[For Seniors] Take on Summer! A Collection of Ocean Trivia Quizzes & Fun Facts

Measure using sound waves

The mainstream method is sonar, acoustic sounding, which emits sound waves toward the seafloor and calculates the depth from the time it takes for the reflections to return. Sound travels well in the ocean. In the past, they used to measure with long ropes, but as technology advanced, measuring with sound waves has become the norm.

118

The emergency phone number for incidents and accidents at sea is 118. Dial 110 for the police and 119 for fire and ambulance, but for trouble at sea you should call the Japan Coast Guard at 118.

Because the salt content in rivers and rain is kept in balance.

Rivers and rain carry various minerals and salts into the ocean, and because their amounts even out over long periods, the saltiness of seawater is kept at nearly the same level worldwide. Even if the amount of salt or seawater decreases, there is always a replenishing effect, so the salinity of seawater does not change. However, there do seem to be slight differences depending on the location.

about 11,000 meters

The place in the Mariana Trench known as the Challenger Deep is about 10,924 meters (around 11,000 meters) at its deepest point. This is much deeper than Mount Everest is tall.

Etorofu Island

Etorofu Island (Etorofu-tō) is a volcanic island located in the southern part of the Kuril Islands off Hokkaido, at Japan’s northernmost extremity, and it contains multiple active volcanoes. It is currently under de facto Russian control, but is officially claimed as Japanese territory.

about 3 meters

The Japanese spider crab has ten legs, and when spread, they can reach a length of up to about three meters. It inhabits the deep waters near Japan and is considered the largest crab in the world due to its size. Its body weight can reach up to 19 kilograms.