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Bell ringer 11/4 List rocks (not Brock) How could rocks be identified? What characteristics could be used?
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Rocks (aka boulders)
Ch 6
List rocks (not Brock) How could rocks be identified? What characteristics could be
used?
Bell ringer 11/4
Igneous Sedimentary metamorphic
3 major types of rocks
igneous
Igneous rock
From fire! Igneous rock is sometimes referred to as fire rock
from its Latin translation 'ignis' which means 'pertaining to fire'. This is an appropriate translation as igneous rock is derived from the cooling and crystallization of magma or lava. Magma is a naturally occurring molten rock material which comes from deep within the Earth's surface. Magma's liquid state allows for it to eventually rise to the surface where it is described as volcanic lava.
https://www.youtube.com/watch?v=UNJU-5vCrJc
https://www.youtube.com/watch?v=vhAfgEnxNc0
Bell ringer 11/6
What processes occur to change rocks from
Igneous-metamorphic
Metamorphic-sedimentary
Sedimentary-sedimentary
Chemical- change in temp and pressure
Erosion, deposition, compaction
Weathering, deposition, compaction, cementation
sediment
Broken pieces of minerals, rocks, and organic matter
For thousands, even millions of years, little pieces of our earth have been eroded--broken down and worn away by wind and water.
These little bits of our earth are washed downstream where they settle to the bottom of the rivers, lakes, and oceans.
Layer after layer of eroded earth is deposited on top of each. These layers are pressed down more and more through time, until the bottom layers slowly turn into rock.
Grand canyon
metamorphic
Altered existing rock Metamorphic rocks are rocks
that have "morphed" into another kind of rock. These rocks were once igneous or sedimentary rocks.
How do sedimentary and igneous rocks change? The rocks are under tons and tons of pressure, which fosters heat build up, and this causes them to change. If you exam metamorphic rock samples closely, you'll discover how flattened some of the grains in the rock are.
The concept of the rock cycle is attributed to James Hutton
(1726—1797), the 18th-century founder of modern geology.
The main idea is that rocks are continually changing from one type to another and back again, as forces inside the earth bring them closer to the surface (where they are weathered, eroded, and compacted) and forces on the earth sink them back down (where they are heated, pressed, and melted).
So the elements that make up rocks are never created or destroyed — instead, they are constantly being recycled. The rock cycle helps us to see that the earth is like a giant rock recycling machine!
http://www.learner.org/interactives/rockcycle/diagram.html
Rock cycle
Process of changing rocks over time and
through a series of ways
Rock cycle
The properties that a rock exhibits are our
main clues to identify them. All three types of rocks exhibit different properties. However, there are some properties that are common among all three types of rocks. These properties are form, color, composition, and texture.
Stability is directly related to the physical properties of rocks Rate of which is breaks/changes
Properties of rocks
1900s studying rocks that form from magma
As it cools minerals crystalize Elements are removed
Change in composition Proposed a theory to explain why this happens
Hypothesis- gradual and continuous formation have similar compositions , mineral types change, as well as the composition
Browen’s reaction scale
Rate of which it breaks down is due to
composition Measure of the rock’s ability to stay in its
original state Strength in bonding- resistant to weathering &
decomposition
Chemical stability of minerals
Like minerals rocks have areas of weakness
Ex- may break in between layers, may break due to cooling in joints, may break due to pressure under the earth’s surface lifting it to the top then exposing the rock to the elements
http://www.youtube.com/watch?v=9Xv1DoqkARQ
Physical stability of rocks
compacted- layers squeeze the rock (lots of
pressure and weight) together
Cementation- “glued” together by water deposits (minerals within the water) Water mixes different rock pieces togetgher
they chemically combine forming a precipate which causes bonding with different atoms Thus forming cement
Sedimentary rocks- formation
The rate at which sedimentation occurs of an
area is 1.5 mm per year. At this rate how long will it take for 10cm of sedimentation to compile?
Bell ringer 11/12/13
Chemical
sedimentary rock Minerals were once
dissolved in water and precipitate out changing composition and concentration evaporation
Organic sedimentary Formed due to the
remains of living things
Ex- coal and limestone Dead fossils deposit
minerals into rock and sand, when the water is compacted out a new cemented sedimentary rock is formed
clastic
Deposits of rock made from the mixture of other bits of rock
Due to erosion and weather Breccias- sharp corners Conglomerate- rounded Sandstone- dusty
texture Shale- flat flaky layers
breccia
Conglomerate
Sandstone
Shale
Sorting- natural separation due to wind or
water based on size Smaller pieces tend to come together due to
mass Angularity- transported naturally but pieces of
sediment collide with each other and other rocks Collisions cause breaking Gives a smoothing effect
Characteristics of clastic sediments
Stratification- layering, caused by conditions Cross-beds- slanting layers, formed in dunes or river
beds Graded bedding- different sizes and shaped bits of
sediment form at different layers Ripple marks- cracks due to wind and water in sand Mud cracks- murky deposits of sedimentary rock dry
out, shrink in volumes, creating gaps Fossils and concretions- remains of dead material
left and preserved in sedimentary rock
Sedimentary rock features
stratification
Cross-beds
Graded bedding
Ripple marks
Mud cracks
Fossils and concretions
Heat, pressure, and fluids cause rocks to
morph or change shape and entity Type of rock that forms after metamorphism can
tell the observer it’s origin, age, and characteristics of it’s environment
Metamorphic rock
Contact
meteaphormism Magma meets up
with pre-exisitng rock
The rock morphs due to the magma’s heat
Fluids may evaporate and cause changes in the rock
REGIONAL
METAMORPHISM Occurs over a large
area during large movement of plate tectonics
Heat and pressure cause chemical changes to the rock’s minerals Volcanism often
goes hand in hand
Regional morphism
Minerals help determine the composition Original rock is exposed to heat and pressure
changing the mineral structure and make up Foliation- texture where it is arranged in
planes or brands May have alternating dark and light bands due
to composition Slate, schist and gneiss
Classification of metamorphic rocks
Non-foliated- no bands of aligned mienrals
Have: may have grains of one mineral or small amounts of others
Grains do not change position
classification
Foliated rocks
Non foliated