Doc ____
SEDIMENTARY ROCKS NOTES
 Sedimentary rocks form a thin layer over 75% of Earth’s surface, but make up only 5% of the
volume.
 Sedimentary rocks form from small pieces of other existing rocks and small pieces of once
living things. Collectively, these small pieces are called sediment.
Formation of Sedimentary Rocks
Lithification is the process that converts these sediments into sedimentary rock. There are five
steps in the lithification process: weathering, erosion, deposition, compaction, and cementation.
1. Weathering - the chemical or physical process in which rocks are worn down by the action of
the atmosphere (water, wind, ice), gravity, and organisms; occurs very slowly
a. Mechanical (disintegration) - takes place when rocks split or break into smaller pieces
without changing chemical composition
a. frost action - ice splits rocks apart
b. temperature change - expansion and contraction causes splitting
c. plants - growth of roots break rock apart
d. animals - burrowing disturbs and exposes rock
b. Chemical (decomposition) - occurs when minerals in rock change into different
substances
a. hydration - chemical action of water causing rocks to decompose
b. oxidation - chemical action of oxygen (usually with iron compounds)
c. carbon dioxide - dissolves in water to form carbonic acid that dissolves
certain minerals in rocks
d. acids from industry - air pollutants that create acid rain
e. decay of plants and animals
2. Erosion - the process of transport of earth materials (sediments) and organic material by
moving natural agents such as water, wind, ice, and gravity
3. Deposition - Sediments are deposited, or dropped off, somewhere else. The Law of
Superposition is a basic law of geochronology, stating that in any undisturbed sequence of rocks
deposited in layers, the youngest layer is on top and the oldest layer is on the bottom, each layer
being younger than the one beneath it and older than the one above it.
4. Compaction - As layers of sediment build up, they are pressed or squeezed together.
5. Cementation - Water containing dissolved minerals seeps into the spaces between pieces of
sediment. The minerals crystallize and glue the pieces of sediment together to form a rock.
Cementing minerals give the rock its color.
Classification of Sedimentary Rocks
1. Clastic - made from pieces of other rock
 conglomerate – rounded rock fragments cemented together
 breccia – sharped edged rock fragments cemented together
 sandstone - cemented sand; porous - has spaces between pieces of sediment that
water can pass through
 shale - compacted silt and clay, splits into flat pieces
2. Organic - made from the remains of plants and animals
 limestone - made from coral reefs and other organic marine materials
 chalk - cemented grains of tiny sea creatures
 coal - decayed plants
3. Chemical - formed when minerals precipitate (come out of solution) or are left behind during
evaporation
 halite - rock salt created from salt water
 limestone - made from tiny grains of precipitated minerals
 geodes - water with dissolved minerals filled a hollow; as the water evaporated,
minerals crystallized and remained behind
Unique Features of Sedimentary Rocks
1. Stratification - Some sedimentary rocks develop visible bands that result from layers of
sediment being deposited one atop another over very long periods of time. These are stratified.
Those without visible bands are unstratified.
2. Fossils - Plants and animals die in water where sedimentation is taking place. Flesh decays
but hard parts remain as sediment becomes rock, creating fossils.
Doc ____
SEDIMENTARY ROCKS NOTES
 Sedimentary rocks form a thin layer over ______ of Earth’s surface, but make up only
_____ of the volume.
 Sedimentary rocks form from small pieces of other ______________ and small pieces of
once ______________ things. Collectively, these small pieces are called ______________.
Formation of Sedimentary Rocks
______________ is the process that converts these sediments into sedimentary rock. There are
five steps in the lithification process: ___________________, ___________________,
___________________, ___________________, and ___________________.
1. Weathering - the chemical or physical process in which rocks are worn down by the action of
the ___________________ (water, wind, ice), ___________________, and
___________________; occurs very ___________________
a. Mechanical (___________________) - takes place when rocks split or break into
smaller pieces without changing ___________________ composition
a. ___________________action - ice splits rocks apart
b. ___________________change - expansion and contraction causes splitting
c. ___________________- growth of roots break rock apart
d. ___________________- burrowing disturbs and exposes rock
b. Chemical (______________) - occurs when minerals in rock change into different
___________________ .
a. ___________________- chemical action of water causing rocks to decompose
b. ___________________- chemical action of oxygen (usually with iron
compounds)
c. ___________________- dissolves in water to form carbonic acid that dissolves
certain minerals in rocks
d. ___________________from industry - air pollutants that create acid rain
e. ___________________of plants and animals
2. Erosion - the process of ___________________of earth materials (sediments) and organic
material by moving ___________________agents such as water, wind, ice, and gravity
3. Deposition - Sediments are ___________________, or dropped off, somewhere else.
The ______________________________is a basic law of geochronology, stating that in any
___________________ sequence of rocks deposited in layers, the youngest layer is on
______________ and the oldest layer is on the ______________, each layer being younger than
the one beneath it and older than the one above it.
4. Compaction - As layers of sediment build up, they are ___________________or
___________________together.
5. Cementation - Water containing dissolved minerals seeps into the spaces between pieces of
sediment. The minerals crystallize and ___________________the pieces of sediment together to
form a rock. Cementing minerals give the rock its color.
Classification of Sedimentary Rocks
1. Clastic - made from pieces of other ___________________

___________________ - smooth rock fragments cemented together

___________________ - sharped edged rock fragments cemented together

___________________ - cemented sand; porous - has spaces between pieces of
sediment that water can pass through

___________________- compacted silt and clay; splits into flat pieces
2. Organic - made from the remains of ___________________and ___________________

___________________- made from coral reefs and other organic marine materials


___________________- cemented grains of tiny sea creatures
___________________- decayed plants
3. Chemical - formed when minerals ___________________ (come out of solution) or are left
behind during ___________________

___________________- rock salt created from salt water

___________________- made from tiny grains of precipitated minerals

___________________- water with dissolved minerals filled a hollow; as the water
evaporated, minerals crystallized and remained behind
Unique Features of Sedimentary Rocks
1. Stratification - Some sedimentary rocks develop visible ___________________that result
from layers of sediment being deposited one atop another over very long periods of time. These
are ___________________ . Those without visible bands are ___________________ .
2. Fossils - ___________________and ___________________die in water where sedimentation
is taking place. Flesh decays but hard parts remain as sediment becomes rock, creating
___________________ .