We all learned in school that there are seven continents, but is that true? In fact, it’s complicated. There may be as few as six or as many as eight.
Looking at a map, it would seem that there are just five major landmasses: the Americas, Africa, Australia, Antarctica and Eurasia. But history and geography make clear that both North America and South America are distinct and separate, as are Europe and Asia. Some argue that Australia is an island, not a continent.
But the question gets even more complicated when you dive under the map. The discovery and mapping of plate tectonics in the early 20th century showed that there are seven major plates on the Earth’s crust, roughly corresponding to the seven canonical continents.
A new study disputes that, though.
A study, published this year in the journal Gondwana Research, posits that we actually only have six continents […]
The paper’s lead author Dr Jordan Phethean, of the University of Derby, explained to Earth.com that his team’s findings indicate that “the North America and Eurasian tectonic plates have not yet actually broken apart, as is traditionally thought to have happened 52 million years ago.”
Like North and South America, Eurasia and North America were until comparatively recently joined by a slender land bridge, where the Bering Strait now lies. But the rising of the seas at the end of the last glacial period, some 10,000 years ago, drowned the bridge.
The new study argues that although the bridge was drowned it was not broken.
Instead, he said, these plates are continuing to stretch and so are still in the process of breaking apart, rather than being wholly separate entities.
In other words, North America and Europe could be considered a single continent, rather than two distinct ones.
The study focuses interest on Iceland. The highly volcanic island, along with the Greenland-Iceland-Faroe Ridge (GIFR), they argue, contains geological fragments from both Europe and North America.
This, they say, suggests that these regions are not isolated landforms, as previously thought: they are interconnected pieces of a larger continental structure.
The scientists have even coined the term “Rifted Oceanic Magmatic Plateau” (ROMP) to describe this new geological feature, which could have fundamental implications for how we perceive the formation and separation of Earth’s continents.
So, are we down to just six continents? In fact, depending on whether you accept that North America and Europe are joined, it could still be seven – or even eight.
Because, as I wrote some time ago, scientists have discovered that New Zealand is just the highlands of a now-drowned, Atlantis-like, lost continent dubbed “Zealandia”. The visible North and South Islands, plus a handful of offshore islands, make up just five per cent of Zealandia. The hitherto-unsuspected continent, only discovered in 2017, is twice the size of India.
Little is known about the recently discovered continent, mainly due to it being almost completely inaccessible. However, a team of geologists from all over the world have compiled a new geological map containing Zealandia. The map was formed using a combination of rock samples recovered from the sea and geophysical mapping methods.
Geologists discovered large sandstone formations and deposits of basaltic rock pebbles, following the outer margins of Zealandia as they searched for samples.
Each of the types of geology tell their own story. The sandstones, believed to be about 95 million years old, contain older granite and volcanic pebbles. This suggests that Zealandia was dry land, with rivers flowing from volcanic highlands carrying the eroded pebbles.
The basalt pebbles hint at the time when Zealandia began to be flooded. Such basalt pebbles are associated with underwater volcanism.
Interested readers can find the original study, “Reconnaissance basement geology and tectonics of North Zealandia” in the journal Tectonics.
