Final answer:
The wave height of a tsunami in the open ocean is low and not dangerous, but as it approaches the shore, its height can dramatically increase, posing severe danger near land. Tsunamis have variable wave heights and are chiefly dangerous near coastlines.
Step-by-step explanation:
The wave height of a typical tsunami away from land is generally low due to the vast expanse of the open ocean which allows the energy of the wave to be spread out over a long distance. In the deep ocean, the wave height of a tsunami can be less than 30 cm (1 foot). However, as the tsunami approaches the shallower waters near the coast, the wave slows down and its height can increase dramatically, potentially reaching heights of up to 30 meters (about 100 feet). Therefore, while the wave height of a tsunami in the open sea is generally low and not inherently dangerous to boats or ships, it becomes extremely dangerous near the coast where it can cause devastating damage and loss of life. The correct answer to the question is c) Variable wave height; Dangerous only near land.
Check Your Learning
If a tsunami travels at a speed of 600 km/h and approaches the shore at a rate of one wave crest every 15 minutes, the distance between wave crests at sea would be 150 km (600 km/h divided by 4 waves/h).