THE RESTLESS EARTH.

New Zealand Herald, Volume LXVI, Issue 20288, 22 June 1929, Page 1 (Supplement)

THE RESTLESS EARTH.

QUAKES AND TREMORS.

331' MATANGA.

"It moves!" was Galileo's stubborn word, acording to modern legend, after a recantation, wrung by torture, of his declared opinion that the earth was not stable. lie was unconvinced by all priestly citations, however numerous and emphatic, that it was " established " and that an attendant sun kept sentry-go around it. His watching of tho oscillations of a swinging lamp in Pisa's cathedral—so unconsciously did tho Church itself set him on tho path of his scientific quest—led him step by step to his renunciation of Aristotelian theories; and in his footsteps it is now easy to walk. We know that the earth spins with high velocity, and that it makes annually a rapid circuit of the sun; and in tho wako of that knowledge has come the truth that the whole solar system, of which our planet-dwelling is but one of many members, a greater company than our fathers guessed, is on a journey through spaco. "It moves!" is to-day much more than a legendary phrase. Our earth is known to be habitually, restless. Not long since it was thought that the axis of the earth, that imaginary line from pole to pole about wnich it. spins, kept a constant relative position. "It moves!" can now be declared pusitivelv of it too. Its rotary swing is now aceur ately measured, thanks in part to the open-eyed investigations of the Pisan scientist, so much can come when honest men follow an honest man. More than that, every little movement of tho earth can be closely watched by sleepless ap paratus. Ohiels Taking Notes. Less than a century ago, Babbage was busy at ai bowl of treacle, gazing often at it with eager eyes, cherishing its every drop, not to edt but to measure as tlio surface changed its shining level'in regis tering the movements of the earth. Now, through the construction of wondrously delicate appliances, movements that es caped Babbage's eyes ca.ll be closely seen. A bifilar pendulum invented in 1894 re ords a tilt amounting to no more than if a line a mile long were lifted at one end only a thousandth part of an inch. This old earth must now have a care how it conducts itself, for there are chiels every where taking notes and printing them. When it shrugs itself with a little more restlessness than usual in a Httle region of our southern island, that is noted far across the world. Someone, perhaps, may feel jocularly prompted to say—" Ah' those ' Shivery Isles ' again." There is, it seems, an impression abroad that New Zealand is for ever rocking, and that its hapless inhabitants have, often to lie fiat, clutching the nearest tree-trunk, lest they be tossed overboard. In the realm of romance, distance has usually the weird effect of giving magnitude, and so it is in this. Thero was once current an idea that the sheep of this country had developed preternaturally strong jaws, as a result of the necessity to hold on to the tussock of their pasture in order to save themselves from being blown away: a deduction, it was discovered to the rescuing of this land's reputation, from some stranger's reference to the sudden loss of his hat, snatched away by a playful zephyr in a town that need not be named. As a matter of fact, when it comes to restlessness in earth or air. New Zealand is much as other lands, and sympathy for us is apt to be greatly overdone. No Terra Pinna. The surface of tho earth is never actually still for long. "Terra firma" is a polite fiction, really a misnomer. No New Zealander need think of emigrating in search of a more settled home. The Old Land, as we fondly call it, has had many movements with which tho politicians and churches have had nothing to do, and is still having them. It is not so long ago, as geological time is reckoned, that the map of the British Isles would have shown a very different shape fron that of to-day, the sea then occupying a large portion of what is now land, quite respectably high. Sweden is getting up in the world, although its neighbour, with whom it has formed a recent happy reunion through the loves of Eoyal households, is going down. Surely no one would suggest that this is a mesalliance. All the islands of the Arctic, as far as their behaviour has been noted, are rising; but this alone is no sufficient reason for, wishing to live on any of them. The bed of the Pacific, as far as observation has gone, is changing, yet, save for one or two instances reminiscent of tho Irishman's " I'm gone to-day and here to-morrow," there is nothing for any of its happy isles to make a work about.

These tilings are all in the day's march of this interesting planet, prone to assert an individual, love of liberty against the orders that keep it swinging on along a defined route. It is not allowed to fall out of rank, but no sergeant-major, however inexorable, can keep it from twitching its skin or shaking an eyelid. He cannot even control the way it fills its uniform. He may not like creases, but he cannot stop tnom coming or going. That is precisely tho case with tho earth. It is for ever wearing its uniform " with a difference." Almost everybody has heard of the temple at Pozzuoli in Italy, sometimes wrongly called the Temple of Serapis. It is near Naples, and was really a popular bathing establishment once upon a time. Some columns remain high above the ground, but 20ft. or so above their bases they are perforated by sea-living molluscs. The place was certainly not built under water, and tho truth to be read in this band of perforations, many of them still holding the shells of the molluscs, the band being in level alignment high above tho ground, is tho gradual and prolonged submergence of the structure and its subsequent lifting so steadily as not to displace tho pillars. This was a very sedate and de corous happening, fully worthy of a classical land. All such changes, however, as we know, arc not so sedatejy made. Sudden Twitcbings. Earthquakes are somewhat sudden twitchings of the earth's skin, tragically sudden sometimes. They occur, quito naturally, in the vicinity of volcanoes very often, for the bursting of a boil is bound to create a physical sensation for some distance around. But to attribute earthquakes and tremors to vplcanic action as a general rule is at variance with facts. What the geologists call faults are chiefly responsible. They are breaks in the continuity of tho strata in earth's skin As tho restless earth has moved in its uniform, become stiff in many places through long wearing and changing conditions of exposure, that uniform, especially the many-layered part out of sight under its overcoat, has buckled a bit, and got cracked and torn here and there. A break has been made in the layers of rock, one portion slipping down relatively to another, the displacement being sometimes a matter of a few inches, sometimes of thousands of feet. Whorever these faults happen there is a liability to some further displacement, not necessarily great; even a small disturbance may set up a tremor as the new position is being taken, while a considerable one may mean a jerk such as some countries have very disastrously suffered. In what has taken place lately in our experience is an instance of this displacement. It belongs to the habits of the earth. There is little reason to fear that this phase of the settlement of New Zealand will supply many disasters, and none to think that it belongs peculiarly to this country.