A sea arch is a natural arch or bridge made of stone that has been created through the process of land, wind, or water erosion. Of course, a natural arch is often made due to a combination of types of erosion. A natural arch or natural bridge is a formation of rock that includes a passage way in its lower half.

Very often, arches are made by the meeting of two types of rock. The rock on at the top of the arch, which forms the bridge is made of a harder type of rock than what is on the bottom. If the bottom rock is a softer type of stone, it will erode away more quickly, thus leaving behind an arch.

Natural bridges commonly form where cliffs meet the sea. In this instance, the formations are called “sea arches.” A sea arch is created when the natural erosive forces of the water break through a slice of rock and leave behind an arch. Water, after all, is one of the most powerful forces on our planet. It has the power to destroy cities, as it tragically did with Hurricane Katrina. It also has the power to make stunning sculptures in the earth, such as the Grand Canyon and some of the more majestic sea arches.

Beautiful sea arches exist all around the world. There was a sea arch known as “London Bridge” in Victoria, Australia that has, unfortunately, collapsed. Other sea arches are the Durdle Door and the Stair Hole on the coast of southern England. If you are a sea arch or natural bridge enthusiast, be sure to take yourself on a trip to the Natural Bridge National Monument in Utah. This national monument features the second and third largest land bridges in the world.

A sea arch is often a former cave. In many instances, a limestone cave full of sinkholes will begin to collapse, leaving behind what was once the mouth of the cave. This former entrance then becomes a sea arch. Because each sea arch is the result of erosion, many of them will eventually collapse like Australia’s London Bridge. Depending on the age and structure of a sea arch, they may look sturdy and everlasting or frail, about to fall in on themselves. However, as one sea arch falls to rubble at the edge of the ocean, another will likely take its place when a cave collapses in on itself or a sliver or weak rock finally gives way to allow the passage of wind and water through the stronger arch above.