Calculating Iridium Fallout From an Asteroid Impact

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Description

This activity allows students to calculate how much iridium was released, and eventually deposited all over the Earth, by the impact of an asteroid that struck Earth 66 million years ago. It supports concepts presented in the short film The Day the Mesozoic Died.

This activity challenges students to develop a reasoned estimate of the amount of iridium contained in an asteroid similar in size and composition to the one that struck Earth 66 million years ago, causing the K-Pg (formerly referred to as K-T) mass extinction. Several correction factors and assumptions are introduced to carry out these calculations.

Student Learning Targets

Apply the law of conservation of mass to estimate the abundance and distribution of a substance, such as iridium.
Evaluate a hypothesis by forming rough estimates to verify data presented in support of the hypothesis.
Synthesize information from multiple sources to develop a coherent understanding of an event.

Estimated Time

One 50-minute class period.

Key Terms

chondrite, Cretaceous Period, iridium, meteor, Paleogene Period, “parts per” notation, stratosphere, Tertiary Period

Primary Literature

Alvarez, Luis Walter Alvarez, Frank Asaro, and Helen V. Michel “Extraterrestrial cause for the Cretaceous-Tertiary extinction.” Science 208, 4448 (2008): 1095–1108. https://doi.org/10.1126/science.208.4448.1095. To access this article, set up a free AAAS account.

Smit, J., and J. Hertogen. “An extraterrestrial event at the Cretaceous-Tertiary boundary.” Nature 285, 5762 (1980): 198–200. https://doi.org/10.1038/285198a0.