The Geology of North America

Featured Speaker: Professor Phil Stoffer

Professor Phil Stoffer

This four-part series will provide an overview of the geologic story of North America’s regional landscapes. Bedrock ages are measured in millions and billions of years to rocks actively forming to record the history of landscape evolution. Processes unique to different regions involving tectonic forces, including earthquakes and faulting and volcanism have created uplands, whereas long-term erosion and deposition have reshaped landscapes. Landscape development has been influenced by climate changes, as well as wet-to- dry and warm-to-cold cycles. This has influenced how plant communities, changing river patterns and continental ice sheets changed the landscape over time. The series will examine over 40 physiographic provinces divided among four regions: West Coast, Rocky Mountains, Midcontinent and the East Coast.

July 11: Geology of California and the Western Cordillera

This presentation will start with a brief overview of how plate-tectonics over time best explain the origin of North American landscapes. Although the majority of the North American continent is vastly older, the rocks exposed in the San Diego region are younger than 200 million years (with rare exceptions). The discussion will follow the chronology of geologic events shaping southern California and how the coastal region “assembled” over time. The geologic record began with deep ocean crust and sediments giving way to the formation of coastal volcanic mountain ranges that endured vast periods of erosion. The chronology will conclude with the formation of the California and western regional fault systems.

July 18: Regional Geology of the Rocky Mountains

This presentation will start with the geology of the Grand Staircase, the incredible sequence of sedimentary rock layers exposed throughout the Colorado Plateau, starting at the base with the billion-year old layer in the bottom of the Grand Canyon and to the top of the sedimentary pile preserved in the uplands of southern Utah, Colorado, Wyoming and beyond. These sedimentary rock sequences preserve evidence related to the formation of both ancient and modern mountain ranges and periods of volcanism. The geologic story involves the evolution of inland seas, vast sandy deserts and forested coastal plains that formed, vanished and reappeared throughout the region through time.

August 1: Regional Geology and Landscapes of the American Midcontinent

The Midcontinent encompasses the region drained by the greater Mississippi River system. Whereas some might think there is little geology to ponder in this vast low-lying region dominated by agriculture, this is simply not true! The region’s sedimentary rock layers preserve a vast history of evolution of life and landscapes throughout the Paleozoic Era, involving the formation and disappearance of ancient mountain ranges, inland seas and a vast coastal swamp associated with coal basins and the region’s cavern systems. The final phase involves the landscape modifications created by the advance and retreat of the continental ice sheets of the Pleistocene Epoch.

August 29: Evolution of the East Coast and Appalachian Regions

This story begins in New York City where the geologic exploration of America really began in the nineteenth century. The building and expansion of our nation were influenced by the shape of our coastline, the available natural resources (particularly coal, metals and water) and the impediment to travel posed by the Appalachian Mountains. The Appalachian Mountains preserve the history of continental collisions and the breakup of the supercontinent Pangaea, as well as the formation of the Atlantic Ocean.

Presenter Biography

Presenter: Phil Stoffer’s career started in Midwestern geology as a science librarian an instructor at Miami University and the University of Kentucky. He then became an earth-science teacher in New York City, where he completed a geology Ph.D. at CUNY/Brooklyn College. He subsequently worked as a field geologist for the U.S. Geological Survey for projects in California and the Colorado Plateau. He is now a professor of geology and oceanography at MiraCosta College.

Coordinator: Jim Brown