FAQ   Search   Memberlist   Usergroups   Register   Profile   Log in to check your private messages   Log in 
There's a huge hole in the Atlantic seafloor

 
Post new topic   Reply to topic    The Next Level Forum Index -> Tomorrow's World
  ::  Previous topic :: Next topic  
Author Message
obeylittle



Joined: 10 Sep 2006
Posts: 442
Location: Middle o' Mitten, Michigan Corp. division of United States of America Corp. division of Global Corp.

PostPosted: Sat Mar 03, 2007 12:13 am    Post subject: There's a huge hole in the Atlantic seafloor Reply with quote

Quote:
There's a huge hole in the Atlantic seafloor

BEIJING, March 2 (Xinhuanet) -- There's a huge hole that extends over thousands of square miles in the Atlantic seafloor between the Cape Verdes Islands and the Caribbean nearly 2 miles below the ocean surface where Earth's deep interior is exposed without any crust covering and a team of scientists wants to find out why.

"It's quite a substantial area," said Chris MacLeod, a marine geologist at Cardiff University in the UK, who will be part of the expedition.

The team of researchers, led by Roger Searle of Durham University, will begin traveling to the site on March 5 aboard the new UK research ship "RSS James Cook." During the course of about six weeks, the team will use sonar to image the seafloor and a robotic seabed drill to collect rock cores.

Earth's crust is constantly being destroyed and created, and this cycle of destruction and renewal occurs faster with ocean crust than with continental crust. New ocean floor crust forms at seams on the Earth’s surface, called mid-oceanic ridges, where the planet's tectonic plates meet and where molten magma rises up from the planet's upper mantle.

The upwelling drives seafloor spreading, which is the movement of two oceanic plates away from each other. Oceanic crust is destroyed at so-called subduction zones where two plates collide and typically the denser one slips beneath another plate.

This is how scientists think it works, but areas of exposed mantle on the Earth's surface aren't easily explained by this theory. They are regions "where this process seems to have gone wrong somehow," MacLeod said. "There’s no crust formed, and instead we've got mantle -- which is normally in the deep Earth -- on the seafloor."

There are two popular theories about how these holes in the Earth’s crust form.

"One is that the original volcanic crust did form but that it's been ripped away by a huge rupture," MacLeod told LiveScience.

MacLeod likens this process to stretching a person's skin until it ruptures, exposing the flesh underneath.

"You take the crust and you stretch it and you pull it and pull it until it breaks," he explained.

The other idea purports that somehow the area of exposed mantle was never covered by a magma crust in the first place.

Regardless of how they formed, the exposed mantle provides scientists with a rare opportunity to study the Earth’s rocky innards. Many attempts to drill deep into the planet barely get past the crust.

"One of our objectives now that we've got direct access to these mantle rocks is to try and look at their internal properties and try to find out about the deep Earth process that we can't get at directly," MacLeod said in a telephone interview.

Getting equipment down onto the seafloor where the exposed mantle is will be difficult, however.

"It's a very hazardous, very unforgiving environment," he said. "There are very steep slopes and huge pressures. So getting samples back from these areas is challenging still."
Back to top
View user's profile Send private message
Hocus Locus



Joined: 22 Sep 2006
Posts: 850
Location: Lost in anamnesis, cannot forget my way out

PostPosted: Sat Mar 03, 2007 6:43 am    Post subject: Reply with quote

Holey moley!



I'd like to correlate this location with ocean surface temp contours, hurricane tracks over time, and thermocline data for the area if available... that looks to be a tad south of the pre-2000 Atlantic hurricane corridor.

RRS James Cook cruise JC007, 5 March 2007 - 17 April 2007
Cruise diary (first update promised Monday 05-Mar-2007)

Quote:
RRS James Cook cruise JC007, 5 March 2007 - 17 April 2007
Visit the web page to see photos

Mid-ocean ridges are a fascinating component of our planet's armour plating. Mid-ocean ridges are the place where new oceanic crust is born, with red-hot lava spewing out along the spreading axis as seafloor spreading progresses. However, the mechanisms by which this occurs are still not well understood by scientists - hardly suprising when you consider that mid-ocean ridges are located thousands of metres below the surface of the ocean.

Scientists have discovered a large area thousands of square kilometres in extent in the middle of the Atlantic Ocean where the Earth's crust seems to be missing entirely. Instead, the mantle - the deep interior of the Earth, normally covered by crust many kilometres thick - is exposed on the seafloor, 3000m below the surface. It has been described as being like an open wound on the surface of the Earth. What scientists don't know is whether the ocean crust was first developed, and then ripped away by huge geological faults, or whether it never even developed in the first place.

In March-April 2007, a team of scientists from Durham University, Cardiff University and NOCS will board the RRS James Cook to visit this special area of the Mid-Atlantic Ridge, which is called the Fifteen-Twenty Fracture Zone (FTFZ for short - the map on the left shows where this is located).

The scientific team on board the ship is led by Prof. Roger Searle from University of Durham, Dr Chris MacLeod (University of Cardiff) and Dr Bramley Murton (NOCS).

Left: Image of the Mid-Atlantic Ridge. You can see how the ridge is broken up into segments by fractures running roughly perpendicular to the ridge axis. The red dot shows the area where the team on board the ship will be working. Bathymetric image courtesy GEBCO.

Equipment

The first step on the expedition is to use TOBI (Towed Ocean Bottom Instrument - right) to build up images of the seafloor surface so that suitable drilling sites can be selected. TOBI images will enable the scientists to identify areas where peridotite is exposed at the seafloor, and give them information on the shape of the ridge, the distribution of faults and identify any areas where magma is erupting onto the seafloor.
[click here for more about TOBI and seafloor surveying]


When the team have selected suitable sites for drilling, they will use a robotic 'BRIDGE' rock drill to take samples of the seabed. The drill is mounted on a metal tripod and is lowered onto the seafloor by a special cable. A camera on the tripod allows the scientsts to see exactly where they are placing the drill. The rotating drill bit is diamond-tipped to ensure that it's hard enough to cut through the rock, and produces cylindrical 'rods' of rock (cores, see below). An important feature of this particular drill is that the cores are specially marked to show which way is north so that the scientists know how they are oriented - very important when you're taking lots of samples across an area and you want to know how certain properties vary across space. By taking a series of these cores across the area and analysing them, the scientists will be able to determine how the seafloor spreading process varies across the region, and how the mantle came to be so close to the surface in this area.
[more about rock drilling]

Above, from left: the BRIDGE drill being recovered after sampling the seabed; an image from the tripod camera, showing the rig sitting on bare rock, covered in the foreground by a dusting of white sediment. Note the leg of the drill rig, and a sea urchin for scale in the centre of the picture. The dark stripes are mineral-filled cracks in the seafloor; Core recovered from the BRIDGE rock drill. The rock is a gabbro – equivalent to the lavas erupted onto the seabed, but which instead crystallised slowly at a depth of a few kilometres below the seafloor.

The team may also carry out dredging - a primitive but still effective way of sampling the seafloor. Methods and equipment have changed little since the pioneering expeditions of HMS Challenger in 1872. A chain-link bag with large metal-jawed opening is lowered to the seabed on a cable, dragged along the bottom for some distance, and then brought to the surface. Although rough and ready, dredging is still a useful way of mapping the broad-scale distribution of rock types on the seafloor. Dredging will only be conducted during the cruise as a backup or in between deployments of the principal tools: the sidescan sonar and seabed rock drill.

Above left: A rock dredge being deployed from a research ship.
Above right: Chris MacLeod plus full rock dredge. Note how the originally rectangular
mouth to the dredge has been bowed open as the rocks were forced in to the chain bag.

The RRS James Cook will set sail from port in Tenerife on 5 March 2007. This is the RRS James Cook's first scientfic mission....keep up to date with all the latest cruise news and developments by visiting the JC007 cruise dairy from 5 March.

More on the science behind this cruise...

Mid-ocean ridges are a fascinating component of our planet's armour plating. Mid-ocean ridges are the place where new oceanic crust is born, with red-hot lava spewing out along the spreading axis as seafloor spreading progresses. However, the mechanisms by which this occurs are still not well understood by scientists - hardly suprising when you consider that mid-ocean ridges are located thousands of metres below the surface of the ocean.


