PETOSKEY STONE/ MICHIGAN STATE STONE EC* EarthCache
PETOSKEY STONE/ MICHIGAN STATE STONE EC*
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Petoskey Stones are more often found in northern Michigan along the shores of Lake Michigan. Petoskey Stones are often found at this sight, I found some here when with a friend who lived nearby. You should have a good chance of finding one too.
In 1965 Michigan Governor George Romney signed a bill making the PETOSKEY Michigan's offical state stone. On the sea bottom in this area were corals, much like the corals you find in the seas and oceans today. Coral grow by stages. They start their life as freefloating planulae. The planulae eventually settle on the sea floor and attach to something hard on the sea bottom where they spend the rest of their life. The coral secretes a calcite external covering around itself called an exoskeleton. The soft-bodied coral lives within this exoskeleton and uses its tentacles to collect food. Hexagonaria percarinatae, the scientific name for the coral who's fossilized remains are known as PETOSKEY STONES, were colonial corals. As the polyp of Hexagonaria grew, it built up a six-sided cup about the size of a six-sided pencil. As the polyp grows it produces buds, which become new colony members. As it continues budding, the colony grows upward and outward. The top of the colony creates the dome-like look of the flowers in a bouquet. Colonies can grow to one half ton or larger. Eventually the coral dies. When the colony dies, it is usually buried by mud, and the mud later covered by other sediments. During burial, calcium carbonate precipitates out of solution and fills in the porous areas of the coral. The mud is eventually compressed to form shale. These shales form a belt that stretches across the upper quarter of the Lower Penninsula of Michigan, beginniong at Lake Huron on the eastern side of the state and going west to Lake Michigan. Fossil corals, like Hexagonaria, or Petoskey Stones, tell us a great deal about their environment. Coral contains algae that lives in their tissues. The algae and coral form a symbiotic relationship, which means that they both benefit from each other. The algae take carbon dioxide from the bodies of the coral to live. The algae get a nice place to sit in the sun, which they need to live. Because of their symbiotic relation with algae, coral cannot live without sunlight, and sunlight only penetrates water well to the depth of around 200 feet. Therefore we know that the sea covering this area of Michigan was less than 200 feet deep.Petoskeys thrieved where there was an abundance of food, warm water and sunlight. This is how billions of colonial corals lived an died in the ancient Michigan Seaway. During a long period of time, they were buried, fossilized, and later brought to the surface by the erosive forces of nature. It is generally agreed that Petoskeys on the west side of the state are superior to those on the east side. Because of the vast quanities of gravel along the shoreline of Lake Michigan, which are constantly being turned over by the pounding of the waves and winter ice, the Lake Michigan shoreline is the easiest place to hunt for them. The Wisconsin Ice Sheet grew in the vicinity of Hudson Bay and moved towards Michigan.This glacier picked up the coral colonies that had weathered to the surface, froze to them and carried them south. In the northern quarter of the state it gouged out and freed billions more from the shales in which they were entombed. When the ice melted the Petoskeys were left behind as glacial eratics-- stones carried by the glacier to places where they didn't belong. The glaciers, because of their size and weight, were not gentle with the coral colonies they carried, and these colonies are much more rounded and are likely to be covered with scratches produced as the glaciers dragged them over bedrock. As the waves on Lake Michigan continue to pound their beaches, the Petoskeys tend to be rounded down to the size and shape of a oval bar of soap. Try Greater Petoskey Area earthcache Challenge at GC2HRCN TO RECEIVE CREDIT for this EarthCache simply: ** YOU may do earthcache GC1YH77 at this site too ! 1) Try to find a Petoskey Stone at this location. There are alot of beach stones to look thru.It is even better to wade into the water. When they are wet their six-sides coral design is more obvious. Did you find one? 2) Can Petoskey Stones be called 'erratics'? Why? 3) What is the large feature at the end of the breakwater, some distance to your right? 4) Post a picture of yourself or group, with GPSr and Petoskey Stone, if you found one.(optional of course) E-mail answers to: ddjoffill@aol.com Information was gathered from: The Complete Guide to Petoskey Stones, by Bruce Mueller & William H. Wilde ***My Earthcache GC1YH77 can be done on this beach too!
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