Where your water goes

Rain that falls on Concord ends up in the Atlantic Ocean

1. Your sub-basin

   Merrimack

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 010700 (USGS hydrologic unit)

Under your feet

Concord sits on Mississippian igneous rock

About 359 million years old — from the age of the first forests, amphibians and reptiles.

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

1. At the surface359 million years oldSours the soil

   Igneous rock

   Mississippian-Pennsylvanian plutonic: undivided granitic rocks · Mississippian

   What it is

   Rock formed by the cooling of magma. Some maps say only this much, which still tells you a good deal: it will be hard, unlayered, and it will not have fossils in it.

   How it wears

   By the breakdown of its feldspars into clay, which releases whatever else was locked between them as sand and grit.

   What it means above ground

   Coarse, gritty soil and rounded outcrops, generally acid and generally hungry, though the dark iron-rich members are much more fertile than the pale ones.

2. Below, layer 2352 million years oldSours the soil

   Granite

   Concord Granite · Late Devonian

   What it is

   Magma that never reached the surface. It cooled kilometres down over tens of thousands of years, and that slowness is why its crystals are large enough to see without a lens: glassy grey quartz, blocky pink or white feldspar, and flecks of black mica.