The Legacy of Chesapeake Geology
A small window to a piece of Maryland's past, Calvert Cliffs are one of many sites around the Mid-Atlantic that allow scientists to dig into the region's geologic history. Sediment captured in these cliffs dates back to 18 to eight million years ago. But look elsewhere, and you can find geologic formations that are as much one billion years old. Photograph courtesy of Steven Godfrey, Calvert Marine Museum.
WHEN PEOPLE THINK OF THE GRANDEUR OF AMERICAN GEOLOGY, their minds usually wander out west. There you can find the Grand Canyon, the arches of Utah, and Devil's Tower, a steep formation that looks so alien that it was featured in a Steven Spielberg movie about, well, aliens.
But for Callan Bentley, that view neglects the amazing rocks and outcrops that can be found along the Chesapeake Bay and the East Coast. The geologist, who teaches at the Northern Virginia Community College in Annandale, is a proud defender of local geology. West of the Mississippi, "they have a lot more blatant geology," says Bentley, who grew up in the Washington, D.C., area. "But ours is better. It's just more subtle."
Bentley's taste in rocks might seem surprising. The Grand Canyon is certainly grand - there, you can easily see in one place a series of rock layers dating back two billion years. But the Mid-Atlantic's geology is special too, just more spread out, he says. Various geologic sites, such as granite outcrops or steep cliffs, each hold a small window to the planet's past.
Those windows also allow scientists to explore some dramatic events that molded and shook the globe. The oldest Mid-Atlantic formations, for instance, can be found in outcrops exposed around the Blue Ridge Mountains. These rocks were formed nearly one billion years ago, geologists suspect, when the landmass that is now North America drifted into modern-day West Africa.
Or take a drive along the shores of the Chesapeake Bay and visit Calvert Cliffs in Maryland. These precipices were once part of an ancient sea floor that dried up around eight million years ago.
Among scientists, the value of these sites lies in what they say about how the planet evolved — how mountains formed, new species emerged, and changes in sea level gave rise to the Chesapeake Bay. In this issue of Chesapeake Quarterly, we describe some important episodes in the natural history of the Bay uncovered by local researchers. Their studies don't just inform our understanding of the past. They can give us a hint of what changes may lie ahead.
In The Day Before Yesterday, Michael Fincham describes how scientists studied the deepest core samples of sediment ever collected from the bottom of the Chesapeake. Their research provides a deeper understanding of an abrupt, big change in the planet's climate about 8,000 years ago that lowered sea levels in the Atlantic Ocean and in the Bay. Today, researchers continue to study whether current climate trends could trigger an equally abrupt shift, a change that could affect Maryland in significant ways.
A second article, The Chesapeake's Excellent Fossils by Daniel Strain, delves into the rich diversity of fossils that paleontologists, working over the decades, have collected along Calvert Cliffs. These remnants of prehistoric life have earned an international reputation as an important record of the whales, crocodiles, and sharks that once swam the oceans.
But, as important as it is, some of the Bay's special geology is also at risk of disappearing, Bentley says. The third article, Saving Calvert Cliffs, examines the future of these famous cliffs. Efforts to slow erosion along Calvert Cliffs and protect houses sitting at the top could destroy whole portions of the cliffs themselves.
In all, geologists say that the Mid-Atlantic's geology is well worth preserving and exploring — and plenty grand.