You will need a tape measure of at least 8 feet in length to complete this earthcache.
This earthcache will take you to what has been called one of America's Most Beautiful City Parks, Presque Isle Park.
This earthcache will teach you about Reduction Spots. At this location you will see many reduction spots and one large reduction zone. At least that is what I'm calling it. Below is a photograph of what I call the “Reduction Zone”.
The sandstone in this area is called the Jacobsville Sandstone. It dates to the late Precambrian period (1.0-1.6 billion years ago). The name comes from the town where it was first quarried for building stones. If you have ever heard of a “Brown Stone” building, well this is the stone that they are made from. Just not from this location.
It is a mottled reddish-pinkish-whitish, fluvial (river system) sandstone that outcrops in many areas of Michigan's UP, especially in the Keweenaw Peninsula, Marquette, and Munising areas. The Jacobsville sandstone varies in physical characteristics from nearly pure quartzose sandstone (consisting of more than 95% clear quartz grains and less than 5% matrix. Also known as quartz sandstone) to arkosic sandstone (derived from the disintegration of granite or gneiss, and characterized by feldspar fragments). Granules, small pebbles, and rip-up clasts (rock fragments or grains resulting from the breakdown of larger rocks) may be seen.
All of the sand grains in any sandstone are held together with some kind of cement. The cement that holds sandstone together isn't the cement that streets and sidewalks are made from, it's the minerals that hold the individual grains of a sandstone together. The cement holding the Jacobsville sandstone together contains feldspar and iron. In the presence of oxygen, iron turns into iron oxide, which is red. So at one time water carrying dissolved oxygen flowed through the Jacobsville sandstone, oxidizing the iron and turning it red.
A Reduction Spot has in it's center a material that likes reacting with oxygen even more than iron likes to react with oxygen. This material consumed all the oxygen in the area before the iron could. Thus preventing the iron from oxidizing and turning red. Materials that react easily with oxygen include certain types of minerals and especially organic matter. This process doesn't just occur in sandstone, it can occur in shale and slate. It is very common to find little bits of ancient organic matter in the center of the little white spots. Iron that has reacted with oxygen is "oxidized" and iron that has not reacted with oxygen is "reduced," hence the name. You may see reduction spot in other areas that are oval in shape. This is caused from the rock being stretched. Geologist can measure the size of the oval to determine the amount stretching that occurred. Other odd shapes of reduction spots do occur. A variety of reduction spot shapes occur at this site.
In the Reduction Zone at this site, a chemical solution flowed within the crack and spread outwards towards the edges of this zone. Causing a chemical reaction with the iron oxide cement, changing it's color.
I would like to make this statement to everyone that attempts to find this cache. This is Lake Superior which can be very dangerous. Even being on the south east side of Presque Isle Park the waves can be rough. You can see from this area the break water that runs out to the light house. A couple of young people went out there and lost there lives due to rough seas. There's a sign stating this info near the start of the break water. Typically this a somewhat calm and peaceful place, just be careful!
Logging requirements of this earthcache are:
Every log must have different photos. Even if several teams or individuals are together for the find. Each any every team and individual must have unique photos. Go to the area where the Jacobsville sandstone drops off about three feet. No need to go down. See the crack that is in the middle of the white zone. Measure back from the drop off 3 feet. Use this point for the answers in the first two questions.
1.)Face the water and measure from the crack to the left edge of the white zone. Report your answer in inches.
2.)Face the water and measure from the crack to the right edge of the white zone. Report your answer in inches.
3.)Find any other reduction spot that strikes your fancy and photograph it with your GPS. Post this photo with your log.
4.)Take a photo of yourself or team holding a GPS with the reduction zone in the background.
Email the answers to questions 1 & 2 to me. Post the photos taken in 3 & 4 with your log.