Lesson 1: Moving Continents PDF

LESSON 1 Dynamic Earth Moving Continents...

LESSON 1 Dynamic Earth Moving Continents Key Concept What evidence supports What do you think? Read the two statements below and decide the continental drift whether you agree or disagree with them. Place an A in the Before hypothesis? column if you agree with the statement or a D if you disagree. After you’ve read this lesson, reread the statements to see if you have changed your mind. Before Statement After India has always been north of the equator. All the continents once formed one supercontinent. Mark the Text Why do some continents have Identify the Main Ideas Highlight two or three matching shapes? phrases in each paragraph Nearly 100 years ago, a scientist named Alfred Wegener (VAY that summarize the guh nuhr) began an investigation. He wanted to know if Earth’s information presented. continents had always been in the same place, or if they had After you have finished the lesson, review the moved. Wegener proposed that all the continents were once part highlighted text. of a supercontinent called Pangaea (pan JEE uh). Over time, Scientific Vocabulary Pangaea broke apart, and the continents slowly drifted to their drift present locations. Wegener proposed the hypothesis of (verb) to slowly and Copyright © McGraw-Hill Education. Permission is granted to reproduce for classroom use. continental drift. The continental drift hypothesis suggested that gradually move continents are in constant motion on the surface of Earth. Wegener looked at the coastlines of continents that are now Scientific Vocabulary separated by oceans. He saw similarities in the shapes of the continental shelf continents, including the continental shelves. For instance, (noun) areas of continent Africa and South America seemed to fit together like the pieces that are under shallow water of a puzzle. Wegener knew that he needed evidence to support his Word Origin hypothesis of continental drift. The most obvious evidence was Pangaea the puzzle-like nature of the continents. But other scientists from Greek pan-, means were doubtful of his hypothesis. Wegener needed more “all”; and Greek gaia, evidence. means “earth” Reading Essentials Dynamic Earth 1 THIS MATERIAL IS PROVIDED FOR INDIVIDUAL EDUCATIONAL PURPOSES ONLY AND MAY NOT BE DOWNLOADED OR FURTHER DISTRIBUTED.  How do rocks provide evidence that continents move? Some of the evidence used by Wegener to support his idea of continental drift came from rock formations on the continents in the Southern Hemisphere. Evidence from Rock Formations Many rock formations and mountain ranges on Australia, South America, Africa, India and Antarctica all seemed to have formed in the same way at the same time. Today geologists know that there were large-scale volcanic eruptions on the western coast of Africa and on the eastern coast of South America hundreds of millions of years ago. Geologists have studied rocks from these eruptions. They Scientific Vocabulary determined that the volcanic rocks from both continents were chemistry identical in chemistry and age. (noun) the structure of More evidence came from the rocks that make up two substances and the way that they combine or mountain chains in Europe and North America. The Caledonian change with each other mountain range is in northern Europe, and the Appalachian Mountains are in eastern North America. Academic Vocabulary Rocks in these two mountain chains are similar in age and compose structure. Both are also composed of the same rock types. If you (verb) to form or make up could place North America and Europe next to each other, these mountain chains would meet. They would form one long, continuous mountain belt. Evidence from Glacial Features Another clue used by Wegener to support continental drift came from glaciers. When Wegener pieced Pangaea together, he proposed that South Scientific Vocabulary America, Africa, India, and Australia were located closer to the ice sheet South Pole 290 million years ago. He suggested that a large ice (noun) a glacier that sheet covered much of these continents. When the ice sheet spreads out over land in melted as Pangaea spread apart, it left rock and sediment Copyright © McGraw-Hill Education. Permission is granted to reproduce for classroom use. all directions behind. Wegener studied the similarities of these sediments. Wegener also studied glacial grooves. Glacial grooves are deep scratches in rocks made as ice sheets move across the land. Wegener found glacial grooves on many different continents. By studying these grooves, he was able to determine the direction that the ice sheet moved across the joined continents. Evidence from Coal Deposits Coal beds are in Antarctica, a polar climate today. Yet coal formed from fossilized plants that lived long ago in warm, wet climates. This meant that Antarctica must have been warmer and wetter when these plants were alive. Wegener used this evidence to conclude that Antarctica must have been much closer to the equator sometime in the geologic past. 2 Dynamic Earth Reading Essentials THIS MATERIAL IS PROVIDED FOR INDIVIDUAL EDUCATIONAL PURPOSES ONLY AND MAY NOT BE DOWNLOADED OR FURTHER DISTRIBUTED.  How do fossils provide evidence that continents move? There are many animals and plants that live only on one continent. For example, lions live in Africa but not in South Academic Vocabulary America. Because oceans separate the continents, animals separate cannot travel from one continent to another by natural means. (verb) to stop being However, fossils of similar organisms have been discovered on together several continents that are now separated by oceans. Evidence from Fossils Fossils of a plant called Glossopteris (glahs AHP tur us) have been discovered in rocks from South America, Africa, India, Antarctica, and Australia. Today these continents are far apart and separated by oceans. The plant’s seeds, which were large and heavy, could not have traveled across the oceans. The figure below shows how some of the continents were joined as part of Pangaea 250 million years ago. The lighter area Scientific Vocabulary on the map shows where Glossopteris fossils have been found. fossil Notice that the plant once grew in parts of five continents— (noun) the naturally South America, Africa, India, Antarctica, and Australia. Because preserved remains, imprints, or traces of these plants grew in a swampy environment, this region, organisms that lived including Antarctica, was different from how it is today. Most of long ago Antarctica is covered in ice sheets. No swampy environments are found there now. Copyright © McGraw-Hill Education. Permission is granted to reproduce for classroom use. Africa South America India Antarctica Australia Reading Essentials Dynamic Earth 3 E130_104A_NGMSS-BANK THIS MATERIAL IS PROVIDED FOR INDIVIDUAL EDUCATIONAL PURPOSES ONLY AND MAY NOT BE DOWNLOADED OR FURTHER DISTRIBUTED.  Academic Vocabulary skeptical What was missing? Wegener supported his continental drift hypothesis until his (adjective) to be doubtful about something death in 1930. Wegener’s ideas were not widely accepted until nearly 40 years later. Why were scientists skeptical of Wegener’s hypothesis? Continental drift is a slow process. Wegener could not Scientific Vocabulary measure how fast the continents moved. Wegener also could not mantle explain what forces caused the continents to move. The mantle (noun) the middle layer under the continents and seafloor was made of solid rock. How of Earth, situated between could continents push their way through solid rock? Wegener the crust above and the needed more scientific evidence to prove his hypothesis. core below The evidence for drifting continents was hidden on the seafloor. During Wegener’s lifetime, scientists did not have the tools to determine what happens beneath the oceans. Wegener also could not have known what the seafloor looked like. The evidence needed to prove continental drift was not discovered until long after Wegener’s death. Reread the statements at the beginning of the lesson. Fill in the After column with an A if you agree with the statement or a D if you disagree. Did you change your mind? Copyright © McGraw-Hill Education. Permission is granted to reproduce for classroom use. 4 Dynamic Earth Reading Essentials THIS MATERIAL IS PROVIDED FOR INDIVIDUAL EDUCATIONAL PURPOSES ONLY AND MAY NOT BE DOWNLOADED OR FURTHER DISTRIBUTED.