"Why Are the Appalachian Mountains So High?"
John Cipar Boston College ISR and Weston Observatory
The Appalachian Mountains are the product of a long history of collisional
tectonics during the Paleozoic Era (480-250 million years ago, My).
Successive
accretion of island arcs and microcontinents formed a complex zonation of
geological formations. During the final phase, North America and Africa collided
to form the super continent of Pangaea, about 250 My. By 200 My, Pangaea was
beginning to rift apart forming the incipient Atlantic Ocean. Since 185 My, the
eastern seaboard of North America and the Appalachians have not endured major
tectonic activity with the exception of passage over the Great Meteor hotspot at
about 110 My. The continued presence of high topography and significant relief
(e.g., Mount Washington) are seemingly inconsistent with this prolonged
tectonically-quiet interval. This topic has been a matter of debate since the
earliest days of geology! I will first discuss the basics of earth structure and
plate tectonics to set the stage for a discussion of modern data and ideas on
formation and persistence of the topography we see today.