Download 3 types of rocks

 There are 3 types of
rocks found on Earth:
 Igneous
 Sedimentary
 Metamorphic
 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 are common along plate
boundaries or mantle hot spots
 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)
 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.
 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.)
 Aphanitic rocks have no
visible crystals, and probably
formed by fast cooling above
ground.
 Phaneritic rocks have
visible crystals, and
probably formed by slow
cooling below ground.
 Porphyritic rocks have
both visible and nonvisible
crystals, and probably
formed by two different
cooling events.
 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.)
 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.)
 Structures and
formations seen in
igneous rocks include:
 Hexagonal columnar




joints
Pahoehoe lava flows
Dikes, sills, and
batholiths (plutons)
Pillow basalts
Volcanoes
 The most common types
of igneous rocks include:
 Rhyolite
 Andesite
 Basalt
 Granite
 Diorite
 Gabbro
 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 are
likely to form in areas
such as:
 Deltas
 Beaches
 Rivers
 Glaciers
 Sand dunes
 Shallow seas
 Deep oceans
 Sedimentary rocks are classified into two
groups:
 Clastic rocks
 Chemically formed rocks
 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.
 Very small particles
make up mudrock.
 Medium sized
particles make up
sandstone.
 Large particles make
up conglomerates.
 Sedimentary rocks that
form from chemical
processes are called
biochemical rocks
(formed from living
things) or Chemical
precipitates (formed
from lakes or shallow
seas.)
 Structures and
formations seen in
sedimentary rocks
include:
 Stratification
 Cross bedding
 Graded bedding
 Ripple marks
 Mud cracks
 Fossils
 Conglomerate
 Sandstone
 Shale
 Limestone
 Gypsum
 Oolites
 Chert (including
black flint and red
jasper)
 Metamorphic rocks are
formed by heat and
pressure changing one
type of rock into another
type of rock.
 Metamorphic rocks form
near lava intrusions, at
plate subduction zones,
and in deep mountain
roots.
 Lava intrusions can
provide heat that
causes metamorphic
rocks to form. These
small areas of
metamorphic rock
form from contact
metamorphosis.
 Rocks that
metamorphose because
of increasing heat and
pressure found at plate
subduction zones and in
deep mountain roots
form large areas of
metamorphic rock
through regional
metamorphosis.
 Metamorphic rocks are
classified into 2 major
groups:
 Foliated
 Nonfoliated
 Foliated rocks form when
differential pressure causes
minerals to form in layers.
 These rocks will have stripes
or planes that they will break
easily along.
 These “stripes” don’t usually
line up with the original
bedding planes in
sedimentary rocks.
 Nonfoliated metamorphic
rocks formed in areas
where the pressure from
all sides was equal, so
there is no “linear” quality
to the rocks.
 Structures and formations
seen in metamorphic
rocks include:
 Folding
 Plastic deformation
 Stretching
 Alternating dark and light
layers (gneissic foliation)
 Some common types of
metamorphic rock include:
 Slate
 Schist
 Gneiss
 Amphibolite
 Marble
 Quartzite
 Metaconglomerate