Lake Erie - and its ancestors EarthCache

At 240 miles long and 60 miles wide, Lake Erie is the 12th largest natural lake in the world. Its depth ranges from an average of 24 feet in its western basin (west of the Bass Islands) to as much as 210 feet in its eastern basin (east of the Ohio/Pennsylvania border). The central basin, where Miller Road Park is located, averages about 60 feet in depth. The lake was named after the Erie ("Cat") tribe, a Native American tribe that lived along its southern shore until they were exterminated by the Iroquois in the 1650s.

But geologically speaking Lake Erie is a mere infant. Millions of years ago there was no lake here at all — it was solid bedrock extending from northern Ohio to southern Ontario. The terrain was rolling hills and streams, split by a major east-west river. Geologists refer to this river as the Erigan. Over the course of millions of years, the Erigan River carved a deep, wide valley through the brittle layers of shale and thin layers of sandstone beneath it.

Then came the glaciers. Starting about 2 million years ago and lasting until about 12,000 years ago, great sheets of ice advanced and retreated through the region. As these glaciers crossed the Erigan River valley, they carved it deeper and wider, eventually carving through the thin layers of shale and sandstone to the harder, thicker layer of limestone and dolomite below. This hard underlying layer slopes gradually downward from the west end of the lake to the east end in what geologists call an arch. The result is that the valley was carved deeper at the eastern end than the western end, forming the 3 basins that exist today.

Each time a glacier retreated northwards across the Erigan River valley, its frozen ice dammed the valley while its melting ice filled the valley with water, creating a huge lake. The southern shores of these glacial lakes were pummelled by wave action, resulting in massive erosion that further widened the valley. No one knows how many such glacial lakes existed over the eons, but three of the most recent ones left distinct terraces (ridges) at their southern shore, much like the cliff wall that can be seen today at Miller Road Park. The oldest of these three lakes is known as Glacial Lake Maumee. About 14,000 years ago it formed a terrace we know now as Butternut Ridge. Lorain Road (Butternut Ridge Road) runs along the top of this ridge. A few hundred years later Glacial Lake Whittlesey formed Center Ridge, which Center Ridge Road runs along the top of. And a few hundred years after that Glacial Lake Warren formed North Ridge. Detroit Road and North Ridge Road follow the top of this terrace today. After the last glacier retreated about 12,500 years ago, the Niagara River opened up, draining the last glacial lake and leaving behind the Great Lake that bears the name of the Cat tribe.

But enough of that already, it's time to head to the beach! Park in the western (boat launch) parking lot at the end of Miller Road (coordinates below) and follow the walkway to the beach. At the coordinates posted at the top of this page, you will see a rocky cliff wall to the south and a big body of water to the north. Ponder for a moment that this body of water was once filled entirely with the same type of rock you see in the cliff wall, layered hundreds of feet above your head! Now take a close look at the cliff wall itself. You should notice two distinct types of rock. Most of the rock is a thin, brittle, dark rock called Cleveland Shale. This rock is ubiquitous in Avon Lake. But mingled in with the Cleveland Shale are bands of a thicker, tougher rock. This is sandstone. Here you can clearly see the classic erosion pattern by which Lake Erie and its glacial ancestors have carved out the terraces on their respective shorelines. Energy-packed waves wear away at the thin, brittle shale, leaving the more durable sandstone protruding out of the cliff wall like a shelf. Eventually, with nothing to support the shelf from below, the sandstone breaks off in big chunks and the shale above comes tumbling down with it. On the ground, the waves continue their relentless assault on the fallen rock until it disintegrates into the sand and silt you see on the beach. As you examine the cliff wall, make sure you pay attention to the logging requirements (listed below). There are three tasks to be performed here.

Once you've had your fill of the beach, return to the car for a 7 mile journey to the prehistoric past. Head east on Lake Road (Route 6) to either Lear-Nagle Road (preferable) or Jaycox Road, then head south to the ancient shoreline of Glacial Lake Warren at Detroit Road (Waypoint 1A or 1B below). Notice how Detroit Road sits on top of a distinct ridge running parallel to the Lake Erie shoreline. It's easy to visualize that this terrace was once a cliff similar in size and shape to the cliff at Miller Road Park. Make sure you take an altitude measurement here.

Optionally, you can continue another 5 miles south on Lear-Nagle Road to the shorelines of Glacial Lake Whittlesey at Center Ridge Road and Glacial Lake Maumee at Lorain (Butternut Ridge) Road (Waypoints 2 and 3 below). Notice how similar these ancient shorelines are to the shorelines you saw before. Take altitude measurements at both sites.

To claim credit for this cache, you must perform any 4 of the following 5 tasks: