You are probably already aware that water covers about 97 percent of the entire planet, right? Then maybe you’re familiar with the concept of the water cycle, a necessary process for life on Earth. However, you should know that the water cycle is more complicated than you think, and there are 15 components or elements in the process.

Water is never still. We’re not just talking about currents or tides, but also changes in their physical state: gaseous, liquid, and solid. The hydrological process is the process in which water moves in, on, and under the surface of the Earth, over and over again. Although it sounds simple, it forms the basis of the existence of living beings, as they use it for drinking and therefore, survival.

The Process of the Water Cycle.

We can’t say when and were the hydrological cycle begins because it never stops. However, you can take the oceans as a starting point for understanding the process.

Although usually a smaller number of steps are mentioned, there are about 15 steps or components in the water cycle:

1. Water stored in the oceans.

Most of the world’s water is in the oceans and a small percentage in glaciers and smaller bodies of water: rivers, lakes, ponds, etc. Oceans are therefore a kind of warehouse for a large quantity of the vital liquid and supply nearly 90% of the evaporate water that is part of the water cycle.

2. Evaporation.

It is a process that converts liquid water into gas or vapor, mainly due to solar radiation. This energy from the sun is essential for water to evaporate, which happens when it reaches 100°C, its boiling point.

At this stage, evaporated water joins with the transpiration of plants, so together the process is often referred to as evapotranspiration. Oceans, seas, rivers, and lakes provide nearly 90% of the moisture that evaporates, while plants provide the other 10%. In concrete terms, this state is characterized by the transformation of water into steam in the air.

The hydrological process is the process in which water moves in, on, and under the surface of the Earth, over and over again.

3. Water in the atmosphere.

At this point, the water in vapor form is contained in the atmosphere. The amount of water is still small. Imagine, if all the water in this layer of gas fell to Earth as rain, it would cover the ground with only 2.5 centimeters of water.

4. Condensation.

Water vapor in the atmosphere becomes drops of liquid water. This process creates clouds and fog, and it is the opposite of evaporation.
How does this happen? Well, the water molecules combine with dust, salt, and smoke and form tiny drops that grow and join to develop clouds; this only occurs at high altitude where there is cooler air which allows this process.

5. Precipitation.

The condensed water vapor falls to Earth’s surface as rain, snow, hail, sleet, fog drip, and snow pellets but most of the water from the clouds returns in the form of rain. All these kinds of precipitation happen due to the collision of the particles in water vapor clouds; it takes millions of cloud droplets to produce one raindrop.

6. Water stored in ice and snow.

The water cycle is not exactly a progression because some processes occur at the same time as others. Thus, the water stored in glaciers, ice fields, and snow plays a significant role in the cycle.

7. Meltwater flows into water bodies.

Frozen water flow contributes to the change and flow of rivers, creating movement and sometimes even natural disasters. However, it is a vital component of the water cycle.

8. Surface runoff.

The ground absorbs a portion of the rainwater and other precipitations. The interaction between precipitation and runoff varies according to time and geography, and can be diverted by human means according to need.

The hydrological process.
The process of the water cycle.

9. Streamflow.

The amount of water flowing in a river, stream, or creek. After rain falls, most of the water runs downhill over land in these bodies of water.

10. Stored freshwater.

Naturally, the water that ran into rivers, streams, and creeks remains in these natural “deposits” on the Earth’s surface.

Stored freshwater is vital for the survival of living organisms since physiologically, they are incapable of drinking salt water. Moreover, the amount of water in rivers and lakes is constantly changing.

11. Infiltration.

A small part of the precipitation water infiltrates the soil and rock materials. While some water remains in the most shallow layer, the rest infiltrates deeper and can replenish groundwater.

12. Groundwater discharge.

Some groundwater discharges into streams of surface water.

13. Springs.

Springs are common water bodies where groundwater flows to the surface.

14. Perspiration.

After discharge and storage, water can evaporate again through plants and re- enter the atmosphere.

15. Stored groundwater.

Water stored underground moves slowly. These aquifers are useful, last a long time, and make up a deposit that is part of the water cycle.

The Antarctic Ocean, or the Southern Ocean, is the last ocean to be designated as such. Indeed, not all countries and researchers recognize it even though the U.S. Board on Geographic Names and the International Hydrographic Organization recognizes it already. Its limits were defined by this organization in 2000 but need confirmation from most oceanic agencies and administrations.

It differs from the other oceans as it is the only one that surrounds a continent. It comprises the waters located in the southern hemisphere, whose boundaries are the Antarctic Convergence or latitude 60° south and the Antarctica coast. It covers all the 360° of longitude. It connects the principal southern oceanic basins as well as the sea surface with deeper layers of water.

The Antarctic Ocean, has an area of about 21.96 million square kilometers and includes:

– the Weddell Sea,
– the Lazarev Sea,
– the Riiser-Larsen Sea,
– the Amundsen Sea,
– the Cosmonauts Sea,
– the Cooperation Sea,
– the Davis Sea,
– the Bransfield Strait,
– part of the Drake Passage,
– the D’Urville Sea,
– the Somov Sea,
– part of the Scotia Sea, and
– the Ross Sea.

