Geochronology

High school (ages 12+)
Geography

Name:

Date:

Step 1 · Read the article

Open the article and read it at the level above. Then answer the questions below in your own words.

https://smallwhale.org/articles/geochronology

Write what each word means, using the article.

Do not copy the article. Write two things you learned, the way you would explain them to a friend.

Answers below are taken from the article’s stored facts, so they match what the student read.

1. What is the oldest known terrestrial rocks?Acasta Gneiss, Canada, dated at ~4.03 billion years
2. What is the key isotopic systems?U-Pb, K-Ar, Ar-Ar, Rb-Sr, Sm-Nd, C-14
3. How do scientists know how old a rock is?They use radiometric dating, which looks at how long it takes radioactive atoms to turn into other atoms inside the rock. By comparing the amounts, they can calculate the time that has passed.
4. Why do scientists use different dating methods like U‑Pb or K‑Ar?Different methods work best on different kinds of rocks and ages. For example, U‑Pb in zircon can date rocks older than 4 billion years, while K‑Ar is good for volcanic rocks.

Radiometric Dating: A method of determining the absolute age of rocks and minerals using the decay of radioactive isotopes.
Half-life: The time required for half of a radioactive isotope to decay into its daughter product.
Isotopic System: A specific pair of parent and daughter radioactive isotopes used for dating.
Thermochronology: The study of the timing and rate of cooling of rocks.