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The Lost Worlds of Planet Earth is the ninth episode of Cosmos A Spacetime Odyssey. It first aired 4 May 2014 on Fox.

Summary

Neil deGrasse Tyson explores the palaeogeography of Earth over millions of years, and its impact on the development of life on the planet. Tyson starts by explaining that the lignin-rich trees evolved in the Carboniferous period about three hundred million years ago were not edible by species at the time and would instead fall over and become carbon-rich coal. Some fifty million years later, near the end of the Permian period, volcanic activity would burn the carbonaceous matter, releasing carbon dioxide and acidic components, creating a sudden greenhouse gas effect that warmed the oceans and released methane from the ocean beds, all leading towards the Permian–Triassic extinction event, killing ninety percent of the species on Earth.

Tyson explains the nature of plate tectonics that would shape the landmasses of the world. Tyson explains how scientists like Abraham Ortelius hypothesized the idea that land masses may have been connected in the past, Alfred Wegener who hypothesized the idea of a super-continent Pangaea and continental drift despite the prevailing idea of flooded land-bridges at the time, and Bruce C. Heezen and Marie Tharp who discovered the Mid-Atlantic Ridge that supported the theory of plate tectonics. Tyson describes how the landmasses of the Earth lay atop the mantle, which moves due to the motion and heat of the Earth's outer and inner core.

Tyson explains the asteroid impact that initiated the Cretaceous–Paleogene extinction event, leaving small mammals as the dominant species on Earth. Tyson describes more recent geologic events such as the formation of the Mediterranean Sea due to the breaking of the natural dam at the Strait of Gibraltar, and how the geologic formation of the Isthmus of Panama broke the free flow of the Atlantic Ocean into the Pacific, causing large-scale climate change,l such as turning the bulk of Africa from lush grasslands into arid plains and further influencing evolution towards tree-climbing mammals. Tyson explains how the influence of other planets in the Solar System have small effects on the Earth's rotation and axial tilt, creating the various ice ages, and how these changes influenced early human's nomadic behavior. Tyson notes how Earth's landmasses are expected to change in the future and postulates what may be the next great extinction event.



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