Astoria Fan

Coordinates: 45°15′00″N 126°15′00″W / 45.25000°N 126.25000°W / 45.25000; -126.25000

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 100 kilometres (62 mi) to its western end, which is the Cascadia Channel. The fan proper ends 160 kilometres (99 mi) south of the canyon mouth, although its depositional basin extends southward another 150 kilometres (93 mi) to the Blanco Fracture Zone.[1]

The fan's dimensions

Astoria Fan is generally asymmetrical. It extends roughly 55 miles (89 km) west of the mouth of Astoria Canyon, and about 55 miles (89 km) 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 2,740 metres (8,990 ft). The fan is approximately 75 miles (121 km) long. It varies in width from 1.5 miles (2.4 km) to 8.3 miles (13.4 km).[3]

The fan extends about 100 kilometres (62 mi) to its western boundary, which is the Cascadia Channel. It depositional basin extends clear to Blanco Fracture Zone 150 kilometres (93 mi) south.

It has numerous tributaries.[4]

Ash from Mount Mazama has been found, in Astoria Fan

Ash from the eruption of Mount Mazama has been found, in Astoria Fan.[1]

When it was cut

It may have been cut in the Pleistocene.[4] It appears the Missoula Floods helped carve the fan.[5]

It merges into Astoria Canyon

Astoria Fan merges into Astoria Canyon, 9 miles (14 km) west of the Columbia River mouth. In the past, buried Pleistocene channels appear to have connected the two.[4]

Nearby submarine canyons

All of the following submarine canyons are near, headed north to south:[6][7]

See also

Local geography

References

  1. 1 2 C. Hans Nelson (1985). "Astoria Fan, Pacific Ocean". Astoria Fan, Pacific Ocean. Springer. pp. 45–50. Retrieved 16 September 2017.
  2. ↑ Cartlon, Hans (1968). "Marine Geology of Astoria Deep-Sea Fan" (PDF). Oregon State University. Oregon State University. Retrieved 2017-09-19.
  3. ↑ Nelson, C. Hans (December 6, 1982). "The Astoria Fan: An elongate type fan" [The Astoria Fan: An elongate type fan]. Retrieved 2017-09-19.
  4. 1 2 3 C.H. Nelson, P.R. Carlson, J.V. Byrne, and T.R. Alpha. "Development of the Astoria Canyon-Fan physiography and comparison with similar systems". Development of the Astoria Canyon-Fan physiography and comparison with similar systems. USGS. Retrieved 18 September 2017.
  5. ↑ Embley, Bob (June 9, 2010). "Astoria Canyon: A Natural Laboratory". Astoria Canyon: A Natural Laboratory. NOAA. Retrieved 2017-09-19.
  6. ↑ Steelquist, Robert (July 26, 2017). "Seafloor". NOAA. Retrieved 23 August 2017.
  7. ↑ "Exploring Olympic Coast National Marine Sanctuary & Quinault Canyon". Exploring Olympic Coast National Marine Sanctuary & Quinault Canyon. Nautilus Live. August 17, 2017. Retrieved 19 September 2017.
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