Scientists have discovered an unexpected new continent hiding beneath Greenland. Zealandia, thought to be a candidate for Earth’s eighth continent, has been almost completely submerged by the sea. The new ocean could split Africa into two continents. Doggerland: Before it was inundated by a tsunami 8,000 years ago, this landmass connected Britain and continental Europe. Archaeologists and citizen scientists have discovered a number of artifacts from Doggerland over the years, including a deer bone with an arrowhead and a fragment of a human skull.
The discovery of a new primitive microcontinent between Greenland and Canada could help scientists understand how microcontinents form. Researchers have studied how the tectonic plates of the Davis Strait moved and eventually pulled apart to form a new microcontinent. The strait is called a proto-microcontinent, and changes in plate movement over millions of years may have played a key role in its creation. It lies in the icy waters off the west coast of Greenland, beneath the surface of the Davis Strait.
When the tectonic plates between Canada and Greenland shifted to form the Davis Strait, which connects the ocean basins of the Labrador Sea and Baffin Bay, the Earth’s crust was transformed. This led to the formation of thick continental crust in the ocean, which is now being heralded as a newly discovered proto-microcontinent (also known as a primitive microcontinent).
In a study published in the journal Gondwana Research, a team of scientists reconstructed plate tectonic movements in the Davis Strait region between 33 and 61 million years ago, which led to the formation of an unusually thick slab of continental crust.
The research team says this submerged piece of crust, about 12 to 15 miles long, is located in the western waters of Greenland and has been named the Davis Strait proto-microcontinent.
“The well-defined changes in plate motion that occur in the Labrador Sea and Baffin Bay, which have relatively limited external complications affecting them, make this area an ideal natural laboratory for studying microcontinent formation,” Jordan Fetin, who worked on the study, told Phys.org.
Fethean added that the rifting necessary to form a microcontinent is an ongoing phenomenon, and each earthquake could play a role in the next microcontinent breakup. “The goal of our work,” Fethean said, “is to understand their formation well enough to predict this future evolution.”
When Greenland and Canada began to move apart about 61 million years ago, the early separation began with the individual plates moving northeast to southwest, coinciding with the formation of the Labrador Sea and Baffin Bay. About 5 million years later, the plate motion switched to north-south, creating a strait and continental crust between them.
The study of the Davis Strait proto-microcontinent and the theorizing around its formation paves the way for understanding similar geographic structures. “Our identified mechanism for microcontinent formation may be broadly applicable to other microcontinents around the world, and further study is needed to understand the role of plate motion changes and transpression in microcontinent breakaway,” the researchers wrote in their study.
A huge rift that opened in northeastern Ethiopia in 2005 appears to have marked the first split in the continent since modern humans emerged, leading to volcanic eruptions, flooded land and inundated by seawater.
Over the course of a couple of days in September 2005, amid a flurry of volcanic eruptions and hundreds of earthquakes, the ground in northeastern Ethiopia split wide open. For millions of years, a bubble of molten rock had been seeping beneath the Earth in the Afar Depression, an inhospitable stretch of desert where summer temperatures can reach 120 degrees. It finally reached the surface, splitting the earth in two and creating a fissure nearly 40 miles long and up to 25 feet wide.
The Dabbahoo Fault, as the 2005 rift became known, is hardly the first geological event to rock the Afar, a remote region dotted with geysers, gas vents, hot springs, volcanoes, and one of the world’s few lava lakes. A mecca for Earth scientists, the Afar Triple Junction sits at the Y-shaped cradle of the Arabian, Nubian, and Somali plates. At about the same rate as your fingernail grows, these plates are moving apart, while processes beneath them generate extreme heat and energy that produce the unique geophysical features for which the region is known. Scientists suspect that the first continental split since Pangea will occur along this fault, and that in a couple of million years or so, Africa could span two continents, allowing Earth to debut its newest ocean.
Panoramic view of Abijata-Shalla Lakes National Park in Ethiopia, Great Rift Valley, Ethiopia
One of the world’s greatest geological wonders, the North-South-East African Rift System (or EARS) is actually a network of faults and valleys caused by the Earth’s crust breaking up. The EARS has been forming for about 25 million years and consists of two branches: the Eastern Rift Valley, which runs from Jordan to the coast of Mozambique. The Western Rift Valley, meanwhile, runs from Uganda to Mozambique and contains some of the world’s deepest lakes.
But of all the lands crowded within the EARS, the Afar Depression is the most extreme, with the highest rates of magma production and the most active volcanoes in the region. Over time, a mantle plume of magma formed beneath the depression, pushing hot rocks to the surface like globules of oil rising in a lava lamp. Eventually, the extreme pressure forced magma into cracks between these rocks, leading to the opening of the Dabbahu fissure in 2005.
