What is meant by Tsunami ? $OR$ What is called a Tsunami ?
Answer
Due to a volcanic eruption or an earthquake on the bottom of the sea, or due to a big large scale landslide, large and powerful waves of unusual length are created on the surface of the ocean and that is called "Tsunami'.
What is an earthquake ? $OR$ What is called an earthquake ?
Answer
Due to the tectonic movements in the interior of the earth, the weak part on the surface of the earth suddenly vibrates (shakes) powerfully. This is called 'Earthquake'.