Posted by Chris M Wednesday, November 21, 2007

Teaching climate change

I am lecturing the introductory level Physical Geography this fall and the last week of the class (3 lectures) is devoted to climate change. I have had several discussion with my teaching colleagues about how to teach it. Of all the things the students will learn, this may be the most important. Of course, I would like them to remember everything, but that seems unlikely. The biggest thing I would want them to take away is not the finer points of climate change, but why we know them. Those of us that are daily involved in doing science often forget that most of the public, including college students, don't have a good understanding about how science is done. The idea of the lone person in a lab coat still reigns. A lot of the popular opposition to anthropogenic climate change has to do with powerful misunderstandings about this.

All of My Faults Are Stress Related did a couple posts about how to teach climate change to students. Sadly given the level of my students (very few are science majors) I don't think a discussion would work. My idea is to talk about the past climate and climate change first. Show them the various types of evidence used from many different techniques and types of scientists. The evidence doesn't point different directions, but converges on an accept view of what the climate was like in the past. Only after this will I talk about present climate change. Then using the same lines of evidence that were discussed before, show them that the climate is now changing primarily because of the actions of us humans. Then end with some predictions about how the world will be different in the future.

There are some excellent resources available, including the IPCC reports, real climate, and nice images at global warming art (see image below) which should make my job easier.

CO2 over time

Posted by Chris M Wednesday, November 14, 2007


September saw the first edition of The Accretionary Wedge, which I took part in. However, I wasn't able to write anything for the second one. The subject of the third edition caught my attention. "Geology and Life", aka "Between a Rock and a Squishy Face" to be hosted by The Other 95%. After I thought about it I decided not to write about my thesis topic. I have just started writing my thesis yesterday and could use a break. Well, technically I haven't start, but instead spent time getting emacs/auctex just right and rsync working for daily backups (aka wasting time). I promise I will start tomorrow. ;-)

Termite MoundAnyways, I thought of another subject that would be perfect and I have an interest. Zoogeomorpholgy is the study of the impacts of animals on the landscape. Man is the most obvious geomorphic agent. Some of our actions are only important on short temporal scales of our perspective, but others will surely be found in the geological record in the future. Removal of natural vegetation cover increases erosion resulting in an larger sediment fluxes entering oceans [1]. Anthropogenic climate change will also have an influence on geomorphology. However, for this I want to focus on non-human animals. A comprehensive review of this subject is available in the book Zoogeomorphology by David Butler [2]. Termite mounds, crayfish burrows (>40,000 kg per hectare), birds ingesting sediment for use in their gizzards, animal paths to salt licks, and rabbit holes are only a sampling of geomorphic roles animals can play. I am going to focus on American Beavers (Castor canadensis) and Gray Whales (Eschrichtius robustus).

Termite MoundBeavers use mixtures of wood and mud to make dams across streams to create ponds. These dams vary greatly in size, with largest dam reported at 652 m long, although they are more typically tens of meters in length [1]. They can store large amounts of sediment. Researchers examining streams in a Quebec, Canada, found that an average size single dam could store 6,000 cubic meters of sediment [3]. Over a watershed of hundreds of square km, this could be on the magnitude of hundreds of thousands. Using estimations of pre-European contact beaver numbers, sediment stored behind beaver dams in North America is greater than 100 billion cubic meters [4]. After dams are abandoned, the ponds often form new valley floors.

In terms of hydrology, beaver dams also raise the local water table. Finally, dam burst can cause extreme floods, greatly affecting stream morphology. Butler reported a dam burst that increased flow 1000 times over normal rates and moving 1 m granite rocks. This flood ended up killing four people. A dam burst in the Sierra Nevada Mts in California resulted in a dramatic drop in local base level and an associated .5 m of stream channel incision [5].

Gray WhaleOne of the more surprising examples of zoogeomorphology is the action of Gray Whale (Eschrichtius robustus) feeding. They winter near Baja California, but migrate to the Chukchi and Bering Seas between Alaska and Siberia during the Arctic summer. This is the longest mammalian migration in the world. In the Arctic sea, they feed on benthic crustaceans, or those that live in or on the sea floor. Using their mouths, gray whales scoop sediment from the sea-bottom. The sediment filtered via baleen, although some is ingest along with crustaceans. This filtered sediment is released near the surface in plumes. Off the California coast, researchers found that in areas of only a few square km, gray whales moved hundreds of tons of sediment [6]. In the Bering Sea, it has been calculated that 120 million cubic meters of sediment is moved by gray whales every year. This is 3 times the annual load of the Yukon River, that also empties into the sea [2].

