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Rocks and The Rock Cycle
Rocks
• All rocks are mixtures of minerals.
• Scientists classify rocks according to how
they are formed.
• There are three types of rocks:
Igneous
Sedimentary
Metamorphic
Igneous Rocks
• Igneous rocks form from cooled magma
or lava.
• When magma or lava cools it hardens to
form a rock.
• Magma is melted rock below Earth’s
surface.
• Lava is melted rock that flows out of the
ground onto Earth’s surface.
Igneous Rocks and Crystals
• Igneous rocks may have small or large
crystals.
• If the rock is made from magma it may
have large crystals because it cools
slowly.
• If the rock is made from lava it may have
small crystals because it cools faster.
Igneous Rocks
Volcano
Examples of Igneous Rocks
Obsidian
Granite
Sedimentary Rocks
• Sedimentary rocks are made of
sediments.
• Sediments are bits of rocks, shells, and
the remains of dead plants and animals.
• Over millions of years sediments that are
buried under ground are pressed and
cemented together to form a sedimentary
rock.
Sedimentary Rocks and Fossils
• Fossils are often found in Sedimentary
rocks.
Layers of Sedimentary Rocks
• Sedimentary rocks often form in layers.
• The oldest layer is on the bottom.
• The youngest layer is on the top.
Oldest or Youngest?
Youngest
Oldest
Examples of Sedimentary
Rocks
Limestone
Shale
Metamorphic Rocks
• Metamorphic rocks are formed from
existing rocks that have been squeezed
and heated deep inside Earth’s crust.
Examples of Metamorphic
Rocks
Marble
Gneiss
The Rock Cycle
• The rock cycle is the process of rocks
changing into other kinds of rock.
Factors of The Rock Cycle
•
•
•
•
•
Melting
Cooling and Hardening
Weathering and Erosion
Squeezing and Cementing
Heating
The Rock Cycle
Questions
What are some factors
that affect the rock cycle?
Are rocks always
changing?
Which type of rock has
layers?
Which layer is the oldest?
Bottom or Top
How are rocks formed?
IgneousSedimentaryMetamorphic-