Iceland. Image: ImpossiAble / Contributor via Getty Images
A vast sunken continent called “Icelandia” may exist under the North Atlantic Ocean, a finding that, if proven, could upend long-standing assumptions about the region’s geological history and inform the search for other submerged continents around the globe. The proposed continent is estimated to extend for at least 230,000 square miles, reaching Greenland to the north and potentially Europe to the east. Iceland is the uppermost tip of this hidden continental mass, according to researchers led by Gillian Foulger, emeritus professor of geophysics at Durham University, who proposed the idea in the forthcoming book In the Footsteps of Warren B. Hamilton: New Ideas in Earth Science.
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As exciting as it is to imagine this immense sunken landmass, Foulger and her colleagues emphasized that Icelandia remains a hypothesis that will need to be confirmed through a range of empirical methods such as deep drilling, geophysical surveys, and analysis of minerals such as zircon.“The existence of Icelandia needs to be tested,” Foulger and her colleagues said in the chapter, adding that Icelandia is “a convenient example” to pioneer new methods and hypotheses that ”could be applied to other candidate sunken continents that are common in the oceans.” With its dramatic landscapes and frequent volcanic eruptions, Iceland is a geological hotspot that has attracted attention from Earth scientists for centuries. The island is located on top of the divergent boundary of the North American and Eurasian continental plates, which cause tectonic turbulence on the island as they move apart. Scientists have long presumed that Iceland is surrounded by a mass of oceanic crust, which is a type of partially melted rock that is distinct in both composition and density compared to the continental crust that forms all the landmasses that we humans live on. Oceanic crust is denser than continental crust, causing it to sink below continental masses but remain above Earth’s mantle, a layer of molten rock. As a result, oceanic crust also tends to be substantially younger and thinner than continental crust because it is constantly being subducted into the mantle and recycled.
Foulger and her colleagues began to suspect that Iceland might be surrounded by continental crust, rather than oceanic crust, because the layer under the island is about 25 miles in depth—much thicker than the average four-mile thickness of oceanic crust. One past study, published in 1977, had also noted that Iceland may be situated on continental crust, but the means to actually test out this hypothesis have matured significantly in the decades since.The new chapter proposes a host of techniques that could help resolve whether the sunken continent of Icelandia really exists. For instance, the team suggests searching for zircon crystals in Iceland. Zircon is an extremely hardy mineral that can survive billions of years of erosion within Earth’s crust, making it especially useful for geological age estimates. Dating these crystals could shed light on the age of Iceland’s underlying crust, which could in turn inform whether it is oceanic or continental in nature.Foulger and her colleagues also suggest conducting seismic profiles or drilling cores miles deep into the crust. These methods would be more expensive than zircon-dating or land surveys, but they could eventually prove or disprove the existence of Icelandia. Perhaps more importantly, these efforts could pioneer new ways to search for several other sunken continents that have been proposed across the world.
“Icelandia is the best and most easily studied of all postulated submerged continents because of the proximity of large landmasses and the exposure of 35 percent of its area above sea level in the island of Iceland,” the team said in the chapter.For this reason, Icelandia may well be the tip of the iceberg in the search for hidden landmasses in the oceans, if only we know where and how to look for them. For instance, microcontinents or continental fragments have been proposed at Walvis Ridge off the coast of West Africa, Lomonosov Ridge in the Arctic Ocean, and the Elan Bank–Kerguelen Plateau in the Indian Ocean. Moreover, the team points out in the study that New Zealand is considered to be the above-water portion of the massive “Zealandia” submerged continent, while a microcontinent called “Mauritia” was recently detected under the island nation of Mauritius.“There is fantastic work to be done to prove the existence of Icelandia but it also opens up a completely new view of our geological understanding of the world. Something similar could be happening at many more places,” said Fouger in a statement.“We could eventually see maps of our oceans and seas being redrawn as our understanding of what lies beneath changes.”