Hudson Canyon
The immense undersea canyon carved out by the ancient Hudson River in the place where it once poured off the North Atlantic plate in a gigantic waterfall. Known to whales and other wizards as "the Gates of the Sea", the Canyon is nearly a mile deep in places. The canyon proper starts at the end of the Hudson Shelf Channel, about a hundred miles south-southeast of Montauk Point, and after "bottoming out", terminates about two hundred fifty miles southeast of Manhattan, near the undersea continental rise.
Hudson Canyon is the traditional approach to Caryn Peak when celebrating the Song of the Twelve. (DW)
(See also: Celebratory interventions (cetacean): Kelvin Seamounts: Lone Power: Matters of place: Topography and wizardry.)
Note: Since DW was written in 1984, this area has been far more extensively mapped under the auspices of the NOAA / Woods Hole Oceanographic Institute (and other bodies) than it was at the time, and much of this data is now readily available on the Web. Googling for Hudson Canyon will reveal many useful mapping links and much other information.
An extremely technical article on sediments in the Shelf Channel can be found here. Why would anybody in their right mind sit here reading something like this? Don't you have a life? Go outside and play. :)