This ocean has the largest ocean current, called the Antarctic Circumpolar Current.

Properties of the Antarctic Ocean.

This ocean has the largest ocean current, called the Antarctic Circumpolar Current, and since it connects the Pacific, Atlantic, and Indian Ocean basins, it influences the climate of the entire planet. It takes 135-145 million cubic meters of water per second from west to east along 20,000 Antarctic kilometers at a speed of 0.5 meters per second. This current distributes heat and influences rainfall patterns and temperatures.

Properties of the Antarctic Ocean.
Antarctic Ocean.

It has an average depth of 4000-5000 meters and touches around 17,968 kilometers of Antarctic coastline. A continental shelf about 260 kilometers wide and a maximum of 2600 kilometers lies beneath this ocean. 
Its temperature ranges between 10°C and -2 °C, but it has the strongest winds and waves in the world, as the temperature of the ice contrasts the open ocean. During winter, the sea freezes at a latitude 65° south at the Pacific and a latitude 55° south in the Atlantic Ocean sector. During winter most coastal waters are frozen except in some areas.

Salinity is lower in the north, near the Antarctic Convergence where the colder waters flow below, the less cold waters of the Antarctic convergence. This ocean is a huge deposit of carbon and contains about 50 times more than the atmosphere.

Economic Importance of the Southern Ocean.

Due to the low levels of iron and sunlight, productivity is not high. It is rich in nutrients and manganese nodules as well as possible oil and natural gas deposits. It is also home to over 10,000 species, all perfectly adapted to the weather conditions, such as penguins, squids, whales, seals, krill, and a variety of fish.

Fishing is relatively fruitful, being krill and hake the most caught species. Between 2006-2007 for example, 126,976 metric tons of these species were captured.

Illegal fishing affects the sustainability of the sea and reduces the availability of food for other species.

In the Antarctic territory, there are two seaports: McMurdo and Palmer. Offshore, there are a few anchor points. Not all the waters of this ocean are navigable due to the presence of ice blocks. Only a few research boats cross the latitude 60° South since neither private nor commercial navigation is allowed.

Conservation of the Antarctic Ocean.

The increase of ultraviolet radiation, as a result of the ozone hole, is a major concern. The ice whiteness reflects the heat and bounces it back into space, which increases the cold. Some experts think that ultraviolet radiation is responsible for the reduction of phytoplankton, the primary link in the food chain. Besides, illegal fishing affects the sustainability of the sea and reduces the availability of food for other species.

Some organizations implemented guidelines to diminish the abuse of its natural resources. For example, the International Whaling Commission prohibits whaling below latitude 40° South.

Quick facts:

• It covers 20 percent of the surface of all oceans and 4.3 percent of the face of the earth.
• Its narrowest part is the Drake Passage, which has only about 1000 kilometers wide between South 
America and Antarctica.
• It’s the fourth largest ocean.
• The maximum depth corresponds to the South Sandwich Trench, which is 7,235 meters deep.
• The Antarctic Circumpolar Current carries 150 times more water than the flow of all the rivers 
in the world.

If you had to pick an ocean to swim, you would not pick the Arctic, right? That’s because it’s the coldest ocean on Earth, and only the species adapted to its temperature are capable of living there.
 This body of water is the smallest and shallowest of the oceans, and it is in the northern hemisphere. Still, it is 1.5 times larger than the United States. The world “Arctic” comes from the name of the constellation Arktos, which in Greek means “bear.”

Regardless its unbearable cold temperatures, this territory has been inhabited for about 20,000 years by the Inuit and the Yupik, who have physical and physiological adaptations to living in these extreme conditions.

This ocean has an area of approximately 15,558,000 square kilometers and a total of 45,389 kilometers of coastline. It covers about 3.17 percent of Earth’s surface. Its waters touch the northern regions of Alaska, Canada, Norway, Iceland, Russia, and Greenland, and it surrounds several islands. Its area includes Baffin Bay, Barents Sea, the Beaufort Sea, the Chukchi Sea, the Greenland Sea, Hudson Bay, the Kara Sea, the Laptev Sea, the White Sea, Hudson Strait, the Siberia Sea and others. It connects to the Pacific Ocean through the Bering Strait and the Atlantic Ocean through the Greenland Sea and the Labrador Sea. Its southern boundary is the Arctic Circle, at parallel 66°33′ north.

In the Arctic, massive ice sheets of two or three meters thick float around freely, continually shifting due to winds and ocean currents. If these ice chunks collide, they form irregular lines of ice, known as pressure ridges, which can be three times as thick as the individual pieces.

In winter, the temperature fluctuates between -50°C and -1.1°C.

Properties of the Arctic Ocean.

