EARTHQUAKES.

Dominion, Volume 23, Issue 257, 26 July 1930, Page 28

EARTHQUAKES.

What causes an earthquake, we awestruck wonder! Solid as the earth looks, we all know that movement in its crust is still taking place. It is shrinking round its molten centre, and just as an apple comes out of the oven with its skin wrinkled into folds and valleys, so the earth’s crust wrinkles to lit this lessening inside. This contraction sets up forces which are one cause of earthquakes, and the places where they usually occur are the weakest parts of the wrinkles or mountain ranges. Japan, which ha.suffered so badly from earth<|u.il;es, is practically all mountains—it is nothing but a series of these wrinkles. From Valparaiso to Iquique in u,. West, of South America Is another »eu sltive region, and again is crossed b_. wrinkles, the Andes. 'Die, Rockier suffer In a similar way, also the Alp., and the mountainous tracts of Central Asia, Water is another cause of vurthquakes! Constantly drlppln.,' through the crust,'lt In time may dissolve lii’..;e caverns in the earth’s lute, lor, e,\ itually the roof of the eiiveiii falls in. causing a series of shock waves to puss through the crust which may cniisi- a movement to be felt on the ttrftici. When volcanoes explode the country around is often rent by long fissures. The cause of the volcanic eruption may have been---steam! The water dripping down toward the earth's interior is heated and eonverted into steam. This can exert great pressure, as we know to our benefit; but in this case the pressure causes a volcanic eruption and movements of the earth’s surface involving loss of lifeIt all simply means that Mother Earth Is still rumbling and shrinking and lias in no way completely settled down.