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Western Slope Skies - The Impact of Outer Space Here on Earth


When most people think of astronomy, they think of planets and galaxies that are far, far away. But one can experience astronomy right here on Earth. Studying the extraterrestrial helps us understand the terrestrial, our own planet.

Geology, the study of the Earth, is more connected to astronomy than you might think. For example, we know that the mass extinction that ended the age of dinosaurs occurred 66 million years ago. Until recently, scientists were unsure of its cause. In the 1970s, renowned geologist Walter Alvarez and his father Luis Alvarez discovered a thick layer of clay full of iridium in Italy. Iridium is an element that is rare on Earth’s crust but is common in asteroids. The iridium-rich clay was also found at many sites around the world, from Italy to Denmark to New Zealand.

At these sites, the iridium-rich clay was deposited around 66 million years ago, the same time as the dinosaur mass extinction. The presence of the iridium at various places around the globe led the Alvarez duo to conclude that an asteroid impact caused the mass extinction. The discovery of a massive crater near Chicxulub, Mexico further supported their asteroid theory. Other geologists dated this crater to be approximately 66 million years old, and the asteroid theory became generally accepted.

We must explore the extraterrestrial to understand the terrestrial; we must look outward to see inward. As we stand here on Earth and look up at the vastness of space, it’s important to remember that astronomy and geology aren’t distinct fields; they are inherently connected. At times, you might even say they collide.


You’ve been listening to Western Slope Skies produced by the Black Canyon Astronomical Society. This episode was written and recorded by Joanne Ensley, interpretive ranger at Devils Tower National Monument.