Terrestrial Sedimentary Systems (February 5 & 7)

This week we continue our discussion of the sedimentology of desert systems. (You’ll have to just endure my enthusiasm for deserts.) To fully sample my joy, I simply must link you to the Wooster Geologists blog entries for our field trips to the Mojave Desert. You may also want to see posts from our geological field trips in the Negev Desert of southern Israel. There are some other more spectacular desert geology websites. Start with the USGS page set on the geology and resources of deserts. The Great Sand Dunes National Monument also has superb geology sections, as does Death Valley National Park. Here is a nice site for Space Shuttle photographs of the Atacama Desert in Chile. The DesertUSAcommercial site will introduce you to other desert pages and images.

Let’s take a moment to remember, as we did in class, a geological and military hero: Ralph Bagnold. He was a pioneering geologist, particularly in deserts. He was also a significant contributor to the Allied victory over the Italians and Germans in North Africa during World War II.

For fluvial systems, here is the Wikipedia page on alluvium (note links within to other specific pages). Here’s a video of a flash flood in southern Utah. (Don’t mess with flash floods!) Here’s another with a drone perspective. Note that people don’t drown as much in flash floods as they get pummeled to death by debris. Be safe out there.

NASA has an extraordinary website called “The Visible Earth“. It is a diverse and large set of satellite and Space Shuttle images of the Earth’s surface, all searchable. Look for views of deserts from space.

Please note again the Geology Department Writing Webpage, the link to which is always on the right side of this page.

Finally, Test #1 will be on Thursday, February 14. As a sample of what to expect, here is a pdf of the 2017 first Sed Strat test. We will not have covered all the same topics, so some questions in that test are on material we may not do this year.

Sand from Kelso Sand Dunes, Mojave Desert, California. (Click to enlarge.)

Geology in the News –

We live in an anti-science age in which scientists and scientific ideas have lost considerable credibility with the public. Here is an interesting take on why we should not call this a “war on science”as so many do. Such aggressive language usually has a negative effect on audiences. What we should do to restore respect for the scientific method and discourse is unclear.

Here is a related study of the public attitudes towards science these days. When it comes to assessing evidence, “people think more like lawyers than scientists“. It is not education levels, knowledge, or even interest in science — people often cherry-pick those “facts” that support their preconceptions. It is the end of the Enlightenment Age.

NASA has released Hubble Space Telescope images showing “the farthest-ever view” of the Universe. Stunning. A triumph of science, creativity and investment. Beautiful perspective, too.


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Principles of Stratigraphy — Introduction (January 29 & 31)

It is difficult to construct an interesting page on stratigraphy. So many lecture outlines, so few useful pages. The Geology and Geological Time page of the University of California, Berkeley, is not bad as an introduction, especially for those of you with just one previous geology course. You can always practice your stratigraphic skills with this elaborate dating assignment you can download and then cut into little cards. (I wouldn’t bother, but maybe you have a roommate with little to do?) Visit Jurassic Tank, an experimental stratigraphy apparatus at the University of Minnesota. This detailed website on the geology of the south-central coast of England is also a very good example of stratigraphy in action (and where I had many students doing fieldwork years ago). For future reference you may want to download a pdf of the latest GSA time scale. Suitable for posting in a room or carrel! For the lab, you can’t beat these brief descriptions and images of sedimentary structures from Wikipedia.

Wadi sediments in Death Valley, California. (Click to enlarge)

Geology in the News –

Earth’s oldest rock was apparently found on the Moon by Apollo 14 astronauts. It is about 4.1 billion years old and was blasted off the Earth by a giant impact. You know there’s a good story here.

The Earth’s magnetic field  is acting strangely of late, and geologists are puzzled. We depend on the magnetic field to protect us from very harsh solar radiation, so this is a bit concerning.

The headline says it well: “People with extreme anti-science views know the least, but think they know the most: study.” No surprise.

