3 types of rocks ppt

3 types of rocks


3 types of rocks
• There are 3 types of
rocks found on Earth:
– Igneous
– Sedimentary
– Metamorphic

• Knowing the differences
between these 3 types
of rocks allows us to
learn about Earth’s past.


Igneous Rocks - Formation
• Igneous Rocks are
formed by melting,
cooling, and
crystallization of other
rocks.
• Igneous rocks form as a
result of volcanic
activity, hot spots, and
melting that occurs in
the mantle.


Igneous rocks
• Igneous rocks are common along plate

boundaries or mantle hot spots


Igneous Rocks - Classification
• Igneous rocks are classified
using their texture in the
following ways:
–
–
–
–

Glassy
Aphanitic (no visible crystals)
Phaneritic (visible crystals)
Porphyritic (Some visible and
some not visible crystals)


Igneous Rocks - Texture
• Crystal size is used to
classify igneous rocks.
• Crystals form as the
rock cools, and the
crystal size can tell us a
lot about its cooling
history:
– The larger the crystals,
the slower it cooled.

Igneous Rocks - Texture
• Glassy igneous rocks
have no crystal
structure, and probably
formed by very rapid
cooling (such as on the
surface of a lava, or
when a lava enters the
water.)


Igneous Rocks - Texture
• Aphanitic rocks have no
visible crystals, and
probably formed by fast
cooling above ground.


Igneous Rocks - Texture
• Phaneritic rocks have
visible crystals, and
probably formed by
slow cooling below
ground.


Igneous Rocks - Texture
• Porphyritic rocks have
both visible and

nonvisible crystals, and
probably formed by two
different cooling events.


Igneous Rocks - Classification
• Dark igneous rocks are
formed from basaltic or
mafic magma. (Mafic
because it contains a lot
of magnesium and iron).
• The magma that forms
these rocks is usually very
hot (around 1000°C) and
viscous (about the same
viscosity as ketchup.)


Igneous Rocks - Classification
• Light colored igneous
rocks are formed from
silicic (high silica content)
or felsic magmas.
• The magmas that form
these rocks is usually
more cool, (lower than
850°C), and more viscous
(about the viscosity of
peanut butter.)

Igneous rocks - Formations
• Structures and
formations seen in
igneous rocks
include:
– Hexagonal columnar
joints
– Pahoehoe lava flows
– Dikes, sills, and
batholiths (plutons)
– Pillow basalts
– Volcanoes


Igneous Rocks - Examples
• The most common
types of igneous rocks
include:
–
–
–
–
–
–

Rhyolite
Andesite
Basalt
Granite

Diorite
Gabbro


Igneous rocks charted


Igneous rocks - Story
• What do you know
about the history of the
Earth in the place where
this rock was found?


Sedimentary Rocks - Formation
• Sedimentary rocks are
formed by weathering,
erosion, deposition,
compaction, and
cementation of other
rocks.
• Sedimentary rocks form
in areas where water,
wind, or gravity deposit
sediments.


Sedimentary rocks - formation
• Sedimentary rocks are
likely to form in areas

such as:
–
–
–
–
–
–
–

Deltas
Beaches
Rivers
Glaciers
Sand dunes
Shallow seas
Deep oceans


Sedimentary rocks - Classification
• Sedimentary rocks are
classified into two
groups:
– Clastic rocks
– Chemically formed rocks


Sedimentary rocks – Classification
• Sedimentary rocks are
Clastic if they are made
of pieces of other rocks

that have been
weathered and eroded.
• Clastic rocks are
grouped based on the
size of grain that they
are made from.


Sedimentary rocks - Classification
• Very small particles
make up mudrock.
• Medium sized particles
make up sandstone.
• Large particles make up
conglomerates.


Sedimentary rocks - Classification
• Sedimentary rocks that
form from chemical
processes are called
biochemical rocks
(formed from living
things) or Chemical
precipitates (formed
from lakes or shallow
seas.)


Sedimentary rocks - formations

• Structures and
formations seen in
sedimentary rocks
include:
–
–
–
–
–
–

Stratification
Cross bedding
Graded bedding
Ripple marks
Mud cracks
Fossils


Sedimentary rocks - Examples
• Some of the most
common types of
sedimentary rocks
include:
–
–
–
–
–
–

–

Conglomerate
Sandstone
Shale
Limestone
Gypsum
Oolites
Chert (including black
flint and red jasper)


Sedimentary rocks - Story
• What do you know
about the history of the
Earth in the place where
this rock was found?