Tsunami Formation
Tsunamis are ocean waves generated by the sudden, large-scale disturbance of water. Unlike wind-driven surface waves, tsunamis originate from impulsive events that displace large water volumes vertically. The most common cause is seismic activity—particularly subduction zone earthquakes where one tectonic plate slides beneath another. The vertical movement of the seafloor during these earthquakes transfers energy directly to the overlying water column, initiating wave propagation across the ocean basin.
Primary Generation Mechanisms
Submarine landslides represent a significant secondary cause of tsunami formation. When large masses of sediment or rock on continental slopes or submarine ridges fail suddenly, they displace water much like seismic uplift. Volcanic eruptions can generate tsunamis through multiple pathways: the explosive collapse of volcanic islands, pyroclastic flows entering the ocean, or submarine caldera collapse. The 1883 Krakatau eruption and the 2022 Tonga eruption demonstrated the destructive potential of volcanically-sourced tsunamis, which can propagate across entire ocean basins.
Wave Characteristics
Once initiated, tsunami waves behave distinctly from ordinary ocean waves. In deep ocean water, tsunami wavelengths are extremely long—typically 100 to 700 kilometers—while wave heights remain modest, often only 1 to 2 meters. This allows tsunamis to travel across ocean basins at speeds of 500 to 800 kilometers per hour with minimal energy dissipation. As these waves approach shallow coastal waters, the seafloor friction slows the wave front while compressing the wave energy vertically, causing the wave height to increase dramatically and potentially reaching heights of 30 meters or more when striking the shore.