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Science Journey: Beyond Bones: Reading the Fossil Record of Earth and Other Worlds

Cecilia Sanders, Graduate Student in Geobiology

This video premiered on Friday, February 5, 2021.

How old is the earth? How long have humans lived on it? How long have other life forms lived on it?

This program includes a discussion of past climate change, and how previous episodes of climate and biological upheaval differ from the human influenced climate crisis of today.

Caltech graduate student Cecilia Sanders explains how the living and non-living parts of our planet have shaped each other.

Some questions to wonder about before watching:

  • What is the difference between a living thing and a nonliving thing? (Or, what is the definition of life?)
  • How do we know how old a rock is? How do we know how old the Earth is?
  • The world has changed in the past, so can we expect it to change again? How quickly or slowly?

About the Speaker

Cecilia Sanders is a PhD candidate in geobiology at Caltech, where she studies the geologic record for information about lifeforms on ancient Earth. This is an extension of her previous work as a Masters' student of planetary sciences, when she was intrigued by the preservation problem: how do living things impact the world around them in a way that is preserved in rocks for millions to billions of years?

Cecilia tries to answer these questions by measuring and sampling assemblages of ancient, sedimentary rock, and by creating models of the ancient world using living organisms in the laboratory. Her work has taken her to Brazil, Namibia, Turks and Caicos, all over the southwestern United States, and even back home to the fossiliferous cliffs of Maryland/DC.

When she isn't doing research, she teaches science to Kindergarten, 1st-, and 2nd-graders in Pasadena Unified schools and is a community activist for racial justice. She loves to paint, to read fantasy novels, and to run tabletop role playing games for her family and friends. Her favorite foods are bolinhos do chuva and doce do leite.

About the Series

Science Journeys online programs are recommended for grades 8 and up, but everyone is welcome to attend.

These programs are made possible through the generosity of the Friends of Beckman Auditorium.

If you have questions, please email Mary Herrera at

Cecilia Sanders
Ceclia Sanders

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