During the summer, the ice caps are surrounded by the ocean, but in the winter they double in size. The Arctic climate is described as polar, characterized by a perennial cold. The islands have a permafrost layer, in other words, a layer of ice on the soil’s surface. Other land regions like Alaska have a tundra biome.

In the winter, the sun is conspicuously absent, the sky is clear, and weather conditions are stable, but summer has permanent sun and humid environments, occasionally pounded by cyclones and snowstorms. In winter, the temperature fluctuates between -50°C and -1.1°C and in summer, the temperature can be up to 10°C. This ocean has the lowest salinity of any ocean due to low evaporation rates and freshwater inflows.

Properties of the Arctic Ocean

The ocean floor has three main underwater ridges:

1. The Nansen-Gakkel ridge, which extends north of western Russia

2. The Alfa mountain ridge, a plane range with peaks of about 3,000 meters.

3. The Lomonosov Ridge, a mountain range between 3,000 to 3,700 meters high.

It is also divided into three large bodies of water, depending on the depth:

1. Arctic Deep Water, the deepest part, beginning at about 900 meters below the surface

2. Atlantic Water, found between 150-900 meters deep and having the same level of salinity as the Arctic Deep Water but warmer.

3. Arctic Surface Water, above 150-200 meters deep and is a subsurface layer with swift currents.

Economic Importance of the Arctic Ocean

The cold conditions do not deter the proliferation of several species there. Narwhals, walruses, belugas, seals, bowhead whales, and Lion’s Mane Jellyfishes, which grow up 2.4 meters long, inhabit the waters of this ocean. Plankton, algae, various fish species, and polar bears also live in this environment.

In the ground, there are vast deposits of oil, natural gas, and metals, which are essential resources for various countries. Its waters are navigable taking the proper care to avoid icebergs; between March and April, ice covers a large part of the ocean. This challenge has become more important as some tests indicate that it could hold more than 25 percent of the undiscovered deposits of oil and gas.

This ocean is also a maritime link between the east and western Russia and North America. However, the center of this ocean is disputed between Norway, Denmark, United States, Canada, and Russia.

Economic Importance of the Arctic Ocean.

Conservation of the Arctic Ocean.

This ocean is evidently affected by climate change as due to the rising of global temperatures, the ice layer gradually thins. The thaw could cause serious flooding in the future, burying some countries under water, pollute some territories because its high concentration of radioactive contaminants, and alter the direction of ocean currents which could cause severe weather disruptions.

Along with the above, animal species would also be affected. Some researchers think that by the year 2040, the Arctic could be entirely melted because the ice pack of this ocean shrinks by eight percent each year.


Quick Facts.

– It is the smallest ocean.
– The Arctic Ocean is the only home of polar bears.
– Its deepest point is the Fram Basin, which has a depth of 4,665 meters.
– It is five times larger than the Mediterranean Sea.
– During summer, its ice shrinks by 50 percent.

The Atlantic Ocean is a huge mass of water covering about 16.7 percent of the Earth and a total area of approximately 85,133,000 square kilometers. To have an idea of its size, it is slightly larger than half of the Pacific Ocean.

This ocean has an average depth of 3,339 meters with adjacent seas, and its volume is 354,700,000 cubic kilometers. Milwaukee Deep is the deepest area, with 8,380 meters.

Its boundaries are the Arctic Ocean in the north, the Pacific Ocean in the southwest, the Indian Ocean in the southeast, and the Southern or Antarctic Ocean in the south. It connects to the Arctic Ocean through the Greenland Sea, the Denmark Strait, the Norwegian Sea and the Barents Sea. Regarding land, it reaches the shores of America in the west and Europe and Africa in the east. The Atlantic Ocean includes the Baltic Sea, the Black Sea, the Caribbean Sea, the Mediterranean Sea, the Gulf of Mexico, and the Norwegian Sea.

The Atlantic is the saltiest ocean in the world.

The northernmost waters sink because they are colder, denser, and saltier than normal due to being cooled by Arctic currents; this creates what is known as “thermohaline circulation” or the “ocean conveyor belt.”

The name Atlantic comes from Atlas, a character from Greek mythology known for holding up the sky on his shoulders.

Properties of the Atlantic Ocean.
Waters of Atlantic Ocean.

Properties of the Atlantic Ocean.

The Atlantic is the saltiest ocean in the world; however, the surface salinity varies with latitude and season. Thus, the saltier waters are at a range of latitude from 25° north to 25° south and in tropical areas of low rainfall and high evaporation. The lowest levels of salinity occur north of the equator.

Temperatures can vary depending on the latitude and the season, but they are about -2 °C. Again, north of the equator, the warmest temperatures are registered while the coldest are in the Polar Regions. Between August and November, hurricanes are common, tending to develop along the coasts of Africa and moving westward into the Caribbean Sea.

The ocean floor is relatively flat but has abyssal plains, ridges, depressions, plateaus, and canyons. In the Labrador Sea, the Denmark Strait, and the coast of the Baltic Sea, the water is usually covered with lots of ice packs between October and June.

Economic Importance of the Atlantic Ocean.

