OSU OC 103 - e-OC103_Lesson09 (8 pages)

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e-OC103_Lesson09



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e-OC103_Lesson09

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Pages:
8
School:
Oregon State University
Course:
Oc 103 - Exploring The Deep: Geography Of The World's Oceans

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OC103 Lesson 9 Hot Spots and Mantle Plumes Tails You Win Heads You Die We have used Plate Tectonic Theory to explain most of the major features we see along plate boundaries in the ocean basins such as mid ocean ridges and deep sea trenches but you can see on the map below that there are some long chains of underwater volcanic mountains that do not correspond to any plate boundary Examples include the long chain of seamounts that extends to the northwest from the Hawaiian Islands and the line of seamounts that extends from eastern India and Bangladesh southward across the Indian Ocean This lesson provides an explanation for these long chains of volcanic seamounts that is consistent with plate tectonics but also may have some serious implications for the past survival of life on Earth Age Progression of the Hawaiian Islands There are other examples but Hawaii is the classic case of a volcanic island chain in the middle of a tectonic plate It is far from any plate boundary so cannot be related to seafloor spreading nor subduction One obvious clue that these volcanic seamount chains have fundamentally different origins than seafloor spreading centers is that the seamounts are not all the same age but instead have a systematic progression of ages In the Hawaiian Islands the youngest island is the Big Island of Hawaii where active volcanism continues today and islands to the northwest of the Big Island get progressively older The oldest major Hawaiian island Kauai is the northwesternmost of the major islands and formed from volcanic eruptions about 4 million years ago The small islands to the northwest of Kauai are even older Farther to the northwest the islands have been eroded down to below sea level but a long chain of seamounts continues to the northwest just barely visible as a thin yellow line on the map on the previous slide all the way up to the oldest seamount about 80 million years old in the northwest corner of the Pacific Ocean near Siberia see figure below



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