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Australia once joined to North America


And one observation you could make from up there in the sky is that the coastline of northern Tasmania is nowhere near resign. A-? Arizona. You could also just look at the map, of course. So how come it seems like they were once joined here. Sancho producer, David Fisher to geologists the rocks along Tasmania's northern coast don't feet they stick out as different from adjacent formations. So where did they come from? How did they get there? And are they related to formations elsewhere in the world? After much searching, the rocks of the US south west with thought to be a possible match and a good place to look and American geologists had a similar mystery to solve anxious formations in the southwest seemed to be sheared off do they extend onto some other continent. So Jack Malda went deep down into the Grand Canyon where anxious rocks are exposed and where stories of our planet's history. Come to light, the first striking thing to me is when we got down to Grand Canyon. He could sit on these rocks. And I would just a dead ring of what we were looking at intense, minus physically the rocks. Look the same. And then when we started doing some chemical analysis, and is dieting that all lined up as well and dislikes very similar on over audio Scouse the age of these rocks is revealed by studying the mineral zircon the rocks. We're talking about here. I ancient sedimentary rocks. That will once lies of sand. Deposited in a shallow election, and some of those grinds these mineral codes, Akon seconds. A really interesting very useful in because we can diet till old that grinds minutes because they are con- contains tiny little amounts of uranium in there, which decays to lead. First thing we do when we get these samples is we essentially crush them up and separate Elise. Tiny little silicon grains out of them. And then once we have those cons. We analyze them on our mass spectrometer, it's linked up to Elisa. So essentially blast these tiny loser on grinds. We can measure the different price shares of uranium and lead coming out of this kind to tell old there's a concert, and how old are they the youngest their consumer finding or about one point one billion years old, and there's a spirit of ages. Although I to about three billion years old. So there's a lot of history preserved in those tiny loser owns the dating process pinpoints a specific time when a crystalline mineral. Who was trapped in its surrounding rock each sample contains a specific quantity of crystals from specific dates together. They form a unique signature if the signatures of two samples match chances are they were produced from the same source. These cons growing in things like Granitz that were originally magmatic rocks when they can start to crystallize at of the magma fell cooldown enough that the lead that's decaying out of the Ryan, we'll get trapped in the mineral and from that point onwards that laid we'll continue to accumulate within as a crystal. And then when we measure the amount of light in there, we can figure out how long that grind must have been sitting there accumulating lead because we know half us uranium decay. Split why could your sample in Tasmania not have come from somewhere else? How can you be sure that it has a good question? That's something we spent quite a bit of time thinking about and essentially it comes back again in a large part to these cones. So these coincidentally rocks coming from older rocks so old mountain belts. Eroding. Eroding. The sand and motto of which eventually gets transported, Dan and rivers and deposited in these sedimentary basins when you look at the range of ages of cones owns within your city Metri rock he can use that as a fingerprint of the oldest source rocks that they sediments came from. So when we did this with TEZ Manion rocks. We compare those ages to nibble at rooks in Astrada, so older rocks in a strategy that could have potentially been the source for the Tasmanian sentiments what you say when you do that is that those two signatures. Don't overlap so desert kinds in the Tasmanian rocks and not coming from anyway in astrology. That's at least exposed at the present. I could not be linked to south. Some buried depositing Europe. How can you be sure that the Grand Canyon deposit was related to your Tasmanian deposit? Look, it's a great question and looking at very action rocks like the ones where by looking at. There's always uncertainty, but I guess one of the strengths of these studies that not only do we have silicon fingerprint. It was been working on the rocks themselves were deposited in very similar environments and Rivera similar ages. So when you start to add up all these different lines of evidence, he can be more confident at indeed, these Tasmanian, Arizonan rooks are very similar. How useful is this information? It's a very useful discovery for a lot of people because it helps us understand the continents about a billion years ago during these Tommy unearth history, must've this contents think we're assembled together in a supercontinent codeine a- and people have debated about how the different continents were arranged within that supercontinent and the. Died of from Tasmania helps link Tasmania and what parts of astrology in Antarctica onto that Wisden margin of the US. So that's exciting discovery. Does this information and this idea feet with what was previously thought? Or is it a completely new idea? Well, it builds on extensive body of work. That's probably really started to get going around the early ninety s on this continent, ROY Denia. So one of the most controversial aspects what continents were assembled along the margin of the west in US. There's a number of different models that have been put forward these include sticking, Australia and Antarctica against that margin. Are the papers stick some blocks in China and threat is you along that margin and the new data from Tasmania privileged support? I think to the kind of a strategy and a stand Taty connection with west and US and narrows, Dan, the relative configuration of those books. So it's not. A completely new model, but it is building and provides some important geological support to previously propose motives, if you've got an idea why there was a supercontinent. I mean, why should the planet have way back as you say in deep time. Why should they have been just one land mess? Look that is one of the big questions and share science sciences. What drives the super continent circle because we haven't just had one of those sober continents. We seem to get them every four to five hundred million years. The continents will join together into these large landmasses and the fundamental driving mechanisms for that process still caught polling on so we make all assembled together again in the future. Absolutely. And we've already named the Knicks supercontinent, and that's code a major it's happening again absolutely beginning now on the present dialogue in the middle of a supercontinent circle. So we call the supercontinent cycles the time from one super continent. Fully assembled it. Tim breaks up the different continents. Drift apart. And then they coalesce into another super continents becomes circle the present day distribution of continents on our planet, largely reflects the breakup of the supercontinent Panja, so we're heading for a new one. How many times has it happened in the past? That's again, something that's debated. But we think the first tree supercontinent was probably formed between about one point five and might be too believes ago that one was code. No no known abroad Cup. The different continents drifted apart. And they came together to form ROY Denia. So that's super contin number two billion years ago in Rudeina broke up and began to assemble into the landmass code Gondwana, which is debated supercontinent bit essentially Gondwana eventually collided with North American film Panja. So there's three maybe four super confidence that most of the geological community would agree on. And this speculation. They might have been some even older ones. But as you get back in time, you get fewer rocks to work with said as things become even more speculative. It's a fascinating story getting back to the site in Tasmania, can you just place it for us where this our croppies? These are not a sacred is not absolutely not one of the great things about those rock scene has various to get to. And the quite literally in papers backyard is probably the best plus two. So these rocks is along the northwest coast between Wynyard and say Stanley all along the coastline there in places like boat. Harborne sisters Bauge how long is that bit of coastline roughly hundred kilometers, maybe these wrecks acquired extensively exposed in office teddy. And then we also saw them down in southwest has minor in a number of places as well quite extensive package of rocks. We're not talking about one outcrop that we stumbled across. This is a regionally extensive group of rocks could be presented as a tourist attraction of yet. Another reason to visit Tasmania. Absolutely. Yep. It it just adds another layer. Loyalty, the iconic scenery that testimony. So find full Jack Malda is a research fellow school of earth sciences at Monash University in Melbourne, and yes, the earth is moving Arizona in Tasmania who'd have thought.

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