We know that mid-ocean ridges form when the earth's plates are pulled apart as part of the plate tectonic process. However, the rate of spreading is not the same all along the spreading ridge, causing the ridge to split into segments - this creates the jagged offset pattern you can see on maps of the seafloor, like the one shown on the left. Some parts of mid-ocean ridges are spreading relatively quickly, others are spreading very slowly. This difference in spreading rates results in sections of the mid-ocean ridge with very different physical characteristics.

Within each ridge segment, particularly where the overall spreading rate is slow, the rate at which molten magma rises to the surface can vary. Scientists have assumed for a long time that the centre of the segment is the place where the magma rises most quickly and intensely, meaning that the centre of the segment is therefore hotter the edges of the ridge segment. The ocean crust in the centre of the segments is often also stretched more thinly, contributing to the higher temperatures in this area. In contrast, the edges of the ridge segments are thicker and cooler.

Left: Image of the Mid-Atlantic Ridge. You can see how the ridge is broken up into segments by fractures running roughly perpendicular to the ridge axis. The red dot shows the area where the team on board the ship will be working. Bathymetric image courtesy GEBCO.

This variation in temperature affects the way in which the ridge segment deforms in response to pressure - hot areas are more "squidgy" and can deform more easily than the edges of segments which are colder and more brittle. This means that at the edges of segments, the spreading motion is accommodated by cracking or tectonic faulting of the crust, instead of a smooth spreading mechanism dominated by the injection of magma into the central ridge axis.

This section of the Mid-Atlantic Ridge is special because it is the best-known example of a 'magma-starved' ridge - in other words, an area where spreading takes place by tectonic (cracking) processes instead of by magma injection. The ocean crust in this area is exceptionally thin, meaning that a rock called peridotite is exposed in the central valley of the ridge. Usually, this rock is buried beneath kilometres of ocean crust, so by taking samples of this rock the scientific team can gather important information about the structure of the ridge in this area and the mechanisms by which seafloor spreading takes place. A key question to answer is whether the oceanic crust has been removed by tectonic processes, or whether it was never there in the first place.

in addition to going to sea to study how the oceanic basement is formed, geologists also study on-land fragments of ocean lithosphere, known as ophiolites. Bram and Chris have extensive experience of working on such rocks, particularly the Troodos ophiolite of Cyprus. The Lizard in Cornwall (UK) is another example of an ophiolite, where plate tectonic processes have resulted in ancient oceanic crust being exposed on land.
___
My friend, take a deep breath, turn off the TV
I can help you if you listen to me
The future's bright, and I can show it to you, for a price
Just for my expenses, you understand, this isn't about money
Look, I'm being nice
I'm letting you in on a something called
The future, it's bright; it's brilliantly millions of things
Tasty, painless and funny
And you, you look great in the future

~Wesley Hsu: "Future Perfect", Bangkok Poetry Archive 2005 (preserved at archive.org)
Back to top
View user's profile Send private message
Hocus Locus



Joined: 22 Sep 2006
Posts: 850
Location: Lost in anamnesis, cannot forget my way out

PostPosted: Fri Mar 09, 2007 9:56 pm    Post subject: Reply with quote

Quote:
From the Cruise diary, RRS James Cook
Cruise JC007, 5 March 2007 – 17 April 2007 (Visit the link to see photos)

___
Day 1: Monday 5 March 2007
Location: Santa Cruz, Tenerife (28º28N, 16º15W)

Michelle writes:

"Today the scientific team embarked on cruise JC007: Roger Searle, Chris MacLeod, Bramley Murton, Jack Casey, Chris Mallows, Samantha Unsworth, Michelle Harris and Kay Achenbach. At the last minute Tina Hayes and Tim Le Bas were unable to join the rest of the team. Today cruise preparation continued with refuelling and the loading of supplies to ensure we have everything on board that is needed for the voyage. Meanwhile the scientists continued to prepare the labs and install computers and equipment. We also ensured all items were well strapped down in case we run into any bad weather on the way. Whilst we were waiting for refuelling to finish we had the opportunity to take a few photos of the final scientific team (all 8 of us!!!!!) on the foredeck. At 18.57GMT we left Santa Cruz and began the long journey to our sampling location, hopefully not shaken and definitely not stirred!!!"

___
Day 2: Tuesday 6th March: On passage to sample area
Position at midnight: 26º17N, 20º 42W

Michelle writes:

Today was the first day complete day of our passage to our sampling area. This morning the two watch shifts, each lasting 12 hours, were decided upon with Chris MacLeod, Roger Searle, Michelle Harris and Kay Achenbach on watch from 12 noon to 12 midnight, followed by Bram Murton, Jack Casey, Sam Unsworth and Chris Mallows on watch from 12 midnight to 12 noon. The first watch began at 12 noon and the key data to log at 30 minute intervals were chosen. At 13.20 the ship stopped at station 1 and our first deployment of the sound velocity probe took place - this instrument records the temperature of the water with depth. This information is needed because the velocity of sound changes with the water temperature. This means that we need to correct for this changing sound velocity when creating the bathymetry to make it as accurate as we can. Bathymetry (the depth from the ocean surface to the seafloor) is measured using soundwaves emitted from a device mounted on the ship's hull. The data collected from this instrument is used to build up a 3D picture or map of the seafloor.

The probe took 55 minutes to reach the seafloor at a depth of 3000m and was back on board at 15.10GMT. At 15.30GMT we continued on our passage. By 12midnight we had travelled 483km (261miles) with an average speed of 8knots.

Quote of the Day
Bram on his musical entertainment: "I’m at a distinct disadvantage not being able to tune or play this churango!!!"... The rest of the group are hoping he learns soon!!!!!

___
Day 3: Wednesday 7 March - Passage to sample area
Position at midnight: 24º20N, 25º29W

The morning watch was quiet with scientists mostly concentrating on setting up computing equipment as well as making records of the ship’s position and speed, and other important readings. At about 02.00GMT depth profile data showed that we were passing over an elevated area, which may have been a submerged volcano, or seamount. The second watch continued with the recordings and observed the XBT deployment, this instrument measures the sound velocity profile, similarly to the SVP we used yesterday. The XBT has the advantage of being used whilst the ship is in motion whereas the SVP requires the ship to stop.

We spent much of the afternoon marvelling and being slightly bemused by the huge media coverage our cruise is attracting from the worlds media. Our three leading scientists Roger, Chris and Bram have been fielding phone calls and interview requests all day, just to mention a few articles…..CNN, Science American.com, Caribbean News, The Times, The Taipei Times, The Lesbian Pirate Queen (don’t ask!!!) and the list goes on! There appears to have been some crossed wires along the way as to what the science of the cruise is, primarily that there is a gaping hole in the ocean crust, as exciting as that would be, in fact the upper layers of the ocean crust are missing leaving the lower oceanic crust units and mantle rocks exposed at the seafloor. We have also received hundreds of questions through the website so please bear with us as we work through them all, unfortunately we won't be able to answer all of them as much as we would like to. On behalf of all the scientific team we would like to thank everyone who has wished us good luck and a safe journey - so far it seems to be working!

The day ended with some dolphin watching off the aft deck.

Quote of the Day:
Jack to Kay: “Keep us in suspenders until tomorrow!”

___
Day 4: Thursday 8 March - Still on passage to sample area
Position at midnight: 22º44N, 29º21W

Today our watches continued as usual and generally it has been a quiet day. We stopped for a short time at 14:15 to deploy the SVP like we did on Tuesday. This deployment was successful. The remainder of day was spent continuing to plan the more specific details of the sites at which we intend to sample and in what order. The highlight of the evening was the musical wonder of a duet between Chris on his Greek bouzouki and Bram on his (finally tuned) churango!

Quote of the day:
Chris MacLeod: "Does anyone want my cherry??!!!!!"

___
Due to circumstances beyond our control...
you are the master of your fate, captain of your soul.
Back to top
View user's profile Send private message
obeylittle



Joined: 10 Sep 2006
Posts: 442
Location: Middle o' Mitten, Michigan Corp. division of United States of America Corp. division of Global Corp.

