Note: This is an Earthcache. There is no physical cache to find. Logging this Earthcache requires that you undertake an educational task relating to the specific Earth Science at the site.
Prior to logging this cache, click on Message this owner, or send an email with answers to the following questions:
- At GZ you will be standing on a bridge overlooking the river. Look upstream, just below the bridge. If the water level is not too high, you will see smaller potholes on either side of the river. What is their average diameter? What is the likelihood that they will get bigger?
- N 47° 33.397 W 090° 52.446 brings you to a spot where you can look down into a large pothole that forms the river. What is the diameter of this pothole?
- Required to log this cache: Please provide a photo of yourself or a personal item in the picture to prove you visited the site. Upload the photo with your log.
Temperance River Potholes
This earthcache is located in Temperance River State Park. If you park at the parking coordinates along Hwy 61, there is no fee required. A steep trail will lead up along the river, to GZ. Be careful with small children!
The bedrock in this park is all igneous (solidified from the molten state) and formed about 1.1 billion years ago. One of the most interesting features in the park is the narrow Temperance River gorge with its many waterfalls. The Temperance River flows 39 miles between its source, Brule Lake, and its mouth in Lake Superior. It is one of the longest rivers on the North Shore.
The steep-gradient river has cut through the fractured, ancient lava flows of the river bed. Swirling water carried gravel and rocks which wore away the basalt and created large potholes.
Over thousands of years, these potholes were dug deeper and wider, eventually connecting and creating the deep, narrow gorge. Nearby, more potholes were left high and dry as the river found its new, lower channel.
The Temperance River was named Kawimbash by the Ojibwa, meaning "deep hollow river". While it retained this name in the earliest geological surveys, in 1864 Thomas Clark reported its present name, which he alleged arose as a pun from the fact that the river has no sand bar near its mouth. The depth of the water where the river enters the lake prevents the river from developing a sand bar.
