Sedimentary Rocks
Compaction
-is the squeezing together of layers of sediment due to the great weight of overlying layers of rock. This squeezing of the layer results in reducing the thickness of the original layer. When the layers are reduced in thickness the pore spaces around the sediments are also reduced, which leads to a tighter packing of the layers.
Cementation
- is the changing of sediment into rock by filling spaces around the sediments with chemical precipitates of minerals. binding the sediments, and forming solid rock. Calcite and silica are common minerals that cement the sediments together.
Clastic sedimentary rocks are
made of pieces of rock or mineral grains that have been broken from preexisting
rock.
Non-clastic sedimentary rocks
form from the precipitation (Precipitation is the separating of a solid
from a solution) of minerals from ocean water or from the breakdown of
the shells and bones of sea creatures. Sea animals such as coral produce
calcium carbonate solutions that harden to form rock.
Organic sedimentary rocks form
from the build up and decay of plant and animal material. The overlaying
layers become so heavy that they squeeze out the water and other compounds
that aid in decay. This compressed vegetation forms coal.