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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Splinters in Dendrochronological Analyses

By Audrey Cross

A tree corer used to drill into a trunk, and two tree cores. Rings are counted from these cores and used to date events or reconstruct climate change.  Wikimedia Commons.

A tree corer used to drill into a trunk, and two tree cores. Rings are counted from these cores and used to date events or reconstruct climate change. Wikimedia Commons.

In dendrochronology, most analyses rely on a number of underlying assumptions. For wood that was used by humans, a tree might have been used immediately after it died, and it could be found at a site nearby where the tree had lived. However, humans could obtain wood in different ways; it could be found, as with driftwood; recycled, as with beams in houses; or transported, as with boats.

The study of driftwood proposes an interesting twist to dendrochronological analysis because the amount of time that wood can spend in transport can vary greatly. Continue reading

What can paleoecology offer Latin American archaeology?

By Audrey Cross

Archaeologists… they need help. They excavate sites, hopefully taking really good notes, ask for help from specialists, read, synthesize information, imagine past cultures and landscapes, theorize, question, and hopefully publish their findings. I don’t want to be an archaeologist, but since both of my parents were, it’s a part of me. Maybe without being an archaeologist myself, I can help them, though, because their work is best done with help from different types of specialists.

In the summer of 2012, I did a field school that my mother was running in the Rio Bravo Conservation Area in northwest Belize. My late mother had done work and run field schools there for as long as I’ve been alive, and I was finally getting a sense of what her work meant. Amongst the many facets of this field school that sparked my interest, the study of the nearby bajos got my mind thinking in terms of paleoecology.

Fig. 1. Members of the 2012 Maax Na field crew at Bolsa Verde, excavating a Mayan plaza. Perhaps 30m from the edge of this picture, there is a steep slope downwards towards to the bajo. (Photo by Audrey Cross)

Fig. 1. Members of the 2012 Maax Na field crew at Bolsa Verde, excavating a Mayan plaza. Perhaps 30m from the edge of this picture, there is a steep slope downwards towards to the bajo. (Photo by Audrey Cross)

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