Download Rocks

Rocks
Rocks!
What makes
up Earth’s
Crust
Three types of rocks…
Igneous
Sedimentary
Metamorphic
What is a rock?
A rock is a solid that forms in nature. It may
have one or more types of minerals within it
(or no minerals at all).
Some rocks have minerals, some don’t…
Minerals are clearly
visible in some
igneous rocks
like…..
There are no mineral
crystals in obsidian.
What is the rock cycle?
Natural
processes
that…



Forms
Changes
Breaks down
rocks
 Rock
is
reformed
into another
type of rock.
The rock cycle in action…
The rock cycle
shows the
three types of
rocks.
 Igneous
 Metamorphic
 Sedimentary
 Listen and watch
how the processes
formed the three
types of rocks.
QuickTime™ and a
Cinepak decompressor
are needed to see this picture.
Igneous Rock


Forms when molten rock
cools and becomes a solid.
Igneous rocks may form
inside Earth or on Earth’s
surface.
Intrusive-forms when
magma cools within the
Earth.
Extrusive-forms when lava
cools on the surface.
What is a rock’s texture?
Texture refers
to the size of
the mineral crystals:
coarse, fine, glassy
Coarse
Pumice
Fine
Glassy
Textures of Intrusive Igneous Rock
Intrusive Rocks



The size of mineral crystals depends on how
quickly the magma or lava cooled.
The high temperatures of the interior of the
Earth causes magma to cool slowly.
Slow cooling allows large crystals to form.
How are we able to see
intrusive rocks?

Ship Rock formed 30
million years ago.

Magma cooled to form
intrusive rock.

Intrusive igneous rock
has been left as weaker
rock (like sedimentary)
has worn away
due to weathering &
erosion.
Textures of Extrusive Igneous
Rock
The surface of Earth is much cooler than the
interior, causing lava to cool quickly.
 There is no time for large mineral crystals to
form.

Composition of Igneous Rocks…


Most igneous rocks are made up of silicate materials
The color tells you how much silica the rock has.

High levels of silica will be
lighter in color.

Low levels of silica will be
darker in color.
What type of rock was carved to
create Mount Rushmore?
Igneous!
Interesting Rock Formations
#1
#3
#4
#2
Which of these is a rock?
A. halite
C. mica
B. granite
D. quartz
Answer: B. granite
Which is formed from cooling magma?
A. metamorphic
C. sedimentary
B. igneous
D. sandstone
Answer: B. igneous
Sedimentary Rocks:
“something that settles”


Small pieces of rock
turn into pebbles,
gravel, sand, clay, and
plant & animal matter.
They tumble down
rivers and streams.
These pieces settle in
a new place and begin
to pile up and the
sediments form flat
layers.
Sediments harden into rock
in two ways.
Compaction- layer after layer of sediments are
deposited, they are pressed together tightly to
form rock.
Cementation- sediments are held together by minerals
that have crystallized between them (acting as
cement).
Sedimentary rocks
may be rich in….
Fossils- Remains or trace of an
organism from long ago.
 Coal-Made up of the remains of dead
plants. The coal we use today formed
millions of years ago in swamps.
 Limestone-made of carbonate
minerals (calcite) from seashells that
settle on the bottom of the ocean.

COAL: Natures rock…..
Coal is made from dead
plants and over time pressed
into the Earth.
Sedimentary Rock tells a story
about Earth’s past…
These rocks are laid
down in layers with
the oldest on the
bottom.
Do you remember
what rock layers are
called?
Law of Superposition or stratification!
Do you remember?
What layer of rock is the… Oldest?
Youngest
Oldest
Metamorphic Rock=
Changed Rock
Sedimentary
Metamorphic
Composition and Texture:
a way to identify metamorphic rock
 When
mineral grains line up in parallel layers, the
metamorphic rock is said to have a Foliated
texture.
Slate
Gneiss
Non Foliated Metamorphic Rock
When a metamorphic rock does not have “foliation” it typically has
only one mineral, therefore no parallel banding patterns.

Typically made
up of one type
of mineral so
different
minerals can not
line up in bands.
Marble
formed
from
limestone
Quartzite forms from Sandstone
Metamorphic Rocks
are formed when…
+
+
Metamorphic Rock
=
How much of Earth’s Crust is
made of each type of rock?
Surface = 75% Sedimentary Rock Entire Crust = 95% Igneous and
Metamorphic Rock
What type of rock is the most common
on the surface of Earth’s crust?
A. metamorphic
C. sedimentary
B. igneous
D. sandstone
Answer: C. sedimentary
95% of Earth’s entire crust consist of what type(s) of
rock?
A. metamorphic
B. sedimentary
C. igneous
D. igneous and metamorphic
Answer: D igneous and metamorphic