50 years ago, scientists thought they had found Earth’s oldest rocks

Excerpt from the July 21, 1973 issue of Science News

photo of bedrock in Canada

The oldest known rock on Earth, dating to about 200 million years after the planet formed, lies within bedrock in northeastern Canada (shown).

Jonathan O'Neil/NSF

cover of the July 21, 1973 issue of Science News

Oldest rocks Science News, July 21, 1973

Until recently, Greenland possessed the oldest known rocks in the world. They date back 3.7 billion years (SN: 12/9/72, p. 374). Now granite and crystalline schist specimens … suggest that the Antarctic Continent is older. These specimens date back 4 billion years.


At about 4.3 billion years old, bedrock in northeastern Canada currently holds the title of oldest known rock on Earth (SN: 4/15/17, p. 8). In Western Australia, scientists have found zircon crystals in bedrock that are even older, dating to about 4.4 billion years ago. For comparison, Earth is only about 4.5 billion years old.

Since these ancient materials preserve information about early Earth, they have fueled ongoing debates about when and how Earth’s crust formed, when plate tectonics started and even when life on the planet first arose (SN: 2/23/14; SN: 5/2/22; SN: 10/19/15). Additional clues that could help resolve the debates might lie on the moon. Lunar samples collected by Apollo 14 astronauts contain 4-billion-year-old zircons that may have been delivered via an Earth meteor, scientists reported in 2019.

Lillian Steenblik Hwang is the associate digital editor at Science News Explores. She has a B.S. in biology from Georgia State University and an M.S. in science journalism from Boston University.

More Stories from Science News on Earth