The pressure was so intense that the plates separated by as much as 25 feet, achieving 400 years of separation in a matter of days, Ebinger said. It was such a large number that one of the scientists using satellite data to measure the new rift was convinced he had miscalculated.
In the weeks following the 2005 event, Ebinger flew to Ethiopia, where she worked with scientists from around the world to quickly get geophysical instruments on the ground. Immediately, the team noticed that the plates that underlie the region were moving much faster than usual because of the volume of magma beneath the surface.
Ebinger says that over the next five years, there were 13 more events similar to the 2005 rift, but less severe. Today, the plates have slowed to their normal speed.
Looking ahead, Ebinger predicts there will be more such dramatic episodes, perhaps once every 50 or 100 years. As the land splits apart, the Afar Depression will sink deeper and deeper, a process known as seafloor spreading. “If we fast-forward about 500,000 years, the Afar Depression could sink below sea level and be flooded with water.”
The new sea may or may not completely split the continent in two. “The rate of separation decreases as you go south,” Ebinger says. “So it could just be a wedge of seawater moving inward.”
Not all continental rifts turn into oceans, and there’s still a chance that the East African Rift could collapse. In fact, scientists have discovered areas of molten rock and crustal extensions for miles around the rift, a discovery that challenges conventional geological wisdom that says all the rifting activity must occur within the rift itself.
The Dabbahoo Rift may follow the fate of North America’s Mid-Continent Rift (MCR), a rainbow-shaped, 1,800-mile-long seam that split more than a billion years ago. The rift, which ran from modern-day Detroit to central Kansas, produced more than 240,000 cubic miles of volcanic rock over 30 million years before it suddenly and mysteriously stopped widening. There are many theories about why this happened, but the MRC remains the deepest rift ever discovered that has not become an ocean. Perhaps the Dabbahoo Rift will follow in its footsteps.
Geologists say they have now mapped nearly two million square miles of the underwater landmass of Zealandia. The research team used rock samples from the seafloor to analyse and date the underwater geology of North Zealand. Zealandia was the eighth continent on Earth until about 95 per cent of it sank beneath the ocean.
While much of Zealandia may never be habitable, at least on land, this potential continent is no longer simply lost. Researchers recently completed mapping the northern two-thirds of Zealandia, documenting nearly two million square miles of submerged land.
In a study published in the journal Tectonics, researchers from New Zealand-based GNS Science document the process of extracting rock samples from the Fairway Ridge into the Coral Sea to conduct geochemical analysis of the rocks and understand the underwater composition of Zealandia.
Zealandia’s history is closely tied to the ancient supercontinent Gondwana, which broke apart hundreds of millions of years ago. Zealandia followed suit — about 80 million years ago, according to the latest theory. But unlike neighboring Australia or much of Antarctica, Zealandia largely sank, leaving behind only a small portion of what many geologists still believe is worthy of being called an eighth continent.
New Zealand is the most recognizable above-water part of Zealandia, although several other islands nearby are also part of the possible continent under consideration.
The latest research, led by Nick Mortimer, examined the northern two-thirds of the flooded area, recovering cobblestone, fine-grained sandstone, mudstone, bioclastic limestone and basaltic lava from a range of time periods. By dating the rocks and interpreting magnetic anomalies, the researchers wrote, they were able to map the major geological units across North Zealand. “This work completes the geological mapping of the entire Zealandia continent,” they said.
The researchers found sandstone about 95 million years old from the late Cretaceous period and a mixture of granite and volcanic pebbles up to 130 million years old from the early Cretaceous period. The basalts are newer, about 40 million years old, and date back to the Eocene period.
Along with the mapping, the paper says that the internal deformation of Zealandia and West Antarctica shows that the stretching caused the plates to crack in a subduction-style fashion, which took in ocean water to form the Tasman Sea. Then, a few million years later, more breakaway of Antarctica continued to stretch Zealandia’s crust until it became thin enough to break apart and seal Zealandia’s largely underwater fate. This contradicts the prevailing strike-slip theory.
The team believes, according to Science Alert, that the direction of the stretching changed by 65 degrees, which could have led to significant thinning of the continental crust.
As New Zealand scientists can tell you, the fact that Zealandia is mostly underwater doesn’t make it any less of a geological wonder.
Zealandia—sometimes called Earth’s eighth continent—spans nearly two million square miles (about half the size of nearby Australia) beneath the South Pacific Ocean. Most of the continent sank about 80 million years ago when the supercontinent Gondwana broke apart, though parts of it still stick out above water, especially the islands of New Caledonia and New Zealand.
