Talk:Continental shelf/Archive 1

Archive 1

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The continental shelf and continental slope are not the same, but if I type in "Continental slope", it redirects me here.

Well clearly they're not exactly the same as the article clearly states. But they are so similar that it makes sense to talk about them in a single article, unless it becomes so long that it would better to split them out again. Not likely to happen anytime soon. Pcb21| Pete 08:00, 25 Nov 2004 (UTC)

This article provides absolutely no explanation for the existence of the continental shelf. TimL 16:40, 10 November 2005 (UTC)

Readability

This article needs to be written in easier forms so that the layperson will be able to understand it. Wikipedia is made for the layperson, not the experts.

I now like omg im like trying o find imformation on the continentale slope and the continentale shelf but reading this it has to much complicated words! —Preceding unsigned comment added by 75.156.66.42 (talk) 01:44, 11 May 2008 (UTC)

Continental Slope

I read this article to say that the continental shelf represents what is believed to be the low point when eglaciation removes water from the oceans in a cycle of ice ages, and the continental slope is the shoreline from that point. If so, there would be a pretty consistent depth for the transition from shelf to slope. Can we get firmer numbers on that depth? FreddyMack 05:23, 21 August 2007 (UTC)

Suggestions

When I searched Continental Rise I came with this. Someone should get rid of the redirect and actually create a page.

Robloxiscoolness (talk) 16:07, 18 May 2010 (UTC)

I think our existing continental margin article is probably a better target for that redirect (and for continental slope), so I'll change them to point there. Feel free to add to that article; it seems too short to split into separate rise/slope articles as yet. --Avenue (talk) 21:41, 18 May 2010 (UTC)

I've changed the continental slope redirect. I see you've already started an article on the continental rise.--Avenue (talk) 21:46, 18 May 2010 (UTC)

total area

According to the following webpages, Continental Shelves make up "7.6%" of ocean area, which works out to 17% of continent area. If so, then 17% of earth's continent area is flooded. 66.235.38.214 (talk) 06:42, 9 October 2012 (UTC) http://www.marbef.org/wiki/Continental_Shelf http://www.worldatlas.com/aatlas/infopage/oceans.htm

evolution of "rift seas" to ocean basins?

According to the Open University textbook From Rifting to Drifting, p.80-90, the mid-Red-Sea-Ridge is a bonafide Mid Ocean Ridge (MOR), which has been spreading at the rate of 10mm/yr for 5Myr; and the depth of the crest of that MOR is about 0.5km. Also, the mid-Red-Sea-Ridge spans the central 100km of that sea, whose average total width is over 200km. Along the coastal flanks of the central ridge, thick sediments (<4km) overlie (extended, and extensively intruded) thinned continental bedrock. At the transition to the central ridge, where the sediments thin away, the thinned continental bedrock mates to the young (<5Ma) oceanic basalt. The shoreline bluffs rise 2-3km above sea-level. Thus, the total drop, from the shoulders of the shoreline bluffs (+2-3km) to the underlying continental bedrock (-4km) is 6-7km.

Now, were the Red Sea to spread into an open ocean, the aged MOR would presumably subside down to a depth of 2.5km (the average depth of all other MOR on earth):

http://geophysics.ou.edu/geomechanics/notes/heat_flow_data/depth_age.htm

And, the aged seafloor, mated to the "toes" of the African & Arabian continental-shelves-to-be, would subside down to a depth of nearly 6-7km (the average depth of old seafloor >80Ma). Thus, as trans-continental rifts evolve, into open oceans, the shoreline bluffs subside, as they are spread away from the hot, expanded, upwelling mantle material doming up at the MOR. Over the ages (Myr), they subside down a couple of km, to sea-level, where they presumably erode into shallow continental shelves. The shoulders of those bluffs become the edges of continental shelves; their faces become the continental rises. And, the "toes" of those continental rises, extending outboard 50-75km, consist of thinned and heavily diked, silled, and intruded continental crust, underlying the overlying layers of sediment(s). Those "toes", so heavily fractured & intruded, might possibly be structurally weakened; at some point, the mated oceanic bedrock might possibly break away, sinking into the mantle, and so starting a new subduction zone (SZ):

