For years, the strangest thing about Australia's location was that its official maps were slowly, silently wrong. Not because the surveyors had erred, but because the entire continent had drifted away from where they had pinned it. In 2016 the country announced that it would move every set of coordinates on the map by about 1.8 metres to the north-east — a correction not to the land, but to the numbers describing it. The reason is simple and faintly astonishing: Australia is the fastest-moving continent on Earth.
Every landmass rides on a tectonic plate, and every plate is in motion, driven by the churning of the mantle beneath. Most creep along at the pace fingernails grow. The Australian plate, however, is the sprinter of the set, drifting roughly seven centimetres a year towards the north-north-east — fast enough that, over a human lifetime, the continent shifts several metres. Australia is, in a sense, slowly gaining on Asia.
When the map falls behind
Seven centimetres sounds trivial, and for most of history it was. Old maps and paper surveys were all measured relative to local landmarks that drifted along with everything else, so nobody noticed. The problem arrived with satellite navigation. GPS coordinates are fixed to a global reference frame anchored to the centre of the Earth, and against that unmoving frame the whole Australian continent visibly slides.
Australia's coordinate system, known as GDA94, had been fixed to the continent's position in 1994. By the mid-2010s the plate had carried the country roughly 1.5 to 1.8 metres away from those two-decade-old coordinates. For a car satnav, a metre or two hardly matters. For precision agriculture, driverless vehicles, drones and automated mining gear — all of which were arriving fast — a metre and a half of error is enormous. A self-driving tractor told it is in the wrong row by that margin is a serious problem.
So in 2017 Australia formally shifted its national coordinate framework, adopting a new datum, GDA2020, which nudged every official coordinate about 1.8 metres north-east to catch up with reality. The quirk is that the authorities deliberately over-corrected: rather than matching the continent's position in 2017 exactly, the new datum was set to where Australia was projected to be in 2020, so that the ever-moving plate would drift into alignment and the numbers would be accurate for a while before drifting out again.
Australia has form as a traveller. Tens of millions of years ago it was joined to Antarctica as part of the ancient supercontinent Gondwana; when it broke away it began a long journey north into warmer latitudes, carrying its cargo of marsupials and other unique creatures into isolation. That northward drift has never stopped, and it is a large part of why Australia's plants and animals evolved along a path all their own.
The 2017 change was also not the country's first coordinate reshuffle. Earlier Australian datums, set in the 1960s and 1980s, had each been overtaken in turn, and each redefinition nudged mapped positions by metres. What made the latest shift different was that ordinary technology — the satnav in a phone, the guidance in a tractor — had finally become precise enough for the discrepancy to matter to everyone, not just to professional surveyors.
A moving target
This is not a one-off fix. Because the plate keeps moving, any fixed coordinate system is out of date the moment it is set. The long-term answer is a dynamic reference frame, in which coordinates are tied to a specific date and updated continuously, so that a point's position is always given for a particular moment in time. It is an odd conceptual leap: the idea that "where somewhere is" now needs a timestamp.
Australia's drift is also reshaping the planet's slow geological story. As the plate pushes north it presses against the plates to its north, crumpling the islands of Indonesia and New Guinea and, over millions of years, helping to build mountains. The same motion that forced a nation to redraw its coordinates is, on a far grander timescale, gradually rearranging the map of the world.
It is a useful corrective to how solid the ground feels underfoot. The continents are not fixtures but passengers, forever on the move — and Australia, quietly travelling north at roughly twice the speed your fingernails grow, is simply the one moving fast enough to catch us out.
Quiz nuggets
- The Australian tectonic plate moves about 7 centimetres a year, making it the fastest-moving continent on Earth.
- In 2017 Australia shifted its official map coordinates about 1.8 metres by adopting a new datum, GDA2020.
- The previous datum, GDA94, had fixed coordinates to the continent's 1994 position.
- The correction was needed because GPS is tied to a global frame anchored to the Earth's centre, against which the continent visibly moves.
- The new datum was deliberately set to Australia's projected 2020 position so the numbers would drift into alignment.