Between a Rock and a Hard Place

By Kevin Selkregg

Cleveland brick on the shore of Lake Erie by Kirsti Scott, Hurricane Sandy, Oct. 30, 2012, by NASA/NOAA/GSFC/Suomi NPP/VIIRS.

In October of 2012, a tropical depression in the Caribbean soon grew into Superstorm Sandy. A hurricane that earned the nickname, Frankenstorm, made landfall on October 29th near Atlantic City. Its force was felt though out much of the Northeastern U.S. with sustained winds reaching the Great Lakes, giving the lakes the opportunity to show their strength.

When the old Municipal Stadium in Cleveland, Ohio, was demolished, its concrete and brick debris were used to build reefs in Lake Erie. It appeared Lake Erie showed its disapproval when Hurricane Sandy’s sweep across the lake brought the bricks up from the depths onto the shore. This was a reminder of the forces the Great Lakes display along their shorelines. 

My earliest memories of rocks are from when I was about nine. My family spent summer vacations in Maine, driving from our home near Erie, Pennsylvania. Along the way, we would stop at various roadside rock shops which sold many kinds of rocks and minerals. Smoky and rose quartz crystals were commonly displayed in piles next to the shop door. Often the shop had an open pit where I could scavenge for rocks and minerals for 5 cents a bucket. I learned the names of many rocks and minerals at this early age, including such catchy names as garnet, amphibole, and feldspar, some of which I still have today. When I saw a dull weathered rock on the outside, I wondered, “what does the inside look like?”

Phantom Ranch by Stanley Ford. Glacial grooves near Lake Erie by James St. John.

My most memorable geology experience was a college field camp course lasting eight weeks in the summer of 1974. Our class of about a dozen students plus Professor Smith, camped all over Arizona, Utah, Colorado, Nevada, and New Mexico. We spent four weeks in Zion National Park in Utah mapping the rock strata surrounding that area. A three-day exploration adventure in the Grand Canyon included hiking the Bright Angel Trail to an overnight camp at Phantom Ranch, which is on the north side of the Colorado River. I vividly remember the full moon lighting up the canyon as I sat on the banks of the roaring Colorado River. Now, retired after a career spanning four decades in the field of ceramic materials and refractories, I can spend more time with
my true love of rocks. 

My passion for geology today includes a growing appreciation for the beautiful glacial rocks deposited on the Great Lake shores. To me, these are treasures left after the last migration of glaciers from the Canadian north. During the geologic past, glacial ice sheets advanced and retreated in cycles numerous times in North America with each cycle lasting thousands of years. The last period of glaciation, informally called the “Ice Age,” peaked about 12,000 years ago with its maximum advance just south of the present Great Lakes in North America. These glaciers originated on land due to the accumulation, compaction, and recrystallization of snow during all seasons of the year. Eventually, as the snow compacted and built up, the glaciers took on a life of their own and would slowly spread out from a central location or move down an alpine valley. This glacier can appear to be motionless, but it is not—glaciers just move very slowly.

With a maximum thickness in some cases reaching one to two kilometers, the immense weight and moving mass of ice leads to a significant erosion process responsible for creating many unique landforms. The shape and orientations of the Great Lakes are due in large part to the erosional forces of the glaciers. The erosional process at the base of the glaciers in contact with the bedrock includes abrasion and plucking, while the advancing front can act as a plow. As the bedrock is abraded, loose fragments of the plucked rock are consumed into the glacial body at the base. This becomes a mode of transport in the glacier as the rock fragments are moved from their origins to the final resting place hundreds of miles from their source. 

Eventually, the climate will warm to the point where the glaciers cease to advance and begin instead to melt. Such is the case when fragments of the Canadian Shield bedrock were removed and transported south to regions of the current Great Lakes. Because of the weight and forces of a glacier slowly moving and causing intense fracturing and abrasion, only the hardest rock will survive. Interestingly, rock plucked from the Canadian Shield bedrock represents some of the oldest rocks in the world, estimated to be 2–4.5 billion years old, transported by a glacial event 12,000 years ago and deposited upon a bedrock of shale and dolomite estimated to be 500 million years old. It is an interesting intersection of geologic events in time at one place.

Walking along the shores of the Great Lakes today, one will likely see significant evidence of transported glacial rock (above left). The Great Lakes, in a sense are reservoirs of transported glacial rock ,which are eroded and tumbled into rounded cobbles by the relentless motions of the waves. 

The bedrock indigenous to the shore will be very different from non-native boulders and stones formed by a geologic process foreign to local geology. The Lake Erie shoreline near Dunkirk, New York, for example, reveals typical shales so flat they could be used for a dance floor (above center). This large boulder (above right), transported by glaciers, now resides on the beach, either due to erosion from the soil in the cliff, or because it washed up onto the beach from the lake by a storm. A closer look at its surface reveals gouges and striations due to glacial abrasion (below left).

The beaches of a small town of Kincardine in Ontario along Lake Huron have myriads of glacier rocks that have been smoothed and rounded over time by lake wave actions (above center). A popular find, affectionately called Puddingstone, can be found here as a conglomerate rock type of dark fine sandstone embedded with fragments of jasper or even granite. On the Lake Erie Freeport Beach of northeastern Pennsylvania, I frequently find a banded metamorphic rock called gneiss. At Lake Ontario’s Fort Niagara beach in Youngstown, New York, one can find an abundance of banded gneiss along with dolomites.

My beachcombing experience involves collecting a variety of rocks along the beaches of the Great Lakes exhibiting unique colors and patterns. Collecting such finds for over ten years I have combed the beaches of Lake Ontario, Lake Erie, and the eastern shores of Lake Huron. My wife, Brigitte, has acquired the passion for finding the perfect specimen along with me. Often, I have to literally drag her away from the beach with the promise to return another day. Hopefully, in future travels, the shores of Lakes Michigan and Superior will reveal finds as magnificent as the other lakes and I have every reason to believe that to be the case. I have not visited there but hope to do so soon.

Many of the beach finds we chose are generally the size of a large grapefruit or slightly larger. The rocks need to be wet in order to observe their patterns and colors, so I hand-select each one as I walk along the beach, often wading through knee-deep water pulling my kayak alongside and loading it up. 

I am looking for pieces that stand out with unique bandings and distribution of colors and minerals. Nearly all of my favorite rocks are igneous (volcanic or solidified from magma) and metamorphic (re-pressurized and reheated) rocks, because I find the geologic process involved in their creation form the most colorful and intriguing rocks. When dry, these can look rather dull, but when wet, the colors are enhanced and vibrant. 

Once returned to the shop, the natural interior colors, patterns, and array of minerals of these rocks are revealed by cutting and grinding. A 16-inch diameter diamond saw is used to cut the rock into slices for coasters, while still maintaining a semblance of the outside rock profile. This allows the original shape with each coaster slice to match the next. Once cut, the piece is trimmed and ground to remove burrs and chips and then later dried. The dried surface is cleaned and treated, giving a polished appearance. The result is a vibrant “wet look” that brings out beautiful colors and patterns unique to that particular rock. 

I enjoy crafting one-of-a-kind pieces into coasters, business card stands, tea light holders, and more. My hobby has expanded into a small business and many people enjoy unique rock décor in homes, choosing those collected from a favorite vacation spot or childhood home as a memento of times past.

Learn more about beach rocks:

Learn more about beach rocks including agates, Cape May diamonds, Yooperlites, fulgurite, puddingstone, and more. Articles ›

This article appeared in the Beachcombing Magazine September/October 2020 issue.