The Earth’s rocky outer layer, or crust, varies in thickness from 3 to 43 miles; that may seem pretty deep, but according to the National Science Foundation, if the Earth were an apple, the crust would be as thick as the skin of the fruit. In other words, the crust makes up only about 1 percent of the Earth’s total volume, but it covers its entire surface. There are two main types of crust: oceanic crust, which makes up the seafloor, and continental crust. Continental crust, whether it’s above or below sea level, is thick and made up of rocks like granite, rhyolite, shale, and graywacke.
Seventy percent of the Earth’s mass and 85 percent of its volume are in the mantle, which is 1,800 miles thick. This layer is extremely hot, ranging from 1,832 degrees Fahrenheit at the boundary with the crust to 6,692 degrees Fahrenheit at the boundary with the core, and is made of hard peridotite rock. Because the mantle is so hot, it flows under pressure, changing shape over time like candle wax (and, remarkably, doesn’t squirt out of vents like a volcanic eruption).
The mantle is divided into two parts: the upper mantle and the lower mantle.
The upper mantle begins at the Mohorovicic boundary, or Moho, which is the boundary between the Earth’s crust and mantle. We know much more about the upper mantle than other layers of the Earth, thanks to seismic studies, mineralogical studies, and geological studies. That’s why we know that convection, or movement in the mantle due to heat from deep within, causes the movement of tectonic plates on the Earth’s surface. This is where continental drift, earthquakes, and mountains originate.
In contrast, very little is known about the lower mantle. At the boundary with the Earth’s core, the lower mantle can reach temperatures exceeding the melting point of mantle rocks, but because of the enormous pressure at this depth, there is very little melting or movement as seen in the upper mantle.
The Earth’s core is its center and consists of two parts: the outer core and the inner core.
The outer core is about 1,400 miles thick and is essentially a shell of liquid iron alloy. Its temperature ranges from 7,280 to 10,340 degrees Fahrenheit, so the outer core never becomes solid; the outer core actually rotates faster than the rest of the planet due to turbulent convection in the layer. The resulting eddy currents are thought to generate the Earth’s magnetic field, which protects us from the Sun’s solar radiation. Deep in the outer core, the magnetic field strength is estimated to be about 50 times greater than the Earth’s magnetic field strength at the surface.
The inner core is the center of the Earth, with a temperature of nearly 9,000 degrees Fahrenheit. Since the inner core has a radius of about 746 miles, it is about the same size as our Moon. Although the inner core is still hotter than the outer core, it is no longer liquid, as the combination of extremely high pressure and temperature actually condenses the metals inside into a solid ball.
Although it is now the most well-studied continent, Zealandia is far from the only “lost continent” on Earth. Using advanced imaging software, seismographs, and good old-fashioned fieldwork, scientists are discovering and describing other lost continents that, due to the tectonic forces that govern our planet, have also disappeared from the map.
Greater Adria: About 240 million years ago, during the Triassic period, a chunk of continental crust the size of Greenland broke away from North Africa. For the next 100 to 130 million years, Greater Adria, as it is now called, lay beneath shallow tropical seas filled with coral reefs. Eventually, Greater Adria began to move again, sliding beneath Europe and into the Earth’s mantle.
Although the former continent was submerged, it was not entirely lost; the upper layers of Greater Adria’s sedimentary rocks were torn away by violent tectonic movement – a process geologists call “exfoliation” – creating mountain ranges in Italy, Turkey, and Greece. Today, the rocks that once belonged to Greater Adria are scattered across 30 countries, but a small strip of the continent remains, running from northern Italy to the heel of the country’s “boot,” in a region geologists call Adria.
Reconstruction of Greater Adria, Africa and Europe around 140 million years ago. Utrecht University
In 2019, scientists completed a decade-long process of reconstructing the size and shape of the continent using plate tectonic reconstruction software and seismic wave technology. They concluded that Greater Adria now lies about 932 miles beneath the Earth’s surface.
Argoland. Around the time Greater Adria began sliding under Europe, a North American-sized chunk of land broke off from Western Australia. Lost in the Indian Ocean, Argoland seemed to split apart, head north, and then disappear for millions of years, much to the chagrin of geoscientists around the world.
While most of Greater Adria sank into the Earth’s mantle and much of Zealandia sank, geologists have been unable to find Argoland, named for the deep depression it created off the coast of Western Australia called the Argo Abyssal Plain, either above or below the ocean.
Partial reconstruction of Argoland’s drift back to 215 million years ago, when its breakup accelerated. Utrecht University
Finally, earlier this year, a team of researchers claimed to have found Argoland – in the jungles of Southeast Asia. After spending seven years painstakingly reconstructing the path of the lost continent, they now believe that the land began to break apart much earlier than previously thought – around 300 million years ago, forming what they have dubbed “Argopelago”. When Argoland broke away from Australia, it was a vast system of islands and ocean basins that all set sail together before breaking apart like a mirror.
