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7. We Cross the Deep

Tuesday, December 30

The talk in the ward room now always turns to the subject of the Trench, for we are exploring one of the most dramatic parts of the Pacific Ocean, the Tongan area, with its long row of volcanic islands paralleling a row of coral islands, the Tofua Trough between them, and a great, deep trench to the eastward. Yesterday, at lunch, we were trying to devise ways of describing this deep gash in the earth's surface. Over 30,000 feet straight down … it is hard to conceive of its dimensions.

Brownie, the cowboy bos'n, suggested, “How about sayin' it's as deep as a lot of Grand Canyons?”

“If we could pile seven Grand Canyons one above the other in the Trench, the uppermost rim would still be beneath the sea,” said Roger. “If we could pile thirty Empire State buildings on each other, the TV mast wouldn't break the surface. That's the Trench!”

If I imagine I am on the moon, and the water on the earth is rolled away, one of the most striking features on the earth's surface and definitely the deepest in the southern hemisphere would be this Tonga deep.

It is 1,500 miles long and 15 to 30 miles wide, extending


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in a nearly straight line across the sea floor between New Zealand and Samoa. The bottom of its narrow central gorge is in places over 35,000 feet beneath the ocean's surface. The only other spots where nearly equal or greater depths are to be found are the similar long narrow trenches off the Philippines, off Japan, and east of Guam and Saipan in the Marianas Islands.

figure

The Tonga Trench is deeper than Mt. Everest is high.


[Full Size]

This Trench, like the other great trenches of the ocean, is rimmed on one side by a series of volcanic islands. It is these volcanoes, Falcon, Tofua, Kao, and our new seamount we crossed on the 27th, that we have been studying these past few days, while our sister ship Horizon has been studying the Trench proper.

In some way the line of volcanoes running along the west side of the Trench is related to the Trench itself. Scientists believe (but are far from understanding how) these volcanoes are the result of the forces that caused the crust of the earth to fold downward to form the Trench. In my own simple fashion I can see how if you suddenly bend the crust of the earth downward to form a narrow, seven-mile-deep Trench, something would have to give somewhere, and perhaps it would be the pushing up of hot lava to form a series of volcanoes.


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figure

Map showing the Tonga Trench region and a perspective cutaway drawing of the Trench.


[Full Size]

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I can also see why this combination of trench and volcanoes should be unstable, or geologically active. This is one of the earthquake centers of the world; I've been told that many of the earthquakes in the region have their origins far beneath the earth's surface. I'm sure they must be bigger than the ones back home in my own state of California.

Five volcanic eruptions have also occurred in this area in the past fifty years. But I am anxious to see the Trench, or see it as best we can, which means watching the record of the bottom as it is slowly traced on the echo sounder in the laboratory.

Now tonight we are to make our first crossing of the Trench since I have come aboard. We shall be crossing approximately at the middle of the 1,500-mile-long chasm. On the route we've selected we shall pass south of the limestone island of Lifuka to reach a point beyond the eastern side, which we have designated as Point How, about 100 miles east of Lifuka. Russell wanted a seismic station here. He had to know more about the earth under the ocean on the east side of the Trench as well as on the west side of the Trench, where we've been. Someday, I knew, we'd be running up and down the axis of the Trench itself, but not tonight.

There is always the slim chance that on some crossing of the Trench we, or the Horizon, might find the deepest place yet to be discovered on the earth.

For a long time the Emden deep, located in the Philippine


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Trench, was believed to be the deepest. And then just last year H.M.S. Challenger from England had found the greatest depth yet to be recorded—35,640 feet—in the Marianas Trench. Our ship, the Horizon, came very close to this, perhaps within 200 feet, when they crossed the Tonga Trench before Christmas, recording a depth of 35,400 feet.

Maybe tonight will be our lucky night. Who knows? One night when the Horizon was crossing the Trench I had heard Bob Fisher say excitedly to us over the radio, “Call us back later. Can't talk now. We're still going down—we're taking soundings on the audible on both fathometers.”

Fisher's main interest is trenches. He studies them whenever he can find them—anywhere in the Pacific Ocean. They are as exciting to him as bull-fighting, his other great passion. It is his responsibility to make the topographic chart of this great trench. It isn't just a hole, as our American oceanographer Alexander Agassiz had described it at the beginning of this century. Men have known about its existence for sixty-five years, but there has been very little exploration of the area with modern techniques. A remarkable and tedious job was done in 1888–1890 by H.M.S. Egeria, when three hundred wire soundings were made.

The most recent exploration was made by the Danish ship Galathea, which left us a picture of soundings going more or less straight along the Trench axis. Now we are to join the Horizon in her systematic survey that will make nearly twenty-five crossings of the Trench and amass records covering over 4,000 miles.

The Horizon's job is to zigzag across the Trench diagonally and to dredge up samples when she can. Our ship is to do most of the coring and to take temperature and water samples. This combined information, when pooled together with the seismic records, may yield important facts.


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We were all standing in front of our echo sounder when the bottom slowly began to recede.

“We're starting down,” I said, thinking how much more simple this was than going down the Grand Canyon on mule-back. The men smiled at my excitement, but I know they, too, were keenly interested. Walter Munk and Bob Livingston had this watch and were in charge of the measurements.

“We'll be going down gradually for quite a ways,” said Roger, “before we really take a dip.”

“If it's 1,500 miles long it must be shallower in some places?” I asked, hoping secretly that we were crossing at a very deep spot.

