Tsunami is caused by

Question

Accepted Answer

The correct option is 4:

A tsunami is a series of extremely long waves in a body of water, typically the ocean, caused by a massive displacement of water. The most common and powerful cause of this displacement is a large-scale **earthquake under the ocean**, specifically a submarine earthquake that occurs along a subduction zone where tectonic plates collide. When one plate suddenly slips beneath the other, it lifts or drops a large volume of the overlying ocean floor. This rapid vertical movement of the seafloor pushes the entire water column above it, generating the immense energy required to create a tsunami wave that can travel across entire oceans at high speeds. This process is known as 'seismic sea wave' generation, confirming the role of underwater earthquakes as the primary trigger.

The incorrect option is 1:
A very warm ocean current is a constant flow of water that circulates heat around the globe (like the Gulf Stream) and does not involve the sudden, massive vertical displacement of water needed to create a tsunami. Ocean currents are steady flows that affect climate and weather patterns, but they do not generate catastrophic wave events.

The incorrect option is 2:
A large bank of fish refers to a substantial school or concentration of marine life. While fish banks are important for the ecosystem and fisheries, they are biological entities that occupy a negligible amount of space in the vast ocean and cannot displace the volume of water required to form a tsunami.

The incorrect option is 3:
A melting glacier contributes to a gradual rise in global sea levels over many decades. Although calving (large chunks of ice breaking off) can cause small, localized waves in fjords or lakes, the slow, ongoing process of a glacier melting does not cause the instantaneous, massive displacement event necessary to generate a devastating ocean-wide tsunami.