Download Slide 1

Physical Science
Sedementary and metamorphic
rocks
Sedimentary Rocks
•
•
•
Most common in the upper portion of the
crust and surface
Form a thin and extensive blanket over
igneous rock
They can provide information about
geological events and time
From yahoo images
How are Sedimentary Rocks Formed
Weathering
Erosion
Sedementation
From yahoo images
Weathering
Weathering – braking down or
decomposing of surface rock
• Mechanical Weathering – physically
breaking rock into smaller pieces
• Chemical weathering – reactions in
water to break down rock
From yahoo images
Erosion
process by which weathered rock
particles are removed and
transported by water wind or ice
From yahoo images
• Sedimentation – deposition of
rocks and minerals in layers over
time
From yahoo images
Sedimentation
• The large the sediment, the stronger
the wind or water current must be
• Typically water currents get weaker as
they move from their source So larger
particles tend to be deposited before
smaller ones
• The size and shape of particles in a
sediment give clues to the time and
distance of transportation
Sedimentation
Sedimentary rock forms in two steps
compaction and cementation
Compaction
• As layers form on layers – pressure is
increased on lower sediments – the
rocks are compacted together
Sedimentation
Cementation
• As pressure increases, water is
squeezed out of the rock leaving small
pores.
• The water tends to contain silica,
calcite and hematite in solution
• as it is squeezed out, these mineral
precipitate partially filling the pores and
cementing the rocks together.
Clastic Sedimentary Environments
• Stream deposition
Clastic Sedimentary Environments
• Wind deposition
Clastic Sedimentary Environments
Deltas and Alluvial fans
• water speed slows as stream reaches
an open flat valley
• deposition occurs and forms a fan
shaped deposit
From yahoo images
Chemical sedimentary environments
• Sediments produced from mineral
precipitation from water
• Either by reaction of ions to form
solids or by the evaporation of water
•
stalactites/stalagmites
and corral reefs
How Do They Form
From yahoo images
Metamorphic Rock – rock formed
under high heat and pressure
without melting
From yahoo images
Metamorphic Rock
Recrystallization – Re structuring of
chemical bonds – many time with
the loss of water or CO2
Mechanical deformation – rocks
under pressure may bend or flow
plastically in to folds or sheer and
break up
From yahoo images
Types of metamorphism
Dynamic – mechanical deformations –
shearing, grinding, flattening,
elongation– produces broken and
distorted textures
Contact – formed by the intrusion of
magma due to the high temperature
altering the structure on the surface
of the rock surrounding the intrusion
From yahoo images
Contact Metamorphism
Types of metamorphism
Regional – alteration due to both
thermal and mechanical
From yahoo images
The Rock Cycle