Significant changes in the world's geography took place during the Devonian. During this period, the world's land was collected into two supercontinents, Gondwana and Euramerica. These vast landmasses lay relatively near each other in a single hemisphere, while a vast ocean covered the rest of the globe. These supercontinents were surrounded on all sides by subduction zones. With the development of the subduction zone between Gondwana and Euramerica, a major collision was set in motion that would bring the two together to form the single world-continent Pangea in the Permian.
In addition to global patterns of change, many important regional activities also occurred. The continents of North America and Europe collided, resulting in massive granite intrusions and the raising of the Appalachian Mountains of eastern North America. Vigorous erosion of these newly uplifted mountains yielded great volumes of sediment, which were deposited in vast lowlands and shallow seas nearby.
Extensive reef building, producing some of the world's largest reef complexes, proceeded as stromatoporoids and corals appeared in increasing numbers. These were built in the equatorial seas between the continents. Large areas of shallow sea in North America, central Asia, and Australia became basins in which great quantities of rock salt, gypsum, and other minerals precipitated.
Near the end of the Devonian, a mass extinction event occurred. Glaciation and the lowering of the global sea level may have triggered this crisis, since the evidence suggests warm water marine species were most affected. Meteorite impacts have also been blamed for the mass extinction, or changes in atmospheric carbon dioxide. It is even conceivable that it was the evolution and spread of forests and the first plants with complex root systems that may have altered the global climate. Whatever the cause, it was about this time that the first vertebrates moved onto the land.
For additional maps of the Devonian world, visit the Devonian page at the Paleogeography Through Geologic Time site by Dr. Ron Blakey of Northern Arizona University.
Read about the Devonian Mass Extinction at the Hooper Virtual Paleontology Museum.
Find out more about the Devonian paleontology and geology of North America at the Paleontology Portal.