Earth has been changing since the beginning of time. Theories like continental drift, plate tectonics, and sea-floor spreading explain what the earth used to look like and why it looks like it does today. Continental drift states that all the continents used to all be one supercontinent called Pangaea, and over the last 200 million years, the continents slowly drifted apart to where they are now (Evers 1). The theory of tectonic plates states that all the continents and oceans sit on plates or large pieces of rock under the earth and slowly move by convection currents in the mantle (Cowan 1). Sea-floor spreading is the process in which magma from a ridge cools and creates ocean floor. This new ocean floor pushes the older floor towards trenches. …show more content…
First, continental drift and sea-floor spreading both involve the movement of crust. Movement of the continental crust causes the continents to move, and movement of the oceanic crust causes ocean floor movement (Bugielski 1; Evers 1). Next, tectonic plates and continental drift theories both relate to continental movement. Tectonic plates are what move the continents, and the continental drift theory states that the continents move (Bugielski 1). In addition, continental drift and the theory of tectonic plates also have similar pieces of evidence. These pieces include the locations of fossils in places where plants or animals do not live today, and landforms that appear to have previously been connected (Hassler 1). Lastly, sea-floor spreading and tectonic plates are similar because for sea-floor spreading to occur, the tectonic plates need to be involved. The tectonic plates coming towards each other collide, also known as a convergent boundary, forming a ridge, and the sea-floor spreading needs a ridge (Bugielski 1; “There” …show more content…
First, continental drift is the movement of continental crust while sea-floor spreading is the movement of the oceanic floor. The part of the earth each theory discusses is different, one is land while one is under water (Bugielski 1; Evers 1). Second, continental drift is more general than plate tectonics. Continental drift just states that the continents were one large landmass and over time slowly drifted apart, but the theory of tectonic plates explains in detail of how the continents moved (“There” 1; Evers 1). Third, continental drift only focuses on movement of the continents while tectonic plates also includes movement under the oceans (“Earth’s” 1). There are a total of 17 plates: some are just under the continents, some are just under the oceans, and the rest are under both (Keener 1). Fourth, tectonic plates are moving slabs of rock moving under the crust while sea-floor spreading is the creation of new rock. In sea-floor spreading, new rock pushes the older rock away (Cowan 1; Evers 1). The continental drift theory actually helped form the sea-floor spreading theory (Bugielski 1). Finally, continental drift is the actual movement of crust while sea-floor spreading is the cycle of new crust being created under the ocean. The older crust is pushed into the mantle and this is called subduction (Bugielski 1; Cowan 1; Evers