Dave Lusch shows us how the Michigan Basin is like a set of nested bowls, with the older rock on the bottom and the younger rock overlying it. This formation helped the “Master Blaster Eroder,” continental glaciers, “scoop out the Great Lakes like a spoon in a melon.”

Walking back in to view the Mystic Sinkhole, we stop to observe some of the surface karst features.

Bopi Biddanda collects samples of the microbial life that surrounds the upwelling of groundwater from one small sinkhole.
A stream of groundwater being discharged into the bay through a sinkhole. Mats of Purple cyanobacteria are the only organisms that appear able to survive in the oxygen-poor water.

The larger, deeper sinkhole provides a perfect place for a few reflective moments.

Cindy and Kim brave the chilly sinkhole waters. It is always 10 degrees Celsius, whether it is July or January. The bottom of the hole, 70 feet below, can be easily seen from the surface as there is no aerobic life that can survive in this water.

We finished up the day at impressive Presque Isle lighthouse. Our fealess leader always has to find the heights.