What Is the Difference between a Sound and a Bay?

Mary McMahon
Mary McMahon
Mary McMahon
Mary McMahon
The mouth of the San Francisco Bay is narrower than the bay itself.
The mouth of the San Francisco Bay is narrower than the bay itself.

Sounds and bays are both indentations in the shoreline along an ocean which take the form of naturally protected harbors. They are formed by glaciers, erosion, and sometimes the hand of man. The terms are often used interchangeably, and there are no governing rules about naming such places in English, other than convention. The habit of using the terms interchangeably, however, can be confusing to people who are trying to get a mental image of the geographic feature under discussion. There are a few small differences between the two which can help distinguish a sound from a bay.

Fishing communities will often base their fleets in sounds and bays as a means of providing protection for their ships.
Fishing communities will often base their fleets in sounds and bays as a means of providing protection for their ships.

A sound is an inlet of the ocean substantially larger than a bay, and it may be less protected. Sounds are often characterized by large open spaces of water. A sound can be deeper than a bay, and is certainly deeper than a bight, a name for a shallow ocean inlet. It is also substantially wider than a fjord, an inlet formed along a shoreline by retreating glaciers.

On some maps, a channel or strait between two bodies of land is identified as a sound; some definitions require a sound to have at least two entrances. This is the case with Long Island Sound, the body of water separating Long Island from neighboring Connecticut. It is also probably an example of the original usage for the word "sound" in regards to geographical features, as the word derives from an Old English word meaning "to swim," suggesting that a person could potentially swim across a sound.

A bay, on the other hand, is a inlet of water enclosed on three sides by the land. The mouth of a bay may be narrower than the bay itself, as in the San Francisco Bay, or it can be much wider, gaping out into the open ocean. The Bay of Biscay, for example, has a very wide mouth, but it is still recognizably surrounded on three sides by land. Bays also tend to be more shallow than sounds, and some of them have to be dredged to admit ship traffic.

Both bodies of water are important geographical features, especially for sailors. Many fishing communities base their fleets in sounds and bays, so that their ships will be protected, and sailors looking for anchor take advantage of the sheltered environment to take a rest from the open ocean. Major port cities are almost universally located along the shoreline of either a sound or a bay, to facilitate a large area for docking so that the city's trade can thrive.

What Is a Sound in Geography? 

There are two different types of sounds. While both types are large bodies of seawater, they have unique qualities.

  • Island Sound – Sometimes, ocean water fills over low-lying land, separating a small portion from the mainland. The water between the nearby island and the mainland is considered a sound. There can be many small islands within a sound. This type of sound has two entrances, one on each side of the island. 
  • River Valley – The second type of sound is formed where seawater meets an outflowing river. When the river valley has tall mountains on each side, the seawater fills in the area creating a sound. Some of these sounds have been created by glacial movement instead of a river cutting through the land. This type of sound only has one entrance, and many are ideal locations for harbors because the water can be deep through the river valley. 

How Many Sounds Are in North America?

The United States and Canada are both popular locations for sounds. While there are 39 sounds in the U.S., the majority are on the east coast between North Carolina and Virginia. This location is commonly called the Outer Banks for the series of shallow islands that create five named sounds.

Albemarle sound is one of the largest areas and makes a fantastic fishing economy for the states. The other sounds are Pamlico Sound, Currituck Sound, Roanoke Sound and Croatan Sound.

Most of Canada’s sounds are located on its west coast near British Columbia and Washington. With a total of 29 sounds, many contain clusters of small islands that have become popular tourist destinations during the summer. Puget Sound shares a border with Canada and the United States, creating heavily traveled water passages between the two countries.




What Is a Bay in Geography?

The land on the coastlines of the oceans is made of various types of rocks. Areas that have softer soil are prone to erosion. Over time, the waves and water break down the softer rock, which creates an inlet in the coastline called a bay. There are many more bays around the world than there are sounds.

What Are the Largest Bays in the World?

The Bay of Bengal, located in the Indian Ocean, encompasses over a million square miles on its surface. It spans from Sri Lanka and India to Bangladesh and Myanmar. Approximately one-third of all the world’s shipping freight travels through this bay before arriving at its destination.

Hudson bay is the second largest and covers 470,000 miles at its surface in Canada. This bay is home to over 50,000 beluga whales during the warm summer months. Hudson Bay has a small bay off its southern edge named James Bay which is where Henry Hudson and a group of explorers struggled to survive the winter during the early 1600s while trying to find a trade route to the Indies.

Where Are the Most Well Known Bays in the United States?

The Chesapeake Bay is the largest in America, encompassing over 64,000 square miles and being nearly 200 miles in length. The Susquehanna River created it while flowing to the ocean. Over time the sea level rose and filled in the valley. The bay is bordered by Maryland, Delaware, and Virginia, and the area is ideal for agriculture in part because of the 150 rivers that drain into it. Fishermen can find over 250 varieties of fish and shellfish in the bay, which makes the area well known for its fresh seafood.

While San Fransisco Bay isn’t as large as the Chesapeake, it is well known worldwide. The bay is around 1600 square miles in size if you include all the smaller sub-bays and wetlands, and nearly 40% of California’s watershed ends up in this body of water. The bay has been used heavily by commercial and military shipping, which led to the rapid development of the Bay Area.

Five islands are in the bay, with Alcatraz being one of the most well-known. A federal prison was built on the island to house some of the most notorious criminals of its time. While the correction department no longer uses it, people can still tour the facility.

