Sedimentary & Metamorphic
Rocks
Formation
o
Much of the Earth’s surface is covered with
sediments
n
Pieces of solid material that have been
deposited on the Earth’s surface
o
Rocks are formed when sediment cement together
Weathering
o
Physical and
chemical processes that break rock into smaller pieces
o
Produce clastic
(fragments) of all sizes
Erosion and Transport
o
Removal and
movement of surface materials from one location to another
n
Wind
n
Moving water
n
Gravity
n
Glaciers
Deposition
o
Sediments are laid down on the ground or sink to
the bottoms of bodies of water
o
Most sediments are deposited in depressions
called sedimentary basins
n
Often contain layers causing lithification
o
Pressure and temperature cause sediment to start
chemical and physical changes (cementation)
n
Can cause different mineral to become embedded
Features
o
Contain horizontal layering (bedding)
n
Graded bedding: heavier and coarser layers at
bottom
n
Cross bedding: inclined layers move forward
across a horizontal surface
o
Contain fossils and other evidence of past life
Classification
Importance
o
Provides a
geological “snapshot” of surface conditions in Earth’s past
o
Provides
information of past rivers
o
Helps geologists
learn how Earth has changed over time
o
Source of oil,
natural gas, and coal
o
Source of Uranium
o
Source of
building material
Metamorphic Rocks
o
Changes of rock
composition from increased pressure and temperature, but still in a solid state
o
High pressure
caused by vertical pressure of overlying rock or from compressive forces from
mountain building
Types of Metamorphism
o
Varies based on
temperature and pressure
o
Regional
metamorphism: large belts of metamorphic rock consisting of low, medium, or
high grade
o
Contact
metamorphism: small zones where high temperature and moderate to low pressure
meet solid rock
o
Hydrothermal
metamorphism: caused by very hot water which change rock composition
Metamorphic Textures
o
Foliated
n
Wavy layers and
bands
n
High pressure
n
Schist and gneiss
are common types
o
Nonfoliated
n
Lack mineral
grains with long axes in one direction
n
Blocky crystal
shapes
n
Quartzite and
marble are common types
o
Porphyroblasts
n
Large crystals
n
Example: garnet
Rock Cycle
o
Any rock can be
changed into another rock over time with the forces of temperature, pressure,
and weathering
o
The cycle may go
in many different directions