Lecturer says Chesapeake shoreline losses are driven chiefly by erosion, with sea‑level rise a contributing factor

Doctor Eshelman, a paleontologist and former Calvert Marine Museum employee, told a public lecture audience that the Chesapeake Bay region’s shoreline losses reflect a complex mix of long‑term geologic change and short‑term coastal processes, and that "relative sea level" (land motion plus ocean change) is the more accurate way to describe local risk.

Eshelman opened by describing temperature and sea‑level cycles over hundreds of thousands to millions of years, including Milankovitch orbital cycles, and noted that instrumental records show a sharp temperature rise in the last ~100–120 years — the so‑called "hockey stick" pattern. He said that while long‑term cycles predict a cooling phase now, the observed twentieth‑century warming departs from that pattern and aligns with rising atmospheric greenhouse gases.

Turning to the mid‑Atlantic, Eshelman explained that the land under the Chesapeake and Delaware basins is subsiding for multiple reasons: sediment loading from eroding Appalachian ranges, residual isostatic adjustments from past ice sheets, and local groundwater extraction. He cited regional tide‑gauge differences (for example, Solomons, Md., showing higher relative rise than some up‑coast stations) and summarized that parts of the coastal plain are subsiding roughly "20 centimeters or more every 100 years," which compounds any absolute ocean rise.

On cultural resources, Eshelman stressed that many island and shoreline losses commonly attributed to sea‑level rise are primarily caused by wave erosion acting on sandy bluffs and spits. "Holland Island disappeared" largely because of wave erosion, he said, adding that sea level played a role but was not the dominant cause in that example. He described photographs and survey work showing exposed wells, eroding cemeteries and washed‑out archaeological deposits along Chesapeake shorelines.

Eshelman summarized archaeological survey results outside Maryland to illustrate the pattern: a survey in Accomack County recorded 198 sites in the 1999–2001 work; by a 2016 resurvey, 36 of those sites were gone and 45 new sites had been exposed — a mix of loss and discovery driven by coastal erosion. He urged systematic local survey work in Maryland, noting limited funding for extensive state surveys.

On future change, Eshelman cited typical model ranges rather than a single forecast: regional projections he showed included warming of roughly 2°C by 2100 in many scenarios, and regional relative sea‑level increase in the range of a few feet (he referenced a 3–5 foot range discussed in the literature). He emphasized that erosion operates on short timescales (hours to years) while sea‑level change plays out over centuries to millennia; that difference matters for planning and for which cultural resources are vulnerable.

During a question period, Eshelman explained data sources for deep‑time temperature reconstructions (fossils, coral isotopes, and ice‑core air bubbles) and addressed local concerns about groundwater and fracking; he said fracking is not allowed in Maryland and raised groundwater contamination concerns where fracking occurs. An audience member from St. Mary's County described widespread fossil shells in local ravines; Eshelman confirmed local Miocene deposits and named the three inland seas preserved in the regional stratigraphy (Calvert, Chop Tank, and Saint Mary's formations).

Eshelman ended by urging environmental communicators to emphasize practical, local consequences (clean water, air and land) and to focus on the tangible impacts residents experience. The lecture concluded with an audience Q&A; no formal actions or votes were taken.