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Rocks (aka boulders) Ch 6

Rocks (aka boulders) Ch 6

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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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Page 1: Rocks (aka boulders) Ch 6

Rocks (aka boulders)

Ch 6

Page 2: Rocks (aka boulders) Ch 6

List rocks (not Brock) How could rocks be identified? What characteristics could be

used?

Bell ringer 11/4

Page 3: Rocks (aka boulders) Ch 6

Igneous Sedimentary metamorphic

3 major types of rocks

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igneous

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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

Page 6: Rocks (aka boulders) Ch 6

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

Page 7: Rocks (aka boulders) Ch 6

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.

Page 8: Rocks (aka boulders) Ch 6

Grand canyon

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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.

Page 10: Rocks (aka boulders) Ch 6

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

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Process of changing rocks over time and

through a series of ways

Rock cycle

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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

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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

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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

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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

Page 21: Rocks (aka boulders) Ch 6

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

Page 22: Rocks (aka boulders) Ch 6

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

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Chemical

sedimentary rock Minerals were once

dissolved in water and precipitate out changing composition and concentration evaporation

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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

Page 25: Rocks (aka boulders) Ch 6

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

Page 26: Rocks (aka boulders) Ch 6

breccia

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Conglomerate

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Sandstone

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Shale

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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

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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

Page 32: Rocks (aka boulders) Ch 6

stratification

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Cross-beds

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Graded bedding

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Ripple marks

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Mud cracks

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Fossils and concretions

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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

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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

Page 40: Rocks (aka boulders) Ch 6

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

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Regional morphism

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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

Page 44: Rocks (aka boulders) Ch 6

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

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Foliated rocks

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Non foliated