The Pacific Ocean is the largest and deepest of the world's five oceans with an area of 60.06 million square miles (155.557 million square kilometers.) It stretches from the Arctic Ocean in the north to the Southern Ocean in the south. It also sits between Asia and Australia as well as between Asia and North America and Australia and South America.

With this area, the Pacific Ocean covers about 28% of the Earth's surface and it is, according to the CIA's The World Factbook, "almost equal to the total land area of the world." The Pacific Ocean is usually divided into the North and South Pacific regions with the equator serving as the division between the two.

Because of its large size, the Pacific Ocean, like the rest of the world's oceans, was formed millions of years ago and has a unique topography. It also plays a significant role in weather patterns around the globe and in today's economy.

Formation and Geology

It is believed that the Pacific Ocean formed about 250 million years ago after the break-up of Pangaea. It formed out of the Panthalassa Ocean that surrounded the Pangaea landmass.

However, there is no specific date on when the Pacific Ocean developed. This is because the ocean floor constantly recycles itself as it moves and is subducted (melted into the Earth's mantle and then forced up again at ocean ridges). Currently, the oldest known Pacific Ocean floor is about 180 million years old.

In terms of its geology, the area encompassing the Pacific Ocean is sometimes called the Pacific Ring of Fire. The region has this name because it is the world's largest area of volcanism and earthquakes.

The Pacific is subject to this geologic activity because much of its seafloor sits above subduction zones where the edges of the Earth's plates are forced down below others after a collision. There are also some areas of hotspot volcanic activity where magma from the Earth's mantle is forced up through the crust creating underwater volcanoes, which can eventually form islands and seamounts.

Topography

The Pacific Ocean has a highly varied topography that consists of oceanic ridges, trenches, and long seamount chains that are formed by hotspot volcanoes under the Earth's surface.

An example of these seamounts that are above the ocean's surface are the islands of Hawaii.

Other seamounts are sometimes below the surface and they look like underwater islands. The Davidson Seamount off the coast of Monterey, California is just one example.

Oceanic ridges are found in a few places in the Pacific Ocean. These are areas where new oceanic crust is being pushed up from below the Earth's surface.

Once the new crust is pushed up, it spreads away from these locations. In these spots, the ocean floor is not as deep and it is very young compared to other areas that are farther from the ridges. An example of a ridge in the Pacific is the East Pacific Rise.

By contrast, there are also ocean trenches in the Pacific that are home to very deep locations. As such, the Pacific is home to the deepest ocean point in the world: the Challenger Deep in the Mariana Trench. This trench is located in the western Pacific to the east of the Mariana Islands and it reaches a maximum depth of -35,840 feet (-10,924 meters.)

The topography of the Pacific Ocean varies even more drastically near large landmasses and islands.

Some coastlines along the Pacific are rugged and have high cliffs and nearby mountain ranges, such as the west coast of the United States.

Other coastlines have more gradual, gently sloping coastlines.

Some areas, such as the coast of Chile, have deep, quickly dropping trenches near the coasts, while others are gradual.

The northern Pacific Ocean (and also the northern hemisphere) has more land in it than the South Pacific. There are, however, many island chains and small islands like those in Micronesia and the Marshall Islands throughout the ocean.

The largest island in the Pacific is the island of New Guinea.

Climate

The climate of the Pacific Ocean varies greatly based on latitude, the presence of landmasses, and the types of air masses moving over its waters. The sea surface temperatures also play a role in the climate because it affects the availability of moisture in the different regions.

Near the equator, the climate is tropical, wet and warm throughout most of the year.

The far North Pacific and far South Pacific are more temperate and have greater seasonal differences in weather patterns.

Seasonal trade winds impact climate in some regions. The Pacific Ocean is also home to tropical cyclones in areas to the south of Mexico from June to October and typhoons in the South Pacific from May to December.

Economy

Because it covers 28% of the Earth's surface, borders many nations, and is home to a wide variety of fish, plants, and other animals, the Pacific Ocean plays a major role in the world's economy.

It provides an easy way to ship goods from Asia to North America and vice- versa through the Panama Canal or the northern and southern ocean routes.

A large portion of the world's fishing industry takes place in the Pacific.

It is a significant source of natural resources, including oil and other minerals.

Which States the Pacific?

The Pacific Ocean forms the western coast of the United States. Five states have a Pacific coastline, including three in the lower 48, Alaska and its many islands, and the islands that comprise Hawaii.

Alaska

California

Hawaii

Oregon

Washington

Environmental Concerns

A giant patch of floating plastic debris, known as the Great Pacific garbage patch or the Pacific trash vortex, is actually made up of two giant patches of plastic garbage, some of it decades old, floating in the Northern Pacific between California and Hawaii.

The plastic is thought to have accumulated from fishing vessels, illegal dumping and other means over the decades from countries in North and South America and Asia. Currents have trapped the ever-growing debris in a vortex that varies in size.

The plastic isn't visible from the surface, but some pieces have killed marine life who have become trapped in netting. Other pieces have become small enough to become digestible to animals and have entered the food chain, affecting hormone levels, which can eventually lead to an effect on humans who consume seafood.

The National Oceanic and Atmospheric Administration notes, however, that there is currently no evidence that the human harm from microplastics from ocean sources is worse than that from other known sources, such as plastic containers.