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Watch out for that Pothole

A cache by FLtravelers Send Message to Owner Message this owner
Hidden : 9/22/2011
1.5 out of 5
2.5 out of 5

Size: Size: other (other)

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Geocache Description:

This is an Earthcache. There is no physical cache to find. Logging an EarthCache requires that visitors undertake an educational task relating to the specific Earth Science at the site. If you don't want to answer the questions, don't log this EarthCache. Your log will be deleted.

The Presque Isle River has riverbank exposures of sedimentary rocks that include Copper Harbor Conglomerate, Freda Sandstone and Nonesuch Shale. These sedimentary rocks are approximately 1 billion years old. The Nonesuch Shale at GZ contains layers of gray to black shale, siltstone and sandstone.


These round potholes form where an eddy current swirls pebbles and grains of sand in a circular path. Over time, the swirling action of these materials wears away the softer shale, forming the large, smooth-sided potholes seen here. This is a type of physical weathering known as corrasion.


Source: Michigan DNR

Prior to logging this cache, email the answers to the following questions:

  1. Estimate the diameter of the largest pothole?
  2. Can you notice water swirling around in any of the potholes?
  3. Some of the potholes are missing a side. Does the water still swirl around in these?
  4. Optional: Post a photo of your visit.

This EarthCache is located in Porcupine Mountains Wilderness State Park. There are quite a few stairs down to GZ, and therefore quite a few to get back to your car. Some of us feel this is a physical challenge that warrants a higher terrain rating. The Presque Isle River has been designated a National Wild and Scenic River.


Additional Hints (No hints available.)



118 Logged Visits

Found it 117     Publish Listing 1     

View Logbook | View the Image Gallery of 133 images

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Current Time:
Last Updated: on 11/15/2017 3:47:24 PM (UTC-08:00) Pacific Time (US & Canada) (11:47 PM GMT)
Rendered From:Unknown
Coordinates are in the WGS84 datum

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