[1]: Walling, D.E. (2006). Human impact on land–ocean sediment transfer by the world's rivers. Geomorphology 79:192-216.
[2]: Butler, D. (1995). Zoogeomorphology. Animals as Geomorphic Agents. Cambridge University Press.
[3]: Naiman, R., Melillo, J., Hobbie, J. (1986). Ecosystem Alteration of Boreal Forest Streams by Beaver (Castor Canadensis). Ecology 67:1254-1269.
[4]: Butler, D., Malanson, G. (2005). The geomorphic influences of beaver dams and failures of beaver dams. Geomorphology 71:48-60.
[5]: Kondolf, G., Cada, G., Sale, M., Felando, T. (1991). Distribution and stability of potential salmonid spawning gravels in steep boulder-bed streams of the eastern Sierra Nevada. Transactions of the American Fisheries Society 120:177-186.
[6]: Cacchoine, D., Drake, D., Field, M., Tate, G. (1987). Sea-floor gouges caused by migrating gray whales off northern California. Continental Shelf Research 7:553–560.

Image Sources:
Termite mound: Litchfield Park - Termite Mound by Daryl Fritz
Beaver: Beaver by Tancread
Gray Whale: Gray Whale by NMFS

Posted by Chris M Monday, November 12, 2007

Angel Falls Overlook

It had been over a year since I last went to Big South Fork so I thought I would go back. The geology of the area is nearly horizontal laying Mississippian and Pennsylvanian aged sandstones and shales. The Cumberland Plateau's topograph in the area is relatively flat, but becomes quite steep and rugged in streams and rivers valleys. Not only has the Big South Fork of the Cumberland River has cut a deep valley, but even small streams quickly cut down (a sample topomap shows this clearly). This results in the largest natural arches in the eastern US, rock-shelters, and cliffs. The first image is of the Angel Falls overlook from a ridge to the west. The next two images are of the Big South Fork from Angel Falls overlook, the third one is a panorama made with hugin). The last one is a site with some interesting weathering.

Angel Falls Overlook Big South Fork Angel Falls Weathering

There is interesting ecology present too. Drier sites are a mixture of White Pine (Pinus strobus), Pitch Pine (Pinus rigida), Virginia Pine (Pinus virginiana), White Oak (Quercus alba), Scarlet Oak (Quercus coccinea), and under-stories of Mountain Laurel (Kalmia latifolia) as shown in the first image. The second image shows a tough Virginia Pine hanging on a cliff and the third a photogenic Common Buckeye butterfly (Junonia coenia).

Big South Fork Forest Pinus virginiana Junonia coenia

Finally, the park has many signs of past human activities, from Native American to European settlers to industrial logging and coal mining. The last image shows the house and English-style barn built around 1900 by John Litton.

John Litton Farm

Posted by Chris M Saturday, November 10, 2007

Another step done...

I passed my comps this week. Now all I have to do is write the actual thesis...... doh.

Posted by Chris M Sunday, November 4, 2007

Big Fodderstack

Last year on November 4, I went to Little Fodderstack in Cherokee National Forest. I thought this November 3 I would go see its neighbor, Big Fodderstack. This fall has been much warmer and drier so I didn't know what to expect. Both of these images are of Brush Mountain, from different sides. Big Fodderstack is visible in the background of the first one.
Brush Mountain Brush Mountain

After spending so much time in wet, cool, and dark cove forests doing my thesis field work, I enjoy going to open oak-pine forest. There was a nice variation in forest composition, based on altitude and location on the ridge. Near the valleys, there were numerous Chestnut Oak (Quercus prinus) and White Pine (Pinus strobus). On closer inspected, I noticed a few Shortleaf pine (Pinus echinata), although most were dead or dying as the more shade tolerant White pine finally made it to the canopy. Further up the ridge, Virginia Pine (Pinus virginiana) dominated, although they too were being replaced. There were also a great number of Black Oak (Quercus velutina), a species I am not very acquainted with. The understory was dominated by Sourwood (Oxydendrum arboreum) which was flame red in color. I was also surprised by the large quantity of American Chestnut (Castanea dentata) sprouts, some up to 20 ft.
White Pine Fall Colors American Chestnut

The trail doesn't go all the way to the top of Fodderstack, although a bushwhack pretty easily gets you there. It is marked by a cairn and a USGS benchmark.