PostPosted: Fri Apr 13, 2007 1:02 am    Post subject: Reply with quote

In addition to the daily Cruise Dairy there is also a Q&A page with email form. While the diary is semi-interesting when geology is discussed and when photos are posted, the Q&A yields some interesting facts and sometimes... just opinion. Here is a small sample:

Question time! wrote:
Q
there have been 18 quakes on the mid-atlantic ridge since feb 1 2007 this is probably more than all last year. all these quakes were about 10 km deep and all 5.0 give or take a couple of points. these quakes go from off brazil to greenland sea and back. what are you finding if anything relative to this movement
John Meller, USA

I am in 6th grade and go to Robert Millikan Junior High School in Sherman Oaks, California. I wanted to wish good luck on your trip. This is my question. How have earthquakes shaped the area that you will be studying? Are earthquakes responsible for the huge chunk that is missing from the ocean crust?
Aleq Quintanilla, California

A
HI ALEQ AND JOHN. UNUSALY FREQUENT EARTHQUAKE ACTIVITTY IN THIS AREA, WHERE THE MANTLE IS BEING EXPOSED AND THE CRUST TORN AWAY, IS ONE OF THE FEATURES THAT FIRST DREW THE SCIENTIFIC COMMUNITTY’S ATTENTION.

Bram

Q
I've read everything on the mission so far and I think that it's really cool with the sound velocity probe and everything!! Anyway, is it possible that these "crust absences" could start appearing in the other ocenas? If so, could this pose a major threat to humanity? Good Luck on you voyage!!

Kevin Kittinger, USA

A
YES KEVIN, THERE ARE OTHER AREAS IN OTHER OCEANS WHERE THE MANTLE IS BEING EXPOSED – THE SOUTHWEST INDIAN OCEAN AND THE GAKEL RIDGE IN THE ARCTIC ARE TWO THAT WE KNOW OF.

Bram

Q
In answers to several questions you point out that the warming effect of the thinner crust in the area concerned is very small but could it not vary considerably over time and in different locations and if the area is so large would not the overall effect of even a small difference be significant in maintaining ocean and atmospheric temperatures and over time contributing to changes? You accept the existence of continuous convective processes from the mantle through the oceans to the atmosphere but as far as I know it has never been properly quantified as part of the planetary heat budget in climate models.

Stephen, Cheshire, UK

A
HI STEPHEN, GEOTHERMAL HEAT INPUT FROM THE SEAFLOOR IS THOUGHT TO AFFECT OCEAN CIRCULATION. IA RECENT NUMERICAL MODEL BY MAROVSKSA, INDICATED ABOUT A 40% INCREASE IN PACIFIC OCEAN CIRCULATION CAUSED BY GEOTHERMAL HEATING. BUT THESE ARE ONLY EARLY DAYS AND OUR UNDERSTANDING OF THE CONNECTION BETWEEN GEOTHERMAL HEATING (RELATED TO MANTLE CONVECTION AND OCEAN CIRCULATION) IS VERY SKETCHY.

Bram

Q
I find this particular piece of research facinating. What has been speculated as a likely reason crustal deposition is so much less here as other places and over such a large area? How much of a differential in crust thickness is there between your location and other similar areas along the mid-atlantic ridge? Are there spurious deep-water currents that would have interfered over time? Is the lack of crustal deposits only a carryover from times past or does the process continue today?

Steve, South Carolina

A
Hi Steve,
Usually, oceanic crust is thought to be 6-7 kilometers thick. We don’t actually know the reason why the crust is missing here—that’s why we’re doing the research! We do have a couple of hypotheses, though; the most likely is that the mantle didn’t melt enough to produce crust. This could happen for because a) the mantle is colder here than is typical, or b) the mantle here might have melted billions of years ago and doesn’t have any melt ingredients left in it now. Since material is still moving away from the ridge axis, we can tell which processes are still active today because they are still in evidence on the ridge axis—things that happened a long time ago have been carried off-axis. Since we find mantle rock in the ridge axis here, we know that the processes that created the missing crust are still active today. Currents don’t have much to do with the missing crust, because the currents on the seafloor are very gentle and don’t have the power to erode much, especially not 7 kilometers’ worth of material.

Q
Retired Organic Chemistry Prof. would like to know how you distinguish Mantle rock from Crust rock.

Prof. Otto Meth-Cohn, Northumbria

A
Hi Professor,
When the mantle partially melts, certain elements “prefer” to be in melt rather than in solid, and these elements become partitioned into the melt. Since the melt is what eventually forms the crust, you end up with different compositions in the crust vs. the residual mantle. These different compositions result in different minerals (or similar minerals but very different abundances). For example, peridotites (mantle rocks) are generally made of (in decreasing order of abundance) olivine, orthopyroxene, clinopyroxene, and about 1% of some aluminous phase (plagioclase, spinel, or garnet depending on depth). Basalts (crustal rocks), on the other hand, contain a lot more plagioclase (because aluminum is partitioned into melt, and plagioclase, as the lower-pressure aluminous phase, is what crystallizes at crustal pressures), and may or may not contain various amounts of pyroxenes and/or olivine. Because the minerals are so different in these different kinds of rocks, we can tell which kind they are right away just by looking at the rocks.

Q
There's rumors that you are looking for Atlantis.... or Lemuria... Are you? What percentage of the earths ocean floor has been explored?

Caleb Brown, aged 11, Minnesota

A
Hi Caleb,

We aren’t looking for any mysterious missing island, although it would be exciting if we were! We just want to know why the normal ocean crust doesn’t seem to form in this part of the world. As for how much of the Earth’s ocean floor has been explored, I can’t give you an exact figure, but I bet it’s less than 10%. We have better maps of the surface of Venus than we have of the ocean floor because it is so difficult to “see” through water. A couple of years ago there was actually an accident where a submarine crashed into an underwater mountain that wasn’t on any maps of the seafloor, so more underwater exploration is definitely needed!

Q
Does this crust defect have any affect on gravitational data? Slight satellite deviations? And I am curious about magnetic deviations as well. This information is very exciting and we wish you all of the best weather.

Mark Fossati, Washington

A
YES MARK, THE HOLE IN THE CRUST MEANS THAT THE DENSER MATERIAL OF THE MANTLE IS BOUGHT TO A SHALLOWER POSITION THAN NORMAL. THIS CAUSES AN INCREASE IN THE EARTH’S GRAVITATIONAL FIELD AT THIS POINT. ONE RESULT OF THIS IS THAT THE SEA SURFACE GETS DEFLECTED UP AND OVER THE STRONGER GRAVITATIONAL FIELD. THIS CAN BE OBSERVED BY SATELLITES THAT USE LASERS TO MEASURE THEIR HEIGHT ABOVE THE SEA SURFACE, MAGNETICALLY, THE MANTLE MATERIAL ADOPTS QUITE A STRONG MAGNETIC INTENSITY AS THE MAIN MINERALS FORMING THE MANTLE (OLIVINE – AN IRON-MAGNESIU,M SILICATE) REACTS WITH THE SEAWATER TO FORM SERPENTINITE (A LOW DENSITY MAGNESIU,M HYDROXY-SILICATE). A BY-PRODUCT OF THE REACTION IS AN IRON MINERALCALLED MAGNETITE. THE REACTION ALSO RELEASES HYDROGEN GAS THAT REACTS WITH THE SEAWATER CARBONATE TO FORM METHANE.

Bram

Q
Would it be possible that all the environmental warm up can be traced back to this fact of the sea is exposed to the mantle? The warm up then carried to the poles and melting the ice caps?

Gene E. Sotory, USA

A
NO GENE. THE GLOBAL CLIMATE WARM-UP IS CAUSED BY THOSE OF US THAT BURN FOSSIL FUELS. AFTER ALL, THINK ABOUT THE FACT THAT COAL AND OIL IS MILLIONS OF YEAR’S WORETH OF STORED SUNLIGHT, AND WE ARE RELEASING ALL THAT ENERGY – AND ITS CO2 – BACK TO THE ATOMOSPHERE IN A FEW DECADES.

Bram

Q
What are the average ocean water temperatures that you will be encountering with this project from surface to where you will be working?

