Fort Hill EarthCache

Note: this cache might not be doable during periods of high water levels or heavy snow cover.

Fort Hill is a scenic hill overlooking the junction of the East and West Branches of the Rocky River. The hill is unique because of its archaelogical content and its geological composition. It is composed entirely of Cleveland Shale and has been a significant source of fossil discoveries in the Cleveland area.

Cleveland Shale is an extremely thin, brittle rock that is coal black in color but turns grayish or reddish brown with prolonged exposure to the weather. It was formed around 375 million years ago when most of Ohio was underneath a shallow inland ocean. Rivers and wave action carried in large quantities of mud, which eventually settled out and accumulated on the ocean floor. Over millions of years, the mud compressed and became cemented together into thin layers, forming a thin and brittle rock called shale.

During the time period that the Cleveland Shale was forming, the sea over Ohio was shallow and warm and the Earth was tilted in a way that put Ohio very near the equator. This tropical environment was home to abundant plant and animal life. When the plants and animals died they decayed in the mud. As a result, the Cleveland Shale is bituminous (which is to say it's so loaded with organic material that it's coal black in color). Many of the plants and animals also became fossilized in the mud, including some enormous fossils like Dunkleosteus terelli, an armored fish that ate sharks! The fossils found in the shale here have had an important influence on our modern understanding of the evolution of fish species.

This cache will take you on a tour of Fort Hill and familiarize you with Cleveland Shale. In the process you will see how Fort Hill was formed many thousands of years ago. Feel free to wander from the tour and explore the many geological, archaelogical, botanical, and historical wonders this area has to offer, but please stay within the designated trails and recreation areas. Do not remove any rocks or fossils from the park (but feel free to carry out any trash you encounter!)

> The tour begins at Big Cedar Point Picnic Area at the coordinates listed above. Follow the paved all-purpose trail and footpaths to the eastern bank of the Rocky River. When you find the right spot you will be at river level with thin, black chips of Cleveland Shale beneath your feet. Examine the shale and notice how flimsy it is. (If you've done the Berea Sandstone at Olmsted Falls Earthcache just 2 miles upriver, contrast this rock to the massive, rugged sandstone you saw there.) Now look directly across the river at Fort Hill, composed entirely of this same Cleveland Shale. Depending on lighting and weather conditions, the hill may appear anywhere from light gray to coal black. In a short amount of time you will be standing on top of that hill, directly across the river from where you are now. Before you leave here take an altitude measurement, you will need it to fulfill the logging requirements.

> Return to the paved all-purpose trail and follow it northwards to the bridge. As you approach the bridge, notice how the opposite riverbank becomes vertical and the Cleveland Shale becomes a rich dark fudge color. This is because it is not as exposed to weathering here as on Fort Hill. You can also see more Cleveland Shale on the near bank of the river just before the bridge.

> Continue across the bridge, then take a left-turn towards Fort Hill. You can either follow a footpath along the river, or go through the Rocky River Nature Center parking lot. Either way will take you past the Nature Center (say hi to Dunkleosteus) and to the base of Fort Hill. You can climb the stairs at the near end of the hill, or continue along the trail to the far end of the hill where you can follow any of several footpaths to the top. (The footpaths will give you more opportunities to get "up close and personal" with the Cleveland Shale.)

> At the top, head to Waypoint 2 at the south end of the hill (N41°24.466 W081°53.293). There is a trail marker at this location. Read it carefully - it contains information on how the rivers carved Fort Hill out of the surrounding Cleveland Shale. Also be sure to take an altitude measurement here. Take some time to explore - there are some beautiful vistas and interesting archaeology up here!

> Return back downhill to the footpath at the north end of Fort Hill and follow it to Waypoint 3 (N41°24.641 W081°53.206). Here you are seeing both the ancient past and the distant future. You are standing in the bed of an ancient river (the one you read about at the top of Fort Hill), and right before your eyes a new ore is being formed (the one mentioned in Question #5 below).

This Earthcache is the third in a series of four Earthcaches that explore the Rocky River:

Logging requirements:

To claim credit for this cache, you must answer the following questions:

1. What is the altitude at the base of Fort Hill (coordinates at top of page)? You might want to hang on to this measurement if you ever plan to do the 4th cache in this series. If your GPSr doesn't support altitude measurements, post a picture of your GPSr sitting in the Cleveland Shale here instead.
2. What is the altitude at the top of Fort Hill (Waypoint 2)? If your GPSr doesn't support altitude measurments, post a picture of yourself up here with Cedar Point Hill in the background instead.
3. Estimate the height of Fort Hill.
4. What river once flowed around the western and northern slopes of Fort Hill? Be specific.
5. What kind of "rock" (ore) is now being formed at Waypoint 3?

Do not include your answers in your log. Instead, geo-mail them to me within 3 days of your visit. (Earthcaching rules require me to delete your log if I don't receive your answers in a reasonable amount of time).

Thanks to the Cleveland Metroparks for supporting geocaching and permitting this cache!

REFERENCES:

• Geological Survey of Ohio, Fourth Series, Bulletin 15: The Devonian and Mississippian Formations of Northeastern Ohio by Charles S. Prosser, December, 1912. (A gold mine of information for NEO Earthcache developers!)
• Roadside Geology of Ohio (First printing) by Mark J. Camp. (This is an excellent book and a must-have for Ohio Earthcachers.)
• "The Story of the Rocky River Valley" (A fact-filled 13-page brochure available at the Rocky River Nature Center)
• Rocky River Nature Center (There are some top-notch exhibits here!)
• Generalized Column of Bedrock Units in Ohio by Dennis N. Hull. (Thanks to the Ohio DNR for sharing this informative document on their website.)