Learning Log
What are the three types of rock, as
defined by how they’re formed?
Give an example of each type.
Essential Question
What are the different types of
rocks?
Earth Day Info
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ourselves
Sedimentary Rocks
Noticeable Characteristics of a
Sedimentary Rock?
• Often have layers or bands across them.
• Often contain fossils which are fragments of
animals or plants preserved within the rock.
• Scrape and often crumble easily
Sedimentary Rocks
• Much of Earth’s surface is covered with sediments –
pieces of solid material deposited on Earth’s surface
by wind, water, ice, gravity, or chemical
precipitation
– Sediments formed through weathering
(breakdown of rocks)
– When sediments become cemented together,
they form sedimentary rocks (form in layers)
The formation of Sedimentary Rocks
Weathering
• Weathering –physical and
chemical processes that break
rock into smaller pieces.
– Chemical weathering – minerals in a
rock are dissolved or chemically
changed (rock changes)
– Physical weathering – minerals are
not chemically changed, rock
fragments simply break off the solid
rock (rock does not change)
Weathering
Chemical Weathering caused by
Physical Weathering caused by
– Water: dissolves minerals
– Temperature: water expands
as it freezes, breaking rocks
– Oxygen: oxygen reacts with
open
substances (oxidation)
• Ex. Formation of pot holes
– Carbon dioxide: forms carbonic
in roads
acid that dissolves minerals
– Acid precipitation: changes pH – Pressure: removing rocks
above decreases pressure and
of water
– Temperature: influences rate of allows layers to peel off
• Ex. Rock removal can
chemical reactions
decrease pressure, causing
large pieces of rock to
explode off walls, burying
miners.
What is Erosion?
Erosion is the removal and movement of surface
material (sediments) from one location to another
location.
Four Main Agents: Water, Wind, Gravity, and Glaciers
–
–
Eroded materials are always carried downhill
Streams and rivers carry the small bits towards the sea
(continually wearing down as they progress).
What is Deposition?
When sediments are laid down on the ground or sink
to the bottoms of bodies of water.
–
–
The sediments are dropped by size. The largest
sediments will drop first and the smallest will drop last.
Sediments deposited when transport stops
What is Lithification?
Lithification is the process where sediments are
converted into solid rock (physical and
chemical process).
Lithification is a two part process:
Compaction: where the particles are
compressed together due to the weight of the
overlying sediments.
As more and more sediment is deposited, the bottom
layers are subjected to increasing pressure and
temperature
Cementation: is where the particles are glued
together.
Lithification
From pile of sand to solid rock
What is bedding?
• It is the horizontal layering of deposits and is the
primary feature of sedimentary rock
Importance of Sedimentary Rocks
• Geologic “snapshot” of surface
conditions in Earth’s past.
– Fossils
– Flow and direction of ancient rivers
– Natural resources-oil, coal, and
natural gas found in sedimentary
rocks
– Deposits of phosphate- used for
fertilizer
– Limestone- used to make
cement; used for building
Rock Identification
Each of you have had the opportunity to
observe at least one sample of a sedimentary
rock. In the space below note all of the
observations you made about it.
IGNEOUS ROCK
What are Igneous Rocks?
• Crystallize from molten material:
Magma – molten rock below the
Earth's surface
Lava – magma that erupts onto the
Earth's surface through a volcano
or crack (fissure)
• Nickname- “fire form rock”
Factors That Affect Magma Formation:
Temperature
• The deeper you go in
the Earth’s crust the
hotter it gets.
Water Content
• As the water content of
the rock increases the
melting temperature
decreases.
Pressure
• The deeper you go
pressure increases.
• An increase in pressure
increases melting
temperature.
Mineral Content
• Different minerals melt at
different temperatures.
Compare and Contrast
Igneous Rock
Types of Igneous Rock
• Extrusive
– Fine-grained rock that cooled
quickly on Earth’s surface when
lava is EXTRUDED from the Earth
• Intrusive
– Course grained igneous rock that
cooled slowly underground
Intrusive or Extrusive
Extrusive Rock
Intrusive Rock
Andesite
Basalt
Rhyolite
Gabbro
Granite
Diorite
Useful Characteristics of Igneous Rocks
• Building Material
– resistant to weathering
– Strength
• Ore deposits- minerals that contain a useful
substance
• Veins
• Pegmatites
• Kimberlites
–diamonds
Rock Identification
Each of you have had the opportunity to
observe at least one sample of an igneous rock.
In the space below note all of the observations
you made about it.
Metamorphic Rock
What is Metamorphism?
Metamorphism is the alteration of existing
rocks by either excessive heat and pressure,
or through the chemical action of fluids.
– During metamorphism, a rock changes form
while remaining solid.
Types of Metamorphism
Regional Metamorphism
•
Occurs when rocks are buried deep beneath Earth’s
surface and changed by increase in temperature and
pressure. Covers a large area
Contact Metamorphism
•
Occurs when rocks are heated by contact with magma
or lava. Covers a small area
Hydrothermal Metamorphism
• Extremely hot water reacts with rock and alters its
chemistry and mineralogy.
• Common around igneous intrusions and active
volcanoes
Metamorphic Rock Textures:
Foliated Texture:
Mineral crystals arranged in parallel
layers or bands (flatten under pressure)
Slate
(from clay
or shale)

Schist
(from granite,
basalt, or
shale)

Gneiss
(from granite)
Foliated Texture:
Slate
Foliated Texture:
gneiss:
Foliated or Nonfoliated
Nonfoliated
Foliated
Rock Identification
Each of you have had the opportunity to
observe at least one sample of a metamorphic
rock. In the space below note all of the
observations you made about it.
The Three Rock Types Re-Cap
• Sedimentary, Igneous,
and Metamorphic
• Grouped according to
how they form:
– Sedimentary rocks form
from cemented
sediments
– Igneous rocks crystallize
from magma
– Metamorphic rocks
form by changes in
temperature and
pressure to existing rock