JOHN PHILLIPS. Observations made in the Neighborhood of Ferrybridge in the Years 1826-1828, Phil. Mag., 2d ser., vol. 4, 1828, pp. 401-409; Illustrations of the geology of Yorkshire, Pt. II, The Limestone District. London, 1836, pp. 90-98.
SAMUEL HAUGHTON. On the Physical Structure of the Old Red Sandstone of the County of Waterford, considered with reference to cleavage, joint surfaces, and faults, Trans. Roy. Soc. London, vol. 148, 1858, pp. 333-348.
W. C. BRÖGGER. Spaltenverwerfungen in der Gegend Langesund-Skien, Nyt Magazin for Naturvidernskaberne, vol. 28, 1884, pp. 253-419.
WM. H. HOBBS. The Newark System of the Pomperaug Valley, Connecticut, 21st Ann. Rept. U. S. Geol. Surv., Pt. III, 1901, pp. 85-143.
WM. H. HOBBS. The Interpretation of Geological Maps, School Science and Mathematics, vol. 9, 1909, pp. 644-653.
THE INTERRUPTED CHARACTER OF EARTH MOVEMENTS: EARTHQUAKES AND SEAQUAKES
=Nature of earthquake shocks.=—Man’s belief in the stability of Mother Earth—the _terra firma_—is so inbred in his nature that even a light shock of earthquake brings a rude awakening. The terror which it inspires is no doubt largely to be explained by this disillusionment from the most fundamental of his beliefs. Were he better advised, the long periods of quiet which separate earthquakes, and not the lighter shocks which follow all grander disturbances, would occasion him concern.
[Illustration: FIG. 49.—View of a portion of the ruins of Messina after the earthquake of December 28, 1908.]
Earthquakes are the sensible manifestations of changes in level or of lateral adjustments of portions of the continents, and the seismic disturbances upon the sea—seaquakes and seismic sea waves—relate to similar changes upon the floor of the ocean.
During the grander or catastrophic earthquakes, the changes are indeed terrifying, and have usually been accompanied by losses to life and property, which are only to be compared with those of great conflagrations or of inundations on thickly populated plains. The conflagration has all too frequently been an aftermath of the great historic earthquakes. The earthquake of December 28, 1908, in southern Italy, destroyed almost the entire population of a great city, and left of its massive buildings only a confused heap of rubble (Fig. 49). Two years later a heavy earthquake resulted in great damage to cities in Costa Rica (Fig. 50), while two years earlier our own country was first really awakened to the danger in which it stands from these convulsive earth throes; though, as we shall see, these dangers can be largely met through proper methods of construction.