What Are Insular Beaches?

Barrier Island

• Barrier beaches are formed when sand or other eroded materials from nearby land areas are washed downstream and deposited at the edge of the sea. These deposits will resemble the substrate from which they originated. For example, dark basalt volcanic rocks will yield a black sand beach. Barrier islands are formed when sand deposits form offshore underwater ridges. They become actual islands when shoreline currents add more sand to the underwater structures. Barrier islands generally follow the outline of the mainland.

Glacial Beaches

• Visitors to glaciated areas will find beaches made from many small rocks and pebbles, which are smoothed and polished by the wave action of the sea. The coast of Maine has many such beaches, as the whole state was once covered by glaciers. As the ice sheets retreated they left behind an uneven terrain along with large deposits of sand, till pebbles and small rocks. As the coastline was flooded by the rising sea, tops of hills and small mountains became islands. Over time both waves and current combined to created stony beaches from glacial remnants.

Mangrove Islands

• In sub-tropical and tropical regions, small islands can grow up around a grove of the saltwater-tolerant mangrove tree. These small islands begin when pods from mature mangrove trees take root in very shallow water. Soon a thick clump of the trees might be found covering a very shallow shoal or natural sandbar. Sand deposits will likely follow leading to the creation of a small spec of solid land and as the tiny island grows other subtropical plants will replace the mangroves, as they prefer shallow standing saltwater for a habitat.

Atoll

• The South Pacific is known for its beautiful, white coral beaches graced with a few palm trees. These places are called atolls and they are not characterized by circular-shaped dots of land surrounded by water. Instead coral reefs form a narrow ring of land with a lagoon in the center and the ocean on the outside. Atolls usually form at the top of inactive sea volcanoes that have sunken into the sea. The underlying structure is coral reefs, which is activity a living organism that secretes a limestone-like substance. This substance, when ground down by wave action forms a coral beach of the atoll.