Updated 9/13/202 -additional clue added
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The ledges at Thompson are a great asset and have contributed much to the community. They offer a unique geological, biological, and scenic feature to the area. Thompson Ledges provides a striking exposure of Sharon Conglomerate (the sandstone and pebble mixture) that underlies much of Geauga County.
The bedrock in this area is part of Pottsville Group-Sharon sandstone/conglomerate of the Pennsylvanian Geologic Period. The surface landscape is ground moraine from the Late Wisconsinan Age of the Quaternary Period.
And an amzing fact is that as the glaciers noved south in this area thy were acttull diverted to the west ad the east!
Thus the edges were the catalyst for forming the Grand River alley to the east and the Chagrin River to the west.
An ancient riverflowing through this area is responsible for the sediments that became the conglomerate. Around 320 million years ago, fast-moving streams from the north and east flowed into an inland sea covering Ohio at that time. Sand, gravel and quartz pebbles were carried by the water and deposited in a wide delta. After millions of years, this debris compacted and became Sharon conglomerate. There isvery little topsoil on the top of the ledges but fertile farmland is found in the surrounding lower elevations.
The kedges were formed at the bottom of a very wide, yet very shallow river some 310 million years ago. In this respect it would resemble the Platte River of today.
The Sharon Conglomerate, a pebbly sandstone, which the local sequence of bedrock, is a river deposit. The rivers were a type known as "braided," very wide and very shallow (one of those "foot deep and a mile wide" rivers), replete with intertwining streamlets. The pebbles—almost all made of quartz from Canada—are known as lucky stones. On the north line of the outcrop of Sharon Conglomerate there are disjunct outliers of conglomerate. These outliers form hills. The most famous outliers are the "knobs" of Lake and Geauga counties.
The porous conglomerate now helps supply much of the county’s groundwater. Along with water, Thompson Ledges once provided building stone. Large sandstone blocks from the quarries traveled throughout the county and beyond as bridges for roads and railroads, bridge abutments and culverts. There are signs of the quarrying activity carried on there over a century ago, but many areas still seem pristine. Benches carved from the conglomerate are placed throughout the park.
Both Paine Creek and Phelps Creeks have tributaries originating in Thompson Ledges and are high quality cold water streams.
Walking south atop the ledges will bring you to 2 distinct ecosystems – the first being the chestnut oaks on the top level and then to the hemlocks growing from exposed cracks and crevices of the upper rim and throughout the ledges. A carpeting of various mosses is found in the area along with an assortment of ferns.
Descending to the bottom of the ledges puts you in another ecosystem with many hemlock trees.
Since the 1800's visitors from miles around have come to see the ledges which encompass a total of 66 acres. In 1868 a hotel was constructed to furnish accommodations to the tourists. The hotel, however, did not last long and was abandoned in 1876. This building was later converted to apartments.
The park was established as the first park district in Geauga County by the township's Thompson Ledges Park Board in 1940.
Logging Requirements: Bring your GPS, camera, and a ruler or short tape measure.
Please - no spoiler photos one the cache page! Such photos are subject to deletion.
1. At N41° 41.373 W81° 02.709 you will be standing on the drive between 2 chestnut oak trees. The leaves are within easy reach. Photograph* one leaf with your ruler ruler in the picture. In the winter you can photograph a twig showing the leaf buds buds. (Forgot your ruler? US currency bills are almost exactly 6" long.) Alternately you can use the measurements of the leaf's over all length, width, and depth of the lobed edges.
2. At N41° 41.342 W81° 02.653 you will find a narrow passage leading down to the base of the ledges.
Altetnately you can use the new stairway at the north end of the park, across from parking.
Descend to the bottom and find an area where the quartz "lucky stones" have left "dimples" in the rock after being eroded out. Measure the width of the smallest dimple you can find; measure the width of the largest dimple you can find.
3. At N41° 41.269 W81° 02.565 you will find how man has utilized a natural feature. Describe in detail what you found here. (Update: This is a man-made use of a natural feature located close to the base of the ledges. (It is NOT the road, parking lot, picnic table, grill etc.)
4. Use this link to email me your photos and the measurements taken for step #2. Be sure to include your caching name if it isn't part of your email address. You may send one email on behalf of a group if you include all caching names in the body of the email.
Or message me through geocaching.com with answers and photo(s).
If you descend to the bottom at the coordinates given in requirement 2, you should proceed south along the base of the ledges. One place to climb out is at N41° 41.190 W81° 02.597. You will find yourself south of the gazebo. Walk north along the Iroquois trail to return to the parking lot.