When Alfred Wegener first made his case for continental drift, he relied on two main lines of argument: the shape of the continents and the relative positions of glacial till deposits. Evidence later accumulated from other areas of research, but the theory was not taken seriously until well after Wegener's death.Continue Reading
The first argument Wegener put forward in support of his theory was that the continents seemed to fit together like the pieces of a jigsaw puzzle. This relationship is apparent from a map, but the exactness of the match improves if the underwater continental shelves are compared. The true edges of South America and Africa, for example, fit together to a high degree of precision, allowing for millions of years of erosion.
Wegener's second argument was more complex. He traveled the world and charted the locations and orientation of glacial till deposits. These deposits are the alluvial remnant of a glacier's progress across the landscape, and they remain long after the glacier has melted away. By plotting out the latitudes of ancient till deposits, Wegener was able to demonstrate that, for his evidence to be consistent with unmoving continents, much of the world would have had to be covered in ice sheets in the relatively recent past, even in the tropics. He argued that this was evidence that the tropical continents had once been at higher latitudes.Learn more about Earth Science
Continental drift is caused by movement of the tectonic plates that continents sit on top of. Continental drift has continuously occurred throughout time, and continues to do so today. Rough estimates say that Europe and North America are drifting away from each other 2.5 centimeters per year.Full Answer >
One of the most common examples of illogical reasoning is the straw man argument, which often entails either isolating a particular part of an argument before then presenting it as an entirely individual or separate position, or using a very early form of a theory to support a case while ignoring the fully developed theory itself (attacking Darwinism using only Darwin's work as a source for example, ignores all the progress made since, so is not valid). Finding a source that offers an extreme view or unrealistic account of a position, then treating it as fact, is also a straw man argumentFull Answer >
A glacier trough is a U-shaped valley that forms after ice glaciers melt or drift. Glaciers move up to a few feet a day, and they remove the debris within the valley as they move, creating the U-shape.Full Answer >
Continents rest on massive plates known as tectonic plates, which are fluid and able to move due to the mantle and magma underneath, and as the tectonic plates move about, they cause continental drift to happen. The concept of continental drift was first described in the early 20th century by German scientist Alfred Wegener, who explained that continental landmasses were actually drifting across the Earth. This is opposed to the original theory that landmasses are fixed and immobile.Full Answer >