Glacial erratics mark the graves of glacial geologists

Monday, May 24, 1999

By: Joe Hannibal, Cleveland Museum of Natural History

For obvious reasons, glacial geologists have long had an affinity for glacial boulders. A number of these geologists, or the families of these geologists, have elected to mark these scientists' last resting spots with such boulders. Indeed, the grave of Alexander Agassiz (1807 - 1873), the great early champion of the glacial theory, is marked with such a boulder. This boulder is from one of Agassiz's Alpine field sites, the Aar glacier in Switzerland. You can visit Agassiz's grave, and the boulder made of a grey granitic rock, in Boston's Mount Auburn Cemetery. The grave of A. P. Coleman (1852-1939), one of Canada's great glacial geologists, is marked by a huge granitic boulder. This pink and grey monument is located in Toronto's Mount Pleasant Cemetery. According to contemporary Canadian geologist, E. B. Freeman, Coleman's monument is composed of stone derived from the bedrock found in the Muskoka area, north of Toronto.

A.P. Coleman monument

Figure 2. A.P. Coleman monument, Toronto's Mount Pleasant Cemetery. (Ed Freeman for scale)  

G.F. Wright jasper metaconglomerate boudler
Wright family monument

Figure 3 (left). G.F. Wright jasper metaconglomerate boudler, Oberlin Cemetery.

Figure 4 (right). Wright family monument, Westwood Cemetery, Oberlin, Ohion. Scale in decimetres.

Geologists in Ohio were likewise interested in glacial boulders. The distribution of these boulders, also known as erratics, was used to trace the extent of the continental glaciers that covered much of Ohio during portions of the Pleistocene. These erratics, derived from the Canadian Shield, include granites, diorites, and gneisses which can be difficult to trace back to their parent outcrops. However, this is not the case for another type of rock - a strikingly beautiful white stone with beautiful red jasper pebbles. These beautiful stones stand out from the typical glacial erratic as well as from rocks derived from the sedimentary bedrock of Ohio. Geologists who found these boulders in Ohio and adjacent areas in the nineteenth century traced them back to their parent outcrops on the north shore of Lake Huron and around the outlet of Lake Superior. This stone, a jasper metaconglomerate, is derived from Ontario's Lorrain Formation, a Huronian (Precambrian) rock unit that formed between 2.1 and 2.5 billion years ago.

Headstone of Charles Whittlesey

Figure 5. Headstone of Charles Whittlesey, Lake View Cemetery, Cleveland, Ohio.

This jasper metaconglomerate has been utilized for the gravestones of several people in Ohio, including two prominent Ohio geologists. The Wright monument, and the headstones of members of the George Frederick Wright (1838-1921) family, are made of boulders of the jasper metaconglomerate, as is the headstone of Charles Whittlesey (1808-1886). George Frederick Wright was one of Oberlin College's most famous faculty members, and his gravesite is located in Oberlin's Westwood Cemetery. He was a theologian and geologist interested in the antiquity of man, the ice age, and in reconciling the Bible and science. Today, however, Wright is probably best known as the advocate of a single glacial advance instead of multiple glacial advances. Clearly, Wright ended up on the wrong side of this argument! Wright was surely correct about choosing the jasper metaconglomerate for a grave marker, however. He has some of this stone moved from Canada to Oberlin. Today, the Wright monument stands out among the other monuments in the cemetery.

Close-up of the Whittlesey monument

Figure 6. Detail of the Whittlesey monument.

Whittlesey is better known than Wright these days for a number of reasons. Lake Whittlesey, a glacial precursor of Lake Erie, was named in his honor because he was one of the first geologists to explore the old shorelines of the precursors of Lake Erie. Whittlesey was also a local historian and an archeologist of note. Whittlesey's grave marker of jasper metaconglomerate is located in Cleveland's Lake View Cemetery, This modest headstone is far less ostentatious than that of Wright. However, for those in the know, the red jasper pebbles stand as bright reminders of Whittlesey's contributions to glacial geology.

Detail of typical jasper metaconglomerate

Figure 7. Detail of typical jasper metaconglomerate (Wright Family monument).

All the pictures are copyright, Cleveland Museum of Natural History.