| 词条 | Juan de Fuca Channel |
| 释义 |
The geography of Juan de Fuca ChannelThe Juan de Fuca Channel is a submarine canyon running from the shelf break, off southern Vancouver Island to Juan de Fuca Strait.[2] The canyon is both narrow and deep and has sides that are steep. Over its {{convert|6|km|mi|adj=on}} width at the rim it drops from {{convert|200|m|ft}} in depth to over {{convert|500|m|ft}} deep at the thalweg.[3] Along a {{convert|350|km|mi|adj=on}} track, seismic profiles over Juan de Fuca Channel show the canyon consists of two distinct parts. The upper canyon is narrow, extending southwestward down the continental slope. This area has an average gradient of {{convert|17|m/km|ft/mi}}. It is there carved in consolidated or semi-consolidated material of the slope.[4] The lower part of the channel trends northwestward, parallel to the shelf edge, with a gradient of only {{convert|7|m/km|ft/mi}}, terminating at the apex of Nitinat fan. The lower channel represents a small fan and valley feature. Further, Nitinat Fan was constructed on the deep-sea floor at what is the presently the terminus of Juan de Fuca Channel.[5] Most of the shelf break canyons from Oregon and north cross only part of the continental shelf, and cut from the shelf break toward the coast. Then well below the mixed layer, they end on the continental shelf. Different from other aquatic canyons, the Juan de Fuca Channel cuts the continental shelf and continues into the Strait of Juan de Fuca[6][5][2] The amount of water in the channelThe Juan de Fuca Channel reaches to the opening of the Juan de Fuca Strait, which separates the United States and Canada. The canyon is just less than {{convert|4|mi|km}} wide and at least {{convert|450|yd|m}} deep, that is, twice the depth of the surrounding seafloor.[1] More detailFor decades, it has been known that 20 to 30 times more deep water flows into Puget Sound than from all Earth's rivers combined, far bigger than the Amazon River.[1] This flow is towards land, not away.[4] New (as of 2017) measurements show this canyon may supply most the water coming into Puget Sound, the Strait of Juan de Fuca, and Canada’s Georgia Strait.[1] The pattern of water circulation sends a dense lower layer of ocean water towards land, while the upper layer flows out to sea. Its roleJuan de Fuca Channel appears to be a pathway, bringing deep Pacific water into the Salish Sea.[7] Life withinPuget Sound has famously rich water. There is reason for this; the channel pulls nutrient-rich water from the deep ocean. Recent measurements (as of 2017) may explain why this canyon helps the Pacific Northwest’s inland waters support so many shellfish, salmon runs and even pods of whales.[1]Water surges up the channel, mixing at surprisingly high rates. The intense flow and mixing measured inside the Juan de Fuca Channel may help explain the formerly mysterious productivity of the shores of Washington; coastal winds usually bring in some nutrients, but the numbers don’t add up: "Washington is several times more productive – has more phytoplankton – than Oregon or California, and yet the winds here are several times weaker. That’s been kind of a puzzle, for years," observes Matthew Alford, an oceanographer with the University of Washington's Applied Physics Laboratory. At {{convert|500|ft|m|disp=flip}} below the surface, water has flowed as fast as {{convert|1.3|ft/s|m/s|disp=flip}}, showing mixing up to 1,000 times the normal rate in the deep ocean. The flow is hydraulically-controlled, which means it flows smoothly over a shallow ridge just off Cape Flattery then on the other side forms a turbulent breaking undersea wave, mixing with surface water far above. The deep water forced up through the channel is rich in nutrients, which support the growth of marine plants, which then feed other marine life. The water is more acidic, and lower in oxygen, both of which contribute to water conditions in the Strait of Juan de Fuca.[1] Fishing in the Juan de Fuca Canyon"The location of this sill would be an outstanding place to fish," observes Matthew Alford, the oceanographer with the University of Washington’s Applied Physics Laboratory. "People fish in Juan de Fuca Canyon pretty actively, and that’s probably no coincidence."[1] See alsoNearby submarine canyonsAll of the following submarine canyons are near, headed north to south:[8][9][10]
