lesson. As with these things the trick is deciding how much detail to keep in and how much to keep out.

What I like is that it gives the general overview of when important things happen while leaving a lot of space for students to investigate. Most of what we’ll be seeing this year happened in the Cambrian and this timeline conveys that this is a very small part of the whole history of life. In fact, it’s only when we cover the biochemistry of genetics that we will be talking about the origins of life.

earth_nucleobases — From the Exploring Earth's Origins website.

The website Exploring Life’s Origins has a great timeline. It also has some really neat sections, with very useful videos, on the formation of protocells and the origin of RNA on the early Earth that lead to life as we know it.

The Magnetic Field?

The one thing I left out that I’m still conflicted about is the Earth’s magnetic field. Recent research indicates it has been around since 3.2 billion years ago and its presence or absence may have had profound effects on life.

Having a magnetic field protects the Earth from the charged particles spewing out of the Sun, the solar wind. This makes life on land a lot easier since the solar wind’s particles are quite damaging to DNA. However, prior to the magnetic field forming all this damage to DNA may have also accelerated mutation and thus evolution.

Scientists tracking oil plumes

filter-1140m-watermk1 — Filter after 10L of plume water was passed through it -- visible oil! (from Joye, 2010)

As oil continues to leak from the damaged well in the Gulf of Mexico and the surface slick is affecting more and more of the coastline, scientists now using research vessels to track the underwater plumes spreading at depth throughout the gulf.

station34b_watermark — Dissolved oxygen, CDOM and beam attenuation with depth (from Joye, 2010).

Satellite imagery from NASA only shows what’s at the surface. To find the underwater plumes, researchers on boats lower instruments on cables that measure the chemistry of the water. Certain chemicals, like colored dissolved organic matter (CDOM) are produced when there is a lot of oil in the water.

Dr. Samantha Joye, from the University of Georgia, is the lead scientist on one such vessel. She started the Gulf Oil Blog where she describes her ongoing work in the gulf and answers readers questions. It is an excellent resource. A great demonstration of science in action, working on a practical problem but using techniques and methods developed over time for answering more abstract questions.