An astronaut from the International Space Station (ISS) captured images of sand banks surrounding Carter's Cays and Strangers Cay in the Bahamas on October 20, 2016. The images display submerged sand banks and a coral reef. The coordinates for this location are 27.105580266, -78.06669135.
Geographic Context
The Bahamas consists of over 3,000 islands and cays, along with coral reefs, tidal channels, and shallow sand bank structures. NASA's Earth Observatory identifies the Bahamas as a geographically distinct region from an orbital perspective. Carter's Cays (lower left in the image) and Strangers Cay (upper right) are among the northernmost landmasses in the Bahamas, situated approximately 125 miles (200 kilometers) east of Florida. Strangers Cay measures approximately 2.2 miles (3.6 km) at its widest point.
Formation of Sand Banks and Coral Reefs
The visible sand banks, which appear to wind around the cays, have been shaped by consistent ocean currents over decades. These currents lead to sand accumulation in specific areas. A coral reef is also present, cutting across the bottom right portion of the image. This reef, older than the sand banks, is estimated to have developed over millennia. Waves can be observed breaking along its outer edge.
Interaction of Features
A prominent U-shaped sand bank in the image center is positioned opposite a significant break in the coral reef. According to the Earth Observatory, this gap facilitates a strong tidal flow that has contributed to the specific configuration of the sand bank. These sand formations are smaller than the Great Bahama Bank, which covers an area of approximately 80,000 square miles (210,000 square kilometers) near the Exuma Islands in the central Bahamas. The Great Bahama Bank supports an extensive seagrass ecosystem.
Visual Characteristics
The apparent luminosity of the sand banks when viewed from above is an optical effect, attributed to their shallow depth. In some areas, the sand is estimated to be approximately 6.5 feet (2 meters) below the ocean surface, as reported by the Earth Observatory. Differences in water appearance are also observable. The water to the upper left of the islands appears lighter with streaking patterns, while the bottom right, beyond the reef, is darker and exhibits traditional wave patterns. This variation is due to a steep ocean drop-off located beyond the coral reef. Ocean currents in this deeper area generate swells, whereas behind the reef, wind patterns create the observed surface streaks. The absence of sand banks beyond the reef is also a consequence of this drop-off.