“In the midst of this ridge, the source of almost all the quakes in the Atlantic,” Tadokoro continued, “there runs a deep crevice containing an extraordinary amount of heat. This heat is being conveyed upward from deep within the mantle by means of convection, and this Mid-Atlantic Ridge itself is nothing else but the upward thrust of this mantle convection. Here we have the motive force that long ago, in accordance with Wegener’s theory, opened up a great chasm in the continental mass and set what is now the American continents moving in a westward direction. Furthermore, this same kind of protuberance, resulting from the upward thrust of the mantle convection and constituting the same kind of break in the crust, runs along the sea floor of all the oceans of the world.” Professor Tadokoro stopped for a moment. He looked around at everyone before going on, his voice somewhat lower. “Now with regard to these mantle convections, using a method that I’ve developed myself, I have not only been able to make a detailed diagram of them and formulate a comprehensive explanation, but I am certain that I can predict the emergence of phenomena that will be completely new.”
Yukinaga felt his pulse quicken. What a sensation Tadokoro’s theory would provoke if he could make it known! But that, of course, was out of the question. And then, too, even granting that the history of man’s scientific scrutiny of the earth was a short one, the thrust of Tadokoro’s argument seemed fantastic. . . .
“All right,” said Tadokoro as he turned a dial and brought a relief map of the Pacific into focus, “now let’s take a look at the Pacific.” He picked up a pointer and indicated the undersea ridge off the coast of Chile. “You see how the ridge line of the Atlantic continues into the Southeast Pacific. Now look here.” He now pointed to an undersea mountain range that extended up through the Indian Ocean. “If one credits Wilson’s theory, it was the upward thrust of the mantle, represented by this range, that pushed the Indian subcontinent, formerly separate from Asia, to the north, thrusting it finally against the continent. And in the process the coastal impact area was pushed upward to form the great Himalayan fold. And even now this seems to be the explanation for the continual increase in the height of the Himalayas.” The pointer moved back to the Southeast Pacific. “It seems evident that the general flow of the Eastern Pacific mantle is from southeast to northwest, something corroborated by the fact that the Christmas, Hawaii, and Tuamotu groups run in that direction. Furthermore, this flow collides eventually, we believe, with the mantle flow coming from the Asian continent, as a result of which a part of it takes a down ward turn, something that would account for the long trenches that characterize the eastern side of the island arcs of the Western Pacific. But now let’s consider how all this pertains to our immediate concern.”
There was dead silence in the room as Tadokoro flipped a switch to change the picture. The area now spread across the screen was the Northwest Pacific, taking in Japan and a portion of the mainland. “The Japan Archipelago was once joined to the continent, and some time in the distant past the continental mantle current I referred to thrust it out into the Pacific in a southeast direction. According to my theory, it is still doing so to this day at a speed of from one to three inches a year. In the first stages of this process, say twenty-five million years ago, the Archipelago lay much farther to the north and it lay straight rather than curving away from the continent. The constant pressure, however, bent it into its present arc shape and opened the fossa magna that divides Central Honshu. Furthermore, at this break line we have the Fuji volcanic zone. But now let’s consider the mantle current coming from the opposite direction, from the Southeast Pacific. What happens when these come together?” Tadokoro paused for a moment and then suddenly looked at Yukinaga, a gleam in his eye. “Yukinaga, what discipline concerns itself with the behavior of masses of fluids of varying temperatures on the earth’s surface?” he asked.
“Meteorology, Professor,” answered Yukinaga, his voice hoarse.
“Good. But you want perhaps to protest that vapors, liquids, and solids are quite different things, isn’t that right? But would it be too absurd to think that, given a sufficiently long period to overreach the difference in nature, meteorological analogies might be used to explain the behavior of the mantle? For it not only forms convections, but in the upper mantle there is a distribution of masses of varying temperatures. Would it be out of the question to think of these as behaving like vapor masses, given enough time?”
They stared at Tadokoro’s unshaven face in amazement. Could there really be any similarity between atmospheric cur rents, ever moving and never knowing rest, and those heavy, solid masses of rock moving deep with the earth at high temperatures?
“To put it in simple terms,” said Tadokoro, “let’s take a look at the kind of pattern that occurs when a cold front meets a mass of warm air.”
Tadokoro drew a horizontal line on the blackboard. Above this he drew a line cutting down into it which formed half an oval, its long axis parallel. Within the curved line he drew an arrow pointing from right to left. “This is a vertical section diagram of a cold front. The straight line below is the earth’s surface. On the right is a mass of cold air. The cold air mass plunges beneath the warm atmosphere on the left. The warm air is pushed upward and is chilled. And along the line of discontinuity, clouds take form and rain begins to fall. In the case of a warm front, the reverse happens. The warm front climbs over the cold mass.” Tadokoro turned away from the blackboard and singled out Onodera this time. “Onodera, do you see where I’m going?”
“I think so, Professor,” answered Onodera. “In terms of your analogy, the cold front moving from right to left is the mantle flow coming up from the Southeast Pacific, and the warm atmosphere on the left is the mantle flow coming from beneath the continent.”
“Exactly. The continental mantle flow is much warmer be cause of the radioactive elements it contains, because the crust of the continent is some six times thicker than the crust of the ocean floor, and for other reasons I needn’t go into now. Thus, it climbs up the advancing mantle. And this is the force that moved the Japan Archipelago away from the mainland, forming the Japan Sea in the process, and eventually bent the Archipelago into its present arc shape. Now bear this in mind: the Archipelago is still bending and moving, and the Japan Trench, formed by the descent of the Pacific mantle, is still growing deeper.”