Critical Thinking

Earth of plates which float on and travel

 Earth is rocky. It’s the one of the largest rocky planet orbiting around the sun. Earth is constantly changing and causing natural events such as earthquake and volcanoes. By studying the structure of the earth’s crust and mantle geologist came up with a theory of plate tectonic. The theory of plate tectonic is the lithosphere of the earth is divided into a small number of plates which float on and travel independently over the mantle and much of the earth’s seismic activity occurs at the boundaries of these plates. It explains the formation and movement of Earth’s plates. There are pieces of evidence to prove the theory which are the shape of the continents, age of rocks at the mid-ocean ridge and the change of polarity. Plate tectonics, or plate movements, have changed the way geologists think about the Earth. A long time ago, people thought earth never changed. Overtime, scientist realized the shape of the continent. They started to notice how the continent would fit like a puzzle piece. Alfred Wegener discovered the all the land was joined into one supercontinent called “Pangaea”  and continental drifted apart about 200 million years ago. Continental drift is the lateral movement of continents resulting from the motion of crustal plates. People started to noticed that South America fits almost exactly into Africa. And if you look at the map you will see the similarity between both continent and how they fit together, also they found the fossil match.  Since Wegener put forward his theory of continental drift there have been several pieces of new evidence that support his unproven theory. And one of them is the age of rocks at the mid-ocean ridge. In 1968 the Glomar challenger proof the sea- floor spreading by drilling into the ocean floor. They sent pipes through the six-kilometer deep hole in the ocean floor to collect the sample. From the sample, they noticed that the youngest rock was always in the center of the ridge. The farther they go away from the ridge the older that rock. Another evidence for plate tectonic movement is the change of polarity. Change of polarity is that earth behaves like a magnet, with a north pole and south pole. Earth magnetic poles have changed over the earth’s history.  Earth’s polarity is not constant; the last change occurred 780,000 years ago. Scientist found out that the oceanic floor rock is in a pattern of magnetized “stripes.” and those stripes reverse the earth’s magnetic field. The rock on the oceanic floor began as molten that cool and harden. And the rock on the oceanic floor contains iron so when the molten rock cools down the iron lined up in the direction of earth’s magnetic poles. Plate tectonic is important to us because of that we can understand how our planet earth evolve. Because they are responsible for many of earth structure and futures. As we learn more about plate tectonic plate we will answer the question about volcano, earthquakes, and tsunami. The better we understand plate tectonic the better we live knowing what’s going on underneath our feet