What Is the Ocean?

Ocean is a vast body of salt water that covers more than 70 percent of the Earth’s surface. It is one of the main components of Earth’s hydrosphere, along with rivers, lakes, and wetlands. Oceans help regulate the climate of our planet by absorbing and storing heat from the sun, distributing it around the globe, and regulating temperature. Oceans are also home to a diverse range of marine life, including microscopic plankton and various species of fish, mammals, and plants.

Oceans are divided into several zones based on physical and biological properties. The first, the photic zone, is at or near the surface where light can penetrate to some depth. This zone is where most ocean creatures live, as they need sunlight for photosynthesis (the process that provides food for the ecosystem).

The next layer down, the mesopelagic zone, begins at about 200 meters (655 feet) below the surface. This is a cold and dark zone where only a tiny fraction of the light that reached the surface can penetrate. This is where most of the deep-sea fish live, but it is also the primary habitat for some microscopic plankton.

At depths beyond the mesopelagic zone, the aphotic zone starts. This is a very dark, almost black area where only a little bit of the light that reached the surface can penetrate. The rest of the depths below this zone are too dark to support photosynthesis and are not considered a part of the marine biome.

There are many human activities that take place in the ocean. These include recreational and commercial fishing, shipbuilding and naval warfare, travel, shipping and trade, power generation (e.g., marine energy and offshore oil and gas drilling), freshwater production through desalination, and exploration of minerals. Human activity can have a negative impact on ocean ecosystems through marine pollution, overfishing, climate change, and more.

Plate tectonics plays an important role in shaping the oceans. It can create and destroy oceanic crust, form underwater mountain ranges, cause volcanic eruptions, and generate earthquakes. The movement of these plates also changes ocean currents and can change sea levels.

The oceans are a dynamic, ever-changing part of our planet. Learn more about the five oceans that make up our world, and find out how you can protect them.

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