Plant remains were also being found. For example the
fossil fern Glossopteris were found sparingly throughout Africa, Australia,
India, and South America. Furthermore, this plant was found in polar climates,
supporting his theory of connected landmasses. Organisms like the Australian
Marsupials and the marsupial opossums found in the Americas, which have a
definite fossil link also supports Wegener’s theory. Alfred Wegener’s theories
were not immediately accepted by the scientific community. One of his faults was
that he could not prove how the continents moved across the globe. Wegener’s
suggestion was that “tidal influence from the moon”(1. Pag. 475) was to be
credited. However the science community proved him wrong. Eventhough he was in
the right direction, he could not completely and precisely determine how the
continental drift was accomplished. Therefore, his theories were dropped as
rubbish. Essentially, Wegener was ahead of his time. It was not until years
later that other scientist cleaned up some of Wegener’s mistakes and resurfaced
the Plate Tectonics theory. Thanks to the study of magnetism a whole new window
of scientific evaluations emerged to support the theory of Plate Tectonics. S.K.
Runcorn proposed an interesting idea. It was found that “the magnetic alignments
in the iron-rich minerals in lava flow of different ages was found to vary
widely.”(1. Pag. 478) This was strong evidence that the magnetic poles of the
earth had migrated through time, meaning that lava flows had moved and so did
the continents. This event is called polar wandering. For a long period of time
there was still a lot of questions that needed to be answered about the Plate
Tectonics theory. Thanks to technological efforts and the mapping of the ocean
floor, it became known that there was an oceanic ridge system.
Ocean Ridges are
slices in ocean floor that extended for 70,000 kilometers. It was not until
1960, when a professor from Princeton University, Harry Hess, suggested Sea
Floor spreading. His idea stated that new sea floor was being spread through
mid-ocean ridges. As scientist clashed ideas they suggested that continental
drift and ocean floor spreading were incorporated in the theory of plate
tectonics. They implied that the outer layer of earth called the lithosphere
overlaid another layer of earth called the aesthenospshere. It was later learned
that the lithosphere was broken into seven large and small plates. Research
concluded that these plates are in motion and have been changing shape through
billions of years. However, scientists were clear to verify that these plates
only moved one to two centimeters a year. Over millions of years these
centimeter accumulated from the big landmass of Pangea to what the continents
look like now. In order to understand the movement of these plates one has to
look at the how and where these plates move. Divergent boundaries are known as
plates that move away from their ridge axis. This is due to the hot molten rock
submerging from the mantel into the ocean floor, creating new oceanic crust,
also known as seafloor spreading. Some of these divergent zones can be found in
the Mid-Atlantic Ridge, Red Sea, and the Gulf of Mexico, where it separates the
Baja Peninsula from Mexico. Convergent Boundaries take place where the oceanic
plates descend into the asthenospshere. This region of activity is called
subduction zone. As the plate bends it creates a deep-ocean trench.
