1.10 Tectonism, Climate, and Geomorphology

Abstract

This essay examines a basic premise of geomorphology, namely that landforms and land-forming processes reflect interactions between Earth's tectonic framework and its atmospheric canopy. Five themes are developed. First, tectonism and tectonic change are outlined in terms of changing tectonic concepts, plate mechanics, continental interiors (cratons, platform covers), and continental margins (passive, active). Second, climate forcing is reviewed by defining weather and climate, early notions of climate change, and probable causes of climate change. Climates change through time in response to several interactive forces: those external to Earth, those related to Earth's orbital relations with the Sun, and those internal to the Earth system among which tectonism profoundly alters the playing field for climate and geomorphic processes. Third, the spatial implications for geomorphology of changing tectonic and climate forcing are viewed in the context of latitude and location, continentality and oceanicity, ocean gateways and land corridors, continental elevation and relief barriers, and vegetation cover. Fourth, prefaced by a discussion of the nature and rate of change, the temporal implications for geomorphology of tectonic and climate change over the past 300 million years are evaluated. Eight topics are discussed: the Pangea supercontinent, opening of the Atlantic Ocean and Tethys, opening of the Southern Ocean, uplift of North America's Western Cordillera, uplift of the Andes, uplift of the Eurasian Cordillera and Tethys closure, closure of the Central American isthmus, and volcanism. Last, three geomorphic feedbacks that affect tectonism and climate are discussed: denudation, sedimentation, and isostasy; biogeochemical cycling; and relative sea-level change.