large submarine canyon incised into the Atlantic continental slope and outer shelf off New York Harbor, U.S. A shallow shelf channel, Hudson Channel, trends south-southeastward from the mouth of Hudson River to the head of the canyon on the outer shelf, where the water is 300 ft (90 m) deep at 20 mi (30 km) offshore. The canyon proper is approximately 58 mi long, passing into a fan valley at the base of the continental slope at a depth of about 7,000 ft. Where best expressed topographically, the canyon's V-shaped walls have a height of 4,000 ft. Hudson Fan Valley, incised into the continental rise below the mouth of Hudson Canyon, has much less relief, although the 1800-ft-high walls about 90 mi down the fan are abnormally high for most fan valleys. The fan valley, at least 230 mi long, probably serves to distribute the sediment supplied from the shelf by Hudson Canyon over the Hudson Fan.