Download characteristics of rocks

CHARACTERISTICS OF
ROCKS
1. Rocks are solid.
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2. Most rocks are mixtures of two or more
minerals.
3. Some rocks have some materials that
were once alive. Coal is a rock. It was
formed from dead trees.
4. A rock has no definite ingredients. One
part of a rock maybe different from
another part.
5. Rocks are grouped by the way they were
formed:
• from volcanoes
• from fine material that has settled, then
hardened
• from heat and pressure
IGNEOUS ROCKS
Rocks that have hardened from liquids are
called igneous rocks. The word igneous
comes from the Greek word for fire.
All rocks did not cool the same way.
Different speeds of cooling made
different size crystals.
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· Slow cooling formed rocks with large
crystals.
· Rapid cooling formed rocks with small
crystals.
· Extra-fast cooling formed rocks with no
crystals.
There are three textures of igneous rocks:
1. Volcanic Igneous Rocks
Extrusive Igneous Rocks
 No or Small Crystals
 Lava Cools Quickly
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2. Plutonic Igneous Rocks
 Intrusive Igneous Rocks
 Big Crystals
 Magma Cools Slowly
3. Porphyries
 Big and Small crystals
Intrusive
Igneous Rock Classification
Diorite
Andesite
Extrusive
Granite
Rhyolite
(Porphyritic)
Gabbro
Basalt
Igneous Rock Textures
Coarse-grained
Fine-grained
Porphyritic
Glassy
Vesicular
Pyroclastic
SEDIMENTARY ROCKS
 There are forces in nature that keep
breaking rocks into smaller and smaller
pieces. These broken pieces are called
fragments. Pebbles, gravel, sand, and
clay are some kinds of rock fragments.
Fragments are moved about by water,
wind, and frozen water called
glaciers. The fragments settle in a new
place and begin to pile up. The settled
fragments are called sediment. Sediment
is always laid down in flat layers.
Sediment can harden into solid rock.
Sediment can harden into sedimentary
rock in two ways:
 From the pressure of its own weight
 by cementing. Minerals dissolved in
water glue the sediment together
There are two textures of sedimentary
rock
 1. clastics-conglomerate, sandstone
 2. non-clastics-halite, limestone
Clastic rocks–made of cemented
sediments—are classified by their grain
sizes.
http://www.volcanoworld.org/vwdocs/vwlessons/lessons/Sedrocks/Sedrocks9.html
Non-clastic rocks form by chemical precipitation
(settling out from a solution.) Limestone is
made from calcite, chert from quartz, and
halite is rock salt.
http://www.volcanoworld.org/vwdocs/vwlessons/lessons/Sedrocks/Sedrocks10.html
Sedimentary Rocks
How They are Made
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Wind and water break down the earth
Bits of earth settle in lakes and rivers
Layers are formed and build up
Pressure and time turn the layers to rock
More about sedimentary rocks
Shale is the most
common sedimentary
rock
 Sedimentary rocks
cover about threequarters of the land
surface
 For more about
sedimentary rocks:
http://www.volcanoworld.org/vwdocs/vwlessons/lessons/Sedrocks/Sedrocks1.html
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Plant Fragments Are Often
Visible in Coal
Breccia
Limestone
Sandstone
Shale
METAMORPHIC ROCKS
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Heat and pressure can change many
things. They can even change rocks. The
name for changed-over rocks is
metamorphic rocks. Metamorphic
comes from Greek words meaning
change and form.
Metamorphic rocks are formed deep in the
earth where there is high temperature and
great pressure. The heat and pressure
change one kind of rock into another kind
of rock. The new rocks become harder
than the old rocks. They also look
different. Sometimes the minerals in
the rocks change too.
How is a metamorphic
rock made?
Metamorphic
rocks are made
deep inside the
earth where heat
and pressure
change the rocks as
shown in the picture.
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The pressure that changes rocks can also
tilt and fold them. Folding can lift rocks
and make them into high mountains.
There are two textures of metamorphic
rocks
1. foliated ( layered )
2. non-foliated
Metamorphic Rocks
Gneiss
Schist
The Rock Cycle
http://www.volcanoworld.org/vwdocs/vwlessons/lessons/Metrocks/Metrocks2.html
More about sedimentary rocks
Shale is the most
common sedimentary
rock
 Sedimentary rocks
cover about threequarters of the land
surface
 For more about
sedimentary rocks:
http://www.volcanoworld.org/vwdocs/vwlessons/lessons/Sedrocks/Sedrocks1.html
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http://www.volcanoworld.org/vwdocs/vwlessons/lessons/Rocks/Rocks8.html
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There are two kinds of weathering.
1. Mechanical weathering
Disintegration, Physical
- breaks rocks into smaller and smaller pieces. It
does not change the chemicals of the rocks.
2. Chemical weathering
Decomposition
- also breaks rocks into smaller pieces. It
changes the chemicals of the rocks.
Weathering breaks rocks into smaller
pieces. It does not carry away the
fragments. Erosion carries the
fragments away.
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CHEMICAL WEATHERING
(DECOMPOSITION)
Chemical weathering breaks up rocks and
changes the chemicals of the rocks.
Most chemical weathering is caused by
the actions of oxygen, rain water, or
carbon dioxide.
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1. Oxygen in the air links up with some
of the elements in rocks. The link-up
forms oxides. The oxides break away from
the rocks.
One oxide that you know is rust.
2. Rain water can change minerals in
two ways. A) It dissolves some minerals.
B) Water links up with other minerals.
3. Carbon dioxide in the air dissolves
easily in rain water. This forms carbonic
acid. Acids dissolve limestone.
Plant Wedging
Limestone
cave
features
chemical
weathering
Streams and Erosion
Glacier Erosion
Mechanical Weathering or
Disintegration or Physical Weathering
There are four main causes:
1. Temperature Change
2. Frost Action
3. Root Action
4. Animal Activity
Water Erosion
Root Growth
Oxidation