Coastal sand crumbles at the human touch but is powerful enough to form barrier islands. Have you ever wondered how this is possible?
is a long, narrow island that lies parallel and close to a mainland to protect the mainland from erosion and storms. Barrier islands only form from coastal sands under three conditions. First, there needs to be enough sand to form an island—though they also often include rock parties supplied by erosion of nearby land. Second, winds and waves have to have enough energy to shift the sand. These winds and waves pick up and deposit sand on long coastlines.
The third condition required for barrier islands to form from coastal sands is maybe surprising: the sea level cannot rise but must remain essentially unchanged over a long period of time. Barrier islands only started forming recently, about 7,000 years or so after ice from the last Ice Age finished melting. Thus, climate change—which causes rising sea levels—may prevent barrier islands from forming in the future.
Coastal sand, water, and wind are all key to the formation of barrier islands.
Coastal Services Center