Arctic Geology | Polar Unbound

Arctic Geology

ARCTIC GEOLOGY 

Over time, the Arctic developed from four core rock shields: 
•    The Canadian Shield, lying underneath the whole of the Canadian apart from the Queen Elizabeth Islands.
•    The Baltic/Scandinavian Shield, which pivots around Finland and includes northern. Scandinavia apart from the Norwegian coast as well as the northwestern region of Russia
•    The Angaran Shield, lying between central Siberia’s Lena and Khatanga rivers. 
•    The Aldan Shield, found in eastern Sibera.

The polar landmasses we see today have shifted in relation to the North Pole as well as to each other over time, transported with shifting tectonic plates. Marine sedimentation throughout the years, largely occurring in between the rock shields, has lent itself to the partial submersion of the shields as well as geologic folding, which produced mountains—many of which have eroded over time.

EARLY GLACIATION
Glaciers and continental-scale ice sheets developed throughout the northern latitudes in early formative periods. Information gathered from the final glaciation occurring 80,000-10,000 years ago indicates that the Atlantic Arctic islands were coated in ice excepting where nunataks—secluded mountain peaks—poked out of the ice shields. The Scandinavian Ice Sheet coated large portions of northern Europe, extending from Russia’s Severnaya Zemlya to the British Isles. While northeastern Siberia appeared to have avoided substantial glaciation during this final period, the region had experienced heavy glaciation during earlier periods. 

The massive ice sheets served to carve unique landforms throughout the Arctic and beyond. Finland the the northern Canadian Shield were left with numerous lakes and lowlands filled with glacial deposits, producing more even terrain interspersed with glaciated ridges such as moraines. Higher elevations were similarly marked with U-shaped valleys—many of which can be partially seen near the Arctic coasts where they peak out of the water as fjords. These fjords can best be seen along Canada’s eastern coast, in southern Alaska, on many of the Arctic islands, and around the coastlines of Norway, Greenland and Iceland. 

CONTINENTAL UPLIFT AND SUBMERGENCE
As the continental ice sheets’ weight pressed down on the earth’s crust, the sea covered most of the coastal areas. However, as the ice sheets melted, the crust regained its original latitude, leaving elevated strandlines coated with the skeletons of marine life, shells and other detritus. 

The Canadian Arctic boasts of some of the highest strandlines, with some reaching 500-900 ft, while the coasts of Labrador and Baffin Bay have lower strandlines. Some lower strandlines, such as those found in the southern and western coasts of Hudson Bay, the elevated beaches form pronounced ridges jutting out of the plains. 

While uplift continues throughout the Arctic, especially in northern Canada and northern Sweden, some Arctic coasts—such as those bordering the Beaufort Sea—continue to experience submergence. 

FUN FACT: Non-glaciated regions of polar continental shelves found themselves exposed at lower sea levels (such as in the Bering Strait), which led to the migration of people to North America. 

ARCTIC GEOGRAPHY
The Arctic covers 14.5 million square km—almost the same size as Antarctica—and consists of the northern regions of Alaska, Canada, Sweden, Iceland, Finland, Russia and Norway as well as the whole of Spitsbergen and Greenland. Despite that massive landmass, the Arctic can be thought of as predominately an ocean encompassed by continents, whereas the much colder Antarctic is predominately a continent encompassed by water. As the Arctic Ocean soaks up so much solar radiation, the overall effect is a much warmer, balmier environment. 

That being said, much of the Arctic’s water is frozen. While frozen freshwater makes up some icebergs and glaciers (about 20% of the world’s supply of freshwater, in fact), most of the Arctic’s water is saltwater found in the Arctic basin. 

There are several ways to define the mass of land embraced by the Arctic. One predominate definition is the land north of the Arctic Circle, which is itself defined defined by an imaginary line of latitude that runs at 66 degrees 33 minutes North. North of this latitudinal line, the summer doesn’t set on the summer solstice. For this reason, the Arctic Circle is also known as the “land of the midnight sun.” The Arctic can also be defined as the region where the average July temperature is less than 10°C (50°F). This isothermal boundary also roughly follows the northern tree line, which can serve as another visual boundary. 

ARCTIC OCEAN SEAFLOOR
The Arctic Ocean seafloor is divided by three large mountain ranges that run parallel between Siberia and Greenland: the Nansen-Gakkel Ridge, which runs across the northern basin of western Russia to Greenland; Lomonosov Ridge, which sits on average about 10,000 ft high above the abyssal plain; and the Alpha Ridge. 

Deep underwater plains, separating the mid-ocean ridges, lie on the Arctic ocean seafloor. The Pole Abyssal Plain separates the Nansen-Gakkel Ridge, while on the Canadian boundary of the Lomonosov Ridge lies the Fletcher and Wrangel Abyssal Plains. Sitting below the Alpha Ridge, north of Canada, lies the Canada Abyssal Plain—the largest of the Arctic sub-basins and a sweeping region with an average depth of 12,000 ft. 

TOPOGRAPHY
Various landscapes can be found throughout the Arctic, providing a range of ecosystems as well. Primary topographical features include: 
•    the massive Greenland ice sheet
•    North America’s Brooks mountain range 
•    the Svalbard archipelago islands 
•    northern Scandinavia’s fjords 
•    northern Siberia’s plateaus and river valleys