Geologic time scale

High school (ages 12+)
Environment & Earth

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/geologic-time-scale

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 basis of chronological dating?The rock record of Earth, organized through chronostratigraphy and geochronology
2. What is the international standardization body?The International Commission on Stratigraphy (ICS)
3. How do scientists know which rock layers are older or newer?In undisturbed rock layers, the oldest rocks are at the bottom and the newest at the top, a rule called the Law of Superposition.
4. Why are fossils important for the geologic time scale?Fossils that lived only for a short time and were found everywhere act as time markers, letting scientists match layers from different places.

Chronostratigraphy: The branch of stratigraphy concerned with time, relating rock strata to time.
Geochronology: The scientific dating of rocks and geological events to determine their absolute age.
Index Fossils: Fossils of organisms that lived for a short, distinct period and are used to date rock layers.