238 Long Waves in Canals and Standing Waves in Closed Basins 



descriptions of such catastrophic dislocation waves. Destruction waves caused 

 by earthquakes, dislocation waves, or tsunamis are in general associated, 

 with submarine landslides which directly create transverse waves. 



The central and eastern Mediterranean (Aegais) has often been the site 

 of such catastrophic events, which were invariably associated with heavy 

 earthquakes. We remember the flood wave that occurred in connection with 

 the terrible Messina earthquake on 28 December 1908, and which destroyed 

 Messina, Reggio and a large number of other places in the Strait of Messina. 

 According to Platania, the height of this wave was at Messina only 2-7 m, 

 it was 8-4 at Giardino and Ali, 8-5 at Briga marina, whereas it amounted 

 to hardly 1 m at Faro and Milazzo. These waves were apparently caused 

 by tectonic changes. 



An example from the North Atlantic coast is the disastrous wave in the 

 wake of the Lissabon earthquake on 1 November 1755. Data on this ca- 

 tastrophe were collected by v. Hoff. In Lissabon there appeared, after the 

 second earthquake shock and with simultaneous changes in water depth 

 off the harbour, a wave measuring 5 m in height. Another three waves 

 followed this first one. Along the entire Portuguese coast the waves were 

 much higher. At Cadiz, the wave was still 18 m high and caused heavy 

 damage. On Madeira the sea rose above the high-water mark by 4-5 m, and 

 the oscillations returned, with decreasing intensity, five times. The flood 

 wave spread over the whole Atlantic Ocean, and as far as the Antilles, favoured 

 by local conditions, considerable amplitudes were reached. 



The main site of these catastrophic waves is the Pacific Ocean, where 

 they originate in the earthquake centres. They occur relatively often on the 

 Japanese coasts, as a consequence of earthquakes and, as already mentioned, 

 they are designated there by the name of tsunami. When they are caused 

 by tectonic changes at the ocean bottom, they can be designated as "seismic" 

 tsunami, in opposition to the meteorologic tsunami. The damages caused 

 by them to the shores, especially in the shallow ocean bays, are considerable, 

 and the loss of human lives is heavy. Recent studies on the origin of these 

 seismic tsunamis can be found in Ishimoto (1933). Hochstetter (1868, 

 p. 837, 1869, p. 112, 1870, p. 818) has given a description of the waves 

 originated by the earthquake of Arica on 13 August 1868, and Gleinitz 

 (1878) has described one of Iquique on 9 May 1877. Both "tidal" waves 

 crossed the entire Pacific Ocean. In the immediate vicinity of the origin, 

 there was first a wave crest and then a wave trough, whereas at a great dis- 

 tance from the origin the wave trough was the most important feature and 

 showed itself by a recession of the water on the beach. 



In the Indian Ocean we have also such gigantic "tidal" waves. The greatest 

 destructive waves ever witnessed were the ones following the eruption of the 

 volcano Krakatoa in the Sunda Strait on 26 and 27 August 1883. There were 

 several eruptions. The last one on 27 August was the strongest. "Tidal" 



