evgeoterra

Giovanni Muttoni - The State University of Milan

This course offers an integrated and unconventional view of Earth history, focusing on the geological evolution of Earth as a habitable planet rather than on geology as a collection of separate disciplines. The course follows a logical progression from the formation of a wet rocky planet, through the origin and long-term maintenance of liquid water, to the physical and chemical feedbacks that regulate climate over geological time. Central themes include plate tectonics, the carbon cycle, planetary albedo, atmospheric oxygenation, and the role of Earth’s magnetic field in protecting the atmosphere.

A distinctive feature of the course is its strong emphasis on climate extremes, planetary thresholds, and system instability, such as Snowball Earth events and mass extinctions, treated as fundamental components of Earth’s habitability rather than anomalies. Biological evolution is consistently linked to geological and environmental change, from the earliest microbial life to the emergence of complex ecosystems and, ultimately, humans. The course concludes by placing Earth in a broader planetary and astrobiological context, discussing habitability, extraterrestrial life, and the uniqueness of Earth-like planets.

Overall, this is a systems-level, process-driven course that connects geology, climate, biology, and planetary science, and is designed to help students understand why Earth remained habitable for billions of years, not just what happened through time.

Cooper : Detach!
Brand : Goodbye TARS.
TARS : Good-bye Dr. Brand. See you on the other side Coop.
Cooper : See you there slick!

LECTURES (* are mandatory)

Part 0. Introduction

Class discussion on the basic requirements for simple life and complex life.

Introductory icebreaker lecture: how many Earths?

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Part I. Setting the scene: the first half billion years. Formation of a wet rocky planet

Early Earth 4.56-3.9 By *

Halliday, A. N. (2006), The origin of the Earth-What's new?, Elements, 2(4), 205-210.

History of the Hadean&Archean

Early Earth additional lectures

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Part II. Liquid water: origin

Origin of Water *

Welcome on a Comet!

Wet Stardust?

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Part III. Liquid water: maintenance. The long-term carbon cycle, planetary albedo and other climatic nuisances

III.1 Zonal climate, plate tectonics & Earth's thermostat

Without the radiative forcing supplied by CO2 and the other noncondensing greenhouse gases, the terrestrial greenhouse would collapse, plunging the global climate into an icebound Earth state.

Additional material for exercises:

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III.2 The role of planetary albedo

The building of polar ice has the effect to amplificate – through enhanced planetary albedo – global cooling resulting from the reduction of greenhouse gases via CO2 weathering consumption of mafic rocks in the tropical humid belt.

Kent, D.V., Muttoni, G. Latitudinal land–sea distributions and global surface albedo since the Cretaceous. Palaeogeography, Palaeoclimatology, Palaeoecology 585, 110718, 2022.

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Part IV. Liquid water: climate extremes

...expectations are that the silicate weathering thermostat would always be operative at the high temperature end and act to limit global overheating. However, at times when continental drift focused the weathering-prone landmasses in the pCO2-insensitive equatorial belt, the low range of the thermostat could become decoupled from global climate, allowing Earth to descend into glacial modes of varying severity.

Snowball Earth *

Hoffman, P. F., A. J. Kaufman, G. P. Halverson, and D. P. Schrag (1998), A Neoproterozoic snowball earth, science, 281(5381), 1342-1346.

Hoffman, P. F., and D. P. Schrag (2002), The snowball Earth hypothesis: testing the limits of global change, Terra nova, 14(3), 129-155.

Documentary 'Snowball Earth'

From the Early Eocene Climatic Optimum to the Neogene Ice Age *

Kent, D. V., and G. Muttoni (2008), Equatorial convergence of India and early Cenozoic climate trends, Proceedings of the National Academy of Sciences, 105(42), 16065-16070.

Kent, D. V., and G. Muttoni (2013), Modulation of Late Cretaceous and Cenozoic climate by variable drawdown of atmospheric pCO 2 from weathering of basaltic provinces on continents drifting through the equatorial humid belt, Climate of the Past, 9(2), 525-546.

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Part V. Oxygen

The G.O.E. and the N.O.E. *

Kump, L. R. (2008), The rise of atmospheric oxygen, Nature, 451(7176), 277.

Shields-Zhou, G., and L. Och (2011), The case for a Neoproterozoic oxygenation event: geochemical evidence and biological consequences, GSA Today, 21(3), 4-11.

LECTURES

Part VI. Earth's magnetic shield

Magnetic shielding of atmosphere *

Tarduno, J. A., R. D. Cottrell, W. J. Davis, F. Nimmo, and R. K. Bono (2015), A Hadean to Paleoarchean geodynamo recorded by single zircon crystals, Science, 349(6247), 521-524.

Tarduno, J. A., E. G. Blackman, and E. E. Mamajek (2014), Detecting the oldest geodynamo and attendant shielding from the solar wind: Implications for habitability, Physics of the Earth and Planetary Interiors, 233, 68-87.

Magnetopause standoff exercise

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Part VII. From simple to complex life

Early life forms: from microbes to Ediacara

-> read also this article

Virtual Field Trip to the Dresser Formation *

Rapid emergence of life shown by discovery of 3,700-million-year-old stromatolites in SW Greenland

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Ediacara Day Students' presentations

(see Students page, top left)

Pick your favourite beast

Trip to Mistaken Point *

Brasier, M., and J. Antcliffe (2004), Decoding the Ediacaran enigma, Science, 305(5687), 1115-1117.

Xiao, S., and M. Laflamme (2009), On the eve of animal radiation: phylogeny, ecology and evolution of the Ediacara biota, Trends in Ecology & Evolution, 24(1), 31-40.

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Part VIII. Evolution of life: the role of catastrophism

The punctuated equilibrium theory of Gould and Eldredge,1993 Jay Gould, S., and N. Eldredge (1993), Punctuated equilibrium comes of age, Nature, 366(6452), 223.

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Case Study #1: The P/T boundary *

Lane, N. (2007), Reading the book of death, Nature, 448(7150), 122-125.

Docu 'The day Earth nearly ended'

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Case Study #2: The K/T boundary *

Impact energy exercise

Impact scaling exercise

Alvarez+1980

Hildebrand+1991

The First Day of the Cenozoic

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Pierazzo, E., and N. Artemieva (2012), Local and global environmental effects of impacts on Earth, Elements, 8(1), 55-60.

LECTURES

Part IX. The last two million years: how humans conquered planet Earth

Ice Ages & First hominin colonization of Eurasia. On the importance of migrations for survival and evolution.

Muttoni, G., G. Scardia, and D. V. Kent (2018), Early hominins in Europe: The Galerian migration hypothesis, Quaternary Science Reviews, 180, 1-29.

Muttoni, G., and Kent, D.V. (2024). Hominin population bottleneck coincided with migration from Africa during the Early Pleistocene ice age transition. Proc Natl Acad Sci U S A. 26;121(13)

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Part X. Final Wrap-up: The importance of the Earth's characteristics for the evolution of complex life: implications for finding extraterrestrial civilizations

Discussion on the Drake equation and the Fermi paradox.

The Drake equation estimates how many ACCs there are in our galaxy. It is formulated as93:

where

R* = number of new stars formed per year,

fp = the fraction of stars with planetary systems,

ne = the average number of planets that could support life (habitable planets) per planetary system,

fl = the fraction of habitable planets that develop primitive life,

fi = the fraction of planets with life that evolve intelligent life and civilizations,

fc = the fraction of civilizations that become ACCs, L = the length of time that ACCs broadcast radio into space.

...and the importance of plate tectonics

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EXERCISES