Download a type of rock that forms when sediments are

Rocks
and
the Rock Cycle
Classifying Rocks
By:
• Texture
• Grain size
• Shape
• Patterns
• Mineral Composition
Texture
• The look and feel of the
rock’s surface.
• Rough, chalky,
smooth or
glassy.
Grain Size
• The size of the actual grain
in the rock.
• They are fined-grained,
coarse-grained, or no visible
grains.
Grain Shape
• Is the way a grain looks on
a rock.
Grain Pattern
• The patterns of the grains
form are wavy, swirling, or
like a stack of planks.
• Some rocks have no visible
grains even under a
microscope.
Mineral Composition
• Will show the mineral
composition in the rocks.
• Minerals are found by a
series of tests.
Types of Rocks
There are three major types:
• Igneous – a type of rock formed
from the cooling of lava.
• Sedimentary – a type of rock that
forms when sediments are
compacted.
• Metamorphic – forms when existing
rocks are changed by heat and
pressure.
Igneous Rocks
• Classified according to their
origin, texture, and mineral
composition.
• Extrusive rocks – igneous rocks
formed from lava that erupted
onto the Earth’s surface.
• Basalt is the most common
extrusive rock.
Igneous Rocks
• Intrusive Rocks –formed when
magma hardened under the Earth.
• Granite is most abundant intrusive
rock in the continental crust.
• Granite forms the core of many
mountain ranges.
Igneous Rocks
• Basalt is an extrusive rock.
• Magma that is high in silica
usually forms lighted colored
rocks such as granite.
• Many igneous rocks are hard,
dense and durable.
Igneous Rock Texture
• Depends on the size and shape of
the mineral crystals.
• Maybe glassy, coarse-grained, or
porphyritic.
• Intrusive rocks have large grains.
• Slow cooling magma forms coarsegrained rocks.
• Extrusive rocks have a fine-grained
or glassy texture.
• Rapid cooling lava forms fine
grained rocks.
Igneous Rock Texture
• Porphyritic rocks have both finegrains and large crystals
scattered throughout.
• Porphyritic rocks form when
intrusive rocks form in 2 stages.
• Magma begins to cool slowly
making large crystals while the
other materials around it cool
quickly making a fine grained
background.
Sedimentary Rocks
What is it ?
• Rocks formed from particles
deposited by water and wind.
• Sediments are small pieces of
material that come from rocks or
living things.
• Sediments may include shells,
bones, leaves, stems, and other
remains of living things.
Erosion and Deposition
• Wind, water, and ice can
carry sediment and deposit it
in layers.
• Erosion breaks up rocks.
• Deposition is the process by
which sediment settles out of
the water or wind.
Compaction and Cementation
• Compaction and cementation over
millions of years, thick layers of
sediment build up Compaction is the
process that presses sediments
together. New layers help compact
layers underneath. While being
compacted minerals slowly dissolve in
the water. Minerals seep into spaces
between particles of sediment. This is
called sedimentation.
Types
• There are 3 major groups of
sedimentary rocks.
• Clastic forms when rock fragment
are squeezed together.
• Organic forms from remains of
plants and animals.
• Chemical form when minerals are
dissolved in a solution crystallize.
Uses
• Sandstone and limestone
have been used as building
materials. Limestone is also
important when smelting
iron ore.
Metamorphic Rock
What is a Metamorphic
Rock?
• Any rock that can be changed
into a metamorphic rock by heat
and pressure.
• Can change from igneous,
sedimentary, and other
metamorphic rocks.
• The deeper the rock in the Earth
the more heat and pressure.
How to classify a
Metamorphic Rock?
• Geologists classify metamorphic rocks
by the arrangement of the grains
that make up the rocks.
• Metamorphic rocks have their grains
in bands said to be foliated.
• Metamorphic rocks without bands are
called nonfoliated.
Metamorphic Rocks
• Most of metamorphic rocks
are extremely hard.
• Some examples are slate,
gneiss and quartzite which
come from shale, granite, and
sandstone.
Metamorphic Rocks
• Metamorphic rocks can be sued
for many different things.
• The Taj Mahal in India is made
from the metamorphic rock
marble.
• Chalkboards, flooring, roofing,
walkways are created from slate,
which comes in different colors.
Metamorphic Rocks
• Heat and pressure deep
beneath the Earth’s
surface can change any
rock into metamorphic
rocks.
Rock Cycle
• Forces with in the Earth
build, destroy, and change
rocks. The different paths
a rock can take form the
Rock Cycle.
Processes within the
Rock Cycle
• Erosion
• Melting
• Heat and Pressure
Melting
Erosion
Rock Cycle and Plate
Tectonics
• Rock Cycle is driven by Plate
Movement
• Plates press rocks into the
mantle, forming magma.
• Plate movement creates the
heat and pressure required
for the formation of
metamorphic rock.