delta

Over time, sediment carried by rivers built deltas at the head of the Gulf, cutting off tidal access to inland areas.

Many of its largest cities -- including Shanghai, Shenzhen and Hong Kong -- sit in delta regions made of soft, water-saturated sediment that naturally sinks over time.

At Martín García Island, Argentina, a series of crags amid the Río de la Plata delta, she tries to make sense of crooked crosses cast from a single mold.

Perched on a delta where the Pearl River meets the South China Sea, it is used to typhoons, and it was prepared for this one.

That means they are also imperiling some of the world’s most important food-producing lowlands in the Nile and Mekong deltas and cities from Shanghai to New York.