Guided Notes About Sedimentary Rocks

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Transcript Guided Notes About Sedimentary Rocks

Guided Notes About
Sedimentary Rocks
1) What are sediments, and how
do they form sedimentary rocks?
 Sediments
are pieces of solid
material that have been deposited
on Earth’s surface.
 When sediments become
cemented together, they form
sedimentary rocks.
2) What is chemical weathering?
 Chemical
weathering occurs when
the minerals in a rock are
dissolved or otherwise chemically
3) What is physical weathering?
 Physical
weathering occurs when rock
fragments break off the solid rock
along fractures or grain boundaries.
 The minerals remain chemically
4) Describe clastic sediment and
state how it forms.
 Clastic
sediments are produced by
weathering. They have worn
surfaces and rounded corners caused
by physical abrasion during erosion
and transport.
5) What is erosion? What are the 4
main agents of erosion?
Erosion is the removal and movement of
surface material from one location to
Moving water
6) In which direction does erosion
almost always carry materials?
 Downhill
7) What is deposition? When are
sediments deposited?
Deposition occurs when sediments are laid
down on the ground or sink to the bottom
of bodies of water.
 Sediments are deposited when
transportation stops.
8) Why do sediments deposit in
sorted layers?
 Faster
moving water can transport
larger particles. As water slows
down, the largest particles settle out
first, then the next-largest, so that
different-sized particles are sorted
into layers.
9) Which erosional forces do NOT
deposit sediment in layers?
 Glaciers
 Landslides
10) What is lithification, and where
does it occur?
Lithification is the physical and chemical
processes that transform sediments into
sedimentary rocks.
 It occurs in sedimentary basins, where the
bottom layers are subjected to increasing
temperature and pressure.
11) What are the 2 steps of
Compaction—the weight of overlying
sediments forces sediment grains
closer together
2. Cementation—temperatures are
high enough to cause mineral
growth, which cements sediment
grains together into solid rock
12) Describe the 2 types of
A new mineral, such as calcite or iron
oxide, grows between sediment grains as
dissolved minerals precipitate out of
Existing mineral grains grow larger as
more of the same mineral precipitates
from groundwater and crystallizes
around them.
13) What determines the primary
feature of sedimentary rocks?
The primary feature of sedimentary rocks
is bedding, which is determined by the
method of transport
14) What is graded bedding, and
where is it most observed?
 Graded
bedding is bedding in which
the particle sizes become
progressively larger and coarser
towards the bottom.
 It is most often observed in marine
sedimentary rocks that were
deposited by underwater landslides.
15) How is an organism preserved
as a fossil?
If an organism is buried before it
decomposes and is further buried without
being disturbed, then it will become a
16) What happens to a fossilized
organism during lithification?
 During
lithification, parts of the
organism can be replaced by
minerals and turned into rock.
17) What 3 important pieces of
information do fossils provide?
The types of organisms that lived in
the distant past
2. The environments that existed in
the past
3. How organisms have changed over
18) How are sedimentary rocks
classified? What are the 3 classes?
Sedimentary rocks are classified by
how they were formed.
1. Clastic
2. Chemical
3. Organic
19) What is the difference between
conglomerate and breccia?
 Conglomerates
have rounded
particles while breccias contain
angular fragments of rock.
20) How and where do sandstones
 Sandstones
form when sand-sized
rock and mineral fragments are
buried and lithified.
 This often occurs in stream channels,
beaches, oceans and deserts.
21) What is porosity, and how does
the porosity of sandstone…
 Porosity
is the % of open space
between grains in a rock.
 Sandstones have high porosity, which
allows liquids such as water or oil to
flow through them.
22) Why doesn’t shale or siltstone
have high porosity?
 Neither
shale nor siltstone have high
porosity because their particles are
compacted very closely together,
resulting in little open space between
23) What are evaporates, and how
do they form?
 Evaporates
are the layers of chemical
sedimentary rocks that result when
minerals precipitate out of saturated
bodies of water.
24) How does limestone form from
ocean animals?
Some ocean animals use calcium
carbonate dissolved in seawater to make
their shells. When these animals die, their
shells settle to the bottom and form thick
layers of calcite, which is buried and
lithified to form limestone.
25) How does coal form?
 Coal
forms when thick layers of
vegetation slowly accumulate in
swamps or coastal areas. This plant
material is slowly buried and
compressed, which lithifies it into
26) List the major resources provided
by sandstone and limestone
Sandstone: uranium, oil, natural gas,
building materials
 Limestone: cement materials,
blocks for construction