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Sediments and Sedimentary Processes II (January 22 & 24)

How can I make sedimentary dynamics, at least the statistical parts, interesting? The Web doesn’t help much. We could learn a bit about Sir George Gabriel Stokes (1819-1903) of Stokes’ Law. Most of the web material, though, consists of calculating pages for the Reynolds Number and the Froude Number, and the details of the Bernoulli Effect and Hjulstrom’s Diagram. Fortunately the US Government has livened things up a bit with a series of Quicktime movies of sedimentary bedforms in action, along with more than you want to know about bedform classes. This is a very nice presentation — you have many viewing choices. The USGS also provides downloadable code and software for simulating ripple and dune bedforms and crossbedding. We’ll have more pretty pictures and movies when we begin studying particular sedimentary environments.

Time to begin thinking about your research project for your paper. We’ll talk about your ideas in lab. Please download the list of 2019 Potential Research Paper Topics and the included form to turn in to me during your lab this week.

Here is a blog post I wrote on our glorious Ro-Tap sieving shaker system.

Sediment plume from DeGeerladen, south shore of Isfjorden, Svalbard, Norway. (Click image for larger view.)

Geology in the News –

The Universe Is Disappearing, And There’s Nothing We Can Do To Stop It.” A dramatic headline that is certainly true. This is a good article in Forbesdiscussing modern ideas of cosmology. The future looks very cold and dark, but at least it is a long time from now!

Interesting idea about extending the Anthropocene concept to Mars(and I would think the Moon as well). This would be the first time an interval of Earth’s geologic time scale (although Anthropocene is not yet approved) to another planet. The Anthropocene is essentially dated as the interval from the time humans first leave a geological record.

Poaching of African elephants for their ivory is apparently producing genetic changes in their populations that favor offspring without tusks. This is a brutal but effective demonstration of selection leading to evolutionary change.

For a lighter touch, puzzle out the origins of giant spinning ice disks!

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Sediments and Sedimentary Processes I (January 15 & 17)

A thorough understanding of geologic time is fundamental in any geology course, and it is especially critical in Sedimentology & Stratigraphy. Because time scales change, I will hand out in class (as part of your first lab) our version of the Geological Time Scale. You will see that I recognize the Ediacaran Period before the Cambrian, and the Paleogene and Neogene instead of the old Tertiary. Remember that geologists make a crucial distinction between relative and absolute time, which is usually calculated radiometrically. Radiocarbon dating is a special case of radiometric dating. (Note that I’m a fan of Wikipedia. If an article there is inaccurate, we can fix it!)

Here’s a page that you may use often this semester: Internet Resources for Sedimentary Geologists (with only a few annoying dead links). It is a bit outdated, but you will still see the range of studies within sedimentary geology, from the interface with chemistry (low-temperature diagenesis) to the combination of sediments and biology (ichnology), along with plate tectonics, radiometric dating, sequence stratigraphy, and paleoenvironmental interpretations.

Our lectures and labs on the fabrics and textures of sediments and sedimentary rocks are not thrilling, although I’ll work hard on them! Here’s a clever graphic for the Udden-Wentworth grain-size scale. The Wikipedia page on grain sizes is very good. (And if it wasn’t, we’d make sure to fix it!)

Middle Triassic marginal marine sequence, southwestern Utah. (Click for larger view.)

Geology in the News —

On New Year’s Day, NASA’s New Horizons spacecraft flew by and photographed the most distant object observed in our Solar System: Ultima Thule. It’s a binary object looking a bit like a snowman. It is apparently reddish in true color. It will take 20 months for all the data collected to be received on Earth. Amazing.

We all know that the asteroid that slammed into the Chicxulub region 66 million years ago generated a huge tsunami that devastated southern North America. Now the global spread of this tsunami has been modeled. May we never see the likes of this in our species’ time!

The Little Ice Age ended more than a century ago, but cold seawater still lingers from that time. Cold waters that were once on the surface of the Pacific have been found very deep, and they’re still sinking. The Earth System responds to climate change on a wide range of time scales.


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