SedimentarySoil pH 5.0–8.0, depending entirely on the beds

Sedimentary rock

Rock built from the debris of older rock, or from the remains of things that lived — laid flat, and buried.

How it forms

Older rock weathers, rivers and wind carry the pieces downhill, and they settle wherever the carrying stops. Burial squeezes the water out and mineral cement locks the grains together.

Sedimentary — laid down in layers

Sediment settling through water in layers, then buried and compacted into rockwaterweight above squeezes the water out and cements the grains

Rock built from the wreckage of older rock, or from the remains of things that lived — sand, mud, shell and skeleton, settled in flat beds and buried until the weight turned them to stone. The only rocks that hold fossils.

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 to know it
Flat bedding you can trace across a cliff face, grains that settled rather than grew into each other, and the possibility of 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.
Where you stand on it
The interior plains and plateaus of both countries, all of the coastal plain, and a thin cover over much of the Shield.
What lives on it
Anything, depending on the beds. That is not an evasion — it is the point.
What it's used for
Nearly all the building stone, cement, aggregate, coal, oil and gas ever extracted.
What it does to the soil
Neither sweetens nor sours — the soil above takes its pH from elsewhere.

Next to it in the cycle

  • Limestone

    the limey end, which sweetens the soil

  • Sandstone

    the sandy end, which sours it

  • Shale

    the muddy end, which holds water

Is this what you're standing on?

Find the rock under your town

Enter a town or postal code and we'll show you the rock beneath it and how old it is, the soil it makes, and the chain of rivers your water joins on the way to the sea.

General descriptions of rock families. Any particular outcrop can differ — rocks grade into one another, and a geological map at this scale describes a district rather than a hillside.