The Atlantic Ocean is the main communication link between Europe and America and has been sailed for many centuries. It has a considerable vessel traffic. At the same time, it has significant oil and natural gas deposits in the sedimentary rocks of the continental shelves, especially in the Caribbean Sea, the Gulf of Mexico, and the North Sea.

The Atlantic is exploited for fisheries, sand, gravel, poly-metallic nodules, and gemstones.

Besides oil and gas, the Atlantic is exploited for fisheries, sand, gravel, poly-metallic nodules, and gemstones. Fishing is plentiful, and the most important fishes are cod, hake, herring, and mackerel.

Conservation of the Atlantic Ocean.

Oil spills pollute the Atlantic Ocean; water drain with toxic substances, and garbage. Some international treaties are concerned about this and have joined forces to reduce the effects. However, many animal species are already endangered such as the manatee, some whales and turtles, sea lions, and seals.


Quick Facts:

• It’s the world’s second largest ocean.
• Among the five oceans, it is probably the last formed on Earth.
• The Ancient Greeks believed that it was an enormous river encircling the world.
• Sometimes, it is called “black Atlantic” for the role it served in the history of dark-skinned 
people, who often traveled from Africa to America by sea.
• In 2013, a crack in the earth’s crust was discovered, it marks the future 
union of the American and European continents and the disappearance of this ocean in about 220 million years.



The Indian Ocean is the third largest, after the Atlantic and the Pacific Oceans. It extends over approximately 9,978 kilometers from southern Africa to Western Australia and is almost six times the size of the United States. Its boundaries include Asia in the north, Africa in the west, Australia in the east, and the Antarctic or the Southern Ocean in the south.

This body of water covers about 19.5 percent of the total water on Earth, or in other words, one-fifth. It covers 13.8 percent of the Earth’s surface. It has an area of 70.56 million square kilometers and includes:

– the Andaman Sea,
– The Arabian Sea,
– the Bay of Bengal,
– the Flores Sea,
– the Great Australian Bight,
– the Gulf of Aden,
– the Gulf of Oman,
– the Java Sea,
– the Mozambique channel,
– the Persian Gulf,
– the Red Sea,
– the Savu Sea,
– the Strait of Malacca, and
– The Timor Sea.

It connects with the Mediterranean Sea through the Suez Canal.

Its volume is 292,131,000 cubic kilometers. Its average depth is around 3,890 meters, and its deepest point is the Java Trench or Sunda Trench, measuring between 7,258 and 7,725 meters. However, sometimes it is mentioned that the Diamantina Trench is the deepest part of this ocean, slightly deeper, about 8,047 meters.

The highest level of salinity is in the Arabian Sea and along a belt of water.

Properties of the Indian Ocean.

Madagascar. Waters of Indian Ocean.

The water salinity in the Indian Ocean is between 3.2 and 3.7 percent. The highest level of salinity is in the Arabian Sea and along a belt of water located between southern Africa and southwestern Australia. It is common to see icebergs at latitude 65° south throughout the year, but their limit is latitude 45° south.

Its surface temperature at latitude 20° south is about 22°C, while in the east can exceed 28°C. From latitude 40° south, water temperatures decrease. Incoming flows from the Atlantic Ocean, the Red Sea, and Antarctic currents control the circulation of water, but the ocean has two basic flow patterns: the northern hemisphere current, which moves to the right, and another stream south of the equator, which moves in the opposite direction.

The weather is variable. North of the equator, it is dominated by a monsoon climate, but in the southern hemisphere, winds are weaker, with occasional summer storms that hit the Mauritius Island. From October to April, there are high winds in the Northeast. The monsoon season causes cyclones that can batter the Bay of Bengal and the Arabian Sea.

This ocean is more recent than the others, so there are crags and ridges in its floor. The South Kerguelen Plateau, a small underwater continent of volcanic origin, is in the south. In the west and near Madagascar, there is an underwater plateau whose length is 2,000 kilometers.

Economic Importance of the Indian Ocean.

The Indian Ocean contains a significant amount of oil and natural gas and is also a source of fish, sand, and metal, relevant to different industries. It has four main waterways: Bab-el-Mandeb, the Strait of Hormuz, the Straits of Malacca, and the Suez Canal.

40 percent of the world’s offshore oil production has its origin in the Indian Ocean.

Marine life is relatively limited in the Indian Ocean due to lower concentrations of phytoplankton. However, the northern part of this ocean is home to a larger number of species, which are essential for human consumption. Fishing fleets from Russia, Japan, Taiwan and South Korea navigate this ocean catching shrimp and tuna.

Moreover, there is a continuous traffic carrying oil from Indonesia and the Persian Gulf, with an average of 17 million barrels of oil per day. In fact, 40 percent of the world’s offshore oil production has its origin in the Indian Ocean.

Conservation of the Indian Ocean.

