Silurian Reef at Quarry Lake Park EarthCache
Silurian Reef at Quarry Lake Park
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An EarthCache adventure is treasure hunting for the caches that the Earth has stored. EarthCache sites do not use stored containers; their treasure is the lessons people learn about our planet when they visit the site. Visitors to EarthCache sites can see how our planet has been shaped by geological processes, how we manage the resources and how scientists gather evidence to learn about the Earth. Read below to find out the requirements to claim your "Found It".
The Silurian Period of geologic time lasted from approximately 438 million years ago until about 408 million years ago. During that period, much of Wisconsin was covered by a shallow sea and that sea was full of living creatures. As those creatures died, their shells and skeletal remains fell to the bottom of the sea and, over the millions of years, piled deeper and deeper. Eventually, these remains compressed under their own weight and became limestone, a calcium-rich sedimentary rock.
Skip ahead to the modern age of man. The sea no longer covers Wisconsin. Under the soil of the intervening years, man discovers the limestone and decides that he needs to harvest it for his own use, primarily as a building material, so he digs a quarry. Now, one might expect that these sedimentary deposits would, on average, form uniformly stacked layers or strata, the newer layers on top of the older layers. But, as is the case here at Racine Quarry Park, that is not always what they found. Instead of uniform layers, they found large mounds with sloping flanks on either side. These mounds, they determined, were ancient reefs.
A reef is a structure built by organisms that rises above the surrounding seafloor. It is similar to how the rest of the strata is formed, but growth of certain types of underwater plants in a given area interfere with the shallow water currents and trap sediment within that confined area. Other plant life, such as algae, would then bind the sediment together. Eventually, a mound would build up and create a reef. Upon close inspection of the reef and its flanks, fossilized remains of some of the plants and organisms that make up its composition can be seen.
In order to log a “Found It” for this earthcache, first send the answers for these questions to me using my profile link at the top of this page.
1. From the posted coordinates, using your GPS or a compass, at what directional bearing is the larger (primary) reef located? For example, if it is due West, you would say it is at 270°.
2. From the posted coordinates, using your GPS or a compass, at what directional bearing is the smaller (satellite) reef located? Which reef are you closer to?
3. How can you tell these are the reef cores? Explain in terms of the layering of sedimentary strata.
4. Using the attached images, try to locate and identify some of the fossils found near the posted Viewing Location. Compare them with reef fossils seen elsewhere within the park. Do you see greater concentrations of different ones at different locations?
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