Orbital View: A Spitting Image of Brazil's Coastline

Editor’s Note: This article previously appeared in a different format as part of The Atlantic’s Notes section, retired in 2021.

There’s a lot going on here, as M. Justin Wilkinson explains:

While in orbit over the Brazilian coast, an astronaut aboard the International Space Station took this photograph of some of the country’s famous coastal lagoons. This view shows a short 20-kilometer (12-mile) stretch of a lagoon shoreline where pointed sand spits jut into waters of Mangueira Lagoon (Lagoa Mangueira). The ends of the spits are under water, growing less visible with increasing depth. [...]

The spits and bays have a somewhat regular spacing, at least in geological terms. They are created as lagoon water slowly circulates while being driven by persistent sea breezes out of the east (top of the image). The water washes into the bays and then curves back out into the lagoon, carrying sand eroded from the shoreline. This sand is deposited in the tight, tan-colored lines we see as spits.

The cells of circulating water tend to be the same size, depending on water depth, dominant wind strength, and the amount of sand available—translating into spits at roughly regular intervals. Regularly spaced spits form in many parts of the world, for instance along the coast of the Sea of Azov in southern Ukraine.

Here’s a view of one of those Ukrainian spits from the ground:

From Azov’s Wiki page:

The sea is largely affected by the inflow of numerous rivers, which bring sand, silt, and shells, which in turn form numerous bays, limans, and narrow spits. Because of these deposits, the sea bottom is relatively smooth and flat with the depth gradually increasing toward the middle. Also, due to the river inflow, water in the sea has low salinity and a high amount of biomass (such as green algae) that affects the water colour. Abundant plankton results in unusually high fish productivity. The sea shores and spits are low; they are rich in vegetation and bird colonies.

That rich vegetation can been seen from this inaugural installment of Azov by Air:

(See all Orbital Views here)