In the late 90’s, a huge quantity of trash was found, suspended on the surface of the Indian Ocean. Thousands of plastic particles, chemical substances, and other garbage are concentrated there, covering about 10 million square kilometers. Meanwhile, the Arabian and Red Seas and the Persian Gulf are contaminated with hydrocarbons from oil and gas.

The ocean is home to some endangered species: the dugong, whales, seals, and turtles.


Quick facts:

• It is the warmest ocean basin on Earth.
• Annually, more than 7,000 humpback whales travel to the waters of Madagascar to breed and give birth.
• The world’s earliest civilizations developed around the Indian Ocean.
• In Sanskrit literature, it is known as “Ratnakara” which means “gemstone mine.”

The Pacific is the largest ocean on Earth; its name comes from the explorer Ferdinand Magellan when sailing the mighty winds of the Atlantic, found calm and favorable winds. Thus he named it “Pacific Ocean.”

This enormous mass of water ranges from the Arctic Ocean to the Antarctic or the Southern Ocean, from the Bering Sea in Alaska to the Ross Sea in Antarctica. It meets the Atlantic Ocean through the Bering Strait in the north and the Drake Passage and the Strait of Magellan in the south. It borders Asia and Oceania in the west and the Americas in the east.

The Pacific Ocean is two times bigger than the Atlantic and also contains twice the volume of water.

In simple terms, the Pacific Ocean is two times bigger than the Atlantic and also contains twice the volume of water: 714 million cubic kilometers. It occupies an area of about 161,760,000 square kilometers and includes the Bali Sea, the Bering Sea, the Gulf of Alaska, the Gulf of Tonkin, the Coral Sea, the East China Sea, the Philippine Sea, the Sea of Japan, the South China Sea, and the Tasman Sea.

Its widest point is at a latitude about 5° north, and its deepest point corresponds to the Mariana Trench, which is about 11.3 kilometers deep.

Characteristics of the Pacific Ocean.

The salinity of ocean water is variable and depends on three factors: winds, precipitation, and evaporation. High salinity values are when there are more than 35 parts per thousand or 3.5 percent and low values, less than 3.5 percent. Given this information, the lowest salinity is found in the extreme northern areas of the ocean (3.2 percent) and the highest occurs in the southeast, where the water reaches up to 3.7 percent. When there is more rainfall, the salinity decreases and when the evaporation increases the salt concentration increases too.

Pacific Ocean.

The temperature of the Pacific Ocean is related to the “layer” of water. Each layer has a different temperature; therefore the lower ones are cooler than, the higher ones, obviously. The temperature of the surface layer, which is between 300 and 900 meters, are very different than the temperatures of the deepest layer, which may be near freezing. Average temperatures range between -1.4°C and 30°C, the latter present in areas close to the equator. In general, the North Pacific is warmer than the South Pacific.

In this ocean, there is a lot of volcanic activity and earthquakes because the “Ring of Fire” surrounds it. From May to December is the tropical cyclone season in South Asia, and from June to October is hurricane season in the American continent, in an area ranging from southern North America to northern Central America. The North Pacific surface currents move clockwise while in the South Pacific, they move in the opposite direction.

Economic Importance of the Pacific Ocean.

The Pacific contains significant deposits of oil and gas, and its waters are home to thousands of important edible species in the fishing industry. It is also a source of minerals, sand, and metal for the construction business. In 1996, approximately 60 percent of the fishing was done in the Pacific Ocean, and its oil reserves have an essential role in the energy supply of the countries bordering its waters.
The Pacific’s waters are used to provide transportation services east to west; strategic navigation routes are in Taiwan, Singapore, and the area known as the Torres Strait, located in Oceania.

The Pacific Ocean is shrinking by one centimeter per year as a result of the movement of tectonic plates.

Conservation of the Pacific Ocean.

The Pacific Ocean is shrinking by one centimeter per year as a result of the movement of tectonic plates. In 2000, the International Hydrographic Organization declared the recognition of a fifth ocean, the Antarctic or the Southern Ocean, reducing a part of the South Pacific.

This ocean is subject to one of the most serious pollution incidents in history; in its waters, there is the Garbage Island or the Great Garbage Patch, a sort of territory made up of waste, mostly plastics. The situation is precarious since thousands of animal and plant species live in the area and the environmental risks that this implies.

Pacific waters are home to some species endangered including sea lions, otters, dugongs, seals, turtles, and whales.


Quick Facts:

• If all continents could be placed over the Pacific Ocean, there would still be room to spare.
• It covers one-third of the Earth’s surface (33.1%).
• It’s about 15 times larger than the United States.
• The Great Barrier Reef, located in the Pacific Ocean, is the world’s largest reef.

The Oceans are large bodies of water that seem to keep many secrets. Even today, while a considerable knowledge exists about the properties and life that develops near the surface, there is still much to discover in its depths.

According to various criteria, researchers have divided the oceans to differentiate the life that exists there and to facilitate their study:

Ocean zones according to their density

Density is the mass quantity by volume of a substance, in this case, the seawater.

Surface zone or Mixed Layer.

