The Astoria Fan is a submarine fan. It has sediment, radiating asymmetrically southward from the mouth of the Astoria Canyon. From Astoria Canyon's mouth, the fan extends about 100km (100miles) to its western end, which is the Cascadia Channel. The fan proper ends 160km (100miles) south of the canyon mouth, although its depositional basin extends southward another 150km (90miles) to the Blanco Fracture Zone.[1]
Astoria Fan is generally asymmetrical. It extends roughly 55miles west of the mouth of Astoria Canyon, and about 55miles north, to Willapa Channel. Others trace different dimensions.[2]
Headed west, the fan crosses the continental shelf, trending sinuously down to the base of the continental slope. Near Astoria Canyon, it is at a depth of 2740m (8,990feet). The fan is approximately 75miles long. It varies in width from 1.5miles to 8.3miles.[3] It has numerous tributaries.[4] The fan extends about 100km (100miles) to its western boundary, which is the Cascadia Channel.
Ash from the eruption of Mount Mazama has been found, in Astoria Fan. It may have been cut in the Pleistocene. It appears the Missoula Floods helped carve the fan.[5]
Astoria Fan merges into Astoria Canyon, 9miles west of the Columbia River mouth. In the past, buried Pleistocene channels appear to have connected the two.[4]
All of the following submarine canyons are near, headed north to south:[6] [7]