Table of Contents
Video
Transcript
- The Great Barrier Reef is the largest living structure in the world, spanning 1,400 miles of Australian coast and roughly the equivalent area of Japan. But how did it come to be that way?
- Coral are an ancient animal, they’ve played a role in shaping coastal seabeds for about 500 million years (Zuravlev, 2001; Lee et al., 2015) — they’re older than trees and they’re older than sharks!
- Coral are really a collection of a bunch of individual coral polyps that each help build up the reef.
- SHANE: Basically, coral will suck water into their stomachs, push out all the water and the things in that water that they don’t need… except for… calcium and carbonate…and when the ions are squeezed together under their tissue, and all the water squeezed out, it creates a really thin layer of rock underneath it
- Over time, that rock base builds into the reef structures that we see today.
- Going back in time, just before we see apes evolve, the continent that Australia is on finally shifts northward enough to have a tropical climate that can support coral reefs. Thus, the Great Barrier Reef begins about 20 million years ago (Hamylton et al. 2022, pp. 104-107).
- But, it wasn’t until about 600,000 years ago that we start to see the reef structures that form the Great Barrier Reef today.
- You see, it’s not actually all one reef. Today, the Great Barrier reef is a system made up of over 2,900 individual reefs (Great Barrier Reef Marine Park Authority, 2006). It’s not just one huge neighborhood, it’s more like a city made up of a bunch of different neighborhoods.
- As sea levels changed during the Ice Age, the Great Barrier Reef tried to keep up and follow the coastline as it moved, but it wasn’t always able to and so the reef died out (Hamylton et al., 2022, pp. 124-130).
- The reef we see today started growing around 8,500-9,000 years ago. It was able to build on top of the old structures made by the ancient reefs that were there thousands of years earlier (Hamylton et al., 2022, pp. 124-130; Great Barrier Reef Marine Park Authority, 2006).
- Together, they build a layered cake of chalk that’s thousands of years old and still being built today!
- That’s the story of why —
References
Great Barrier Reef Marine Park Authority. (2006). Reef Facts for Tour Guides. Australian Government.
Hamylton, S. M., Hutchings, P., & Ove Hoegh-Guldberg. (2022). Coral Reefs of Australia. CSIRO PUBLISHING.
Lee, J.-H., Chen, J., & Chough, S. K. (2015). The middle–late Cambrian reef transition and related geological events: A review and new view. Earth-Science Reviews, 145, 66–84. https://doi.org/10.1016/j.earscirev.2015.03.002
Strauss, B. (2025, May 14). Prehistoric Life During the Miocene Epoch. ThoughtCo. https://www.thoughtco.com/the-miocene-epoch-1091366
ŽuravlevA. J. (2001). The ecology of the Cambrian radiation. Columbia Univ. Press.