Overall Habitability: Connections with Geological and Astronomical Events and Processes

Abstract

This book investigates the billion-year takeover of planet Earth by its organisms and ecosystems. This chapter considers the Earth’s overall habitability, that is, the proportion of the surface of the planet that is habitable. It examines variations in the extent of the Earth’s habitable environments over a wide range of periods: diurnal, annual, within centuries, and from tens of thousands to hundreds of millions of years. These variations include the recurrence of large and very large volcanic eruptions, the Ice Age of the Quaternary period (last 2.6 million years), the three snowball Earth episodes, long periods of high and low temperature during the last half billion years, and the alternation of greenhouse and icehouse Earth since 4.5 billion years. The chapter also examines the five mass extinctions documented by the fossil record of the last 540 million years, which are witnesses of major crashes in habitability. Biological innovations have also caused major changes in overall habitability. These innovations include oxygen-producing photosynthesis, calcification, silicification, methanogenesis, oxygen respiration, and multicellularity. The overall habitability of Earth is affected by astronomical and environmental factors that include the Earth’s rotation and orbit around the Sun, the Milankovich orbital cycles, changes in the positions of continents, the impacts of large meteoroids, large volcanic eruptions, and climate changes. In addition, it is presently affected by anthropogenic changes of atmospheric gases. The chapter ends with a summary of key points concerning the interactions between the Solar System, Earth, its overall habitability, and organisms.

Figure Credits

Fig. 4.1 Extracted from Figure 1 of Schokraie et al. (2012) https://journals.plos.org/plosone/article/figure?id=10.1371/journal.pone.0045682.g001, used under CC BY 4.0.

Fig. 4.2 Figure 7j-1 of Pidwirny (2006) http://www.physicalgeography.net/fundamentals/7j.html. Figure produced by Dr. Michael Pidwirny, University of British Columbia, Canada, and reproduced with his permission © Michael Pidwirny.

Fig. 4.3 This work, Fig. 4.3, is a derivative of a figure in Lecture 19.1 “Advanced topic: Heat transport decomposition. 7. Calculating the partitioning of poleward energy transport into different components” of Rose (2020) https://brian-rose.github.io/ClimateLaboratoryBook/courseware/advanced-heat-transport.html by Dr. Brian Rose, State University of New York at Albany, USA, used under CC BY 4.0. Figure 4.3 is licensed under CC BY 4.0 by Mohamed Khamla.

Fig. 4.4 Modified after Figure 2A of Smith and Pickering (2003). With permission from Prof. Kevin T. Pickering, University College London, England.

Fig. 4.5a This work, Fig. 4.5a, is a derivative of https://commons.wikimedia.org/wiki/File:Vostok_Petit_data.svg by NOAA (Vostok-ice-core-petit.png) https://commons.wikimedia.org/wiki/File:Vostok-ice-core-petit.png), derivative work used under CC BY-SA 3.0 and GNU FDL. Figure 4.5a is licensed under CC BY-SA 3.0 and GNU FDL by Mohamed Khamla.

Fig. 4.5b This work, Fig. 4.5b, is a derivative of https://earthobservatory.nasa.gov/Features/BorealMigration/boreal_migration3.php by NASA’s Earth Observatory, in the public Domain. I, Mohamed Khamla, release this work in the public domain.

Fig. 4.6 This work, Fig. 4.6, is a derivative of https://commons.wikimedia.org/wiki/File:2000_Year_Temperature_Comparison.png by Robert A. Rohde https://en.wikipedia.org/wiki/User:Dragons_flight, used under GNU FDL and CC BY-SA 3.0. Figure 4.6 is licensed under GNU FDL and CC BY-SA 3.0 by Mohamed Khamla.

Fig. 4.7 https://commons.wikimedia.org/wiki/File:Rodinia_reconstruction.jpg by John Goodge, United States Antarctic Program, in the Public Domain. Change in the positions of the two colour legends.

Fig. 4.8 This work, Fig. 4.8, is a derivative of https://commons.wikimedia.org/wiki/File:Phanerozoic_Climate_Change.png by Robert A. Rohde https://en.wikipedia.org/wiki/User:Dragons_flight, used under GNU FDL and CC BY-SA 3.0. Figure 4.8 is licensed under GNU FDL and CC BY-SA 3.0 by Mohamed Khamla.

Fig. 4.9 This work, Fig. 4.9, is a derivative of https://commons.wikimedia.org/wiki/File:LateCretaceousMap.jpg by Philip D. Mannion, Figure 3 in Mannion et al. (2014), used under CC BY-SA 3.0. Figure 4.9 is licensed under CC BY-SA 3.0 by Mohamed Khamla.

Fig. 4.10a https://www.climate.gov/sites/default/files/paleo_CO2_2018_1500.gif, from https://www.climate.gov/news-features/understanding-climate/climate-change-atmospheric-carbon-dioxide by NOAA, in the public domain. Some indications inside the figure removed, and titles of two axes rewritten.

Fig. 4.10b This work, Fig. 4.10b, is a derivative of https://commons.wikimedia.org/wiki/File:All_palaeotemps.svg by Glen Fergus https://commons.wikimedia.org/wiki/User:Glen_Fergus, used under CC BY-SA 3.0. Figure 4.10b is licensed under CC BY-SA 3.0 by Mohamed Khamla.