p The sinking of the Darwin Rise is connected, some scientists say, with the Early Cenozoic era, when great changes ushered in the present period of geological history.

p Volcanism continued in the Pacific in the Early Cenozoic era. But the Mid-Pacific Mountains and other underwater ridges now lying at a depth of many kilometres gradually began to sink. Coral islands and atolls started to grow in place of the submerged Tuamotu Ridge; other oceanic volcanoes and mountains also acquired their coral “tombstones”. Some, however, were unable to leave traces of their existence on the surface of the ocean. Coral colonies did not settle on their peaks, the peaks were planed almost flat by wave erosion, and today a tremendous number of submarine volcanoes—called guyots—with broad, almost flat, tops is to be found in the Pacific.

p While the Darwin Rise was sinking, the East Pacific Rise, stretching all the way from the Gulf of Alaska to the Galapagos Islands, was born. The East Pacific Rise is one of the largest sections of the chain of abyssal ridges that encircle the globe.

p The Hawaiian Islands rose, and so did many other volcanic islands of the deep basin. Some of the present atolls were elevated and forested for a time and then again subsided. New islands arose and then sank in the eastern part of the Pacific.

p The Gulf of Alaska and the west coast of the United States had islands that cannot be found on maps today. Numerous islands and banks were present in what is known as the Baja California Seamount Province and on the ridge that runs near the Pacific coast of South America.

p Simultaneously the so-called Melanesian Rise may have developed in the Southwestern Pacific, although ocoanographers are still debating its existence. According to Menard, "Melanesia is structurally complex and little known, and not much can be said about it that is not conjectural”. The Chatham Rise east of New Zealand was likewise at sea level, forming a very extensive bank.

p There was a time when scientists, influenced by the Bible, believed in the idea of a great flood. When viewed not as God’s punishment for man’s sins but as an actual event, a flood explained many facts that science could not yet explain, such as the discovery of fossils of fishes and seashells on mountains. Early in the 19th century, the famous French naturalist Georges Cuvier advanced a theory of cataclysms, according to which life on earth is periodically destroyed by great “explosions”, such as volcanic eruptions, earthquakes and floods, and then, like the Phoenix, is resurrected.

p Before very long, however, Cuvier’s theory of cataclysms was refuted by the large amount of data collected by new sciences like oceanography, paleontology, geology and climatology. By the beginning of our century, one hundred years after Cuvier, the majority of scientists held a diametrically opposite view, believing that the earth’s crust, very old, was ’little affected 55 by the turbulent events taking place inside the earth and reacted to them—in the shape of earthquakes, floods and volcanic eruptions— only in exceptional cases and on a local scale.

p However, each decade of the 20th century has brought new discoveries that enableus to penetrate deep into the bowels of the earth and down to the ocean floor. The data that science has accumulated speak of the opposite. Although the earth is thousands of millions of years old, very substantial changes are still taking place. The earth’s crust can be “rejuvenated”; continents and oceans can change their outlines; plains can turn into mountains or sink below sea level.

p Neotectonics, a science concerned with movements and deformations of the earth’s crust during the past 25 million years (the name “ neotectonics” was proposed by Academician Obruchev in 1948), has developed into an independent branch of geology with a promising future.

p When measured in human terms, 25 million years is an enormous span of time. But it is only a tiny fraction of time in the history of our planet.

p In the past 25 million years the face of the earth has undergone important changes, whether in the relief of the mountains or the contours of the oceans. The greatest mountain ranges—the Himalayas, Pamirs, Alps, Caucasus, Cordilleras and Andes—have developed in this period, as has the present Pacific basin, with all its underwater mountains and ridges, islands and archipelagoes, coral reefs and atolls, inner seas and island arcs.

p Still, modern earth science considers 25 million years too long a period. The time scale has to be reduced if we are to understand the 56 processes that have given our planet its present appearance.

p The Quaternary, the geological period during which man became Homo sapiens, a period that has lasted about one million years, up to the present time, was previously considered to be the least significant division in geological history. But more and more new scientific findings are changing the attitude to the Quaternary.

p The rise of Homo sapiens took place against a background of extremely abrupt climatic shifts and contrasts. Grassy plains turned into barren deserts, which again became covered with vegetation, and then again turned into sands. (Take, for example, the Sahara, the world’s largest desert, where man has lived since remote times.) In the north, great glaciers advanced and retreated, causing the ocean level to fall and rise. The relief changed as well as the climate. Mountains rose, volcanoes erupted (Mt Elbrus in the Caucasus was an active volcano several thousand years ago), and the configuration of the ocean floor was altered. Along with the climate and the relief the organic world of our planet also changed.

p The appearance or melting of glaciers in the temperate zone led to fluctuations in sea level. An idea of how great these were can be gained from the International Geophysical Year data on the approximate volume of ice that covers Antarctica and parts of the other continents. If this ice were to melt, the level of the World Ocean would rise 66 metres, and many cities and tracts of land would be drowned.

p When cold set in on earth the accumulation of glaciers enormously lowered the sea level, exposing land that had been covered in places 57 by as much as hundreds of metres of water. When it grew warmer the glaciers began to melt, the sea level rose, and land was submerged. This process has taken place several times throughout the Quaternary period.

p Exactly how many times we do not know. Some scientists believe the ocean rose and fell greatly at least three times. Others set the figure at four, seven and even twelve times. There is also a view that there was only one vast glacial epoch broken by short warm periods. Finally, there are scientists who maintain that our planet had no ice age at all!

p These questions of Quaternary period geology and glaciology are indeed highly interesting, but we shall not go into them here. The important thing as far as the present subject is concerned is merely to note that individual parts of the Pacific as they are today—the shape of coastlines, islands, etc.—developed after Homo sapiens had come on the scene and was beginning to explore and settle his planet.

p The marginal seas of the Pacific—the Sea of Japan, the Sea of Okhotsk, the Yellow Sea, the Bering Sea and the inner seas of Indonesia— acquired their present shape only at the end of the last glacial epoch, about 10,000 to 12,000 years ago. The Pacific coasts of Asia, America and Australia preserve traces of the rise and fall of the ocean level. Underwater banks, guyots and shallows were islands and islets not so long ago. In a word, man was a witness to the last great changes in the relief of our planet—and more than merely a passive witness, at that.

p During the glacial period the ocean level was much lower than it is today. Chains of land bridges ran from island to island, from 58 archipelago to archipelago. Along these bridges Ihe primitive explorers of the Pacific ventured ever farther out into the ocean, peopling more and more archipelagoes.

What is more, that is how the American and Australian continents were in all likelihood settled in the remote past. Land bridges enabled primitive Columbuses to discover the New World thousands of years before Columbus, and Australia thousands of years before Captain Cook and the Dutch seafarers.