Bever Park Glacial Erratic and Old Martin Marietta Quarry

Who doesn't know "The Rock" at Bever Park?

As far back as I can remember "The Rock" has always been a part of the Bever Park landscape. The giant rock, the roaring lions, the wooded oasis set amid a residential backdrop. According to Jean Prior it is the unusual size of many Iowan Surface boulders that characterize this region. "Many of the largest erratics have been broken apart by dynamite for use in building foundations or simply to remove them from cropped fields." She sites examples of many erratics that still exist, but our Bever Park Boulder is not one that she mentions.

The rock sits next to a small stream that winds its way through the park. The stream seems to originate from underground out of nowhere and it flows through a V-shaped valley. As we walked through the park many questions came to mind. Was this stream once more powerful and did it carry more water that carved out this river valley? We can only guess the answers to these questions, but we believe that this erratic was deposited during the Pre-Illinoian Glacial and Interglacial stages some 500, 000 years ago. Since the rock sits in a valley, we conclude that this glacial erratic was revealed by the down-cutting of the once more powerful stream over time.

Here is a response from the Cedar Rapids Parks Superintendent to a query I made regarding the rock...

We do not have any information on this boulder. It seems to me that there was some research being done a few years ago on these big boulders that are scattered around and serve as a kind of “ landmark” but I never got a copy of the article if the author actually compiled his information and printed it.
Sorry I could not help you on this. We have had questions on this boulder from time to time which have ranged from people thinking it was a meteor to a former Parks Commissioner who asked me why we left the rock down in the creek and did not pull it up by the playground when we put it in the park. Apparently he missed his geology training altogether.
Dave Smith
Parks Superintendent
Cedar Rapids, Iowa

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Less well-known is the old Martin Marietta quarry near the Cedar River with clear water, good fishing and a garden variety of glacial till. The lake is well over 60 acres, with an informal two-mile walking trail which circles the lake. Native fish include bass, bluegill, and walleye. Grasses and poison ivy are the dominant vegetation. The quarry was a rich source for sand and gravel. The steep banks along the edge of the lake reveal a mixture of sedimentary, igneous, and metamorphic rocks and fossils. The sheer volume of this glacial till is evidence of massive glacial outwash. According to Bill Desmarais, geologists can determine the origin of these rocks based on their mineral structure. While these are just "garden variety samples" they are local and easy to access. (Watch out for the poison ivy!)

Questions: Where are other notable examples of "glacial erratics" in the area to observe? Is there a difference between an "erratic" and just a glacial boulder? (This comes from a question posed at the July meeting about how we know this is an erratic?)

Directions: Travel South on Memorial Dr. SE. At Otis Rd. Turn west. At intersection of Otis Rd SE and Otis Ave (how brilliant is this!) is Cole St SE. Drive down Cole St. Cross on set of tracks. Park before the active tracks. Walk West about 1/4 mile to the Quarry. A rough trail circumnavigates the quarry. Beware Poison Ivy!

to Bever Park travel Bever Ave. Between Memorial Dr. SE and 30th St. SE is the park. Enter and look for the boulder just west of the swimming pool.