Leaf Physiognomy Offers clues to the Past

By Eric Atkins

There are many techniques that can be used to offer insight to the past–a family of proxies that range from gas found in ice cores to fossilized feces. I have always been interested in fossils. The allure of something so ancient was introduced to me as a child. At the age of eight, I found a veiny imprint of a leaf in a chunk of sandstone. Fossils are a great tool for looking into the past. For nearly a century by paleoclimatologists and paleoecologists have been using leaf physiognomy as a proxy to deduce past climate environments. By looking at leaf mass per area, teeth area, number of teeth, and degree of blade dissection we can extrapolate information about past climates.

Fossilized Platanus leaf, Paleocene, Alberta, Canada. Via Wikimedia Commons.

Fossilized Platanus leaf, Paleocene, Alberta, Canada. Via Wikimedia Commons.

In recent years this type of proxy has evolved along with technology. Continue reading

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The past’s mark on the present as seen through LIDAR

By Erika Lyon

Light Detection and Ranging, also known as LiDAR, is a form of remote sensing used by various professions to examine landscape features in three-dimensions.  Imaging is generally performed by aircraft (though not always) that use lasers, scanners, and GPS to measure reflected light from Earth’s surface.  This light describes changes in distance between the aircraft and surface features (National Ocean Service 2013).  For terrestrial systems, a near-infrared laser is used to collect data (this is known as topographic LiDAR), while aquatic systems make use of green light, which can break through water surfaces (bathymetric LiDAR) (National Ocean Service 2013).  Data on height, latitude, and longitude of geographic features are generated and used to create models of the landscape (National Ocean Service 2013).  LiDAR’s applications have been used in the fields of archeology, geology, and paleontology to study natural and human history, but it is not fully utilized in paleoecological studies.  LiDAR is a powerful remote sensing tool that can provide invaluable information about Earth’s surface and can be especially useful for looking at evidence of past events and land use.

Past events can leave behind footprints on the Earth’s surface, and these footprints may not be easily distinguished from an aerial or satellite imagery alone.  For example, during the summer months of 2012, I inventoried abandoned mine lands in the Midwest, which are notorious for their dangerous highwalls and sinkholes that are often hidden from view by overgrown trees and shrubs.  LiDAR was a very valuable tool in the field because it made many of these hazardous features evident (Fig. 1).  Needless to say, I didn’t go to a mine site without a LiDAR hillshade map.

Fig. 1: Example of an aerial photo (left) and LiDAR hillshade image (right) of an abandoned surface mine.  Maps, like the ones above, are often utilized by state agencies to assess site conditions of abandoned mines.  For more maps of Iowa’s abandoned mines (including 1930s, 1950s, 2008 aerials, and LiDAR hillshade) click here. (Images created by GeoTREE and the Iowa Department of Natural Resources).

Fig. 1: Example of an aerial photo (left) and LiDAR hillshade image (right) of an abandoned surface mine.  Maps, like the ones above, are often utilized by state agencies to assess site conditions of abandoned mines.  For more maps of Iowa’s abandoned mines (including 1930s, 1950s, 2008 aerials, and LiDAR hillshade) click here. (Images created by GeoTREE and the Iowa Department of Natural Resources).

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