Superior 2007 Field Excursion

Large Lakes Observatory

 

 

Large Lakes Observatory

Canal Park

Marine Museum

Coastal Development

Team: A LLO & Canal Park
  B Park Point
  C Geomorph Processes
  D Rouche Moutonnee

Dr. Jol's Site


 

The Large Lakes Observatory (LLO) as part of the University of Minnesota -Duluth, dedicates its time to research on large lakes around the world; from the East African Rift Valley to Central Asia and as close to home as the Great Lakes of North America.  A vast amount of the research focuses on aquatic chemistry, circulation dynamics, geochemistry, acoustic remote sensing, plankton dynamics, sedimentology and paleoclimatology.

P1080220The LLO was the first stop on the class trip to Duluth.  Steve Coleman (in Figure 1) of UMD spoke to the class about what LLO does and the research it conducts.  There is a mission for oceanography that dedicates time to inland seas.  The Blue Heron is one of their research vessels that ventures worldwide to conduct research.  The Blue Heron is used to conduct a lot of sea floor mapping.  With this technology a lot of data can be gathered and analyzed to establish history of some of these lakes and predict what may happen in the future. 

Figure 1 Steve Coleman, of UMD talking about the Blue Heron at LLO,
Photo provided by Beth Ellison

Sea Floor Mapping
LLO
The Blue Heron uses different techniques to obtain data from the bottom of the lakes to be able to perform quality analysis.  Three different types of techniques used are: side-scan sonar, swath bathymetry, and seismic reflection.  The swath bathymetry collects data by sending many beams traveling in all directions to collect sound waves to analyze the bottom of the lake.  The radar is sent over a wide area in the lake compared to side-scan sonar.  Side-scan sonar is over a smaller area.  It looks at the reflectivity of the bottoms and depends on hardness and the angle of the bottom of the lake.  Seismic reflection sends sound waves directly below the boat.  It uses low frequency sound that goes through the ground as well allowing for further analysis compared to the other two techniques.  Figure 2 shows the different approaches to the sea floor mapping techniques.

 

 

Figure 2 Sea Floor Mapping Techniques and how the sonar works, Diagram by Beth Ellison

Great Lakes of North America

Research conducted on Lake Superior has provided evidence that historical ice coverage of the region is causing drastic change in the today’s lake.  According to Mr. Coleman the temperature of the outflow of Lake Superior has risen rapidly since the 1990s; .12°C/year (water temperature) and .06°C/year (air temperature).  This is hypothesized that after the retreat of glaciers (decrease in amount of ice) it created less reflectivity of the landscape which increases the amount of heat that the water absorbs from the sun.

The Laurentian ice sheet covered and aided in the creation of the Great Lake Region.  As seen in Figure 3, the retreating of the ice sheet uncovered the lakes.  As the ice sheet retreated the land began to rise, which is defined as isostatic rebound.  This occurs because of the weight of the glacier that once created extreme amounts of pressure on the crust is now lifted allowing the land to expand once again.  Because of this rebound the lake level is starting to shift towards the Eastern side of the lake.  Research is currently in progress to see how this isostatic rebound will affect the way the landscape is run and developed. 

gl_ice
Figure 3 The retreat of the Laurentian Ice Sheet, Army Corps of Engineers

For a humorous understanding of the history of the Great Lake Region see “The Rise and Fall of the Great Lakes”, a Canadian short film starring Blake James.

Constructed by Beth Ellison

Further References

Emporia State University: http://www.emporia.edu/earthsci/student/damery1/gl_form.html#Pre-Wisconsin_Drainage

Army Corps of Engineers

Large Lake Observatory: http://www.d.umn.edu/llo/

 
 
 
 

 

Last Update: December 17, 2007
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