Pamela, North Carolina

A
HI PAMELA, THE SEA SURFACE TEMPERATURE HERE IN THE TROPICAL MID-ATLANTIC IS ABOUT 26 DEGREES CELCIUS. HOWEVER, AT THE BOTTOM, 400 METRES BELOW US, IT IS ONLY 2 DEGRESS CELCIUS. THERE ARE A COUPLE OF SITES NEARBY, ON THE SEAFLOR, WHERE THE SEAWATER IS HEATED GEOTHERMALLY BY THE HOT ROCKS NEAR THE SEAFLOOR. THIS WATER REACHES NEARLY 400 DEGRESS CELCIUS – ENOUGH TO MELT LEAD.

Bram

Q
How long has this 'hole' been in the ocean floor? This press talks like it just popped up overnight and took everyone by surprise.

D. Taylor, Virginia

A
GOOD QUESTION D. GEOLOGICALLY THIS HOLE IS VERY YOUNG. A FEW THOUSANDS OF YEARS OLD. AND IT IS GETTING BIGGER EVERY YEAR – THE TEAR IN THE SEAFLOOR GROS BY ABOUT 3 CM. NOT MUCH, BUT OVER THOUSANDS OF YEARS IT ACCUMULATES. THE FACT THAT IT IS THE PRESS IS BECAUSE IT TOOK US ALL BY SURPRISE – WE DIDN’T THINK THIS COULD HAPPEN OUT HERE IN THE ATLANTIC.

Bram

Q
My understanding of the mid-Atlantic ridge is that it is an area where the American and European plates are separating. This being the case I would assume fresh mantle material would constantly be welling up to the ocean floor to fill in the gap between the two plates. Could you please explain the differences between normal oceanic crust, mantle material that is filling in the gap, and the material you are studying? Thank you, and I hope you have good luck and good health on your journey. P.S. Enjoy your warm weather. We did not get above freezing until yesterday.

Patrick Findling, Michigan

A
OKAY PATRICK, THE MANTLE THAT WELS UP TO FILL THE GAP BETWEEN THE PLATES AS THEY DIVERGE DECOMPRESSES AND AS A RESULT IT MELT. THINK OF A BOTTLE OF SODA WATER. WHEN THE LID IS ON, IT IS JUST LIQUID WATER AND CO2 MIXED– ALBEIT UNDER PRESSURE. POP THE LID AND IT BOILS AS THE PRESSURE SUDDENLY DROPS. SAME HAPPENS TO THE SOLID MANTLE. IT GOES FROM SOLID TO PARTIALLY SOLID PLUS MELT. THE MELT FORMS THE VOLCANOES AND THE LAVAS THAT GENERATE THE CRUST. THE DIFFERENCE HERE IS THAT THE MANTLE ISN’T MELTING. WE DON’T KNOW WHY – WHICH IS WHY WE ARE HERE – BUT THINK IT MIGHT BE TO DO WITH WATER IN THE MANTLE…….. WATCH THIS SPACE.

Bram

Q
Hi, basic question here: Are the mantel and crust in the OCEAN very different from the mantel and crust of the (above-water) continents? Have the underwater parts of the world always been underwater? And the Above-water parts always above water (except for the continental shelf border)? I don't understand why, as the new mantel is born (surfaces), why doesn't it send the above-water land underwater? Is sea mantel/crust heavier or denser than continental mantel & crust? Why do these above-water parts (pangea/continents) seem to just keep moving around but staying up? Thanks!

Good luck with your project.

Vicki, Minnesota

A
THANKS VICKI FOR YOUR KIND WISHES, THEY ARE APPPRECIATED OUT HERE IN THE MIDDLE OF THE DEEP, DARK ATLANTIC OCEAN. YES, THE OCEANIC CRUST AND MANTLE ARE VERY DIFFERENT FROM CONTINENTAL CRUST AND MANTLE. THE OCEANIC CRUST IS YOUNG – LESS THAN 100 MILLION YEARS OLD. IT IS MADE OF BASALTIC MATERIAL, LAVAS AND GABBROS. THESE ARE MUCH DENSER THAN THE CONTINENTAL CRUST WHICH IS MADE UP OF LARGELY ALUMINOSILICATES AND QUARTZ. THE CONTINENTAL CRUST IS MUCH OLDER – UP TO 4 BILLION YEARS IN PLACES (4,000,000,000 YEARS). BOTH TYPES OF CRUST FLOAT ON THE MUCH DENSER MANTLE. THE HEAVY OCEANIC CRUST SITS MUCH LOWER THAN THE LIGHTER CONTINTAL CRUST. THE MANTLE BENEATH THE OCEANIC CRUST IS WARMER THAN BENEATH THE CONTINENTAL CRUST, AND PROBABLY SLIGHTLY MORE MAGNESIUM RICH.

Bram

Q
What evidence do you have that the area you intend to study is actually mantle? Is it likely that other such regions exist elsewhere, or is this probably a one-of-a-kind geologic feature? Thanks in advance for your response.

Jeff Wolinski, Grove City, USA

A
Hello Jeff- Yes, there are other regions like this elsewhere on some of the mid-ocean ridges. We use sonar to image the seafloor, and some of the features we see here in our study area look very much like those in other areas that have been sampled and have been found to have exposed mantle rocks on them. As to whether there actually ARE mantle rocks exposed here in the way we suspect, we will have to await the results of our sampling to find out for sure!

SAM

Q
Since I can't conceive of an area this size all-bubbling up with lava, there must be sections that are quiet. What is the difference between crust and mantle? Or in other words, how do you tell that this area is mantle and that is crust?

Glenn Jorgenson, Sacramento

A
Hi Glenn – Yes, you’re right, the exposed mantle that we are investigating is all solid, not molten. In fact, very little of the mantle is molten – it only melts beneath the ridge axis, and even then only a tiny amount of it melts at any one time. It melts because as the ridge plates move apart, it decompresses. The mantle rocks we are looking at are made up of the material that is left over once melt has been extracted, whereas the crust is made of the basalt that cools from the melt. The rocks are related, but due to the fact that the melt comes out of the mantle, taking some elements with it but leaving others behind, they have different chemistry.

SAM

Q
I was wondering if you know or are maybe expecting to find hydrothermal vents in this ridge since no cracks or fissures have not created new crust? Also, compared to other ocean ridges what is the spreading rate of this area (fast or slow)? Thanks and good luck!
Steve Durango, Colorado.

A
Hi Steve,
Great question, and thanks for the good wishes. There are actually two kinds of hydrothermal vents: black smokers and white smokers. Black smokers form at fast-spreading ridges (that is, ridges that separate at a rate of 5 cm/year or faster), and they are powered by the very hot magma that heats the area up to very high temperatures. The water that comes out of black smokers can be as hot as 400oC. Meanwhile, slower-spreading ridges like the Mid-Atlantic Ridge (which spreads at 2.5 cm/year) have white smokers. These hydrothermal vents may be powered by the exothermic reaction of mantle minerals altering upon contact with seawater or by magmatic intrusion, and the typical water temperature from these vents is about 250oC or less. We’ll be keeping our eyes peeled for any hydrothermal vents we might run across (or rather, TOBI will keep its eyes peeled for us!).

KAY

Q
The big chunk of exposed earth's mantle underneath the Atlantic...how old is it? Is it relatively (geologically) newly formed? Are there other locations on the planet where there isn't a crust, just the mantle?
Scott Jay Regner, Baltimore, USA.

A
Hi Scott. The question of the mantle's age is an interesting one! In a sense, much of the mantle is as old as the Earth, and may have been moving around deep in the Earth for hundreds of millions of years. However, the mantle we see has only just appeared at the surface, geologically speaking (perhaps in the last million years or so), so in that sense it's very young. Yes, there are other places where there is no crust, such as parts of the Arctic mid-ocean ridge, which is spreading very slowly and apparently producing little or no lava.


Lots more at the LINK
Back to top
View user's profile Send private message
obeylittle



Joined: 10 Sep 2006
Posts: 442
Location: Middle o' Mitten, Michigan Corp. division of United States of America Corp. division of Global Corp.

PostPosted: Fri Apr 13, 2007 1:16 am    Post subject: Reply with quote

I am interested in the Gakkel Ridge (misspelled above) in the Arctic because the Global Warming scam being run for the G8 governments in the corporate medias have leaned primarily on melting of the polar ice caps as their catastrophic proof for Global Warming. Maybe they feel "safe" lying about the polar regions, because we can't easily visit the areas to find the evidence ourselves.

