All About Oceans
There are five main oceans on Earth: Pacific, Atlantic, Indian, Arctic, and Southern. About 70% of the Earth is covered with the salt water in the oceans and in smaller seas such as the Red Sea, Caspian Sea, Black Sea and several others. Whether it is a sea or an ocean, both contain salt water. Most of the seas are surrounded by land and there is one spot that opens to one of the larger oceans. In the ancient past, people were familiar with the Seven Seas of the world, with each of the seven being different depending on the time-period in history and the place. Ancient people in one part of the world did not know about oceans, seas, or continents in another part of the world.
The oceans and the seas are what divides many of the seven continents by thousands or hundreds of miles. In fact, the Earth is covered by one giant ocean with only the continents separating the differently named oceans.
Though there are different oceans, nearly all of them have several common characteristics. For example, there are waves, tides, ocean floors, and much more. Of course, if the ocean is frozen like the Arctic or the Southern Ocean, there are no waves, but there is still an ocean floor and many other common characteristics.
Every ocean has water, salt, floor, coastlines, depth, living and non-living things, and much more. People use the oceans for transportation, fishing, exploring, natural resources, and for many other reasons such as swimming, surfing, collecting seashells and more.
Water in oceans is always moving and one type of motion is called waves and are places where water above the surface is higher. Most waves are caused by the wind blowing over the ocean's surface as it pushes the water and water piles up to form a wave. The stronger the wind the higher the waves and they can travel for miles. Breaking waves are those that 'fall over' at the top usually with some white foam along the water.
A tide is the rising and falling of the oceans or seas, usually twice each day. The gravitational pull of the moon is responsible for creating ocean tides. The moon's gravity pulls the ocean water towards the side of the Earth facing the moon, and at the same time, the rotation of the Earth causes water to move away from the side of the Earth that is away from the moon. There is a high tide and a low tide, and the times change about 50 minutes each day.
All oceans have depth as well. The Continental shelf is a flat area around the continent and is about 500 feet deep. Abyssal plains are very flat areas beyond the shelf and are 7,000 to 18,000 feet deep and cover about 40% of the ocean floor. The continental slope and rise are like the sides of mountains between the shelf and plain. Finally, trenches are the deepest parts of oceans, and the Pacific Ocean has the most and is where volcanic and earthquake activity take place. The Mariana Trench is the deepest in the world in the Pacific Ocean- 36,163 feet deep.
Every ocean and sea have a floor or bottom as well. The ocean bottom near the land is usually rocky or sandy and during low tide more of the land is exposed, while during high tide the water covers more land. Coastal wetlands are a marine environment that exists in shallow saltwater near shores, and the bottom of wetlands includes sediment that accumulates from nearby land. Coral reefs thrive in warm climates and in shallow waters and warm tropical waters. The abyssal plain is covered with sediment and few plants live in the muddy, dark, and high-pressure environment. There are also underwater volcanoes that discharge scalding hot water and mineral mud from hydrothermal vents.
And of course, all oceans are salty, but billions of years ago the ocean waters were not salty. Water comes into the ocean by rain, rivers and streams, and groundwater. As the water flows across the land, it collects minerals from rocks, and as volcanoes erupt in the ocean other chemicals are released resulting in sodium and chlorine to make salt. Ocean water is 96.5% pure, 2.9% salt, and rest is a mixture of other chemicals & minerals.
The oceans of the world are important resources for many people, have an influence on the lives of people throughout the world, and contain 97% of the all the water found on Earth. In addition, 80% of the world's population lives within 60 miles of an ocean coast. Finally, the oceans are so large that only about 5% of the ocean has been explored. The other 95% remains a mystery.
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