http://s11.postimage.org/3p5bgmz2b/Evolving_Ocean_Basins.png

If so, then new SZs open up at or near the base of continental rises, when cooling, "densifying" oceanic crust "sinks away" from the continental "toes", subsiding down into the mantle. Now, the crust (down to the MOHO boundary) under Brazil & western Africa is extremely thin (<10km), presumably extended & thinned over the past 200Myr, as South America & Africa have been pulled away from the Atlantic MOR. But North America has obducted a MOR (the east Pacific rise), and seems stalled there-atop (e.g. coastal California has broken away). And, back under the east coast of North America, the continental crust is thick. Meanwhile, judging by widths of magnetic anomalies near the MOR in the north Atlantic, spreading there-from has slowed over the past 40Myr. Perhaps, as pressures build, either the Atlantic ocean slab will remain mated to the continental "toes" of North America, and the north Atlantic MOR will jam shut; or the oceanic slab will sink away, opening a new SZ ? Popular geology programs speculate about such an event; is the foregoing explanation an accurate sketch of the geologic reasoning behind such speculations? 66.235.38.214 (talk) 12:19, 27 October 2012 (UTC)

From 200-100Ma, as Pangea rifted apart, oceans drowned the continents, e.g. Western Interior Seaway. Young seafloor is hot, expanded, comparatively buoyant, and rides higher, than older cooler seafloor. The early Cretaceous marine transgression can be explained, by the youth, of the "rift seas", e.g. proto-Atlantic, then swaddling the globe. And, the subsequent fall of sea-levels, can be attributed, to the aging, cooling, and subsiding of the same seas' floors. According to Robert Henson's Rough Guide to Climate Change (p.211), plate speeds were 50% faster 100Ma vs. today. Ocean floor always covers about the same fraction of earth's surface (the volume of buoyant aluminosilicate "continental" crust is constant). So faster spreading, and younger seafloor, would both be expected to co-occur. Ipso facto, the rifting apart of Pangea after 200Ma coincided with a 100Myr of "fast" plate tectonics, young-and-shallow oceans, and epicontinental seas. 66.235.38.214 (talk) 12:35, 27 October 2012 (UTC)

New NEWS today, for future editing

The new disaster film, 'San Andreas', has put the major Californian fault in the spotlight.

Headline-1: It's not just San Andreas: Scientists reveal the hidden hazards that could trigger huge quakes and tsunamis off Californian coast

• http://www.dailymail.co.uk/sciencetech/article-3103187/It-s-not-just-San-Andreas-Scientists-reveal-hidden-hazards-trigger-huge-quakes-tsunamis-Californian-coast.html

QUOTE: "The new disaster film, 'San Andreas', has put the major Californian fault in the spotlight. But a new study has found it isn't just the San Andreas fault we should be worried about; a very real threat of earthquakes and tsunamis lurks offshore Southern California. Researchers say that several long faults could cause magnitude 8.0 quakes and tsunamis within 90 miles (145km) of the coast." -- Charles Edwin Shipp (talk) 11:25, 30 May 2015 (UTC) -- PS: FYI for future editing.

• Study looked at structure of two large seafloor faults in the Borderland
• They found the Santa Cruz-Catalina Ridge Fault has been lifted upward
• It is also slipping sideways like the plates along the San Andreas Fault
• Could cause 8.0 quakes and tsunamis within 90 miles (145km) of coast

I've checked out the original scientific paper and it doesn't quite match the hype of the news stories. The main question, however, is how is this relevant to the continental shelf article? Mikenorton (talk) 16:22, 30 May 2015 (UTC)

Assessment comment

The comment(s) below were originally left at Talk:Continental shelf/Comments, and are posted here for posterity. Following several discussions in past years, these subpages are now deprecated. The comments may be irrelevant or outdated; if so, please feel free to remove this section.

I'm going to delete some profane vandalism on the first two lines of the article. I'd appreciate it if someone would make sure that the hoodlum didn't delete some substantive remarks. Thank you. Mike Bandy

Last edited at 02:43, 3 December 2008 (UTC). Substituted at 19:53, 1 May 2016 (UTC)

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