I know everyone is lying about Global Warming. But have they left enough evidence lying around out on the Internet to prove them criminal scammers? I'm pretty sure of that too, because their skills are narrow and limited to people manipulation via media lies and psyops, rather than data scrubbing and censure. They aren't competent in areas outside their expertise and narrow fringe of direct control.

Anyway, this gives me an opportunity to prove to you guys and gals that I will hijack my own thread as readily as I DO go off topic in yours. Laughing

Lotsa hits on: http://www.google.com/search?hl=en&q=gakkel+ridge&btnG=Google+Search

Quote:
ARK XX-2 Lena Trough and Gakkel Ridge July-August 2004

Scientific Prospectus

Summary
The arctic spreading system is the slowest spreading mid-ocean ridge on Earth. For this reason, its lavas and residual peridotites have unique characteristics as a result of extremely low degrees of partial melting. This is important for a number of reasons. First of all, low degrees of melting are extremely difficult to study via direct experiment. Until now well controlled melting experiments have only been successful at melting degrees of 10% or higher, much higher than the 2-5% expected for Gakkel Ridge.

A second point is the nature of fertile upwelling MORB mantle. Abyssal peridotites are notable for their depletion in basalt-forming elements, This leaves a great deal of room for speculation as to just how these elements (Especially Ca, Al and incompatible trace elements) are distributed in the mantle. Are they in incompatible-enriched garnet pyroxenite veins? Or are they disseminated in a homogeneous fashion? Or are there larger regions of incompatible enrichment (mantle plumes or a marble cake mantle)? Direct study of abyssal peridotites that are relatively undepleted should shed considerable light on this ongoing debate.

For a further discussion of the science, see The Interridge Arctic Working Group (1998) "Mapping and Sampling the Arctic Ridges: A Project Plan" here.

Introduction
The natural history of the ocean basins has been well-understood since at least the early 70's. At that time new results from ocean drilling were put being together with the then-new science of marine geophysics and the geologic study of ophiolites (oceanic fragments superimposed onto the margins of continents), which resulted in a completely new framework for the understanding of how the ocean floor is formed. The concept of sea floor spreading provided a plausible mechanism to explain how continental drift (then regarded as a sort of crackpot fantasy) was possible. This scientific framework, plate tectonics, became and remains today the guiding paradigm for the understanding of most aspects of the evolution of the earth's crust and mantle.

The Arctic Ocean, a basin some thousands of km across, is somewhat of an enigma in that regard, as the history of its opening is not nearly as well understood as that of the other major ocean basins. Partly this is due to the inaccessibility of the arctic ocean floor. But this does not explain everything: If the Arctic ocean were like every other ocean basin, the data available about it now would be sufficient to define the entire history of its formation. Instead it has become clear that quite different processes formed the Arctic Ocean basement than those we can observe today at other ridges.

From the International Bathymetric Chart of the Arctic Ocean (IBCAO) (Great maps here folks!--obeylittle)
C: Chuchki Plateau, A: Alpha Ridge, L: Lomonosov Ridge, G: Gakkel Ridge.



The arctic ocean is made up of a series of elongate basins separated by submarine ridges that stretch approximtely from the North American shore to the Siberian shore. From the Bering straight these are the Chuchki Plateau, Canada Basin, Alpha Ridge, Makarov Basin, Lomonosov Ridge, Amundson Basin, Gakkel Ridge, Nansen Basin, and finally the Siberian continental shelf.

The first three ridges are features that are relatively poorly understood. Some of the main open questions are their age, composition, and how they formed. Gakkel ridge by contrast is a relatively young (perhaps less than 100 million years) and still active mid-ocean ridge, where sea floor spreading is taking place.

Lomonosov ridge appears to be a narrow sliver of continental crust sliced off of the eurasian continental margin by the eastward propagation of Gakkel Ridge. This would suggest that it is significantly older and granitic in composition, in contrast to the young, basaltic Gakkel Ridge. Where Gakkel ridge intersects the Siberian platform, the rifting extends seamlessly into the rift valley of the Lena river.

About Alpha Ridge and the Chuchki Plateau very little is known at all. They are speculated to be possibly oceanic plateaux, that is large flood basalt provinces where thick lithosphere is generated. The origin and age of the intervening basins is even less understood. So far there has been little magnetic data collected from these basins of a quality sufficient to identify seafloor spreading anomalies. If the basement of these basins was generated by sea floor spreading, then they are almost certainly older than the Amundsen and Nansen basins on either side of Gakkel Ridge. This would make them arguably the oldest in-situ ocean crust in the world.

Gakkel Ridge
Gakkel Ridge is the only actively spreading mid-ocean ridge in the Arctic basin, and is the northward continuation of the Mid-Atlantic ridge. After exiting Iceland, the Northern Mid-Atlantic Ridge undergoes several very interesting twists and turns going from nearly orthogonal spreading until after the Jan Mayen Fracture Zone, through a broad curve to the east along Mohn's Ridge to highly oblique spreading along Knipovitch Ridge. The northernmost end of Knipovitch ridge ends at an unusual area composed of an extreme deep (Molloy Deep) and a ridge, which appears to be a small amagmatic spreading segment.

Molloy Deep lies approximately at the margin of the polar ice sheet. It is composed of several deeps and highs within an oblong area approximately XX km across. It has been dredged several times (Devey, et al.; Bonatti, et al.; Schilling et al.; Hellebrand et al., 2000). In 8 total dredge hauls, none has ever returned anything except mantle peridotite. It appears that there is no magmatic crustal construction at Molloy Deep. However, many of the peridotites recovered from Molloy Deep are impregnated with what are obviously basaltic magmas of some type (Hellebrand et al., 1998), suggesting that melting is not entirely absent.

Figure 2. Spreading geometry of the Arctic Ocean.



Lena Trough

Northward from Molloy deep, the Spitzbergen fracture zone continues to the northeast. The northern end of the Spitzbergen fracture zone is not marked by typical ridge-transform topography, but seems to simply turn by about 45 degrees to the north, and as a long linear trough enters the Arctic Ocean through Fram Straight. This feature, known as Lena Trough, is not fully understood, but appears to be an extremely oblique spreading center similar to the one at 11-15 degrees east on the SW Indian Ridge (refs). The chemistry of the lavas in both locations is quite similar, indicating that their tectonic environment and petrogenesis are linked. This is unusual, since the usual linkage of geochemistry and tectonic setting is generally agreed to be via the interaction of hotspots with ridges, and to a lesser extent the influence of fracture zones.

Arctic Ridge Sampling

The first Gakkel Ridge samples were collected by accident during coring operations on cruises ARK IV/3 and ARK VIII/3 of PFS Polarstern. The ARK IV/3 gravity core samples included serpentinites and volcanic rocks from the axial valley of the Gakkel-Ridge [GR] at 86°N (Mühe et al., 1991 and 1993). During ARK VIII/3 in 1991, Polarstern crossed the Gakkel Ridge farther east compared to ARK IV/3 cruise, approximately along 60° E. The rift valley there is about 4500 m deep. A box corer (GKG 2167-2; 86° 56.1´N, 59° 4.5´ E) recovered 42 cm of sediment from the southern foot of the rift valley in 4425 m water depth. The sediments were covered by about 1 to 2 mm of fresh basaltic glass shards, lying on top of the muddy sediment surface (Mühe et al., 1997).

Basement samples from the high arctic ridges were recovered intentionally for the first time from Lena Trough on PFS Polarstern cruise ARK XV/2 in 1999. The first successful hard rock dredging operations ever in pack ice recovered glassy vessicular basalts, peridotites and massive hydrothermal sulfides from three dredge hauls.

In summer 2001, a 2-ship expedition conducted the fist systematic exploration of Gakkel Ridge, conducting dredging, seismic and hydrographic investigations from the juction with Lena Trough to approximately 90°E. This very successful expedition, AMORE 2001, recovered in almost 200 successful dredging, grabbing and rock coring stations all the major rock types found on mid-ocean ridges, including basalts, peridotites, metamorphic and hydrothermal rocks.

Basalts

The many basalt and peridotite samples from the AMORE expedition are still under investigation, and reports of their chemistry and of the evolution of the region are in progress.

