Nearly Naked: Large Swarth Of Pacific Lacks Seafloor Sediment

Science News ^ | 10-14-2006 | Sid Perkins

[blam]

Nearly Naked: Large swath of Pacific lacks seafloor sediment

Sid Perkins

Oceanographers have discovered a broad, almost-bare patch of seafloor in the remote South Pacific. An unusual combination of circumstances has left the region without the mineral and organic sediments hundreds of meters deep that are typical elsewhere in the world's oceans, the scientists say.

BARE FACTS. A 2-million-square-kilometer region (orange) is almost devoid of seafloor sediment. E. Roell

The sediment-poor region is about the size of the Mediterranean Sea and centered approximately 4,000 kilometers east of New Zealand. Researchers discovered the area, which they dubbed the South Pacific Bare Zone, during a cruise early last year, says David K. Rea, a marine geologist at the University of Michigan in Ann Arbor.

The scientists were surprised when their seismic equipment, which detects sediment only when it's at least 5 meters thick, indicated that there was no sediment in that region. The team then sent sampling equipment more than 4 km to the seafloor and discovered as little as 50 centimeters of sediment in some places.

A unique combination of factors seems to have dictated the area's dearth of sediment that's accumulated since the basalt crust below formed between 85 million and 34 million years ago, Rea and his colleagues report in the October Geology.

First, the area has nutrient-poor surface waters and so is home to few organisms. Therefore, there aren't large quantities of plankton to die, fall to the bottom, and accumulate, as they do in seas with high biological content, says Rea.

Second, the deepest waters in this area contain less carbonate and silica than those in other locations do, so skeletons of organisms that reach the seafloor dissolve.

Third, the bare zone is far from any major landmass, so little windblown dust ends up in the surface waters and eventually sinks. Finally, the region has little if any hydrothermal activity to spew water containing dissolved minerals that would precipitate.

Rea says that he and his colleagues had expected to find at least a dozen meters of sediment in the region. "It's fun to be wrong sometimes," he notes.

Neil C. Mitchell, a marine geologist at Cardiff University in Wales, suggests another factor that may contribute to the sediment skimpiness of the area. It's out of the path of major ocean currents, so Antarctic icebergs carrying material scraped from that continent don't pass over the bare zone and drop sediment, says Mitchell.

The sparse sediments may permit researchers to find seafloor substances that are typically hidden, says David Scholl, a marine geologist at Stanford University. For instance, meteor dust, which falls evenly over Earth's surface, may be more easily detectable in the bare zone than elsewhere, says Scholl.

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[F.J. Mitchell]

While others will perceive it as proof that the earth is several trillion years older than first believed, thus allowing mindless matter more time to accident itself into what we are today.

[perfect stranger]

Ain't it the truth. LOL

[burzum]

What is your point? This ocean area or the size of the Mediterranean Sea is only 0.5% the size of the entire Pacific Ocean. But then again, the entire United States (including Alaska) is only 2.2% of the size of the entire Pacific Ocean. In other words, you are saying that a sea that has an area 26% the size of the entire United States (or 32% minus Alaska and Hawaii) is small. Sounds sort of silly to me.

[elkfersupper]

Someone will find a way to construe this as evidence that the Earth is only a few thousand years old.

Those who would do so neither need, require, nor use evidence.

[TNdandelion]

It was me. I was testing out my new vacuum cleaner. Works pretty good, doncha think?

[ThreePuttinDude]

Sounds sort of silly to me.

What I'm saying is, the Med. isn't as large a body of water as I thought.

Sorry if it sounds silly to you.

[FreePaul]

Bush should start a campaign for the UN to add the necessary sediment to this section of the Pacific Ocean. Financed by the US, of course.

[grjr21]

"It's fun to be wrong sometimes,"





But when your wrong all the time you end up looking like this

[grjr21]

Sorry my bad ... wrong thread

[Jonah Hex]

"ph'nglui mglw'nafh Cthulhu R'lyeh wgah'nagl fhtagn"

("In his house at R'lyeh dead Cthulhu waits dreaming")

Don't wake up the Cthulhu. ;-)

[Sundog]

I see where we could dump some nuclear waste.

[gorush]

They've discovered the secret location where Oreck tests his vacuum cleaners.

[blam]

"Well from my experiences sailing the seas on a submarine, the size of an area in the ocean is just a number."

Mine as well. I was on diesel subs in the early 60's.

[Kirkwood]

"Sorry my bad ... wrong thread"

Actually it strangely fits... all of the sediment was sucked up by Max Factor to be used as foundation makeup for Pelosi.

[burzum]

Don't take too much offense because none was intended. I'm just trying to point out that in my experience there are very few bodies of water that have sizes of which people can really get a grasp. Humans like to compare things (which is because we are intelligent), but certain things just don't make sense in comparisons (in other than a completely abstract sense). The Mediterranean Sea is an enormous sea. You could spend a lifetime sailing around it in a sailboat. Or you could spend less than an hour flying across it in a 747. Or you could get a complete picture of it in a couple of minutes from the ISS. Its size depends on how you look at it. The Pacific Ocean is enormous as well. It used to take years to perform survey missions in a sailboat, but a jet airplane could survey the same area in hours. These comparisons are what are valid in my opinion. People intuitively understand time.

Probably the best way to compare the areas of the block in the Pacific to the Mediterranean would to be to see how long it would take to survey the area for survivors from a shipwreck. This grounds the problem in the real world instead of the abstract. But the problem is that both of these areas are too large for any possible search mission.

[Muleteam1]

Sounds like some sort of Canadian Shield in the Pacific but probably has no comparison in geologic terms.

[Atchafalaya]

Is it described as naked or nekkid? There is a difference.

[blam]

"Is it described as naked or nekkid? There is a difference."

Ahem, around these parts, it would be nekkid.

[onedoug]

Thanks for your "silent service".

[Iscool]

Someone will find a way to construe this as evidence that the Earth is only a few thousand years old.

Ain't that the truth...Everybody knows that this sediment just grew legs and walked away...Some of 'em are probably in NZ right now sittin' in a Starbucks sippin' on a Latte'...