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[For Seniors] Take on Summer! A Collection of Ocean Trivia Quizzes & Fun Facts
Summer is the perfect season for enjoying the beach.
Some older adults may remember playing in the ocean until it got dark.
Others might have grown up in landlocked prefectures and have memories of the sea from their travels.
In this article, we’ve gathered quizzes and fun trivia about the ocean to try in summer.
It’s packed with questions you might think you know but actually don’t—like why waves form, why seawater is salty, and why the sea looks blue.
The questions are easy multiple-choice, so feel free to join in.
Please make use of them during recreation time!
[For Seniors] Summer Challenge! Sea Trivia Quiz & Fun Facts Collection (1–10)
The phenomenon of the sea turning red is called “red tide.” What is causing this?
- seaweed
- plankton
- fish blood
See the answer
plankton
Red tide is a phenomenon in which the sea appears reddish, primarily caused by a massive bloom of phytoplankton. Some types of plankton contain red pigments, and when they proliferate in large numbers, they make the seawater look red.
What causes the waves we often see on the coast to occur?
- Because fish gather
- Because the water is warmed by the sunlight.
- Because the wind blows across the surface of the sea
See the answer
Because the wind blows across the surface of the sea
The sea surface is flat when there’s no wind, but many ocean waves are caused by wind blowing over the surface of the sea. The force of the wind transfers energy to the water’s surface, creating waves. Even if you don’t feel any wind while standing on the shore, waves still wash in and out because winds blowing somewhere far away generated waves that have traveled a long distance to reach the coast.
The sandy beaches in Okinawa are much whiter than those in other regions. What is the reason for that?
- Because it contains a lot of volcanic ash
- Because it is formed from crushed coral and seashells.
- Because it’s after the snow has piled up
See the answer
Because it is formed from crushed coral and seashells.
Usually, beaches are formed by rocks and stones being worn down into smaller particles. The reason Okinawa’s beaches are white is that coral and seashells living in tropical seas are finely crushed and become sand. As a result, they appear whiter and more beautiful than other beaches.
Why does the sea appear blue?
- Because the blueness of the sky is reflected
- Because seawater is originally blue
- Because when sunlight hits seawater, blue light is more easily scattered.
See the answer
Because when sunlight hits seawater, blue light is more easily scattered.
Sunlight is a mixture of seven colors: blue, red, yellow, green, orange, purple, and indigo. Of these, colors other than blue are absorbed by seawater and become invisible, while blue light is absorbed less and remains. The blue light then travels through the water and reflects off the seafloor, making the ocean appear blue to our eyes.
What is the salinity level contained in seawater?
- about 0.5%
- About 1.0%
- About 3.5%
See the answer
About 3.5%
The salt concentration of seawater is said to be about 3.5% overall. This means that there are roughly 35 grams of salt per liter of seawater. By the way, seawater consists of water and salt, with the remaining 96.5% being water.
What percentage of the Earth’s surface is covered by oceans?
- About 30%
- About 50%
- about 70%
See the answer
about 70%
About 70% of Earth’s surface is covered by oceans, totaling approximately 361.06 million square kilometers. Land makes up only about 30%. For this reason, Earth is also called the “Blue Planet.” The words of the astronaut Yuri Alekseyevich Gagarin—“The Earth was blue”—are especially memorable.
Why does the ocean’s water rise and fall—what causes the tides?
- Caused by the gravitational pull of the Moon and the Sun
- It happens because the wind blows strongly.
- It happens because fish gather.
See the answer
Caused by the gravitational pull of the Moon and the Sun
Tides occur mainly because seawater is pulled by the gravitational forces of the Moon and the Sun. This is called “tides” (chōseki), and the Moon has the greatest influence. The seawater on the side of the Earth facing the Moon is lifted by the Moon’s gravity, resulting in high tide.