PATER'S CHATS WITH THE BOYS.

Otago Witness, Issue 2719, 25 April 1906, Page 81

PATER'S CHATS WITH THE BOYS.

THE UPHEAVAL OR DOWNHEAVAL AT SAN FRANCISCO. We were all appalled to read of the terrible manifestations of Nature which have laid San Prancioco in ruins and have taken so many lives. I intended to-day to note, as supplementary to my chat on Vesuvius last week, the results of the Krakatoa outburst some years ago, when the atmosphere was tinged through«out the world with an almost impalpable dust as an outcome of ths temSc explosions j and to allude to the effects of the Mount Peke and Mount Soufriere outburst in the West Indies; but instead I'll take this latest disaster, especially as my chats are read in 6ome schools as a reading lesson. In one of mj- books the following is recorded: — "The ranges of Nevada, like the ridges of Oregon, seem to have been formed by the uplifting of long blocks of tha earth's crust ; but in Nevada the blocks must have been larger and the uplifting ' greater ; and the uplifting must have be- | gun earlier than in Oregon,for the work oi dissection by streams is here much advanced. The ranges of Nevada are thoroughly or maturely dissected. Yet, as in , Oregon, occasional earthquakes show that : the mountains are M.-UL growing." j In another place, where the gTowth of I mountains is being considered, the same • writer says: — "The process of bending and | breaking" the rock structures within a j mountain mass is certainly very slow, but I it sometimes causes sudden snaps and slips of a few inches or a few feet. Tremors "tliea, spread ig'aji direcfcioiis from the seat

of disturbance, diminishing in force "as they advance. On Teaching the earth's surface they are felt as earthquakes,- producing more or less destruction. -Shocks of-' this kind are comparatively common , in, and near, most of the lofty mountains ' of the world. Earth tremors travel through the earth's crust with great velocity, — from ten to forty miles a minute ; but; as in the case of water wavesj the actual movement of the quaking earth at any point may be only a few inches or a few feet a second, backward and forward. The shocks, produced by earthquake waves are most violent at places distinctly over the 6eat of chief disturbances. They may be very faint, causing no damage ; they may ba strong enough to be felt violently over hundreds of square miles, less distinctly over many thousands, and very faintly (by the aid of delicate instruments) all over tiw world." Is the casting down of San Francisco one of the growing efforts of the mountains of tho west of the United States? Has the folding or crumpling of the earth's' crust been going on there imperceptibly up to now, but have natural forces now suddenly made a Titanic effort to readjust the earth's surface there? Perhaps one of the most-easily read pages of tibe Book of Nature is the folded mountains in France. To quote again: — "Tlie Jura Mountains, along the border oi France and Switzerland, ' occupy a belt oi ■■ country where the rock layers, , ona j horizontal, have been slowly pressed into, a series of wave-like folds. The mountains consist of a number of parallel; ranges and valleys trending about. N,E. " S.W. j Each -range consists : of "a senes of' Tods

[ layers "bent iipwaid v like* : an arch : leacK 'valley is-, und^aid-by^.the'Va.me series of flayers bent downward, like,' a > trough.' / . . .'■ ; The" rock -layers ,of these : mbuni tains contain sea fossils';- tie' layers 'inustr, j originally have been horizontal etrata onr < > tb.3 floor of an ancient 'sea: "Since " thei> . i they have gradually .. been pressed* and folded into their arch-and-trough structure* * by a powerful side pressure."., - Now, unfortunately for me, my know : kdge of the geology of New. Zealand is not * extensive enough for me to name a clearv easily -read, folding-rock structure in Otago; i though, no doubt, there are many » easily ! recognisable. " ' * But before I go any further, take out your a-tlas and follow me in a brief sketch of volcanic and earthquake activity; after that we shall return to d-ataiis. .The Pacific is encircled by a belt of volcanic and earthquake action. Directly south of New. Zealand, we have Erebus and" Terror, both active, I think\ Coming to New Zealand, we all know tremors are experienced from Auckland to the Bluff. - It is only a or -two ago that ! the. earthquake, earthcracking, and earth- " 1 tilting at the Cheviot startled us. .Wasn't it last^year that Wellington folkwere scared' out _of their wics. . When the Maoris see the large buildings now being ' erected in. Wellington do- they 'not. say,. > - iir- the^r own "tongue, . " Wait^a^bitr" ? Hasn't ' Mr. Hoben. just been acting -a Job's , febmfogter-'iby-'saying."' thitA Wsllngi,pn ia • < ' ;rt>n the^line^ b£ .weakness?', he , Cwritten,' foo', in " The' Geography •%£ -New " : Zealand " -that' more" thVn "half-the"'earth-quakes recorded in-New Zealand originate, in Cpok-'Stjrait? Wasn't Lyttelton Har-, : bour formed by volcanic explosions?!