The bay was most likely created from the intersection of two significant faults, the San Andreas and the Hayward, which made valleys. After the last ice age, the ocean levels rose over 300 feet, filling in the valleys and forming the bay.

What Is a Bay? 

A bay is a body of water surrounded by land on three sides. Bays are found in coastal areas and provide access to larger bodies of water, such as lakes, rivers, or oceans. The land that surrounds a bay protects it from rough waters, waves, and heavy winds, which is why the water in bays tends to remain relatively calm.

In some cases, you might hear the word "bay" used interchangeably with "gulf," such as the Gulf of Mexico. If you take a look at a map, you'll see that a gulf is, in essence, a large bay. Most bays are the result of some type of natural disaster. For example, the Chesapeake Bay is the result of an Eocene-era meteor strike, and the Bay of Bengal resulted when the Indian subcontinent crashed into Eurasia roughly 50 million years ago.

Bays played an essential role in human history. The calm waters provide excellent places for fishing, trapping, and anchoring boats, which is why coastal areas have always been so popular for settlements. As time went on, simple human settlements turned bays into large ports that allowed for expanded trade and the exchange of goods.

Unfortunately, human activity in those bays can lead to the destruction of natural resources and habitats. Many of those bays are used for tourism and commercial purposes. Pollution from boats makes fishing and trapping in bays unfavorable, which leads to those activities shifting to other areas or bodies of water.

What Is a Sound? 

The definition of a sound varies somewhat, but essentially, it's a large, narrow body of water that connects to an ocean or sea. Sounds get their name from the Old Norse and Old English word for "narrow access," which aptly describes a sound's appearance and location. Sounds are usually located between a barrier island and the mainland, such as Long Island Sound in North America.

Sounds can contain or consist of other geologic features, such as lagoons, jetties, islands, or deltas. Man-made features, such as artificial shorelines, are also found in sounds. However, when it comes to natural sounds, there are two common ways they're formed, both of which are due to natural geologic processes.

In some cases, seas will rise up and flood river valleys, leaving behind large bodies of water when they recede. When the valley floods, the area is left with a long, large inlet that cuts into the mainland. In other instances, receding glaciers carved out sections of land, resulting in deep bodies of water. This is especially common in areas such as Greenland, Norway, or New Zealand.

Common European usage designates sounds as either a strait or the narrowest section of a strait. These straits typically separate an island from the mainland. However, in North America, sounds also describe inlets that have large islands. Puget Sound in Washington is one example of a sound that boasts islands.

Why Is a Bay Called a Sound?

Bays and sounds are actually quite different, which is why it's very rare to hear a bay referred to as a sound and vice versa. However, because there's quite a bit of inconsistency in how the term "sound" is applied to bodies of water, there are a few reasons you might hear someone call a bay a sound.

Some sounds refer to inlets, which is essentially what a bay is. Inlets are carved into the mainland, allowing for calmer waters and more human activity. The main difference between "sound" inlets and "bay" inlets is that bays are often more protected than sounds. So, although human activity such as fishing and anchorage will be possible in a sound, they might be a bit more complicated than in a bay.

Some sounds are also called lagoons, such as Palico Sound in North Carolina, separating the Outer Banks from North Carolina's mainland. These sounds are calm, small, and relatively well-protected from the open ocean. When you consider the fact that "sound" is also derived from the Norse word "sund," which means "swimming," the idea of a bay or lagoon being a sound is pretty logical since those waters are typically calm. Conversely, sounds tend to have stronger currents that can become quite dangerous in major storms, such as hurricanes or blizzards.

However, one of the main ways in which sounds and bays differ is because sounds often have islands in them, whereas bays are simply open bodies of water. In addition, sounds are essentially leftover water from melting glaciers or floodwaters, whereas bays are the result of natural catastrophes.

Mary McMahon
Mary McMahon

Ever since she began contributing to the site several years ago, Mary has embraced the exciting challenge of being a AllThingsNature researcher and writer. Mary has a liberal arts degree from Goddard College and spends her free time reading, cooking, and exploring the great outdoors.

Mary McMahon
Mary McMahon

Ever since she began contributing to the site several years ago, Mary has embraced the exciting challenge of being a AllThingsNature researcher and writer. Mary has a liberal arts degree from Goddard College and spends her free time reading, cooking, and exploring the great outdoors.

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Discussion Comments

anon992739

How is a sound formed?

anon989687

Sounds great but, that's not the way they are on a map. There are a lot of sounds that, according to these definitions, are bays, especially in Alaska.

anon61089

In geographical usage, a bay is an inlet or indentation of the coast, whereas a sound is a channel either connecting two bodies of water or between an island and the shore. That is a bay has one entrance, a sound has more than one. There may be a different local usage for W coast of the US.

anon43073

Thanks. As someone who visits Seattle frequently and lives in the San Francisco area, I was trying to figure out why one body of water was a "sound" and the other was a "bay." Many thanks for this explanation.

anon42728

An excellent explanation!

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    • The mouth of the San Francisco Bay is narrower than the bay itself.
      By: Mariusz Blach
      The mouth of the San Francisco Bay is narrower than the bay itself.
    • Fishing communities will often base their fleets in sounds and bays as a means of providing protection for their ships.
      By: Glendon Pardy
      Fishing communities will often base their fleets in sounds and bays as a means of providing protection for their ships.