electrical resistance imaging looking beneath the surface… or finding where the bodies are buried...

Electrical Resistance ImagingLooking beneath the surface…

OrFinding where the bodies are buried without a backhoe…

AndLooking for buried ice on the side of

a mountain…

Dr. Greg Gaston, Department of Geography, University of North Alabama

Dr. George Makowski, Department of History, University of North Alabama

Changing lives. Creating futures.

Looking beneath the surface…Or

Finding where the bodies are buried without a backhoe…

AndLooking for buried ice on the side of

a mountain…

Dr. George Makowski, Department of History, University of North Alabama

Remote Sensing?

• Subsurface targets

• Simple technology with high order data processing

Significance?

• Big target technology searching for small targets

• Potentially a significant tool in exploring the impacts of climate change

• Identification of historical and recent archeological sites without damage

• High resolution images

• Flexibility

Why Electrical Resistance (ER) Imaging?

• Non-invasive • Widely used tool in archeological investigations• ER tools are more capable of recording data

where sub-surface water is present (Ground Penetrating RADAR [GPR] has difficulty penetrating saturated ground conditions)

• Relatively low cost• Buried ice has very high electrical resistance

The physical principles…

Penetration is a function of the length of the electrode line and the distance between electrodes. Functionally, depth is 10-20% of the total length of the electrode array and the minimum target discrimination is ½ the electrode spacing.

Testing the ER system

Known Steam Tunnel

Steam Tunnel to adjoining building

Compaction and moisture near sidewalk

Case Study 1

Sweetwater PlantationER Data collected 15 December ‘06Additional Field Mapping 16 Feb. ‘07

Historical Applications:

Cemetery Site

(Approximately 450 feet from the house)

Survey Lines

Survey Line 3Data line 5 Schlumberger electrode firing pattern

Survey Line 4Data line 7 Schlumberger electrode firing pattern

Case Study 2: Coffee Plantation

Coffee Cemetery Line 8

LaGrange Mountain Cemetery

• Experimental Data Collection

• Field Methods Class 6 March 2007

Results:

• Initial results at the Sweetwater Plantation site are encouraging.

• Results from the Coffee Plantation site are not as expected.

• The interpretation of ER images can change with different environmental conditions.

• The ‘Art’ rather than the ‘Science’ of image interpretation and analysis

Next steps in the research program:

• Test ER imaging at additional sites with known and suspected burial sites.

• We will retest Coffee cemetery with drier conditions.

Changes in glacial ice and ice marginal features of the

Cascades

Research sponsored by a grant from the College of Arts and Sciences at the University of North Alabama.

Thanks also to the UNA Department of Physics and Earth Science for the loan of the Electrical Resistance Imaging equipment.

Why glacial features in the Cascades?

• Glaciers exist at comparatively low elevationsIt is possible to measure moraine

features at 6000-7000 feet• Changes in ice and ice marginal features are

fairly well documented including a long record of aerial photography

• A wide variety of glacial features have (relatively) easy accessibility

• Previous Research Experience

The Pacific Northwest

The angle of repose of dry earth materials is generally 25-40 degrees.

35 degrees is the accepted ‘normal’ angle of repose

A steeper angle implies some sort of cohesion between particles.

1990

2006

http://glaciers.pdx.edu/gdb/maps/oregon_website/or_glaciers.html

1901

Carver Lake…

An example of a glacial lake created by ice cored moraines.

Site 2: Known Glacial Ice

Site 1:

Suspected Ice Cored Moraine

Conclusions • The steeper angle of repose in many of the moraines of

the Cascades is caused by an ‘ice core’.• Electrical resistance imaging equipment was useful in

confirming the presence of ice in the moraine.• Interpretation of the levels of resistance suggest

discontinuous ice lenses rather than a solid mass of ice.• Lakes in the Cascades dammed by moraines with

similar slope are likely to fail as ice in the Cascades continues to melt.

• Mountains are taller and gravity appears to have dramatically increased over the last 16 years!