Ontario
The Nastapoka Arc carves a perfect semicircle into the southeast shore of Hudson Bay. Scientists disagree on the origin of the arc and the reason for its uniform curvature.
The final days of Henry Hudson are a Hudson Bay mystery, as is the odd shape of the Nastapoka Arc, a stunningly visible arc forming a portion of the bay’s shore. Seen from above, Hudson Bay is a vast inland waterway in northeastern Canada; the Nastapoka Arc is a uniformly curving coastline in the bay’s southeastern corner. Nastapoka’s nearly perfect semicircle covers 160 degrees of a 280-mile-wide circle about the size of Wisconsin.
Hudson Bay is the world’s second-largest bay (after the Bay of Bengal in the Indian Ocean), draining the watersheds of much of central Canada and parts of the northern United States. With its high northern latitude, the bay is iced over for about half the year—from mid-December to mid-June—and the huge expanse of ice is prime seal-hunting grounds for a large population of polar bears. But from a geological standpoint, the Nastapoka Arc is perhaps Hudson Bay’s most compelling element. Because of its smooth shape, the arc was long thought to be the remnants of an impact crater from a meteorite strike. The Belcher Islands seen in the middle of the arc were considered the remains of the raised, central high point of the crater. However, a 1972 study found no evidence of the shocked rocks, radial fractures, or other melted rocks that would back up the impact theory.
Instead, many scientists today ascribe the unusual geometry of the Nastapoka Arc to plate tectonics, with the curved boundary possibly having been created during a mountain-building episode that took place around 2 billion years ago. This time of mountain building also gave rise to the basement rocks known as the North American Craton, the precursor of what would become the North American continent. Some scientists still doubt the theory, however, as this would be the only known example of a perfectly curved tectonic boundary on Earth.
Hudson Bay is named for Sir Henry Hudson, who explored the bay in 1610 on his ship Discovery, in search of the mythical Northwest Passage from Europe to Asia. Hudson did not know that while the bay is salt water, it is significantly less salty than ocean water and therefore ices over earlier in the year than the Atlantic Ocean. Much to its crew’s dismay, the Discovery became trapped in ice and was forced to spend the miserably cold winter of 1611 on the shore of James Bay, the southern arm of Hudson Bay. When the ice melted in late June, a determined Hudson proposed continuing the mission west to find a route to China. The exhausted crew mutinied and put Hudson, his son, and seven supporters adrift on a small boat, then set sail back to England. Hudson was never seen again; he presumably died not long after being abandoned.
Some flights from the eastern United States to Europe fly over northern Canada and the Arctic, offering views of Hudson Bay, but there are no commercial airports near the bay itself.
