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1月7 Fun Holiday – Old Rock Day

January 7 is Old Rock Day. The unofficial holiday encourages people to acknowledge, celebrate, and learn more about old rocks and fossils.

Ammonite fossil.

Old rocks can contain fossils.

©iStockphoto.com/Matauw

A rock is a solid mass made of minerals or mineral-like substances. Used for a variety of purposes throughout the history of humankind - as tools, musical instruments, weapons and for mining - rocks form the outermost layer of Earth.

A Peek Into Earth's History

While natural processes - volcanic eruptions and erosion - continually help create rocks on Earth, old rocks are especially important to those who study the Earth and its history. Old rocks hold many answers to the mysteries of Earth's formation - they can tell scientists about natural events that played a role in the formation of the rocks and the effects that event had on other life forms in the area.

Old rocks can also sometimes hold fossils - the preserved remains of animals, plants and other organisms. These fossils can help scientists find out the kind of flora and fauna that existed in the past and what may have caused them to evolve or go extinct.

Finding the Age of Old Rocks

Geologists date old rocks using a technique called radiometric dating or radioactive dating. The process involves looking at the decay of radioactive elements available in rocks. The oldest rock of terrestrial origin to be dated using this method is a zircon found in the Jack Hills of Australia. Scientists estimate that the rock could be as old as 4.4 billion years.

How to Celebrate?

  • Learn more about the types of old rocks.
  • Pick up a book about fossils and learn how fossils tell us more about the Earth’s past or visit your local natural history museum.
  • Take a walk in the park and collect interestingly shaped rocks.
  • Buy your loved ones some pretty looking rocks. And by rocks, we mean jewels. After all, diamonds are old rocks.
  • Looking for a new hobby? May we suggest collecting rocks?
  • Find rocks boring? Listen instead to music from old rock bands.

Did You Know…

...that Petrology is the scientific study of rocks?

Old Rock Day Observances

Fun Holiday: Old Rock Day Observances
YearWeekdayDateName
2025火曜日1月7日 (火)Old Rock Day
2026水曜日1月7日 (水)Old Rock Day
2027木曜日1月7日 (木)Old Rock Day
2028金曜日1月7日 (金)Old Rock Day
2029日曜日1月7日 (日)Old Rock Day
2030月曜日1月7日 (月)Old Rock Day
2031火曜日1月7日 (火)Old Rock Day
2032水曜日1月7日 (水)Old Rock Day
2033金曜日1月7日 (金)Old Rock Day
2034土曜日1月7日 (土)Old Rock Day

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