Where your water goes

Rain that falls on Miami ends up in the Atlantic Ocean

1. Your sub-basin

   Southern Florida

2. then

   Atlantic Ocean Seaboard

3. It arrives here

   Atlantic Ocean

Everything that falls here works its way east and north to the Atlantic. It is the drainage that carried the fur trade inland and the log drives back out, and the one Atlantic salmon and American eel still use — the eel travelling the whole length of it to spawn in the Sargasso Sea.

Basin 030902 (USGS hydrologic unit)

Under your feet

Miami sits on Cenozoic sedimentary rock

About 66 million years old — after the dinosaurs, as mammals and grasslands spread.

All the kinds of rock, and how each one forms →

1. At the surface66 million years oldNeither way

   Sedimentary rock

   Cenozoic sedimentary rocks · Cenozoic

   What it is

   The family that covers about three quarters of the land surface, in a thin skin over everything else. Some geological maps say only this much, which still tells you it will be layered and may hold fossils.

   How it wears

   Along its bedding planes, layer by layer, at a rate set by whatever the layers are made of — which is why sedimentary country weathers into steps.

   What it means above ground

   Layered country with flat-topped hills and stepped valley sides. What grows on it depends entirely on whether the beds are limey or sandy, which is the question worth asking next.

2. Below, layer 2527,000 years oldSweetens the soil

   Limestone

   Miami Limestone · Pleistocene

   What it is

   Nearly pure calcium carbonate, most of it the shells and skeletons of animals that lived in warm shallow water where this place now sits. Break a fresh face and you can often see them.