You will investigate the hypothesis that the continents were once joined together in a supercontinent called Pangaea.
After completing this tutorial, you will be able to complete the following:
Prior to Alfred Wegener's proposal of the continental drift hypothesis, the prevailing view of the Earth was that large-scale horizontal movements did not occur. Instead, the presence of similar fossils on widely separated continents was explained by the existence of "land bridges" which had once connected the continents but had subsequently sunk beneath the oceans. The fit of the coastlines was, if anything, viewed as coincidence. Wegener's hypothesis provided a much simpler explanation and was supported by abundant evidence. However, because he was unable to adequately explain how an object the size of a continent was able to move across large distances, his hypothesis did not immediately gain widespread acceptance.
Later discoveries provided some of the answers that Wegener lacked, and eventually the continental drift hypothesis was combined with several other hypotheses to form the theory of plate tectonics. Rather than continents moving through an unchanging sea floor, it is now thought that the continents and sea floor both move as parts of tectonic plates.
Several different driving mechanisms have been proposed for the movement of plates. One is that convection currents in the mantle carry the continents, as well as the sea floor, along like a conveyor belt. Other ideas are that seafloor spreading actively pushes plates apart, that subducting slabs of oceanic lithosphere pull along the rest of their plates, or that plates just passively slide downhill from relatively high areas (at mid-ocean ridges) to relatively low areas (the trenches at subduction zones).
|Approximate Time||20 Minutes|
|Pre-requisite Concepts||Students should have an understanding of climates, continents, fossils, landmasses, and rock strata.|
|Type of Tutorial||Concept Development|
|Key Vocabulary||asthenosphere, continental drift, convection|