Chemical Signatures of Asteroid Impacts
This activity allows students to analyze the chemical data that led researchers to conclude that a layer of clay at the boundary between the Cretaceous and Paleogene rock layers (the K-Pg boundary) contained an extraordinary concentration of iridium. It supports concepts presented in the short film The Day the Mesozoic Died.
After watching the film, students will calculate the chemical signatures of two K-Pg (formerly referred to as K-T) boundary samples and compare them to those of a chondrite, a rock that originated from space, and a typical basalt, a rock that originated from Earth’s mantle. Students then evaluate elemental ratios to determine how well the evidence supports the conclusion that the iridium signal in K-Pg sediments was produced by an extraterrestrial impact.
Student Learning Targets
Calculate and use ratios to identify the source of a sample based on its chemical composition.
Evaluate the hypotheses, data, analyses, and conclusions in a scientific or technical text, verifying the data when possible and corroborating or challenging conclusions with other sources of information.
basalt, C1 chondrite, Cretaceous Period, differentiated, iridium, “parts per” notation, platinum-group elements, Tertiary Period, ratio
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HS-ESS1-6, HS-PS1-5; SEP4, SEP6
ELA.RST.9–12.4, ELA.RST.9–12.7, ELA.WHST.9-12.9
Math.N-Q.1, Math.A-REI.2, Math.A-REI.3; MP1, MP2