Tag: Basics

Natural History / Natural History - 9 years ago

What are tides?

The rise and fall of the tides play an important role in the natural world and can have a marked effect on maritime-related activities. The image aboves shows the NOAA San Francisco Tide Station, in operation for more than 150 years. Tides are...

Natural History / Natural History - 9 years ago

Why do we have oceans?

Over vast periods of time, our primitive oceans formed. Water remained a gas until the Earth cooled below 212 degrees Fahrenheit. At this time, about 3.8 billion years ago, the water condensed into rain which filled the basins that are now our oc...

Natural History / Natural History - 9 years ago

How many oceans are there?

While there is only one global ocean, the vast body of water that covers 71 percent of the Earth is geographically divided into distinct named regions. The boundaries between these regions have evolved over time for a variety of historical, cult...

Natural History / Natural History - 9 years ago

How does sound travel in the ocean?

Water temperature and pressure determine how far sound travels in the ocean. While sound moves at a much faster speed in the water than in air, the distance that sound waves travel is primarily dependant upon ocean temperature and pressure. Wh...

Natural History / Natural History - 9 years ago

Why is the ocean blue?

Big Sur coastline looking north to Bixby Canyon Bridge in California. The ocean is blue because water absorbs colors in the red part of the light spectrum. Like a filter, this leaves behind colors in the blue part of the light spectrum for us...

Natural History / Natural History - 9 years ago

How much water is in the ocean?

The ocean covers more than 70 percent of the surface of our planet. It's hard to imagine, but about 97 percent of the Earth's water can be found in our oceans. Of the tiny percentage that's not in the ocean, about two percent is frozen up in g...

Natural History / Natural History - 9 years ago

Why is the ocean salty?

Some areas of the ocean are saltier than others. This image shows methane mussels living at the edge of a underwater brine pool in a cavern at a depth of 650 feet in the Gulf of Mexico. The pool of brine in the foreground is nearly four times as...

Natural History / Natural History - 9 years ago

What is a sonar?

A three-minute video about multibeam and side scan sonar, including a visualization that shows how sonar data is used to make products like nautical charts. | Download: Soundscapes (75 MB) Sonar, short for Sound Navigation and Ranging, is he...

Natural History / Natural History - 9 years ago

What is hydrography?

By mapping out water depth, the shape of the seafloor and coastline, the location of possible obstructions, and physical features of water bodies, hydrography helps keep our maritime transportation system moving safely and efficiently. Download...

Natural History / Natural History - 9 years ago

Is sea level rising?

With continued ocean and atmospheric warming, sea levels will likely rise for many centuries at rates higher than that of the current century. In the United States, almost 40 percent of the population lives in relatively high-population-density c...

Natural History / Natural History - 9 years ago

What is an estuary?

Estuaries: Where the River Meets the Sea Get to know estuaries with this two-minute video. Estuaries and their surrounding wetlands are bodies of water usually found where rivers meet the sea. Estuaries are home to unique plant and animal c...

Natural History / Natural History - 9 years ago

How deep is the ocean?

The Spanish Dancer, a type of sea cucumber, hovers at 9,150 feet near the Davidson Seamount off the coast of California. That's 1.7 miles down! The average depth of the ocean is about 12,100 feet. The deepest part of the ocean is called the Ch...