Poipu Beach Tombolo
June 14, 2013
Photographer: Thomas McGuire; Tom's Travel and Earth Science Images
Summary Author: Thomas McGuire
Tombolos are depositional landforms that connect an island to the mainland. They form where waves are refracted (bent) around an island or a reef into shallow water. A tombolo is actually a temporary isthmus created by longshore transport of sand or another kind of sediment. The tombolo shown above (top photo) at Poipu Beach, along the south shore of Kauai, Hawaii, is an ephemeral feature. It’s often covered with sand and then uncovered as waves and tides come in and go out. Examples of seashore tombolos include the Rock of Gibraltar in the Mediterranean Sea, Biddeford Pool (island) in Maine and Morro Rock in California. Also, several islands in the Great Lakes are connected to the shoreline by tombolos. Note that the bottom satellite image of Poipu tombolo clearly shows wave refraction.
Photo details: Top - Camera Model: Canon PowerShot SD1100 IS; Focal Length: 6.2mm; Aperture: f/8.0; Exposure Time: 0.0031 s (1/320); ISO equiv: 80; Software: Adobe Photoshop Elements 9.0 Macintosh.