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Common Core Reading
Pangaea
Looking at a globe reveals coincidences that are difficult to ignore. The Eastern coast of South America seems to fit perfectly, almost like a puzzle, into the Western coast of Africa. At the same time, North America can be rotated slightly, and made to fit comfortably next to Europe, and Asia. These clues have lead geologists and other scientists to examine the relationships of other clues. Ancient fossil records show that the same plants and animals lived along the Eastern coast of South America, as did along the Western coast of Africa, as did other places. With this over whelming evidence, it became clear that at some point many millions of years ago, these continents must have in fact been connected. Scientists now believe that about 250 million years ago, a supercontinent known as Pangaea existed. This supercontinent was made up of all the continents on Earth. Over time, these continents have broken apart, and slowly drifted away from one another. This drift continues today, so that the form the Earth takes today is not by any means the final shape of our Earth. Pangaea was a supercontinent that existed at the time of the Dinosaurs. The word Pangaea comes from an ancient Greek word meaning “all lands.” Pangaea was created when all the continents we know today smashed together like some giant car wreck. This crashing together was not a gentle process. The Appalachian Mountains in North America and the Ural Mountains on the boundary of Europe and Asia are the results of some of these collisions. That's right -­‐ the continents smashed together hard enough to form mountains! Pangaea was shaped like a giant letter C. It sprawled across the equator and extended from the North Pole to the South Pole. If you lived at the time of Pangaea, you could walk from the North Pole to the South Pole without getting your feet wet... well, unless you had to wade in a river or something. Pangaea started to form about 540 million years ago in the late Cambrian time period. It didn't finish forming until the Triassic period approximately 200-­‐250 million years ago. Because all the land was in one big mass, the scientists believe that the climate of Pangaea was much drier and hotter than it is now. Pangaea started to break up into the continents that we know now during the middle of the Jurassic time period, about 175 million years ago. Have you ever noticed that the east coast of South America and the west coast of Africa look like they could fit together like a giant jig saw puzzle? That's because they used to be stuck together. It's harder to see but, if you look at the North American Continent and Greenland you can see that they look like puzzle pieces, too. At one point North America, Greenland and Europe were all connected; because North America and Europe were connected, you can find the same rock formations in New York and in Scotland. Geologists call the process of breaking up rifting. Rifting happens when two tectonic plates move apart on what geologists call a divergent plate boundary. That's how scientists talk. Here's how it works. The Earth's crust is not a single piece but is broken up into several pieces called plates. These plates float like giant rafts on a sea of melted rock called the mantle. At some places the plates crash into each other and one plate is shoved under the other and starts to melt. This kind of boundary is called a convergent boundary. In other places the plates are forced apart when melted rock flows up from the mantle and cools forming new crust. This type of boundary is called a divergent boundary. As the continents move far enough apart, the water from the ocean flows in to fill up the space. This process happens very slowly as the tectonic plates only move from 0 to 100mm (0 to 3.9 inches) per year. The rifting of Pangaea started with North America and Africa, and rifting continues on the east side of Africa near the Red Sea in an area called the Great Rift Valley. The land mass that would become North America was twisted so that the Mississippi River Valley would have been running east to west, not north and south. In fact, the Mississippi River Valley is the result of a failed rift. When North America finally rifted away from Africa, it formed the beginning of what is now the Atlantic Ocean. At the same time, rifts were forming between Africa, Antarctica and Australia, forming the start of the Indian Ocean. The Cretaceous period was when North America and Europe rifted apart. The continents wouldn't reach their current arrangement until 35 million years ago when India crashed into Asia forming the Himalayan Mountains. 1. What is the author’s purpose? Use evidence from the article to prove your point. (ANALYSIS RI 8.6) 2. What does the word Pangaea mean (Knowledge, RI 8.1)? 3. Is the theory of Pangaea believable? Use evidence from the article to prove your point. (Evaluation RI 8.2,RI 8.8) 4. Summarize the this article in 8 sentences OR write at least 10 facts your read from it. (ANALYSIS RI 8.1, RI 8.2)