Our major goals for this class are to cover (1) two major topics, Convergent Boundaries and Hot Spots, in a bit more detail than the videos did, and (2) to provide an overview of the material we have covered in this class.
Everything apart from the overview is enumerated in the notes for Class No. 7.
Your combination of keen attention and mellow amiability has made our association with this group a great pleasure for us. Thank you, all, very much.
We’ll begin the class by viewing the video episode on Iceland. Then our Iceland native, Hildur, will take us through a photo tour assembled from contributions of several people in the class. Continue reading
The videos we’ve been watching in class are from the History Channel series How the Earth Was Made. The copies I have are DVDs I purchased from Amazon. The two season-length series consist of 13 episodes each and cost $20 apiece; the pilot program is 94 minutes long and cost about $17 for the single DVD. I’ve put some links to them below as well as a list of the individual episodes.
Hildur has been buying individual episodes from iTunes for $2 each which is a bargain if you want fewer than 10 episodes from a season. Continue reading
Most of class 5 will be devoted to a visit from Marjorie Gale, a Geologist and Environmental Scientist with the Vermont Geological Survey. Ms. Gale will discuss local geology and it’s relation to plate tectonics and the new bedrock geologic map of Vermont, as well as other topics of her choosing. We will provide ample time for discussion, so bring any geologic issues of interest to you, including rock samples.
The website Ars Technica has this summary of an article in Nature Geoscience by a team of scientists who built a scale model of the Pacific Northwest in an attempt to explain some paradoxical features of the area’s complex tectonics. Although the results from a scale model may not be definitive, in this case they’re very interesting and the (short) Ars Technica article is well worth reading. Continue reading
(Dodd originally posted this as a comment where I was afraid it would pass unnoticed. I moved it up here as a post where the whole world could benefit.)
It’s exciting to see how all of this slo-mo geological movement is playing out day by day in real time while we’re reading about plate collisions. Tuesday’s earthquake in Iran is explained as resulting from collision of the Arabian and Eurasian plates, described here:
The next three classes, apart from Marjorie Gale’s talk on April 17 and Hildur’s discussion of Iceland, will be devoted to inspecting the major phenomena associated with, and explained by, plate tectonics (with the exception of hotspots and plumes which we will discuss in the seventh meeting on May 1). The first of these classes, April 10, will focus on divergent boundaries such as mid-ocean ridges.
These three classes will cover pages 29-46 in This Dynamic Earth. You can spread this out any way that suits you: one possibility is to read through page 35 for Wednesday, through page 42 the Wednesday after, and page 46 for the third Wednesday.
In this comment Dodd points to a recent paper in Nature that proposes a reevaluation of how western North America was assembled by a series of plate tectonic events over the last 200 Myr. Dodd’s comment includes a link to a press release describing the research in plain language. Hildur sent a link to a different release about the same paper.
The paper’s results look very interesting and I will try to be ready to summarize them by the time we get to the topic of convergent boundaries in class – sometime in the next three classes. (The argument in the paper itself is complex and depends upon the recent availability of massive amounts of seismic data in the western U.S. I may have to fake it.) In the meantime, for the hardy souls among us (or if you’re just curious to take a look at a modern scientific paper on plate tectonics) our document repository has a copy of the paper in a file named nature12019.pdf.
In This Dynamic Earth, read pages 14-28. This assignment begins to cover the accumulation of data and insight that ultimately turned the unprovable idea of continental drift into the modern paradigm of plate tectonics. It leads us through the importance of ocean-floor bathymetric (depth) mapping and the central concept of polar reversals and ocean-bottom magnetic striping. It then discusses seafloor-spreading and exploring the deep ocean floor. It includes a short portrait of Harry Hess, who was known by several members of the class, and some nice photos of ocean-bottom exploration.
In class we will finish our tour of the large-scale features of the Earth and focus on topics related to plate tectonics. We will survey the geodynamo, the source of the Earth’s magnetic field, and how its behavior provided important markers for plate tectonics. We will discuss sea-floor spreading in some detail, including the nature of seismic (earthquake) activity near mid-ocean ridges.
A news release from the Scripps Institute of Oceanography, a part of the University of California at San Diego, included the below image of the huge magma chamber beneath a portion of the northern East Pacific Rise, a mid-ocean ridge where new crust is being formed. Continue reading
This list was provided by the Education Department of the Montshire Museum of Science. It’s oriented toward general earth sciences. It overlaps our other lists somewhat, partly because we used this document while developing the study group cirriculum. Continue reading
We’ll finish the map exercise we began last class. We will rearrange ourselves temporarily to form new groups with members from each of the data specialties. These new groups will look for features that show up in more than one data type (such as seismic and topographic data). Finally each group will offer a brief summary of their findings and we will collectively try to synthesize a consensus. (Many of you know part or all of the answers we hope to find; please do your best to forget what you know. (Age helps here.))
Following all that we will take a tour of the large-scale features of our planet, including its composition with depth and some aspects of its material behavior. Plate tectonics tends to focus on the Earth’s outermost regions: we hope to show you how that fits in to the larger picture.
In This Dynamic Earth, read the Preface (page 0) and Historical perspective (pages 1-13) for this week. That will carry you through the parts about the ill-fated Prof. Wegener and polar dinosaurs in Australia. Many of you will elect to read ahead; if you do so, reflect on how the processes discussed in the book manifest themselves in the data maps we are working with. (I realize I just ended a sentence with a preposition; my excuse is that its complement was consumed by a subducting clause.)
Bring $5.50 if you want to purchase a copy of “This Dynamic Earth”. You have the option of downloading it from here but the government-printed hardcopy is very nice. The price includes the shipping cost and $0.03 cents extra which we will donate to the ILEAD coffee fund. (The USGS gave us an educational price break; usually the publication is $7.00 plus shipping.)
The first class will begin with a discussion of the history of continental drift, the precursor to plate tectonics. (If you can’t wait, the material is covered in some detail here.) After that we’ll begin an exercise with a variety of maps, based on the materials from Rice University offered here. The map work will likely bleed over into the second class.
We will post, from time to time, links to the sources we used in developing the
course study group curriculum.
- Historical Links
- Educational Materials
The above image shows the age of the oceanic crust in an area roughly centered on the equator and the Americas: red represents the youngest crust and blue the oldest. Both the Mid-Atlantic Ridge and the East Pacific Rise, regions producing new oceanic crust, stand out clearly. The image is taken from a figure on the Wikipedia page for Oceanic Crust, in turn based on a figure by NOAA.
The bar under the header image contains several buttons:
- Home – a button to take you back to the blog (here)
- Syllabus – a button to take you to the latest version of the syllabus (the formatting is a little baroque)