Did you ever wonder where the continents came from? Their creation is related to plate tectonic subduction zones and the melting of ocean crust. The subduction zones are like a giant “refinery” which results in the gradual accretion of continents. In this chapter we will learn how to think in “deep time”: thousands, millions, and billions of years. The first sexual reproduction occurred in the ocean less than a billion years ago, but for over 3 billion years before that, the oceans contained strange-shaped mounds made of sediment called “stromatolites” created by cyanobacteria. The Cambrian Period saw the explosion of life, but the fossil record we have is very patchy because the chances for any plant or animal to become a fossil are less than one in a million. The formation of the modern ocean basins began only around 180 million years ago – isn’t it strange that the ocean floor and ocean basins are so much younger than the ocean water they contain?
KeywordsSubduction zone Stratovolcano Pillow lava Zealandia Deep time Stromatolites Sexual reproduction Cambrian explosion Census of Marine Life Fossil Sedimentary rock Trenches Spreading ridges Wilson cycle
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