Samples from 86°N

The Gakkel Ridge [GR] basalts are fairly primitive, with high MgO and Ni (i.e., mg > 70, MgO > 9 wt%, Ni > 165 ppm). The concentrations of incompatible elements correspond to those of enriched MORB. Dark spherical droplets of basanitic composition within the basalts are believed to be relicts of an incomplete magma-mixing whose basanitic end-member could well account for the enriched character of the GR basalts in terms of rare earth elements, Ti and incompatible trace elements.

Isotopically, the GR samples (KAL 11-370-5-1 and 3) are characterized by Sr-Nd ratios which place them above the MORB array on a Sr-Nd isotope diagram (Mühe et al., 1993). This may indicate assimilation of seawater- contaminated sediment or basalt by the magma chamber. The positive D 8/4 values (a Pb-isotopic measure of ancient sediment assimilationn) of the GR basalts show their source region to possess traces of an enrichment similar to the DUPAL signature. This is remarkable since so far the DUPAL signature is believed to be present only in Indian but not in Atlantic or Pacific MORB. These results also argue against a model of whole mantle convection (Hart, 1988) in which upwelling of enriched material at the equator is balanced by downwelling of depleted material at the Poles.

Samples from 87°N

During the ARCTIC ´91 expedition aboard RV ´Polarstern´ (ARK VIII/3) to the Central Arctic Ocean, a box corer sample on the Gakkel Ridge at 87° N and 60° E yielded a layer of sand-sized dark-brown volcanic glass shards at the surface of the sediment core. These shards have been investigated by petrographical, mineralogical, geochemical and radiogenic isotope methods (Mühe et al., 1997).
The nearly vesicle-free and aphyric glass shards bear only minute microphenocrysts of magnesiochromite and olivine (Fo 88-89). Most glasses are fresh, though some show signs of incipient low-temperature alteration. From their shapes and sizes, the glass shards most likely formed by spalling of glassy rinds of a nearby volcanic outcrop.
Geochemically, the glasses are relatively unfractionated tholeiites with E-MORB trace element compositions. Thus, they are quite similar to the previously investigated ARK IV/3-11-370-5 basalts from 86° N (Mühe et al., 1993).

The Nd- and Sr-isotopic ratios of PS 2167-2 glasses are significantly lower than for ARK IV/3-11-370-5 basalts and suggest an isotopically heterogeneous mantle source of Gakkel Ridge MORB between 86° and 87° N. The positive D-8/4 Pb value (~16) and high 87Sr/86Sr ratio (0.70270), found for PS 2167-2 glasses are similar to that of ARK IV/3-11-370-5 basalts and show the influence of the DUPAL isotopic anomaly in the high arctic mantle. These results argue against the presence of an `anti-DUPAL anomaly´ in the mantle below the North Pole region and simple models of whole-mantle convection.

Serpentinites

Samples from 86°N
Several kg of serpentinite were also present in the ARK IV/3 box core. These consist of highly altered serpentinites that show typical pseudomorphous replacements of mantle minerals (olivine, orthopyroxene, clinopyroxene and spinel). They are texturally and compositionally similar to abyssal peridotites dredged the world over (Mühe et al., 1989). They are thus very likely to be the residues of melting beneath Gakkel Ridge.

In some places spinel relicts are fresh enough that their primary major element compositions can be determined (Hellebrand et al in press). These measurements indicate a low degree of partial melting in the peridotites, about 10 percent. This is not as low as had been expected for Gakkel Ridge, and implies a crustal thickness of about 4 km, as opposed to a "normal" oceanic mean crustal thickness of 6 km.

References

Hart, S.R., 1988. Heterogeneous mantle domains: signatures, genesis and mixing chronologies, Earth Planet. Sci. Lett., 90, 273-296.

Hellebrand, E., R. Mühe, J. E. Snow (2001) Mantle melting beneath the Gakkel Ridge (Arctic Ocean): Abyssal peridotite spinel compositions. Accepted to Chemical Geology.

Hellebrand, E. and J. Snow (2003) Deep melting underneath the highly oblique-spreading Lena Trough (Arctic Ocean) Earth and Planetary Science Letters 216:283-299.

Mühe, R., Bohrmann, H., Stoffers, P., Hörmann, P.K. and Thiede, J. 1989. Petrology of komatiitic basalts and serpentinites from Nansen-Gakkel-Ridge at 86° N and 23° E (Arctic Ocean). Terra Abstracts, 1, 204.

Mühe, R., Bohrmann, H., Hörmann, P.K., Thiede, J. and Stoffers, P. 1991. Spinifex basalts with komatiite-tholeiite trend from the Nansen-Gakkel-Ridge (Arctic Ocean). Tectonophysics, 190, 95-108.

Mühe, R., Devey, C.W. and Bohrmann, H. 1993. Isotope and trace element geochemistry of MORB from the Nansen-Gakkel Ridge at 86° North. Earth Planet. Sci. Lett., 120, 103-109.

Mühe, R., Bohrmann, H., Garbe-Schönberg, D., Kassens, H., 1997. E-MORB glasses from the Gakkel Ridge (Arctic Ocean) at 87deg. N: evidence for the Earth´s most northerly volcanic activity, Earth Planet. Sci. Lett., 152, NO 1-4), 1-10

Snow, J., W. Jokat, E. Hellebrand, R. Mühe and Shipboard Scientific Party ARK XV/2 (2001)Magmatic and Hydrothermal activity in Lena Trough, Arctic Ocean. EOS, Trans. AGU. (article) V. 82:193-198.


Some good references to snoop into there to go along with the many Google hits on Gakkel Ridge. That'll chew up some time... heres something interesting too:


Last edited by obeylittle on Fri Apr 13, 2007 2:07 am; edited 2 times in total
Back to top
View user's profile Send private message
obeylittle



Joined: 10 Sep 2006
Posts: 442
Location: Middle o' Mitten, Michigan Corp. division of United States of America Corp. division of Global Corp.

PostPosted: Fri Apr 13, 2007 1:31 am    Post subject: Reply with quote

Quote:
No hole at the Pole October 17, 2001

A major collaborative expedition to the waters of the North Pole has brought new insights into the structure of the Gakkel Ridge, and shown that rumours of the North Polar Ice Cap's death have been grossly exaggerated.


The polar research vessels RV Polarstern and USCGC Healy returned after a ten week successful expedition to the high arctic regions.

Together with the new US Coast Guard icebreaker, the USCGC Healy, the Polarstern, run by the Alfred Wegener Institute for Polar and Sea Research (AWI) explored the Gakkel Ridge, the most northerly extension of the Mid-Atlantic submarine mountain chain during a combined AMORE-expedition (Arctic Mid-Ocean Ridge Expedition). Both ships managed to reach the North Pole - exactly 10 years after RV Polarstern and the Swedish icebreaker Oden had steamed to this magic location.

For the first time an important part of the geologically active Gakkel Ridge has been mapped and sampled – and with the highest precision, according to Jörn Thiede, director of AWI, and chief-scientist on the expedition.

The 1800km long Gakkel Ridge represents the most northerly extension of a 60,000 km long globe-encircling submarine volcanic mountain chain named the Mid Ocean Ridge System. Through the central fissures of the Mid Ocean Ridges magma forms in the earth's mantle and extrudes on to the sea floor, thus forming new oceanic crust.

The Ridge systems represent the borders of about a dozen of plates, making up the entire Earth's crust, which resembles the seamed surface of a soccer ball. Spreading rates of the diverging plate boundaries can be as much as 10 to 20cm per year, (East Pacific Ridge), though much lower rates are known.

The Gakkel Ridge, situated in the central part of the eastern north Polar Sea forms the most northerly boundary between Eurasia and North America. At the same time it represents the ridge segment with the lowest known spreading rates – less than 1cm per year on the average. The northern Atlantic ocean and the eastern Arctic ocean formed in early Tertiary period, i.e., during the last 55 Ma or so. These two oceans and the Northern boundaries of Europe are therefore geologically young, explains Jörn Thiede, a specialist in palaeoceanography.

For the first time, as a result of this expedition, ocean geologists now have precise maps of the Gakkel Ridge. “During the AMORE cruise the western part of the Gakkel Ridge has been mapped, measured and sampled precisely by both the Healy and the Polarstern in a combined effort. We now have a clear picture of this submarine mountain chain, which has for a long time been nameless and mysterious: below a deceptive, drifting Arctic sea-ice cover, a mountain chain is hidden which in places rises thousands of meters over the neighbouring deep sea basins. The crest is divided by an elongated, narrow and not continuous rift valley, where dramatic volcanic processes recently occurred.” says Thiede.

