“It appears that the lithosphere, which is the rocks on the outside of the world, has a pretty significant role to play in why the tectonic plates are moving the way they are.” This is the insight from geophysicist Jordan Phethean, released in the September 2024 edition of Gondwana Research, highlighting a finding that is writing stealthily in the textbooks about the planet’s design: a newly identified microcontinent now referred to as the Davis Strait proto-microcontinent is hiding under the sea ice between Canada’s Baffin Island and Greenland.
The Davis Strait, which is a channel as much as 400 miles wide, has been confounding geologists for years with its unusually thick seafloor. Plate tectonic models had trouble for decades understanding why this patch of oceanic crust was so dense and strong. The solution, it seems, lay in plain sight: the crust is actually not oceanic, but a piece of continental crust that didn’t quite manage to separate completely when Greenland and North America rifted apart beneath the sea between Canada and Greenland.
To piece together this geological drama, scientists used a toolkit of state-of-the-art geophysical methods. Gravity data from satellites, in the form of free-air and vertical gradient maps from the Sandwell and Smith dataset, picked up on subtle changes in gravitational pull signs of rock density and composition deep beneath the waves. Marine seismic surveys utilized acoustic waves to sound out layering and thickness of the crust. By merging these data sets, researchers constructed elaborate computer models that turned back the clock to the Mesozoic and Cenozoic periods, tracing the tectonic dance that created the Davis Strait based on gravity and seismic data.
The result of this reconstruction is a plate tectonic reorganization saga. About 120 million years ago, North America and Greenland started their gradual drifting apart, a movement that gained speed some 61 million years ago. In this period, Greenland moved northeast along a recently discovered fault system the Pre-Ungava Transform Margin before changing course northwards. This redirection, between 58 and 49 million years ago, was contemporaneous with the calving of a thick, cut-off block of continental crust 19 to 24 kilometers thick by 12 to 15 miles wide block of continental crust, thickness ranging from 19 to 24 kilometers. In contrast to typical classic microcontinents that move away from their parent continents, the Davis Strait proto-microcontinent is still only partially severed a geological “failed rift.”
The evolution and destiny of this microcontinent are closely linked to changing directions in plate movement and the influence of transpressional forces plates not only moving apart but also sliding past one another. As the North American plate was starting to move apart, the proto-microcontinent began to split. But tectonic momentum was lost: a new fault system developed, rifting ended, and by 33 million years ago, Greenland’s collision with Ellesmere Island shut the process down. Today the area is tectonically tranquil, with no significant earthquakes or continued rifting no significant seismicity, which means that tectonic activity has ceased.
The ramifications of this finding ripple far beyond the icy North Atlantic. The Davis Strait proto-microcontinent provides insight into processes creating and rifting microcontinents globally. Such processes have been recognized within the Indian Ocean, where the Comoros and Mauritia microcontinents carry signs of transpressional transform faults and plate motion change role of plate motion change, causing transpression along active transform faults. In the southwest Pacific, Zealandia now identified as Earth’s largest submerged continent was mapped through similar gravity and seismic methods and found to consist of a huge, thinned-out continental crust 94% submerged Zealandia is everywhere significantly raised above the surrounding oceanic crust. These results altogether refute the textbook picture of continents as fixed and detached, demonstrating instead that Earth’s surface is a collage of drifting, rifting, and occasionally “failed” continental pieces.
The instruments that enabled these breakthroughs satellite gravity mapping and marine seismic imaging are now the norm in the search for undiscovered continents. Gravity measurements locate differences in rock density, and seismic waves reveal the structure and thickness of crustal sections. Combined, they enable geologists to discern between oceanic and continental crust even when it is miles under the ocean floor. These techniques have uncovered not only the Davis Strait microcontinent, but also submerged microcontinents Jan Mayen, East Tasman Rise, and Gulden Draak Knoll, each with its tectonic history Jan Mayen microcontinent. East Tasman. Gulden Draak.
Discovery of Davis Strait proto-microcontinent is more than a geological oddity. It serves as a reminder that the edges of continents are not as solid as classroom maps imply. As Phethean explained to Live Science, “If we can understand why the plates are moving in the directions that they are, it allows us to understand what’s controlling plate tectonics.” Each new microcontinent discovered submerged beneath the oceans is another page in the developing saga of Earth’s turbulent surface, and an invitation to peer deeper both physically and metaphorically into the concealed structure of our world.
