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...