Some of the Argoland fragments were swallowed up by the Sunda Trench subduction zone, while others were thrown onto the seafloor and other landmasses throughout Southeast Asia, including what is now Myanmar and Indonesia, where they have lain hidden for millennia.
Zealandia. Technically speaking, neither Argoland nor Greater Adria are actually lost, according to Nick Mortimer, the geologist who led the project to map Zealandia. They were broken up and buried deep in the solid Earth; they used to exist on the Earth’s surface, but they no longer exist. In contrast, Zealandia still exists today, although mostly underwater. For this reason, Mortimer prefers to call Zealandia a hidden continent.
Mortimer had been studying Zealandia (called Te Riu-a-Māui in Maori, after a hero of Polynesian mythology) for more than 30 years when marine geophysicists brought him rock samples they had collected from the sea. “We gradually realised that the rocks in the sea matched the rocks on land, and a picture of a continent began to form in our minds.”
In addition to fully mapping Zealandia, Mortimer and his colleagues discovered what likely caused the landmass to separate from Gondwana between 60 million and 100 million years ago. Using magnetic surveys of the seafloor, the researchers found a giant volcanic region where “for at least 40 million years, molten magma poured out of cracks and faults as the continent stretched and thinned like pizza dough,” Mortimer wrote.
Some of the other (non-continental) lost lands of the Earth:
➤ Beringia: A land bridge that once connected Asia and North America, covering more than 4 million square miles, is actually a vanished subcontinent, according to scientists. The National Park Service describes the lost land as “a vast tundra landscape bounded by the rugged shoulders of two continents and stretching more than a thousand miles from north to south.”
➤ Doggerland: Before it was flooded by a tsunami 8,000 years ago, this land mass connected Britain and continental Europe. Archaeologists and citizen scientists have discovered a number of artifacts from Doggerland over the years, including a deer bone with an arrowhead and a fragment of a human skull.
➤ Ferdinandea: Also known as Graham Island, Ferdinandea is a submerged volcanic island off the coast of Sicily that has resurfaced and sunk four times since around 250 BCE. The island rises above the water when lava flows from the volcano’s summit and solidifies in the cold water, and disappears when seawater erodes it, usually within a few months. A number of countries have claimed the island since it last surfaced in 1831. In 2000, Sicilian divers planted their country’s flag on the submerged spit of land to avoid further territorial disputes the next time Ferdinandea resurfaces.
Among the planets in the solar system, Earth is unique in that it has plate tectonics. Its rocky surface is divided into fragments (plates) that crash into each other to create mountains, or split apart to form chasms that are then filled with oceans.
In addition to causing earthquakes and volcanoes, plate tectonics also pushes rocks from deep within the earth to the tops of mountain ranges. In this way, elements that were deep underground can be leached out of the rocks and eventually washed into rivers and oceans. From there, living things can use these elements.
Among these essential elements are phosphorus, which forms the backbone of DNA molecules, and molybdenum, which is used by organisms to extract nitrogen from the atmosphere and produce proteins and amino acids, the building blocks of life.
Plate tectonics also exposes rocks that react with carbon dioxide in the atmosphere. Rocks that trap carbon dioxide are the primary regulator of Earth’s climate over long timescales—much, much longer than the turbulent climate changes we are responsible for today.
Iceland is located on a plate boundary, which causes frequent volcanic activity. Thorir Ingvarsson
Mapping the planet’s past plate tectonics is the first step toward creating a complete digital model of the Earth throughout its history.
Such a model will allow us to test hypotheses about the Earth’s past, such as why the Earth’s climate went through extreme “snowball Earth” fluctuations, or why oxygen was building up in the atmosphere when it happened.
Modeling our planet’s past is essential if we are to understand how nutrients became available for evolution. The first evidence of complex cells with nuclei – like all animal and plant cells – dates back to 1.65 billion years ago. That’s close to the start of this reconstruction, and close to the time the supercontinent Nuna formed.
Most life on Earth photosynthesizes and releases oxygen. This links plate tectonics to atmospheric chemistry, and some of this oxygen dissolves in the oceans. In turn, a number of critical metals – such as copper and cobalt – are more soluble in oxygen-rich water. Under certain conditions, these metals then precipitate out of solution: in short, they form ore deposits.
Many metals form in the roots of volcanoes that occur along plate boundaries. By reconstructing where ancient plate boundaries have passed through time, we can better understand the tectonic geography of the world and help mineral scientists find ancient metal-rich rocks that are now buried beneath much younger mountains.