Multiple Plate Collisions, Six Ice Ages, Climate Change, and New England’s Earthquake Problem

A lot has happened to the land we now know as Northwest Connecticut! From mountain ranges to climate change, geology helps us understand the world around us. On June 22, Weantinoge presents Dr. James Lawford Anderson, professor and Director of Undergraduate Students for the Department of Earth and Environment at Boston University, for a fascinating talk about our region’s past, present, and future. Dr. Anderson is an igneous petrologist and much of his work has been devoted to an understanding of crust formation and plate tectonics. Join us as we learn how the Appalachian Mountains formed, what evidence the six ice ages left behind, and what New England’s earthquakes mean for coastal dwellers.

The process of continental collisions has rearranged the continents over Earth’s history. In the past 3 billion years, continental collisions have created four supercontinents. The last two, Rodinia (one billion years ago) and the better-known Pangea (400 million years ago) formed the rocks of what is now New England. The formation of Pangea created the Appalachian Mountains, now mostly eroded, which once stretched from present-day northern Europe to Mexico.

The Earth has also had six ice ages in the past billion years. Our most recent ice age was during the Pleistocene which began 2.5 million years ago and involved over 20 glacial events, each lasting 40,000 to 100,000 years. The last glacial epoch ended 10,000 years ago and left glacial outwash plains, kettles, and drumlins throughout New England.  There was a Medieval warm period around 1000 AD which allowed human settlements to occur in Greenland, Iceland, and perhaps Newfoundland.  These disappeared when a small ice age occurred from 1600 to 1850.

Even though the Earth has gone through cycles of cooling and warming, today the Earth is warming at a rate it has never experienced in human or geologic time. The warming is all tied to the Industrial Revolution and our use of fossil fuels, mostly coal but also petroleum, because they are very carbon rich. Due to current global warming, sea level rise is happening and is well measured everywhere.  Future New England must address this.

And there is one more issue. New England does have an earthquake problem. We are not near a continental plate boundary so the occasional earthquakes travel far. Many of our cities are near sea level and in liquefaction zones, where earthquakes encounter subsurface groundwater and amplify. Intraplate earthquakes, as they are called, do not happen often, but they do at on average every 300 years. The last one was near Cape Ann in 1755 and was a 6.3 on the Richter scale.