Cemetery Geology

Goals

• Working knowledge of chemical and physical weathering processes
• Susceptibility of different rock types to weathering

Skills

• Practice recognizing rock types
• Calculation of approximate weathering rates

This is an excellent lab to use in an urban area where there are few natural outcrops. It is also a good lab to assign for homework if the lab periods are short (or nonexistent) and the cemetery is easily accessible by car, foot or public transportation.

Students should have some experience recognizing sedimentary, igneous and metamorphic rocks and also be able to distinguish felsic and mafic igneous rocks and volcanic and plutonic igneous rocks. The lab could either precede or follow a classroom lecture and discussion on weathering. In the latter case, students could be asked to summarize some specific observations and then these could be used to develop a list of weathering types. As with outcrops, tombstones weather by a combination of chemical and physical weathering processes that are easier to separate out in the abstract than in the concrete, so to speak. Nevertheless students generally have little trouble distinguishing the relatively slow weathering of granites from the more rapid weathering of marble and sandstone when comparing inscriptions and dates.

Cemeteries are wonderful ways to tie geology into human history. Commonly the tombstones are in languages of immigrant groups (in the Northfield, MN area, these include Norwegians and Czechs; one feature of the Bolton St. Cemetery in Wellington, NZ was the section with tombstones in Hebrew). There may be explicit stories (one of the earliest tombstones at Bolton St. is from a shark attack victim in Wellington Harbor) or implicit stories (the several children from one family who died within a few weeks of each other) on the gravestones.