“Yes. In the south, below 25° latitude, where we were before Christmas, the Trench is shallower and wider in cross section,” said Roger. “Now, farther north, the Trench has become deeper, and so far it has stayed deeper. In a little while you'll see.”

Roger spoke truly. Suddenly our echo sounder began to take a downward path with a vengeance. The slope became progressively steeper and more irregular as the depth increased.

“Bob Fisher and the others have discovered a fact not previously known, that in the center of the Trench there is a deep, steep-walled inner gorge only two to four miles wide,” said Roger. “The deeper we go, the steeper it gets.”

At the rate our little black wavy line was going down, I guessed the Trench must be steep. The 3,000-fathom contour was passed, and then soon the trace showed 4,000 fathoms—24,000 feet, nearly five land miles.

We were coming closer to the center. Many echoes were being received simultaneously because the bottom was so rough. These echoes grew progressively weaker and harder to identify as we still went steadily downwards.


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“This trench is so steep and narrow that it is difficult with the echo sounder to sort out a true picture of it. Sometimes the echoes from the sides show up before the bottom echo and we are not able to tell which is which without a lot of work,” said Roger.

“Is this what Bob Fisher will be spending months doing when he gets home, trying to find the real profile?” I asked.

“Yes,” answered Roger.

“Then it isn't just Russ who doesn't like to commit himself on shipboard about his findings!”

Roger laughed. “We're all alike about that, Helen. Look now, we've reached the 5,000 fathom mark,” he said.

That's 30,000 feet straight down. How much further could it go? I looked at the clock. It was 3:45 in the morning. Suddenly the little black line was staying constant, not going down any more. We were at the bottom of the Trench.

“How deep, how deep?” I asked.

“Approximately 5,160 fathoms—30,960 feet,” said Walter, writing busily on a scratch pad. “We'll have to do some computing and correction.”

Now, in a few minutes, we had started up, and it began to shoal just as rapidly as it had dropped before.

I hurried out to the fantail. Dawn had come. Our little white ship plowing her way through the water looked as she always does—as did the ocean beneath. It was difficult to believe that we were over an area of water nearly six miles deep and that below us were shattering pressure, glacial cold, and unending night.

I thought of this least-known region of the sea, the icy desert where life barely survives, and I wondered at its great age. Why should this deep water be so close to freezing here in the tropics? Most of the water in the oceans flows down from the Arctic and Antarctic. How old is this water?


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And what kinds of marine life are found in this world of unrelieved darkness, pressure, and cold? The pressure increases nearly 15 pounds per square inch for every 33 feet of depth. That means there's about 15,000 pounds per square inch in a place like the bottom of the Tongan Trench.

What strange creatures can withstand such pressure? There is evidence that marine life exists at all depths and everywhere in the ocean. The bottom muds of this deep Trench teem with bacteria. The Galathea brought up sedimentary bottom animals such as sea anemones, sea cucumbers, worms, mollusks, and such in its trawls. The Danish scientists aboard who had explored several trenches just two years earlier, had reported that trench fishing was best in this Tonga deep and that they caught fish in their trawls at a depth of 3,660 fathoms. And yet just a hundred years ago scientists believed that no life existed in the deep ocean water where no sunlight penetrates. The Danish ship had a big winch and long cable, as did ours, which enabled their men to bring up living bacteria and sea slugs from the very bottom. In one of their trawls at a depth of 4,500 fathoms they found a thousand specimens of one kind of sea slug and two hundred of another.

They had fished in these same waters for the eerie creatures they thought might inhabit deep water, just as we are fishing for rocks, sediments, and sand. They hoped to find a relic of prehistoric life, an ancient monster. This Trench yielded no fifty-million-year-old creature, but many strange fish were caught in their huge nets—fish with large protruding eyes that do not perceive color but only dim light. Many fish are blind and have large antennae or feelers with which they grope their way about in the unending night. Except for prawns, which are brilliant red, most of the fish are


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brown, black, or deep purple. Many species are luminescent.

In this deepest world the fight for existence is keenest. Consequently, the fish below are armed with saber-toothed jaws, immense mouths, and distensible bodies. They can even swallow a creature larger than themselves.

I went back to the echo-sounder. I saw that we were now climbing somewhat less steeply.

“The west flank or shoreward flank is steeper than the slope we are climbing,” said Roger. Then as the fathometer went down again to 4,700 fathoms at six o'clock, I realized that we had crossed a little ridge.

“The Horizon found this 600-foot ridge at the eastern edge of the Trench too,” Roger explained.

Now we were climbing the eastern slope again and had crossed into the area of the great deep Pacific basin. It was nine o'clock in the morning. We had traveled 45 miles in crossing the Trench. Some trench crossings had only been 15 miles wide, Roger explained. And we have not found the deepest spot. The Horizon is still ahead of us with her depth of over 35,000 feet.

The seismic crew is busy on the fantail paying out the hydrophones for another loud day of receiving explosions from the Horizon. Weather is rough, there is no sun, and “the noise level caused by the storm resulted in instrumental difficulties,” says my log. By 10 o'clock Bob Dill and his coring crew of Phil Jackson, Dick Blumberg, and Art Maxwell were back on the job, putting down a large corer. Will they be successful this time in bringing up a long tube of mud?

So it has gone all day—combination of the storm, the lurching boat, the terrific clatter of gears as the winch rolled out its 6,158 meters of wire, and the loud announcements over the radio from the Horizon. It is nerve-racking. It makes


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me realize again that bad weather or need for sleep—nothing stops these men. They are pounding at the ocean all around the clock. Even after this long, hard day they had a conference in the ward room—subject, the Tonga Trench.


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