NATURE 



*2,7 



THURSDAY, JANUARY 15, 1885 



THE EARTHQUAKES IN SPAIN 



EVEN the most conservative believer in the stability 

 of Mother Earth must by this time have had his 

 faith sorely shaken. Year after year, and month after 

 month, we receive tidings of more or less serious shakings, 

 varying from slight movements, such as merely set bells 

 ringing and disturb the crockery on kitchen-shelves, to 

 such shocks as convulse wide districts and bring with 

 them disaster to life and limb as well as destruction to 

 property. As if these tangible proofs of insecurity were 

 not enough, we have learnt further that what we have 

 been in the habit of dignifying with the name of the 

 "solid" earth is really in a state of perpetual tremor. 

 The thud of falling rain-drops, the patter of birds' feet, 

 the tread of cattle, the gambols of children, so affect the 

 ground on which we walk that the vibrations which they 

 cause in it can be made clearly audible by the microphone 

 and visible by the galvanometer. The position of the sun 

 in the sky, the rise and fall of the tides, the thermo- 

 metrical and barometrical oscillations of the atmosphere, 

 produce in the outer parts of the earth corresponding 

 pulsations, which, though not always certainly referable 

 to their originating source, are perfectly recognisable, and 

 can be registered by sufficiently delicate instruments. So 

 that, instead of being on the whole a motionless, inert 

 mass, the land is, in its way, almost as restless as the 

 sea. 



Fortunately, we are not sensible of these daily and hourly 

 vibrations. It is only from time to time, by the news of 

 earthquake-shocks from different quarters of the globe, 

 that our attention is vividly drawn to the subject, and we 

 are made to realise how little right we have to count on 

 the continued stability of our own district. The daily 

 tidings from the south of Spain, coming after so many 

 recent chronicles of earthquake disaster in Europe, can- 

 not but recall our thoughts to this subject. When the 

 peace and goodwill of Christmas-tide were once more 

 brightening the close of the year all over Christendom, 

 the inhabitants of a wide tract of Andalusia were sud- 

 denly thrown into consternation by a succession of power- 

 ful earthquakes. The district most severely visited lies 

 in the province of Granada and Malaga, and forms a 

 parallelogram measuring about 70 miles from east to 

 west and about 35 from north to south. The eastern 

 part of the affected district passes into the great range of 

 the Sierra Nevada, of which the highest peaks rise 

 between 11,000 and 12,000 feet above the sea. West- 

 wards, this range throws off some minor spurs, particu- 

 larly the Sierras Tejada and Alhama, which curve round 

 towards the north-west. The chief mass of the Sierras 

 consists of crystalline schists stretching east and west, 

 and flanked with Tertiary strata, from beneath which 

 various Jurassic and other Secondary rocks emerge. 

 The area of maximum destruction appears to be among 

 the Western Sierras, and on the ground to the south and 

 north of them. 



The greatest amount of damage has been done at 

 Alhama, which is almost entirely ruined. This little 

 town stands nearly on the junction of the Tertiary rocks 

 Vol. xxxi. — No. 794 



with the schists that rise into the more rugged ground of 

 the mountains. A little to the south-east Abunuelas has 

 also suffered severely. From that central area the shocks 

 seem to have lessened outwards, but to have been felt 

 most along the northern and southern flanks of the 

 Sierras. According to one account the shocks have indi- 

 cated earth-waves from south to north, with return move- 

 ments in the contrary direction. Not improbably the 

 actual focus of disturbance lies along the axis of the 

 Sierras Alhama and Tejada. But the shocks have been 

 felt over a much wider area. They have extended along 

 the line of the mountains at least as far as Gibraltar in 

 the west, though they are not recorded as having been 

 marked in an easterly direction. Northwards, the towns 

 and villages lying nearest to the centre of commotion 

 have suffered most — Antequera, Loja, Granada. But fat- 

 beyond these districts, terror was occasioned to the people 

 of Cordova, Cadiz, and Seville, and the first shock was 

 felt even at Madrid. No sea-wave has been chronicled 

 as having affected any part of the coast, whence we may 

 reasonably conclude that the earthquakes have not 

 originated under the sea. 



The Spanish peninsula has long had an evil reputation 

 for the frequency, destructiveness, and long continuance 

 of its earthquakes. In the present case the shocks are 

 said to have begun three days before Christmas ; but the 

 first destructive wave arose on Christmas day. Since 

 that date there has been an almost daily continuance of 

 shocks of varying intensity. Such was also the case in 

 the summer of 1863 along the great range of Sierras from 

 Malaga to Alicante, and still earlier, in 1849, the same 

 district continued to vibrate for several months. 



Unfortunately, no accurate registers have been kept of 

 these earth-tremors. Observations on earthquake pheno- 

 mena made after the event, though useful so far, are now. 

 recognised as altogether insufficient to enable us to solve 

 the problems presented by this interesting, but difficult, 

 branch of geological physics. The establishment of self- 

 registering apparatus, which was temporarily assisted 

 many years ago by the British Association in the case of 

 the simple instruments set up at Comrie in Perthshire, 

 and which, more perfectly developed in Italy, has recently 

 been so well inaugurated in Japan by Profs. Milne and 

 Ewing, is the only satisfactory method of accumulating 

 the necessary data. Until facts thus chronicled have 

 been patiently gathered for some years in regions widely 

 separated from each other, alike in distance and in geo- 

 logical structure, seismology must be content to remain 

 very much at a stand. Of course, speculation will be as 

 rife as ever, but cautious men of science will probably 

 withhold their judgment until they are in possession of 

 data of a kind that has not yet been systematically 

 observed and registered. 



But even before these data are gathered for the 

 region of Andalusia, we can hardly doubt that funda- 

 mentally the shocks so often felt there arise from the 

 process of mountain-making. The vibrations are propa- 

 gated along the Sierras, and are felt with most violence 

 near their flanks. They are probably in some way con- 

 nected with the movements of the terrestrial crust that 

 first started and have successively upraised the long 

 parallel lines of mountainous ridge that diversify the 

 surface of the Spanish tableland. Among the questions 



