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Crank Engineer's Dream Solves

The Secrets Of The Sea-Bed

With much interesting, hitherto un published information regarding most Island regions of the Pacific, com piled by authors from several nations and assembled into this large new volume, The Western Pacific-Island Arcs, Marginal Seas and Geochemistry is a recent concensus of general scien tific knowledge.

Its editor is no stranger to the peoples of Melanesia where he, with his colleagues Dick Stanton et al, shared the hardships and triumphs of pioneering discovery, with hammer, hand lens and bag—the tools with which the frontiers of Empire were being mapped 20 years ago.

The changes since then—and the contents of this volume—have been primarily due to developments in electronics that have been little short of astonishing. Data has been collected and processed at a tremendous rate.

Individual pigeon-holes of 20 years ago have had their partitions disinte grate through sheer activity; each sub ject has been rejuvenated by other branches of science. In particular geology has been transformed by the impact of geophysical and geochemi cal findings by land, sea and air.

After lying on the shelf for 120 years as the dream of a “crank” en gineer, computers have become a rea lity. A university master’s degree in mathematics is said to deal with knowledge only to the year 1904. The full implication of computer availa bility to earth scientists boggles the imagination.

In the 19505, a sea gravity survey required a submarine; each single reading was a separate naval opera tion involving a star-sight for loca tion and a dive to lie at 200 ft so that two pendulums could be swung in opposition on the same bar, and timed. Today, shipboard gravity meters make continuous recordings —teething troubles had been ironed out by the time of the Solomons Sea Gravity Survey by HMS Dampier in 1965. Magnetic measurements used to involve cumbersome equipment. Today it involves an ordinary plastic bottle

of water with an intermittently-acti vated coil of electric wire around it, held by hand or towed in a “fish” by a ship or in the tail “stinger” of an aircraft—with continous recording.

In the Solomons in 1960 a seven year Tellurometer survey began with distance being measured to a fraction of an inch in 40 miles. In 1967 these measurements were extended beyond the horizon by three army-manned mobile satellite tracking stations— with satellites sent up specially from Cape Kennedy.

Aerial photography permits the most precise measurement of river widths, bank heights, tree and grass heights and contoured maps. Side-look radar can produce maps by electro magnetic responses that closely re semble aerial photos—taken through impenetrable cloud cover as though it does not exist. Similarly—and it is described in this volume —towed vehicles travelling close to the sea

bed exploring valleys and plains are equipped with side-look sonar that plots sea-bed outcrops and structures to 1 km on each side. The American Government has presented countries around the world with World Stan dard Seismological Stations and all accoutrements —this has helped us im measurably in earthquakes studies by providing more accurate hypecentres.

Developments have been startling in any language, making such a volume as this possible.

Heavily dominated by the so-called “New Global Tectonics” or “Plate Tectonics” hypothesis referred to sceptically by one writer as the“ Co nveyor Belt Theory”, Coleman asks whether this aspect of the volume is essentially an American phenomenon.

Nearly all scientists have come to accept that the ocean floor is being added to out of mid-oceanic rises because magnetic surveys show strips of matching magnetism, signifying comparable volcanic extrusions equi distant on each side of these mid oceanic rises. But “Plate” supporters say that Earth does not expand and there must be comparable “conveyor belting” of crust down into the tren ches (“subduction”) —the present fashionable hypothesis.

Only one contributor, Professor Sam, Carey, throws very heavy, well reasoned doubts, believing it to be a passing fad, pointing out that earth quake profiles below the trenches do not show thousands of km of crustal shortening but rather expansion of the Earth: recent work in New Britain and Solomons seems to lend support.

In 1939 “continental drift” was similarly denied and supporters were scorned until the mid-fifties. Today, while proclaiming this separation of continents, geophysicists deny ex pansion, insisting on “subduction” in to the trenches, while most geologists rush to concur and will not look at contrary evidence. Why is expansion so unspeakable?

Space will not allow treatment of individual papers by a distinguished collection of authors, well illustrated

by maps and sketches.

A list of Collected References con tains all references named by authors.

Although seismicity of the New Heb rides is a subject, the absence of mention of Blot’s papers from a de cade of five-dimensional studies by ORSTOM is notable. It would also seem that most workers are not aware of the five volumes published by the British Solomon Islands Pro tectorate Geological Survey and other publications by the ensuing United Nations Project. Fortunately, the works of Woollard, Laudon, Rose and Furumoto on this critical area have received honourable mention.

A useful comprehensive index con cludes the volume.

Those involved in island arc or marginal field studies or in teaching earth sciences would do well to pos sess a copy of this volume as a con venient reference to current thinking.

John Grover.

(The Western Pacific-Island

Arcs, Marginal Seas And Geo

CHEMISTRY. Edited by P. J. Coleman.

Western Australian University Press. $24).