In this layer, the temperature and salinity of the water are continuously changing due to the direct contact with air. Thus, reduction of the air temperature also causes lower surface temperatures.

The Pycnocline.

Changes in density do not frequently occur in this zone because there is not much movement in this area, and it is not in direct contact with air or with the ocean floor.

The Deep Zone.

The water of this layer is colder and denser than in the other areas.

The ocean is divided into three main areas: pelagic, demersal and benthic.

Ocean zones by depth

It is more common to classify the ocean layers according to their depth because many species are categorized according to the depth zone where they inhabit. Have you heard that there are deep-sea fish? They have this name precisely because they live in the abyssal zone.

The ocean is divided into three main areas: pelagic, demersal and benthic, depending on the sunlight that reaches the water and illuminates below the surface.

Ocean zones

1. Pelagic Zone

In Greek, the word means “open sea.” Pelagic is the upper layer of the oceans and covers about 360 million square kilometers of the Earth, and its volume is about 1,330 million cubic kilometers. It has a mean depth of 3.68 km. And a maximum depth about 11 kilometers. It is also called the “open-ocean zone,” and the species that live there are called “pelagic.” The pelagic zone has the following areas:

a. Neuston zone.

The neuston zone is the area that is in direct and immediate contact with air and extends to 1 meter deep. The word neuston refers to the microscopic organisms that live right in this area. It is rich in plankton; so many animals that live in lower areas tend to climb here to feed. Some authors do not consider the neuston area as an individual part of the pelagic zone.

b. Epipelagic zone.

The epipelagic zone is the surface layer extending to 200 meters deep and reaching about 60 kilometers off the coast. It is an area with lots of sunlight and home to numerous species, apparently more than any other.

c. Mesopelagic zone.

This area ranges from 200 to 1,000 meters deep. It is also known as the “twilight zone.” The temperature varies less than in the epipelagic zone, but similar to a thermocline region, meaning that the temperature varies with depth. Sunlight penetrates to a lesser extent, and from here downward some fish manifest bioluminescence. Octopuses, squid, and fish inhabit this zone.

d. Bathypelagic zone.

This zone extends from 1,000 to 4,000 meters deep. Sunlight does not reach this area, and there is an intense hydrostatic pressure. Its temperature is constant and freezing, around 4°C. About one percent of oceanic species live in this zone, and because of this, food is scarce for those who do live there.

abyssal zone.

e. Abyssalpelagic zone.

It comprises the region between 4,000 and 6,000 meters deep. As expected, its temperature is constantly cold, 2°C to 3°C. Life is very scarce because there are very few nutrients around, but some creatures can withstand the dark and pressure of this zone and can bear up to 76 megapascals of pressure.

f. Hadalpelagic Zone.

The hadalpelagic zone is the deepest part of the ocean, with a temperature barely above the freezing point. Sunlight does not penetrate to this depth, and nutrients are very scarce, though some unicellular organisms, worms, and sea cucumbers live there. It extends beyond 6,000 meters deep.

2. Demersal zone

The demersal zone is located near the ocean bottom layer and above the benthic zone. The species found in the demersal layer usually look for food on the seabed or feed on other demersal species.

3. Benthic zone

The benthic zone is the layer at the very bottom of the ocean floor, comprising the surface region and some sediment layers beneath the surface layer. It contains low levels of oxygen and cold temperatures.

Ocean currents are continuous and directed movements of water produced by multiple factors. Currents can happen in rivers, lakes, swamps and other water systems, although in the oceans, because of their size, a higher number and stronger currents exist.

These ocean currents flow over long distances and sometimes significantly influence life on Earth. What changes their direction and strength? The topography of the seabed, their interaction with other currents, and the configurations of the shorelines.

Causes of ocean currents

The effect of several factors acting over the water that generates currents like the wind, the rotation of the Earth, the gravitational force of the moon, differences in temperature and salinity, the topography (shape) of the seabed, the heat from the sun, etc. Let’s review the three most important factors that generate currents:

1. Wind.

Drives currents that are near or on the water surface. Seasonal winds push surface waters away from the coast, so the water rises in the western edges of continents.

2. Tides.
Tides, created as the result of the gravitational pull of the moon and the sun, create currents near the coasts, bays, and estuaries. Their pattern is regular. Therefore changes are predictable.

3. Thermohaline Circulation.

Density differences, due to salinity and water temperature differences, drive this flow. It causes the bottom topography influence on deep currents.

Types of ocean currents:

Surface Currents.
The wind usually drives them and are almost 8-10 percent of ocean water. In the northern hemisphere, they move in a clockwise direction, but in the southern hemisphere, they move in the opposite direction. These waters are rich in nutrients, causing a large population of marine life to inhabit there.

Types of ocean currents.

Surface currents can be of two types:
1. Warm, ranging from the tropics to high latitudes and
2. Cold, originating in polar and temperate latitudes and flow toward the equator.

When several ocean currents are connected, they form the so-called gyres, in which water moves in a circular pattern while maintaining the clockwise motion in the northern hemisphere and the opposite in the southern hemisphere.