The region has not wanted for attention. In 1999, during the SCICEX-program (Scientific Ice Experiment), US nuclear submarines were used to do research under the Arctic sea-ice and studied the Gakkel Ridge using Side-Scan Sonar, discovering - in the centre of the Gakkel Ridge, at 85° East - evidence of submarine volcanic eruptions.

The Gakkel Ridge is the ideal place to test present models of global sea floor spreading on ultra slow ridges, says Dr. Wilfried Jokat (AWI). “A preliminary evaluation of seismic data shows pronounced variations in crustal thickness along the Gakkel Ridge. The crustal thickness values do not reflect any model predictions, varying between two and six kilometres. Apparently in a few places mantle rocks are displayed within the rift valley and are altered exclusively by penetrating seawater and resulting hydrothermal convection cells.”

Also spectacular are the seismic profiles through the bordering deep-sea basins. They allow, for the first time, a clear estimation of the variations in thickness of the oceanic basement, which is covered by kilometre-thick sediments. Following precise bathymetric measurements the Polarstern and the Healy have revealed the existence of complex volcanic cones in many areas of the Gakkel Ridge.

These measurements also clearly demonstrate, says Jokat, that the central Gakkel Ridge rift valley is deeper than any other mid-ocean ridge valley known on Earth. “This is clearly controlled by its slow spreading rate. Furthermore, it appears that an unexpectedly high number of volcanoes can be seen in the rift valley. These phenomena are revealed by the high quality of our bathymetric maps, which allow a surprising view of the structure of this ridge and thus clearly constitute one of the most spectacular results of our journey.”

The work of rock sampling and sediment coring in the vicinity of the Gakkel Ridge was truly "done by hand". Sampling rocks was done by dredging or with the help of a giant TV-controlled grab. Sediments were recovered using a gravity and kasten corer. The results of the sampling campaign were excellent, and helped to throw considerable light upon the origin and nature of the Gakkel Ridge. Some scientists had predicted that the Ridge had expected to sample mainly peridotites - rocks from the Earth’s mantle – emplaced on the sea floor by tectonic processes. “However, instead of peridotites the samples brought up mainly basalts, which struck me absolutely by surprise” says Dr. Jonathan Snow of MPI Mainz.

Sediment cores recovered from close to the Siberian shelf also give new insights into glacial history. It now appears that the glacial maximum in Northern Siberia happened some ten thousand years before the maximum observed in Scandinavia and the Alps, (which took place before 20,000 years) explains Dr. Robert Spielhagen from GEOMAR Research Centre in Kiel, Germany. “We intend, with our investigations on the sediment cores, to date the arrival of the glacial maximum on the Arctic Ocean and show that the resulting melting waters influenced oceanic circulation and the world's climate.”

Another discovery of the expedition was that the Central North Polar Sea is indeed permanently covered by sea ice. Last year, however, news focused public attention on a giant open water pit that opened at the North Pole – trumpeted (wrongly) as an impressive proof of the effects of global warming. AWI specialists believe that such open water pits, called polynia, exist every summer in great numbers within the sea ice cover, and are nothing unusual.

Therefore one of the goals of this expedition was the observation of variations in sea ice thickness and distribution in the Arctic Ocean, and to compare this to data from 1991 and 1998. “The ice is back. We saw normal conditions this summer on the North Pole, kilometre-wide large ice flows with numerous small and larger polynias in between. The ice was already covered by fresh snow and on the water new ice was forming relatively early compared to previous seasons. The sea ice thickness however, was less than our previous measurements, 2m compared to 2.5m in 1991” according to Dr. Christian Haas from the AWI, head of the ice researcher group.


Oceanic Geothermal/Goechemical/Geophysical Mantle Exposure GW scam snooping I shall go... now returning temporarily to the original post subject. Feel free to hijack at any time. Very Happy
Back to top
View user's profile Send private message
Hocus Locus



Joined: 22 Sep 2006
Posts: 850
Location: Lost in anamnesis, cannot forget my way out

PostPosted: Fri Apr 13, 2007 5:06 am    Post subject: Reply with quote

Diamonds! I think DeBeers might be in big trouble. What are the odds? If a simple dredge operation yields a haul like this... what is the extent of the lode...? No big math necessary I should think.

This discovery hasn't hit mainstream news yet. Another Breakfornews 'exclusive'. ;-)

The human race should get ready for quite a ride. If we could just get this fucking neocon war machine re-tasked for -- oh, for God's sake give us fifty whole years! -- we could be in space. For keeps.

I find it pretty interesting to think -- with no small amount of pride -- that even if we may have just found the most lucrative source of natural crystalline perfect diamonds, with carbon nanotubes we have already exceeded nature's spec.

obeylittle wrote:
Anyway, this gives me an opportunity to prove to you guys and gals that I will hijack my own thread as readily as I DO go off topic in yours. :lol:

We're the greatest hijacked thread nature has yet devised. So hijack away!

It's time to dust off old dreams and polish them again.

Quote:
Diamonds!!

From the Cruise Diary
Day 28: Monday 2 April 2007
Sampling area: Dredging
Ship's position at midnight: 12º57N, 44º56W

The Start of a New Month Brings a Gem of a Find

Diamonds may be a ‘girls best friend’ but they are also the shape of pure carbon while under the enormous pressures encountered deep within the Earth’s mantle. Most diamonds are found in volcanic ‘kimberlite’ pipes that cut through ancient continental crust. But we weren’t expecting to find any diamonds in the mantle that is exposed on the seafloor out here, at 13°N on the Mid-Atlantic Ridge.

This is because the mantle pressures are too low and the carbon concentrations too scarce to make diamond. However, as dawn broke at the start of our second month at sea, we were amazed to find small, clear crystalline shapes in the gravel from the latest dredge. In amongst fragments of fresh mantle peridotite, sparkles and glints of blue-white light caught the eye of Bob Spencer, the Deck PO on the 4-8 watch.

Photographed below are the small, clear crystal sifted from the gravel. Without access to geochemical analyses, we cannot be sure of the nature of these crystals. However, a carefully controlled scratch test by Glyn Collard, the 2nd Engineer, proved them considerably harder than a pint beer-glass. Their refractive index is much higher than either water or gin, and their shape is also reminiscent of the cubic crystal structure of diamond. In a subsequent dredge we found more of the same, and even some quite large ones (although these are a bit worn and dirty on the outside). All of the crystals are clear, inclusion free, and white in colour; so only of the best quality.
While we await the outcome of chemical analyses, the ‘samples’ are being kept locked up in the ship’s safe - just in case the gleam of ‘promised riches’ causes the ship’s company to mutiny.....

Quote:
Space Elevators

Inspired partly by science fiction, NASA scientists are seriously considering space elevators as a mass-transit system for the next century.

[...] In a 1998 report, NASA applications of molecular nanotechnology, researchers noted that "maximum stress [on a space elevator cable] is at geosynchronous altitude so the cable must be thickest there and taper exponentially as it approaches Earth. Any potential material may be characterized by the taper factor -- the ratio between the cable's radius at geosynchronous altitude and at the Earth's surface.

For steel the taper factor is tens of thousands -- clearly impossible. For diamond, the taper factor is 21.9 including a safety factor. Diamond is, however, brittle. Carbon nanotubes have a strength in tension similar to diamond, but bundles of these nanometer-scale radius tubes shouldn't propagate cracks nearly as well as the diamond tetrahedral lattice."

___
Michel found himself in the Alchemist's Quarter. He exerted himself to pay attention to it. Here men used arcane knowledge to make diamonds out of carbon, and they made it so easily and precisely that all their window glass was coated in a molecular layer of diamond to protect it from the corrosive dust; and their great white salt pyramids (one of the great shapes of ancient knowledge, the pyramid) were coated in layers of pure diamond. And the one-molecule diamond-coating process was just one of thousands of alchemical operations performed in these squat buildings.

