Busy Field Season

Quite a busy summer this year. Lots of time in the field, both downhole logging landslide deposits and in trenches across active faults. This is what I like to do and why I became a field geologist. Tomorrow I put on one of my other hats and present at the Geological Society of American annual meeting in Denver. I'm dusting off some older work on anthropogenic change to water systems - fancy words for man-made modifications. Now that more folks are aware of possible global warming impacts, the other ways man changes the landscape to fit human needs is getting more attention...and rightly so.

Treasure Island being built in San Francisco Bay.

Man-made: New Landscapes

http://www.flickr.mud.yahoo.com/photos/38318523@N00/293700514/
Keta, Ghana in 1985...source is flicker_user bknittle
excellent blog about technology in the classroom at: http://www.bethknittle.net/WP_Blog/

The truly amazing thing about the study of the earth surface is how often it is necessary to look through the overprint of man's existence. Often the changes to hillside, bay side, or ocean beach to fit in houses results in major problems over time, or during extreme events. An earthquake or a long and heavy storm can start to unravel these marks made into the earth or simply erase them.

Tornado Marks

August 24th, 2006 F3 tornado over southern Minnesota...photos by NWS.

More tornado marks...2004 vintage in Conway Springs, KS

Tornado track is the light colored area in the center of the photograph. View is to the northeast in Google Earth. I wanted to find some tornado-generated surficial marks similar to those historic photographs of the Scottsbluff, Nebraska (6/27/1955) tornado that I posted earlier. Some information and chase photos for the F3-F4 tornados on May 29, 2004 can be found here.

My goal was to use Google Earth to find similar marks with nothing other than the general location of the tornado to start with - sort of an exercise. A tornado can be a truly devastating force of nature and the question for me is how long after one can you still detect the signs on the earth's surface.

Note the circular marks...pretty interesting.


Note the damaged trees and marks on the plowed fields...

Stuck in the mud

An excavator used by a state contractor was buried by tons of dirt and debris after a hillside collapsed recently along I-890 near Michigan Avenue in Schenectady. (Cindy Schultz / Times Union)

Link to the whole story...

Rain Drops and Erosion

Raindrops from...

http://www.flickr.com/photos/allyrose18/210964120/

There is a dark side to even the humble raindrop. A single drop is harmless, but when billions of raindrops from a cloudburst fall on bare soil they strike like billions of tiny hammers, dislodging tons of soil per acre which is carried away by surface runoff.

This process, called splash erosion, is of critical importance to agriculture... In addition, rain splash has played a major role over geologic time in sculpting the features of the mountains and cliffs of the world, particularly those in arid and semi-arid regions... Individual raindrops, which travel at speeds up to 20 miles per hour, can splash soil particles up to five feet horizontally and two feet in the air.

Recent raindrop research at Vanderbilt University

Mapping landforms - Aerial Photographic Interpretation

Interpretation of stereo-paired aerial photographs probably is one of the most useful tools to the geomorphologist in the office. Traditionally this has been accomplished by putting a transparent overlay on the photos (0.3mm acetate working best) and using a stereoscope to map contacts and surfaces. I usually use different colored pencils and colored lead in mechanical pencils (red and blue 0.5mm leads). The mapping on the overlays then needs to be transferred, usually to a USGS topographic map.

By photocopying the air photo overlay and enlarging or reducing it to fit the map scale, I then transfer the information to the base map. Often during this process, the mapping changes as the topographic contours on the map provides additional information on the geomorphic contacts and extent of surfaces. A good writeup of how this approach works using more modern tools is given for shoreline mapping below.

Coastline Mapping in Texas

So much has changed with GIS and the ability to combine multiple layers of information but I still rely on the stereoscope, although I can no longer easily find 0.3 mm acetate...

Sand Fountain

Interesting...apparently a fountain of sand appears in the desert.

Coastal Erosion Biting Away

Captures the process perhaps better than anything I've seen in the classroom. Quiet crisis indeed and all too heartbreaking for those living on the coast. Okay - I need to stay away from YouTube...

Close Call

Sorry, I like landslides...