12 1 Evidence for Continental Drift Early maps

12. 1 Evidence for Continental Drift • Early maps of the world caused __________ to propose the ___________________. w The continents looked as though they might fit together like ______________. § The _________________actually fit together even better. w The original supercontinent was named __________by Wegener. w Wegener also realized that other evidence also supported his theory. Like pieces a § of There were matching _________and rocks on jigsaw puzzle, different continents. the continents fit together § into There were matching _____, like Mesosaurus, on See pages 506 - 509 one, large whole. different continents. (c) Mc. Graw Hill Ryerson 2007

How Can Continents Move? • Wegener’s evidence for continental drift did not explain how ____________could change _________. w New scientific equipment allowed scientists to measure the ______________ drift of Earth’s tectonic plates. w It was noted that __________ and __________ appear in certain patterns along the edges of tectonic plates. w Mapping of the ocean floor revealed the ________________, a long mountain range running down the middle of the Atlantic Ocean. w Rocks taken from the Mid-Atlantic Ridge were Volcanoes are frequently found on boundaries between _________ than other ocean rocks. tectonic w Sediments along the ridge became ______ farther away plates. from the ridge. w _________ shows that See pages 510 - 512 iron-based rocks along the (c) Mc. Graw Hill Ryerson 2007

Sea Floor Spreading: An Explanation • ________ suggested that magma rose to form new rock at certain places. w Magma (___________) rises and falls like warm and cold liquids. w The convection currents of magma formed a spreading ridge where they broke through Earth’s crust. § Like a “_________” conveyer belt § Magnetic striping of basalt rock shows long stripes of new rock moving away from ocean ridges and also reveals the direction of Earth’s _________________at that time. • ___________ then unified the ideas of Wegener and Hess into the ___________________. w Continental drift occurs because of areas like Mc. Graw Hill that Ryerson 2007 See pages 512 these - 513 (c)ridges