AE 1439 - 5-Minute News: You Could Once Walk Across the Great Barrier Reef!

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1. 0:03G'day guys, Pete here from Aussie English.
2. 0:05Welcome to today's episode of 5 Minute News.
3. 0:08So the goal here is to cover a recent news story in around 5 minutes, okay?
4. 0:13So let's get into it.
5. 0:19Picture the Great Barrier Reef today.
6. 0:21Clear blue water, coral reefs, islands, fish, boats.
7. 0:27Now travel back in time about 20,000 years, and take away more than 120 meters of ocean.
8. 0:35Suddenly, parts of the Great Barrier Reef region look completely different.
9. 0:39In places where you'd need a boat today, you could have been standing on dry land.
10. 0:45And during the long periods when sea levels were lower, this region had rivers, lakes, beaches, forests, and estuaries, places where rivers meet the sea.
11. 0:56It was a completely different Australian coastline.
12. 0:59And people were already here.
13. 1:01First Nations people had been living in Australia for tens of thousands of years while these landscapes existed.
14. 1:08So what happened to all that land?
15. 1:10Well, around twenty thousand years ago, during the last ice age, huge amounts of the world's water were locked up in ice, so sea levels were much lower than they are today.
16. 1:21Then the climate warmed, ice melted, and the ocean rose.
17. 1:26But the land didn't suddenly sink beneath the sea.
18. 1:30Over thousands of years the ocean gradually moved across the land.
19. 1:34The coastline moved further inland, and areas that had once been dry land became submerged, covered by the ocean.
20. 1:42By around seven thousand years ago, sea level was roughly where it is today.
21. 1:47The old landscape was underwater.
22. 1:50So if it disappeared thousands of years ago, how can we possibly know what it looked like?
23. 1:55Well, that's where this week's news comes in.
24. 1:58Thousands of years later, a research ship called the RV Investigator has been floating above the ancient landscape.
25. 2:06Researchers recently completed a twenty four day expedition to the southern Great Barrier Reef using sonar to map what's hidden below.
26. 2:15Sonar uses sound waves to map the sea floor, and with the equipment on this ship, researchers could also investigate the layers underneath it.
27. 2:25And there, beneath the modern ocean, they could detect the shapes of an older world ancient river channels, lakes, estuaries, beaches.
28. 2:36Now these aren't rivers still flowing underneath the sea, they're the remains of old river channels preserved beneath layers of sediment on the seabed.
29. 2:45So scientists are effectively reconstructing a map of a coastline that hasn't existed for thousands of years.
30. 2:52But they didn't just map it from above, they also pulled more than twenty long samples called sediment cores from the seabed.
31. 3:01Think of the seabed slowly building up in layers, sand, mud, and other materials settling there over thousands of years.
32. 3:09Those layers can preserve information about the environment at different points in the past.
33. 3:15Researchers will analyze the cores to learn more about ancient vegetation, climate, changing sea levels, and how the southern Great Barrier Reef developed over time.
34. 3:25And that analysis is still underway.
35. 3:28But there's another layer to this story.
36. 3:30This expedition wasn't designed by scientists alone.
37. 3:34The project was co-designed with Durumbao traditional owners and Wapabura people, and land and sea country rangers joined researchers aboard the ship.
38. 3:44Traditional owners are First Nations people with deep cultural connections and responsibilities to country.
39. 3:51They're bringing scientific evidence from sonar and sediment together with cultural knowledge and song lines, knowledge connecting places, stories, and country.
40. 4:01That's especially important because this isn't simply the story of an old geological landscape.
41. 4:08It's part of a much longer human history of this region.
42. 4:11And scientists have only just brought the new data and samples back.
43. 4:15They still need to analyze the sediment cause and other data to reconstruct how the landscape changed over thousands of years.
44. 4:23But the maps they've already produced reveal something pretty extraordinary.
45. 4:28We tend to look at a map of Australia as though that's simply what Australia looks like.
46. 4:33But coastlines move, sea levels change, and the map we know today is only one version of Australia.
47. 4:40Go back far enough, and places where Australians now sail over the Great Barrier Reef were dry land.
48. 4:46There were rivers where there's now ocean.
49. 4:49And thousands of years after that landscape disappeared beneath the sea, scientists are beginning to map it again.
50. 4:57Okay, so one useful word from today's story is submerged.
51. 5:02If something is submerged, it's completely underwater.
52. 5:06For example, after the heavy rain, part of the road was submerged.
53. 5:11Or in today's story, scientists are mapping ancient landscapes that are now submerged beneath the Great Bayer Reef.
54. 5:18So submerged means completely underwater.
55. 5:22Hope you enjoyed this episode today, guys, and I'll see you in the next one.