Study sheds light on how US east coast was formed as supercontinent Pangea broke up

A recent study published in the Geophysical Research Journal: Solid Earth sheds new light on the formation of the eastern seaboard of the United States – a “passive margin,” in geological terms – during the breakup of the supercontinent Pangea and the opening of the Atlantic Ocean about 230 million years ago ‘years.

In geology, passive margins are “quiet” areas, places with minimal faulting or magmatism, where the land meets the ocean. Understanding their formation is crucial for many reasons, including the fact that they are stable regions where hydrocarbon resources are extracted and their sedimentary records preserve our planet’s climate history dating back millions of years.

The study, co-authored by scientists from the University of New Mexico, seismologist Maria Beatrice Magnani of SMU, and scientists from Northern Arizona University and USC, explores the structure rocks and the amount of magma-derived rocks along the east coast and how they change along the margin, which may be related to how the continent was split when Pangea broke up. This event may also have influenced the structure of the Mid-Atlantic Ridge, a vast underwater mountain system that extends across the central Atlantic Ocean.

The study team analyzed rocks deep beneath the ocean floor, about 10 to 20 kilometers deep, using special instruments called ocean floor seismometers. The instruments measure the speed of sound of rocks beneath the surface, helping scientists determine the composition and type of rock. This research is part of a larger effort to study how continents break apart, one of the most important questions in Earth science.

“Passive margins define the majority of Earth’s coastlines and are home to much of the world’s population,” Magnani said. “They are vulnerable to changes caused by long-term climate variations and sea level rise. Understanding their beginnings and the processes that shape them offers clues about how they may be affected and respond to geohazards, including earthquakes, underwater landslides and erosion.”