Deep Currents.
Also called submarine rivers; they flow at more than 100 meters deep and move because density differences about salinity and temperature.

Coastal Currents.
The wind blowing along the coast affects the waves and these, in turn, the currents.

Tidal Currents.
They are the result of the high tides and the low tides. When tides close to the shore move vertically, up or down, they move water horizontally, creating currents. These are the only type of currents generated by the gravitational attraction between the sun, Earth, and moon.

Ocean currents affect the regional climates, marine life, and the cycle of nutrients in the water.

The importance of Ocean Currents.

Ocean currents affect the regional climates, marine life, and the cycle of nutrients in the water. In this regard, the transport of nutrients promotes the prosperity of many species of plants and marine animals, and sediment transport or harmful particles in the surface currents gives an overview of the effects of pollution and its causes.

Moreover, the preparation of navigation by observing the direction of the currents ensures safe travels. In the case of shipwreck, rescuers can determine the location of the missing persons.

It is also important to note that the currents generate high temperatures in parts of Western Europe and promote plant and animal life in Antarctic waters.

Examples of ocean currents.

In the world, there are several ocean currents, like
– Antarctic Circumpolar Current.
– Eastern Australian Current.
– Gulf Stream.
– California Current.

Definition of Tides.

Tides are increases and decreases in the sea level. Surely you’ve noticed this because it is a common and easily witnessed phenomenon. For a while, a boat floats near the shore, and after a few hours, the boat rests on the sand. When this occurs it is said that is low tide, and when the opposite happens, it is said that the high tide.

There are four stages of tides:

1. Sea level rises gradually over several hours.
 Flood tide.
2. The water level is at its highest level.
 High tide.
3. Sea level falls slowly for several hours. Ebb tide.
The water stops falling reaching its lowest level. Low tide.

The tides are not unique in the oceans; they can occur in other water systems as long as the required conditions happen.

Types of tides

There are two types of tides: high tide and low tide. Also, tides may be semidiurnal or diurnal. These tides have one tidal cycle per day, meaning one low tide and one high tide, while the semidiurnal tides have two high tides and two low tides per day.

Causes of tides

The tidal phenomenon was the subject of various theories until Sir Isaac Newton in 1687 explained that tides are the result of the gravitational attraction of the moon and the sun. However, first things first.

Some factors influence tides called tidal constituents. They are the rotation of the Earth, the position of the moon and the sun to our planet, and the shape of the shore and the seabed. Thus, the duration of the tides and their amplitude depend on these components and can last hours.

Definition of Tides

According to the mass of the objects, and the distance between them, the gravitational force varies; this is the fundamental principle for understanding the cause of tides. Knowing this, the moon’s gravitational pull on the Earth is the primary component. The moon’s gravitational pull is so strong that it “pulls” the oceans, creating a lump. This pull is stronger on the side of the planet facing the moon because it’s where the moon and Earth are closest.

The force of inertia (property of staying in rest or motion) tries to keep the water at its normal level. Also, Earth rotates continuously generating a centrifugal force which causes oceans to protrude on the on the opposite side of the moon.

Tides are essential to generate tidal energy through turbines or other methods that generate electricity.

The inertia exceeds the gravitational pull and in short, two bulges of water that align with the moon are created as the Earth turns.
Oceans protrude two times in one period when they are on the side of the Earth closest to the moon and again when they are on the far part of the planet. In coastal areas, high tide occurs approximately every twelve hours and 25 minutes. If the moon is above your head and you’re on the coast, you should see high tide.

Tides are essential to generate tidal energy through turbines or other methods that generate electricity. Tidal energy is a renewable, clean energy and contributes to sustainability. Tides are also relevant for sea travel, and thus they are placed in nautical charts, indicating the direction and the speed that ships must observe during high and low tides.


Quick Facts:

The Tsunamis, are not related to tides.

There are tide-measuring stations that measure, describe, and predict tides.



A Tsunami is a series of gigantic water waves that causes a surge of water onto land. These surges can reach heights up to 100 feet. The massive height of the surges can lead to devastating effects when it crashes over land. It can occur in large lakes but mainly occurs in seas.

Here are some terms that are associated with tsunamis:

Tide: The term ‘tide’ refers to the alternate rising and falling of the sea level at shores.

Seismic waves: Seismic waves of energy that travel through the Earth’s crust layers or plates, and are a result of an earthquake or a volcano eruption which can lead to causing tsunamis.

Surge: A surge of water is a strong swelling volume of water.

Earthquake: A sudden and violent movement of a portion of the earth’s crust, and the series of vibrations that follow.

Earth’s crust: This is the solid thin layer that covers the outside of the earth. Is the solid layer upon which we live. To put it in perspective, think of it as the skin on the outside of an apple.

Plate: A plate is a section of the earths crust. Plates slide along either beside, over or under each other, causing friction and pressure between the plates.

