Transcript Elephants Under Attack

The Rock Cycle
Chapter 7
Lesson One- What are Minerals
Lesson 2- How Do Rocks Form
Lesson 3- How are Rocks Changed?
Lesson 1 What are Minerals
Mineral- is a naturally occurring, nonliving solid that has
a specific chemical makeup and a crystalline, or
repeating, atomic structure
Examples are quartz, diamonds, and salt
There are hundreds of different minerals
One property that is easy to see is COLOR
Streak- the color of the powder left behind when you
run a mineral against a rough white tile, or a streak
plate.
Luster- the way a mineral’s surface reflects light
Mineral Hardness
-An important property of minerals is their hardness
Hardness- a minerals ability to resist being scratched
-some minerals are so hard that they can’t be scratched by
anything
Friedrich Mohs, found that minerals can be classified by how
are they are to scratch. He came up with a scale that ranks
minerals from 1 to 10 according to their hardness (talc=1 and
diamond=10)
-Your fingernail has a hardness of about 2.5
-Steel nails have a harness of about 5.5
Unique Properties of Minerals
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The crystal structure of
calcite refracts, or bends,
light a certain way.
Lodestone can be used in
a compass to help you
find your way. Some kinds
of minerals glow under
ultraviolet, or “black” light.
Quarts develops an
electric potential when
pressurized.
Calcite
Lodestone
Lesson 2: How do
Rocks Form
Igneous Rocks
Rock- a natural solid made of one
or more minerals
-rocks are classified into
three groups depending on
how they form
Igneous Rock- rock that forms
when melted rock cools and
hardens
-these rocks that form
underground have large
crystals that form
Sedimentary Rock
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These are rocks that have been formed by weathering and erosion.
This causes “sediments” to relocate and set down or deposit in
another location.
Deposition- the process by which sediment settles out of water or
is dropped by the wind.
Some minerals dissolved in water come out of solution, forming a
kind of cement
Sedimentary rock- rock that is formed by cemented sediments
Think of worn away or layered rocks!!
Examples:
 Sandstone
 Limestone
Metamorphic Rock
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Rocks can change form under certain conditions
Metamorphic rock- rock that is changed by heat and
pressure
These rocks are found in every mountain range on
Earth
Because of weight and pressure, rocks get very hot
which causes them to change into a new rock
They also form on the ocean floor
Examples:
 Slate
 Marble
 Quartzite
Lesson 3 How Are Rocks Changed
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Rocks get broken down by weathering
Weathering- the process of wearing
away rocks by a natural process like,
wind, rain, earthquakes, floods and
volcanoes
All rocks on Earth’s surface are
weathered, but not all rocks weather at
the same rate
Rocks that contain mostly hard
minerals weather much more slowly
than rocks that contain mostly soft
minerals.
Erosion- the process of moving
sediments by wind, water, and ice
The Rock Cycle
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Weathering, erosion,
deposition, heat, and
pressure can all
change rocks
Rock Cycle- is the
continuous process in
which one type of
rock changes into
another type
Soil Formations
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Some soil is good for farming
Rich farming soil contains small pieces of
decayed plant and animal matter, called
humus. This provides additional nutrients
that plants need to grow.