Shoreline Waves and Currents (Part 2)
Deposition
• Deposition occurs when the eroded sediment is deposited. This process creates depositional features such as beaches, barrier islands, and spits.
Beaches are made up of sediment, usually sand, deposited along a shoreline. This beach is in First Landing State Park, near Virginia Beach. (Photograph by Robert Whisonant)
Barriers and spits can be found along Virginia’s shoreline, as shown in these satellite photographs. Barrier islands are long, narrow bars of sand detached from the mainland. Spits are also sandy bars, but are attached to land and extend into the water (arrows on right photo). (Photographs courtesy of NASA)
Tides
• Tides are the rise and fall of sea level that occur mainly because of the moon’s gravity. Tides generate currents that move sediment.
Estuaries
• Estuaries are bodies of mixed salty and fresh water along coastlines. The Potomac, Rappahannock, York, and James Rivers are the largest estuaries in Virginia.
Virginia has an estuarine coastline. Major estuaries are the Potomac River, the Rappahannock River, the York River, and the James River. These rivers are affected by tides and salt water at their mouths. (Image courtesy of the United States Geological Survey)
James River estuary, near Jamestown (Photograph by Robert Whisonant
This typical view of a Virginia estuary shows the James River near Jamestown. Rising sea level is drowning river valleys such as the lower James. These drowned river valleys create the many estuaries along Virginia’s coast.
Sea Level Change
• Changes in sea level over long periods of time occur two ways.
• Sea level can rise or fall as more or less water is present in oceans. Glaciers around the world are currently melting, releasing water and causing sea level to rise.
• The land can uplift or subside, causing sea level to fall or rise. For example, as land uplifts, sea level drops.