Teletsunami: A tsunami which causes damage a long distance away from the source has been given the name ‘teletsunami’. These types of tsunamis are not produced by horizontal motions, but by vertical motions in the seabed.

Tsunami waves are caused by large underwater earthquakes where there are tectonic plate boundaries. They can also be caused by volcano eruption under the ocean or lake. Even giant landslides have been known to cause large tidal waves or tsunamis in the past.

Tectonic plates are sections of the earth’s crust that move against each other.

When the pressure of the tectonic plate at the ocean floor releases pressure, it causes the water above to create a series of rolling waves which will build up to cause more turbulent and fast moving waves. These waves will turn into one large wave and will eventually result in a tsunami.

Tsunamis do not appear as a breaking wave. Initially it may resemble a tide that is rising rapidly. Tsunamis generally consist of a series of waves with periods ranging from minutes to hours, arriving in what can be called a “wave train”.

Tsunami Facts and information
Tsunami in Morocco

The Pacific Ring of Fire

Almost 80 percent of tsunamis occur within the Pacific Ocean’s ‘Ring of Fire’. This is due to the amount of earthquake and volcanic activity in the area, which occur due to the tectonic shifts in the earth’s plates.

Tsunamis can reach speeds up to 500 miles per hour, racing across the sea. That is about as fast as a jet plane! Tsunamis can travel the entire length of the Pacific Ocean in less than a day. There is virtually no energy lost along the way due to their extremely long wavelengths.

The formation of a Tsunami

When tsunamis begin to form, they only appear a foot of so high in the deep ocean. This makes them impossible to distinguish. The closer they get to the shoreline and enter shallower water, their energy and height grow to drastic measures. The speed and momentum increases due to the top of the waves moving faster that the bottom does.

The lowest point under the wave usually reaches the shore first. When it reaches the shore, it produces what is described as the ‘vacuum effect’, which sucks the coastal water into the sea and gives the opposite effect of a tsunami. When this occurs, the sea floor is left completely waterless and the seafloor is totally exposed. This is the first sign a tsunami is about to hit.

The next stage causes the most serious and devastating effects. About five to ten minutes after the water retreats, the tsunami will hit. This gives people little time to escape the wrath of the tsunami; however the warning can save lives. When a tsunami hits it is important for people to remember that the danger may not have passed with the first wave or two. The aftershock of earthquakes can cause more waves to occur, sometimes even hours after the initial wave hits. The best defense against any tsunami is early warning that allows people to seek higher ground.

Pacific coastal countries are some of the most Tsunami prone areas in the world. Here is a list of some of the countries who have been affected or that could be affected by tsunamis:

  • Japan
  • United States
  • Mexico
  • Philippines
  • Russia
  • Ecuador
  • China
  • Chile
  • Papua New Guinea
  • Maldives
  • Indonesia
  • Italy

Problems caused by Tsunamis

Tsunamis can cause great loss of life and a serious decrease in population. Drowning is the most popular cause of death when a tsunami hits. Here are some dangers it can cause to the environment.

  • Shipwrecks can be left ashore when tsunamis hit. This can cause major pollution and can take time and money to remove.
  • Animals can be washed up to shore and die.
  • They can also flood the lands near the shore. This leaves crops damaged and the community can suffer from a lack of food and work.
  • Some people might left be trapped under buildings for long periods of time while search and rescue teams attempt to get a hold on the situation. The damage can be so great that people often die while trapped.
  • Tsunamis can cause economic decline as they have to spend a lot of money rebuilding the houses and restoring the original landscape. As the devastation can occur in very poor countries, there is usually not be enough help or money to completely rebuild entire livelihoods.
Water wave facts
Tsunami Recreation

Strongest Tsunami in history

One of the most well known and recent incidence of a tsunami was in Indonesia, on the 26th of December 2004. A 9.3 magnitude earthquake triggered a series of giant tsunamis along the coasts of most landmasses that bordered the Indian Ocean. This was also one of the largest earthquakes recorded. It killed over 230,000 people in fourteen different countries. It was recorded as one was one of the worst natural disasters in history. Indonesia was hit the hardest and Sri Lanka, Thailand and India also suffered greatly.

Due to the distances involved, the disastrous tsunami took between fifteen minutes and seven hours to reach the all the different coastlines. The tsunami took seven hours to hit Somalia. Sumatra, and Indonesian island was hit very quickly especially in the northern regions. The east coast of India and Sri Lanka were hit somewhere between 90 minutes to two and a half hours later. Thailand was hit around two hours later despite the fact that it was closer to the epicentre The reason for this is because the water was more shallow in the Andaman Sea, which is off the western coast.

The earthquake which caused the tsunami affected many countries even beyond Southeast Asia. These other countries included Sri Lanka, India, Malaysia, Thailand, Myanmar, the Maldives, Seychelles, Somalia, Tanzania and South Africa. Australia and Europe had a large number of their citizens in the region at the time of the disaster, along with many other countries. There were 543 Swedish people and 539 German people lost in the disaster.


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