Local geography
References1. ^1 2 3 4 5 6 {{cite web | url=https://www.washington.edu/news/2014/04/14/puget-sounds-rich-waters-supplied-by-deep-turbulent-canyon/ | title=Puget Sound's rich waters supplied by deep, turbulent canyon | work=Puget Sound’s rich waters supplied by deep, turbulent canyon | date=April 14, 2014 | accessdate=24 September 2017 | author=Hickey, Hannah}} 2. ^1 {{cite journal | url=https://onlinelibrarystatic.wiley.com/store/10.1029/1999JC900240/asset/jgrc7948.pdf?v=1&t=j84onzel&s=c624c73e1a51abe34bcbc83b962f07722b2b98ca&systemMessage=Wiley+Online+Library+will+be+unavailable+on+Saturday+7th+Oct+from+03.00+EDT+%2F+08%3A00+BST+%2F+12%3A30+IST+%2F+15.00+SGT+to+08.00+EDT+%2F+13.00+BST+%2F+17%3A30+IST+%2F+20.00+SGT+and+Sunday+8th+Oct+from+03.00+EDT+%2F+08%3A00+BST+%2F+12%3A30+IST+%2F+15.00+SGT+to+06.00+EDT+%2F+11.00+BST+%2F+15%3A30+IST+%2F+18.00+SGT+for+essential+maintenance.+Apologies+for+the+inconvenience+caused+. | title=On subinertial flow in submarine canyons' Effect of geometry | journal=Journal of Geophysical Research: Oceans | volume=105 | issue=C1 | pages=1285–1297 | date=January 15, 2000 | accessdate=28 September 2017 | author=Allen, Susan E.| doi=10.1029/1999JC900240 | bibcode=2000JGR...105.1285A }} 3. ^{{Cite journal |url=https://onlinelibrarystatic.wiley.com/store/10.1002/2013GL058967/asset/grl51395.pdf?v=1&t=j8557ai7&s=1d6abea01296862316bec852fcce2a06dcb91524&systemMessage=Wiley+Online+Library+will+be+unavailable+on+Saturday+7th+Oct+from+03.00+EDT+%2F+08%3A00+BST+%2F+12%3A30+IST+%2F+15.00+SGT+to+08.00+EDT+%2F+13.00+BST+%2F+17%3A30+IST+%2F+20.00+SGT+and+Sunday+8th+Oct+from+03.00+EDT+%2F+08%3A00+BST+%2F+12%3A30+IST+%2F+15.00+SGT+to+06.00+EDT+%2F+11.00+BST+%2F+15%3A30+IST+%2F+18.00+SGT+for+essential+maintenance.+Apologies+for+the+inconvenience+caused+. |title=Flow and mixing in Juan de Fuca Canyon, Washington |journal=Geophysical Research Letters |volume=41 |issue=5 |pages=1608–1615 |last=Flow and mixing in Juan de Fuca Canyon, Washington|doi=10.1002/2013GL058967 |year=2014 |bibcode=2014GeoRL..41.1608A }} 4. ^1 {{cite web | url=http://www.fondriest.com/news/submarine-canyon-puget-sound-juan-de-fuca.htm | title=Submarine canyon flow feeds Strait of Juan de Fuca like an underwater Amazon River | publisher=Environmental Wanderer | accessdate=24 September 2017 | author=Gillies, Jeff| date=2014-04-23 }} 5. ^1 {{Cite journal |bibcode=1969JGR....74.1052C |title=Seismic reflection profiles across Juan de Fuca Canyon |journal=Journal of Geophysical Research |volume=74 |issue=4 |pages=1052 |year=1969|last1=Carson |first1=Bobb |last2=McManus |first2=Dean A. |doi=10.1029/JB074i004p01052 }} 6. ^{{cite journal | title=On subinertial flow in submarine canyons: Effect of geometry |journal = Journal of Geophysical Research: Oceans|volume = 105|issue = C1|pages = 1285–1297| date=January 15, 2000 | author=Allen, Susan E.| doi=10.1029/1999JC900240 |bibcode = 2000JGR...105.1285A}} 7. ^{{Cite web |url=http://cedar.wwu.edu/cgi/viewcontent.cgi?article=1169&context=ssec |title=Observations of Flow and Mixing in Juan de Fuca Canyon |last=MacCready |first=Parker}} 8. ^{{cite web | url=http://www.ccpo.odu.edu/~klinck/Reprints/PDF/hickeyHawaii95.pdf | title=Coastal Submarine Canyons | publisher=School of Oceanography, University of Washington, Seattle, Washington | accessdate=23 August 2017 | author=B.M. Hickey}} 9. ^{{cite web | url=https://olympiccoast.noaa.gov/living/habitats/seafloor/seafloor.html | title=Seafloor | publisher=NOAA | date=July 26, 2017 | accessdate=23 August 2017 | author=Steelquist, Robert}} 10. ^{{cite web | url=https://pubs.usgs.gov/of/1999/0173/pdf/of99-173.pdf | title=THE WASHINGTON AND OREGON MID-SHELF SILT DEPOSIT AND ITS RELATION TO THE LATE HOLOCENE COLUMBIA RIVER SEDIMENT BUDGET | publisher=USGS | accessdate=27 September 2017 | author=Wolf, Stephen C.; Nelson, Hans; Hamer, Michael R.; Dunhill, Gita; Phillips, R. Lawrence}} External links and references
8 : Ocean currents|Currents of the Pacific Ocean|Geography of the Pacific Northwest|Submarine canyons of the Pacific Ocean|Strait of Juan de Fuca|Coastal and oceanic landforms|Submarine topography|Marine geology |
| 随便看 |
|
开放百科全书收录14589846条英语、德语、日语等多语种百科知识，基本涵盖了大多数领域的百科知识，是一部内容自由、开放的电子版国际百科全书。