Transcript Formation of Sed Rocks ppt - Tanque Verde Unified School District

Formation of
Sedimentary Rocks
1. What is sediment?
a) Sediments are pieces of solid material that
have been deposited on Earth’s surface by
wind, water, ice, gravity, or chemical
precipitation.
b) When sediments become cemented together,
they form sedimentary rocks.
2. Weathering
a) Earth’s surface is subject to weathering, a set
of physical and chemical processes that break
rocks.
b) During physical weathering, rocks break into
smaller pieces.
2. Weathering
c) Chemical weathering occurs when minerals in
a rock are dissolved or chemically change.
d) During chemical weathering, less-stable
minerals break down and stable minerals get
smaller.
3. Erosion and Transport
a) After weathering, rock fragments are
transported to different locations.
b) The removal and movement of surface
material from one place to another is called
erosion.
c) There are 4 main agents of erosion: wind,
water, gravity and glaciers.
3. Erosion and Transport
3. Erosion and Transport
4. Deposition
a) Deposition occurs when sediments are laid
down on the ground or sink to the bottom of
water bodies.
b) Particles settle in layers. Largest sediments
will settle first, followed by smaller sediments.
Why?
c) Sometimes sediments do not form layers.
Glaciers move all sediments equally.
Great Salt Lake in Utah
Glacial Movement & Deposition
5. Burial
a) Most sediments eventually end up in the
lowest places on Earth, called basins.
b) Basins can be over 8 km thick.
c) As more sediment is deposited, increasing
pressure and temperature cause lithification.
d) Lithification is the physical and chemical
process that transforms sediments into
sedimentary rock.
Tucson is in a basin.
6. Lithification
a) Lithify comes from the Greek word lithos,
meaning rock.
b) Lithification begins with compaction. The
weight of over-lying sediments forces the
grains closer together, causing physical
changes.
6. Lithification- compaction
Draw this!
6. Lithification
c) Sediments buried deep enough (3-4 km)
experience temperatures that are high enough
for cementation to occur.
d) Cementation occurs when mineral growth
cements (glues) sediment grains together.
e) Calcite and Iron oxide are common cements.
The process of lithification
Different cement types
7. Features of Sedimentary Rocks:
Bedding
a) Bedding – horizontal layering of sediments.
b) Graded bedding – When bedding becomes
progressively heavier and coarser towards
bottom layers.
c) Cross-bedding – horizontal layers that are
inclined and cross each other.
Bedding examples: horizontal
Bedding examples: horizontal
Bedding examples: graded
Bedding examples: cross-bedded
7. Features of Sedimentary Rocks:
Fossils
d) Fossils – the preserved remains, impressions,
or other evidence of once-living organisms.
e) When an organism dies, it may be buried
before it decomposes. If remains are
undisturbed, it might become preserved as a
fossil.
7. Features of Sedimentary Rocks:
Fossils
f) During lithification, all or parts of the organism
can be replaced with minerals and turn into
rock.
Shale with Plant Fossils
Fossiliferous Limestone = Coquina
Fossil Fuels…where does that term come from?
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