Geologic Column: Celebrating Old Rock Day

by John Copeland
Thursday, December 14, 2017

Move over New Year’s: There’s a new favorite holiday in January, at least for geologists. Jan. 7 marks “Old Rock Day.” No, this is not the day to celebrate old rock ‘n’ roll music or the elderly musicians still playing it. Old Rock Day is the day that geoscientists and rock enthusiasts encourage people to celebrate and learn more about old rocks and fossils.

There are a lot of holidays spread across the year. Some are major holidays, like Christmas and the Fourth of July; others are unofficial holidays that are quirky, not widely observed and yet still have passionate aficionados, like Talk Like a Pirate Day or National Nothing Day. Many of these unofficial holidays, April Fools' Day and National Grilled Cheese Sandwich Day among them, have unknown origins. The same is true of Old Rock Day. Not even those of us considered to be fossils in our own right know the origin of this rocky holiday.

Throughout human history, rocks have been important to us and we have found many uses for them: as tools, musical instruments, weapons, adornments, building materials, and as sources of fuel and crucial elements. Like our ancestors, I have always been intrigued by all kinds of rocks. So even though I’m a filmmaker and not a geologist, I’m always on the lookout for cool rock formations.

When I was scouting locations for a Discovery Channel documentary, my travels took me to Dove Lake near Cradle Mountain in Tasmania. Above the lake, I came upon an area where, over a distance of just half a kilometer, you can walk across rocks formed over hundreds of millions of years from the Precambrian through the Jurassic Period. As I walked among these ancient relics of Earth’s past — from ages almost unfathomably distant — I felt like I was time traveling. It was a very moving experience.

On another occasion, in Iceland, I encountered an entire hillside of obsidian — the vast package of black glass, relatively young by geologic standards, was stunning to behold. Iceland hosts a lot younger rocks than most other sites in the world, including Cradle Mountain, and new rock is formed there every day! Later the same day, I found myself standing with one foot on the North American Plate and the other on the Eurasian Plate. This was another moment of feeling a connection with Earth’s processes.

Old Rock Day also celebrates fossils. The processes that produce fossilization are rare, and only a tiny fraction of the plants and animals that have inhabited Earth are preserved as fossils. We know of about 250,000 species that have been fossilized. But today alone, upwards of 4.5 million species are estimated to be living on Earth. If you do a rough calculation multiplying the present biodiversity by the 600 million years over which life has existed, you can see that it’s only a minute percentage of life that’s been fossilized.

Studying the fossil record — which comprises all fossils known and unknown, as well as the rocky context in which they’re found — is what began our understanding of evolution; and the fossil record is still used as a source for broadening our knowledge of the history of life on Earth. For example, earth scientists use the fossil record, and the surrounding rock record, to figure out what may have caused various species to evolve or go extinct.

Since distant antiquity, people have noticed and gathered fossils, including pieces of rock and minerals that long ago replaced the remains of organisms, or preserved their external form. A few years ago, I was in Phil Currie’s lab at the Royal Tyrrell Museum in Drumheller, Alberta, Canada. Phil pulled a T. rex tooth out of a specimen drawer and handed it to me. The tooth had been fossilized as agate. It was truly amazing to hold something that had once been a tooth in the mouth of a living dinosaur and was now a semiprecious stone.

Old Rock Day offers a perfect opportunity to learn — or to teach someone else — a little something new about fossils and other old rocks, whether you’re more apt to celebrate dinosaur or trilobite fossils, gemstones or coal, or any of the myriad rock and mineral types that compose our planet. The nice thing about this ill-defined holiday is that the interpretation and the means of celebration are really up to you.

However you decide to celebrate Old Rock Day, just make sure it totally rocks!

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