In recent years the buildings had taken on a faintly Moslem look, their white brick walls displaying equation after equation, all rendered in black flowing mosaic calligraphy. Michel ran into Sax, who was standing next to the terminal velocity equation displayed on the wall of the brick factory, and he switched to the common band:

"Can you turn lead into gold?"

Sax's helmet tilted quizzically. "Maybe," he said. "A little of it, anyway. But it would be hard. Let me think about it some."


~Kim Stanley Robinson, "Red Mars"
Back to top
View user's profile Send private message
Hocus Locus



Joined: 22 Sep 2006
Posts: 850
Location: Lost in anamnesis, cannot forget my way out

PostPosted: Tue Apr 24, 2007 9:25 pm    Post subject: Reply with quote

Hocus wrote:
It's time to dust off old dreams and polish them again.

That's done. Time to be wearily confused again.

The slightly odd end of RRS James Cook cruise JC007
05-Mar-2007 > 17-Apr-2007: Drilling the Mid-Atlantic Ridge

Quote:
Day 28: Monday 2 April 2007
Sampling area: Dredging
Ship's position at midnight: 12º57N, 44º56W

Bramley writes:

The Start of a New Month Brings a Gem of a Find [...'diamonds'! above...]

Day 29: Tuesday 3 April 2007
Sampling area: Dredging

Sorry - the team are flat out with their sampling programme nad haven't had time to report on their activities today. However, check out the profiles of Greg Lewis, the ship's Chief Petty Officer, and Deck Engineer Pete Allery below... [...]

Day 30: Wednesday 4 April 2007
Sampling area: Dredging

Sorry - the team are flat out with their sampling programme and haven't had time to report on their activities today. Meet ETO Phil Parker and Deck Hand Charles Cooney below....[...]

Day 31: Thursday 5 April 2007
Sampling area: Dredging

Sorry - the team are flat out with their sampling programme and haven't had time to report on their activities today. Instead, meet Pete Robinson, the ship's Steward, and X [Philip Andrews] below... [...]

Day 32: Friday 6 April 2007
Sampling area: Dredging

Sorry - the team are flat out with their sampling programme and haven't had time to report on their activities today. Instead, let us introduce you to Second Engineer Glynn Collard and Seaman Ian Cantlie... [...]

Day 33: Saturday 7 April 2007
Sampling area: Dredging

Sorry - the team are flat out with their sampling programme nad haven'tr had time to report on their activities today - please check back again soon.

Day 34: Sunday 8 April 2007
Sampling area: Dredging

Sorry - the team are flat out with their sampling programme nad haven'tr had time to report on their activities today - please check back again soon.

Day 35: Monday 9 April 2007
Sampling area: Dredging

Sorry - the team are flat out with their sampling programme nad haven'tr had time to report on their activities today - please check back again soon.

Day 36: Tuesday 10 April 2007
Sampling area: Dredging

Sorry - the team are flat out with their sampling programme nad haven'tr had time to report on their activities today - please check back again soon.

Day 37: Wednesday 11 April 2007
Sampling area: Dredging

Sorry - the team are flat out with their sampling programme nad haven'tr had time to report on their activities today - please check back again soon.

Day 38: Friday 12 April 2007
Sampling area: Dredging
Ship's position at midnight: 12º57N, 44º56W ((( same pos as 02-Apr entry )))

Bramley writes:

Gems, Lies and Video-diaries.

While some people seek solace at the bottom of a glass, we found ‘Truth’. Or rather, the absence of the bottom of a beer-glass led to the discovery of the truth about the source of our ‘diamonds’. But before that, as the First of April passed into the Second, and then to the Third, our delight turned from scientific wonder, to greed, and finally to suspicion concerning the amazingly prolific haul of gems from the abyss. Questions were raised and answers sought, but not before ‘diamond fever’ had spread through the ship’s company like an over-ripe banana through a chimpanzee. Whereas the rock-sample laboratory had once been the exclusive haunt of gaunt, exhausted and goggle-eyed petrologists, it had suddenly become ‘The Place’ for deck-crew, engineers and officers alike to hang-out. Such was their new-found fascination for all things Geological that we began drawing up a lecture series, starting with ‘Hutton’s Unconformity’ and the “Abyss of Time”, progressing through ‘Plate Tectonic Theory’ and concluding with ‘What Isotope Geochemistry Can Do For You’. Yet despite their obvious delight in our science, the plan of a lecture series met with little enthusiasm.

No, the interest of the ship’s company strictly lay in a ‘hands-on’ approach. So much so, that a photograph taken discreetly by a hidden camera caught them rummaging through the dredged gravel with eyes sparkling like magpies, picking at glittering gems dotted here and there. At least this explained the sudden and apparent decrease in the numbers of ‘diamonds’ we were recovering. Or so we thought.

In an attempt to recover our scientific samples, a polite notice was put-up around the ship. The emphasis was not to seek blame (we already had our suspicions), but rather to encourage the return of the material for the benefit of the scientific community. And so we went on, each eyeing the other, no-one mentioning what was on everyone’s mind. “Was that a change in ship’s course towards the Caymen islands?”. “Did you hear footsteps in the sample-store last night?”. “Who’s got the key to the safe?”. That was, until this morning. As dawn broke over a tranquil sea, the sun rising into a crystal-clear blue sky, a cry echoed out from the rock-saw lab. Tucked away at the back of a cupboard was a heavy, clear-glass beer-mug: a typically British, clear-glass beer-mug. A facetted, barrel-shaped glass, with a looped handle at its side, and a thick glass base. Or rather more idiosyncratically, this beer mug was without its thick glass base. A fact that rendered it inadequate for its originally intended purpose. Suspiciously, the base had been sawn off. On close inspection, fragments of the sawn glass base were found lying in the dirt beside the saw. Some if these had been crudely fashioned into diamond-shaped crystals, but discarded because of some flaw or other in their manufacture. A quick comparison with our ‘gems’ revealed the ghastly truth. On reflection, it was obvious really. The fact that it deceived such an experienced and sceptical geological team like ours was embarrassing. Obviously, someone had swapped our real gems for these fakes!

So, as we approach Tenerife, on behalf of us all on the maiden science voyage of the RRS James Cook, its been great having you along with us to share in our adventure. Take care.


The infamous beer mug



JC007 bids you farewell!

A naughty and clever April Fool's ruse? ... and after a few terse days where the one posting the diary has naught to say, pasting the same "we're busy" entry time and again with no ship's position (maybe Michelle is kind of pissed about it because she was not in on it and the story made its way to classrooms all over?) finally, it's all explained and that early scratch test

Quote:
... a carefully controlled scratch test by Glyn Collard, the 2nd Engineer, proved them considerably harder than a pint beer-glass. Their refractive index is much higher than either water or gin, and their shape is also reminiscent of the cubic crystal structure of diamond.

not so careful after all, or too hasty and not mutual (same-material same-hardness will scratch: the crystals scratched glass, but a shard of glass was not procured in an attempt to scratch the crystal?)... or it was hearsay in the first place... or simply forgotten.

As it happened April 1st did occur on the second day of actual dredging. Fair enough for happenstance.

Perhaps chums more schooled in British humor could have a go at getting a read on this, especially the cheekily-written capper. It really does look like a classroom science diary gone awry -- noted in classrooms and by at least one other on the web. No diamonds here! But then again,

___
It is sometimes necessary to play the fool to avoid being deceived by cunning men.
~François de la Rochefoucauld
Back to top
View user's profile Send private message
mark1360



Joined: 05 May 2007
Posts: 16

PostPosted: Thu May 24, 2007 9:41 pm    Post subject: Reply with quote

hole in the ozone layer now...a hole in the oceon...what will we do we are all doomed...will we get flooded...or have no water though???
_________________
hgfdhgs
Back to top
View user's profile Send private message
paradox



Joined: 11 Feb 2007
Posts: 212

PostPosted: Sat Jun 16, 2007 3:22 pm    Post subject: Reply with quote

Hocus, I love you. In the kindest, gentlest agape sense of the word.
________
Roll a joint
Back to top
View user's profile Send private message Visit poster's website
Display posts from previous:   
Post new topic   Reply to topic    The Next Level Forum Index -> Tomorrow's World All times are GMT - 5 Hours
Page 1 of 1

 
Jump to:  
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum


Powered by phpBB © 2001, 2005 phpBB Group

Theme xand created by spleen.