Extraterrestrial Life Exam Practice 2026

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The discovery of rocks dating to about 4.0 billion years ago implies crust formation happened during which time interval?

First billion years

Rocks dated to about 4.0 billion years ago show the crust was already in place by that time, which means crust formation happened very early in Earth’s history. Since Earth formed around 4.56 billion years ago, having crust by 4.0 billion years ago places crust formation in the first billion years after formation. So the interval that best fits is the early first billion years. That’s why later intervals can’t explain the existence of 4.0 billion-year-old crust, and why the other options aren’t as consistent with the dating evidence.

Second billion years

Third to fourth billion years

After four billion years