Geology Bites

• Lindy Elkins-Tanton on the Origin of Earth's Water

  The planets formed out of a cloud of gas and dust around the nascent Sun. Within the so-called snow line, it was too hot for liquid water to exist. Since the Earth lies well within this line, why does it have water? Did it somehow manage to retain water from the outset or did it acquire its water later? In the podcast, Lindy Elkins-Tanton explains how these two scenarios might have played out but she says the evidence strongly favors one of these theories. Elkins-Tanton has concentrated much of her research career on the formation and evolution of planets, and especially the role of water. She is a Professor in the School of Earth and Space Exploration at Arizona State University and Principal Investigator of the NASA Psyche mission.

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• Joeri Witteveen on Golden Spikes

  Golden spikes are not golden, nor are they generally spikes. So what are they, and, more importantly, what exactly do they represent? In the podcast, Joeri Witteveen explains how we arrived at our present system of defining the boundaries of stages in the rock record with a single marker. Paradoxically, it turns out that the best place for a golden spike is where “nothing happens.” Listen and find out why.Witteveen is Associate Professor of History and Philosophy of Science at the University of Copenhagen.

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• Using the Late Paleozoic Ice Age as an Analog for Present Day Climate

  The late Paleozoic ice age began in the Late Devonian and ended in the Late Permian, occurring from 360 to 255 million years ago. It was similar to the present day in two key respects: rising atmospheric CO2 and recurrent major ice sheets. In the podcast, Isabel Montañez explains how we can use proxies to learn about the climate and ocean conditions that prevailed then. And with the help of a model, she says that we can also learn about sensitivities and feedbacks of Earth systems to rising CO2. Among other things, the model suggests that when the atmosphere reaches the present day level of CO2, significant parts of the ocean may become anoxic and ocean circulation patterns alter.Montañez is a Distinguished Professor in the Department of Earth and Planetary Sciences at the University of California, Davis.

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• Ruth Siddall on Urban Geology

  At first sight, urban geology sounds like an oxymoron.  How can you do geology with no rocky outcrops anywhere in sight within the built-up environments of cities?  It turns out you can do a great deal of geology, and Ruth Siddall has been doing just that for the past 10 years. In the podcast, she describes some of the many aspects of geology, from petrology to paleontology, that can be seen very clearly in building stone. She also takes us on a walking tour in London from the Monument to the Great Fire of London to the Tower of London.Siddall has developed nearly 50 urban geology-themed walks and built up a database of over 4,300 urban localities of geological interest. She is a postdoctoral researcher at Trinity College, Dublin, studying the social history and geological provenance of stone in 18th century buildings in Britain and Ireland.

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• Richard Fortey on Deep Time

  The Earth is about 4.5 billion years old. How can we begin to grasp what this vast period of time really means, given that it is so far beyond the time scale of a human life, indeed of human civilization? Richard Fortey has devoted his long and prolific research career at the Natural History Museum in London to the study of fossils, especially the long-extinct marine arthropods called trilobites.  In an earlier episode of Geology Bites, he talked about measuring time with trilobites. In this episode, he describes how it was the fossils in the geological record that gave us the first markers along the runway of deep time, providing the structure and language within which our modern conception of deep time emerged.

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