Many people acted heroically in the aftermath of Hurricane Katrina. The Coast Guard, for instance, rescued some 34,000 people in New Orleans alone, and many ordinary citizens commandeered boats, offered food and shelter, and did whatever else they could to help their neighbors.
Tidal waves, or tides, are a predictable, com-mon occurrence along coastal communities, generated by forces beyond Earthâthe gravitational pull of the sun and moon. However, tsunamis are not predictable. They are often generated by earth-quakes, volcanic activity, and slope failure.idal waves, or tides, are a predictable, com-mon occurrence along coastal communities, generated by forces beyond Earthâthe gravitational pull of the sun and moon. However, tsunamis are not predictable. They are often generated by earth-quakes, volcanic activity, and slope failure.
Those tsunamis were of the ordinary type, seismic tsunamis caused by earthquakes that suddenly lift or drop the seafloor. But a second type of tsunami can arise from landsliding with or without an earthquake, and shorelines of every kind, even lakes on land, are susceptible. 1  Landslide tsunamis are harder to predict, harder for scientists to model and harder to defend against. Landslide Tsunamis and Earthquakes. Landslides of various kinds can push water around. Mountains may crumble to the sea, as the song goes. Mudslides may plop into lakes and reservoirs. And land that lies entirely beneath the waves may fail. In all cases, the landslide material displaces water, and the water responds in very large waves that spread rapidly out in all directions. Many landslides occur during earthquakes, so landslides can complicate seismic tsunamis. The Grand Banks earthquake in eastern Canada on 18 November 1929 was tolerable, but the ensuing tsunami killed 28 people and ruined the economy of southern Newfoundland.