Transcript Formation of Sedimentary Rocks

Formation of Sedimentary
Rocks
SWBAT sequence the formation of
sedimentary rocks; explain the formation and
classification of clastic sediments; describe
features of sedimentary rocks
Sedimentary Rock Formation
• Sediments
– Pieces of solid material that have been deposited on
Earth’s surface by wind, water, ice, gravity, or
chemical precipitation
• How does the formation of sedimentary rocks
begin?
– Weathering and erosion produce sediments
• Weathering
– The breakdown of rocks by physical or chemical
means
• Erosion
– Movement of weathered materials
Weathering
• What is the difference between chemical
and physical weathering?
– Chemical weathering occurs when the
minerals in a rock dissolve
– Physical weathering occurs when minerals
remain unchanged. Rock fragments break off
• Clastic
– From Greek klastos - broken
– Rock and mineral fragments
– Classified by size
4 main agents of erosion
• Wind
– Blows broken particles to other locations
• Moving water
– Large and small particles are transported by the
currents
• Gravity
– Pulls particles downward from hills and mountains
• Glaciers
– Particles are dragged or frozen in glaciers and
deposited when they melt
Erosion and Transport
• Deposition
– When sediments are laid down on the ground or sink to the
bottom of water
– Large particles settle first, then second largest, and so on
– Different sized particles are sorted into layers
• Lithification
– Transformation of sediments into rocks through compaction and
cementation
• Compaction
– Overlying sediments force sediment grains closer together
causing a physical change
• Cementation
– Mineral growth cements sediment grains together into solid rock
Features of sedimentary rocks
Bedding
Horizontal layering that can range from
millimeters to many meters thick. The type of
bedding depends on transport.
Graded
bedding
Particle sizes become progressively heavier
and coarser toward the bottom layers. In
water heaviest particles settle first, followed
by progressively finer material
Crossbedding
Formed when inclined layers of sediment
move forward across a horizontal surface.
Evidence of Past Life
• Fossil
– Preserved remains, impressions, or any other
evidence of once-living orgainisms.
– During lithification, parts of the organism can
be replaced by minerals and turned into rock