CAPE POINT, N.C. (WAVY) — NASA recently released satellite images that show the formation of a new shoal off Cape Point at Cape Hatteras National Seashore.
The first image of the new shoal, nicknamed “Shelly Island,” was captured by the Landsat 8 satellite in November 2016. When the second image was taken in January, waves could be seen breaking on the shallow region off the cape’s tip. Where those waves were breaking is where Shelly Island eventually formed, which is visible in the third image, taken this month.
“What exactly causes a shallow region to become exposed is a deep question, and one that is difficult to speculate on without exact observations,” said Andrew Ashton, a geomorphologist at the Woods Hole Oceanographic Institution. “A likely process would be a high tide or storm-driven water elevation that piled up sediment to near the surface, and then water levels went down exposing the shoal. Waves then continue to build the feature while also moving it about.”
The island is about a mile long and 300 yards wide.
While it’s still mostly unknown how Shelly Island formed, NASA says this phenomenon is not uncommon.
The shoreline and cape tips along North Carolina’s coast are constantly changing. Cape tips are sculpted by waves and currents that come from all different directions, while sediment moves up and down the coastline and is often deposited near the cape tips. According to NASA, each cape tip has a so-called “cape-associated shoal” underwater. These sand piles can be tens of kilometers long and are also very shallow.
“Tidal flows moving up and down the coast are diverted by the capes and result in a net offshore current at cape tips and deposition at the shoals,” Ashton said. “Occasionally, a portion of the shoal becomes exposed and forms an island.”
Shelly Island Satellite Images
Shelly Island Satellite Images x
Read more from NASA here.