Landforms are natural features that shape the Earth’s surface. Coastal areas exhibit a wide array of these formations. Sounds are distinct bodies of water with specific characteristics and origins.
Defining a Sound Landform
A sound is a marine geographical formation found along coastlines, characterized as an inlet of seawater branching off from the main ocean or sea. It can also describe a narrow sea or ocean channel between two landmasses. Sounds are typically larger than a bay and deeper than a bight, often connecting two larger bodies of water or separating an island from the mainland. They are partially enclosed by land but maintain a clear connection to a larger body of water.
How Sound Landforms Develop
Sound landforms result from various geological processes that alter coastal topography.
Many sounds are relict glacial valleys, carved out by massive glaciers during past ice ages. As these glaciers retreated and global sea levels rose, these U-shaped valleys became inundated with seawater, forming the sounds observed today.
The submergence of coastal areas also contributes to sound formation. Tectonic activity can cause land to sink, or global sea level rise due to melting ice sheets, can flood existing low-lying coastal regions or river valleys. This process creates long, often branching, inlets where the original river valley’s sloping hillsides extend beneath the water, forming a sloping seafloor. These types of sounds are sometimes referred to as rias.
In some cases, sounds can form behind natural barriers. Sediment accumulation, driven by currents and waves, can lead to the creation of barrier islands or spits. The protected body of water that then develops between these newly formed landforms and the mainland is also classified as a sound.
Key Characteristics and Global Examples
Sounds exhibit varying depths and widths. Their water can be saltwater, often becoming brackish where freshwater rivers flow in. This dynamic environment supports rich biodiversity, making sounds important habitats for marine life like fish, shellfish, marine mammals, and numerous bird species.
Prominent examples include Puget Sound in Washington State, a large inland estuary shaped by ancient glaciers. It spans 95 miles, averages 450 feet deep, and supports over 200 fish species and 14 marine mammal species. Denmark’s Limfjord, a shallow 180-kilometer body of water, separates the North Jutlandic Island from the Jutland Peninsula and is known for its mussels and oysters. New Zealand’s Queen Charlotte Sound, part of the Marlborough Sounds, is another drowned river valley popular for sailing.
Differentiating Sounds from Similar Coastal Features
Understanding sounds requires distinguishing them from other coastal formations that can appear similar.
Bays are indentations of a coastline, typically smaller and shallower than sounds, and are generally enclosed by land on three sides. While a bay is usually connected to a single larger body of water, a sound may connect two or more bodies of water.
Fjords and sounds, though both often glacially carved, have distinct differences. Fjords are deep, narrow inlets with very steep, often vertical, sides, formed by glaciers eroding U-shaped valleys. Sounds, conversely, are generally wider, less steep-sided, and more open, sometimes originating from flooded river valleys rather than solely glacial action.
Straits are narrow channels of water that connect two larger bodies of water. While some sounds can function as straits, particularly in northern European usage, they do not necessarily possess the same degree of land enclosure or internal complexity as many sounds. Sounds often feature a more complex system of inlets and islands compared to the typically narrower and more direct path of a strait.