Inorganic Land-Derived Sedimentary Rocks
Inorganic land-derived sedimentary rocks are
clastic. Clastic means they are made from particles that have become
cemented together.
How these rocks form: (see Rock Cycle, ESRT page 6)
1) Other rocks (any other rocks) on the
land are weathered into smaller particles.
2) The smaller particles are transported (eroded) by wind, water,
ice or gravity alone.
3) The particles are deposited either on land or at the bottom of
a lake or ocean.
4) Over time they are buried under more sediment.
5) They become compressed and compacted by the weight of the
sediment on top of them.
6) Over time the particles are cemented together forming
sedimentary rock.
Important Facts: These clastic sedimentary rocks.....
> are classified according to particle size.
> are inorganic: They were not
formed by living things or from the products of living things.
> are land-derived: The rocks that originally weathered to form
sediment were
on the land.
> were deposited in horizontal layers (law of
original horizontality).
> are the only kind of rocks that contain fossils (if a rock
contains a fossil, it's sedimentary).
Since the sediments that form these rocks are deposited on the surface, it is often said that "sedimentary rocks form a thin veneer over the surface of the Earth". A veneer is a thin layer. Sedimentary rocks are usually found on or near the surface. Most of the rest of the crust, the deeper parts, are igneous or metamorphic.