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Rocks and Minerals
Most rocks are composed of minerals
Descriptive terms about minerals found in rocks Shape Color Luster Texture Hardness
Igneous Rocks
Froms from magma (below ground) or lava (above ground)
Has crystals Classified by
Origin Texture Mineral Composition
Igneous Rocks
Texture Depends on size and shape of minerals (if
present) Rapidly cooling lava forms fine-grained
rocks with small crystals Slowly cooling magma forms course-
grained rocks with large crystals Does intrusive or extrusive rock have
larger crystals? Intrusive, it takes longer to cool so there is
more time for the crystals to grow
Igneous Rocks
Mineral composition Silica is found in magma and the
quantity varies. Low-silica magma forms rocks that are
dark in color. High-silica magma forms rocks that are
light in color. Different minerals determine colors in
the rock
Sedimentary Rocks
Sediment is small, solid pieces of material that come from rocks or living things.
Formed from other rock and exposed to forces that wear away Earth’s surface. Erosion – breaking up of rocks due to wind, running
water, ice (glaciers) Deposition – particles broken down by erosion are
deposited as loosely packed sediment Compaction – process that presses sediments together Cementation – while compaction is taking place,
minerals slowly dissolve in the water. The dissolved minerals crystallize & glue particles of sediment together.
Types of Sedimentary Rock
Clastic Rock fragments are squeezed together.
Fragments may be microscopic or large Shale, sandstone
Organic Forms from the thick layered remains of plant
and/or animals Coal, limestone
ChemicalCrystallized minerals that dissolve in a solution
Rock salt
Metamorphic Rocks
Heat and pressure deep beneath the Earth’s surface can change any rock into a metamorphic rock
High temperatures change the size and shape of the grains and crystals
Classified according to the arrangement of the grains that make up the rock
Types of Metamorphic Rocks
Foliated Grains arranged in parallel layers or bands,
may split into layers Slate
Nonfoliated Mineral grains arranged randomly, does not
split into layers Marble
Bookwork
Mass movement of landforms Gravity plays a role Water plays a role
Water erosion by rivers, ect How does the speed of the water affect the
amount and size of particles moved? Movement of rocks
The further a boulder moves down steam, the smaller it gets. Why?
Bookwork
Glaciers Leave behind U-shaped valleys Move the most material over time Form when more snow falls and melts
Waves Ocean waves are created by wind on the
surface Water particles move up and down, but not
in any other direction Wear down beaches and rocks
Rock Cycle
What process leads to the formation of sediment? Erosion! How is weathering related? What is soil sediment? How is it formed? Weathering and erosion of rocks into
smaller and smaller pieces makes soil
Soil Formation
Soil is made of tiny pieces of eroded rock and HUMUS HUMUS is a mixture of organic material. It
comes from broken down plant and animal matter
Majority of HUMUS comes from earthworms
The higher the HUMUS content, the better the soil
Rock Cycle
Three main types of Rocks: Sedimentary, Metamorphic, Igneous
Energy used to form or change rocks: Heat & Pressure (melting, etc)
Processes used to change rocks: Erosion, weathering, deposition,
cementation, melting
Rock Cycle
Metamorphic
Igneous
Sedimentary
Igneous Igneou
s
Metamorphic
MetamorphicSedimentary
Sedimentary
Age of Rocks
How do scientists determine the age of rocks? This age is often referred to as “relative age,” why? For very old rocks, scientists typically use a process
called carbon dating to determine their relative age. This process is based on the assumption that carbon has degraded at a particular rate for the entire history of the Earth.
Are the oldest rocks always at the bottom of the layers?
How could older rocks end up on top of younger rocks?
Folding & Faulting
The Earth’s surface goes through folding and faulting which pushes and turns the rock layers .
At fault lines, there will be noticeable “movement” in the rock layers. Pg G119
Earth’s surface is constantly changing and this can include the rock layers, especially at fault lines
Fossils
An index fossil helps to date rocks. Must be widely distributed Must represent an organism that existed
briefly Tell the age of the rock based on when the
fossil occurred
Fossils
How are fossils formed? Die, sediments are deposited on top,
compact down, pressure eventually cements all and turns the bones into rock
Will everything that dies turn into a fossil? What type of rock are fossils found in?
Sedimentary, sometimes in metamorphic How do fossils show evidence of the
changing surface of the Earth? Moving sediments, changing species, and?
Fossils, con’t
Why are more recently deposited rock layers more likely to contain fossils resembling existing species than older rock layers? Older fossils tend to represent species that
are extinct If an old fossil looks like a modern
organism, what can you conclude? The evolutionary rate of the organism is
slow.