Chapter 4 Rocks

1
Chapter 4Rocks
2
Why must scientists who study rocks look at the
inside of them?

• Because the outside surfaces have been exposed to
  the effects of ice, water, and weather (Erosion).

3
Mineral composition and color

• 2. What three important things do scientists
  observe when studying rocks?
• -Mineral composition, color, and texture
• 3. What are rock forming minerals?
• -About 20 minerals that are found in the
  earths crust that make up rocks.
• 4. What minerals are found in granite?
• -Quartz, horneblende, mica, and feldspar

4
5.Some other ways scientists study rocks include

• Shape and color of the crystals
• Mineral content
• Color
• Texture
• And some other tests similar to the tests for
  minerals

5
Mineral Composition(This is also in the igneous
section on page 2)

• Most of Earths minerals contain Silica
• Silica is a material formed from oxygen and
  silicon.
• The silica content of magma and lava will affect
  the types of rock that form
• High silica usually forms light colored rocks
• Low silica usually forms dark colored rocks

6
Texture

• Grains- Give the rock texture
• What is texture?
• Texture is the look and feel of the rocks
  surface.
• The three grain sizes that make texture are
• Fine
• Coarse
• No visible

7
Texture Grain Size

• Coarse grained large grains and easy to see
• Fine grain microscopic and too small to see

8
There are two grain shapes

• Jagged
• Round
• There are two grain patterns
• Banded
• Non- banded

9
There are three main groups of rocks

• Igneous forms from cooling of magma or lava
• Sedimentary forms when particles of other rocks
  or the remains of plants and animals are pressed
  and cemented together
• Metamorphic forms when an existing rock is
  changed by heat, pressure or chemical reactions,
  forms deep underground

10
Section 2 Igneous Rocks

• An igneous rock is any rock that forms from magma
  or lava.
• The name igneous comes from the Latin word
  meaning fire
• Igneous rocks come from deep within the ground

11
Igneous Rock Identification

• 1. Igneous rocks are classified according to
  origin, texture and mineral composition
• Origin
• Texture
• Mineral composition

12
Intrusive and Extrusive

• 3. Extrusive rock is formed from lava that
  erupted onto the earths surface.
• 4. Intrusive rock is formed when magma hardens
  beneath the surface.
• Molten rock below the earths surface is called
  magma. When it makes it to the surface it is
  called lava.

13
Igneous IDQuestions 5-7

• Texture depends on the size and shape of the
  mineral crystals. The only exceptions are those
  rocks made of glass.
• Rapidly cooling lava forms fine-grained rock
• Slowly cooling lava forms coarse-grained rocks
  with large crystals
• Intrusive rocks should have coarse-grained
  texture while extrusive rock will have
  fine-grained texture.

14
Igneous Rocks ContinuedMineral Composition

• 1. Most of the earths rocks contain the mineral
  silica.
• 2. Silica content of rocks can affect the rocks
  color.
• Examples of Igneous rocks
• Rhyolite, Porphyry, Pegmatite, Granite, etc.

15
Uses of Igneous Rock

• Building Material
• Granite
• Cleaning and polishing
• Pumice and obsidian
• Sharp tools for cutting or scraping

16
Section 3 Sedimentary Rock

• Sediment - small, solid pieces of material that
  come from rock or living things.
• Ex. rock, shells, bones, leaves, stems, etc.
• Sedimentary rocks are formed through the process
  of
• 1.Erosion
• 2.Deposition
• 3.Compaction
• 4.Cementation

17
From Sediment to Rock
- Sedimentary Rocks

• Most sedimentary rocks are formed through a
  series of processes erosion, deposition,
  compaction, and cementation.

18
Sedimentary RocksErosion

• 2. Erosion- destructive forces including heat,
  cold, rain, waves, grinding ice, running water,
  wind and ice loosen and carry it away.
• (The forces of erosion form sediment)

19
Sedimentary RocksDeposition

• 3. Deposition - the process by which sediment
  settles out of the water or wind carrying it

20
Sedimentary RocksCompaction

• 4. Compaction - the process that presses
  sediments together
• Thick layers build up over millions of years
• The more layers, the more it presses down on the
  layers beneath them.

21
Sedimentary RocksCementation

• 5. Cementation - the process in which dissolved
  minerals crystallize and glue particles of
  sediment together
• While compaction is occurring, the minerals
  slowly dissolve in the water

22
Sedimentary Rocks

• 6. The 3 types of sedimentary rocks are
• Clastic
• Organic
• Chemical

23
Sedimentary Rock Clastic

• 7. Clastic rock- a sedimentary rock that forms
  when rock fragments are squeezed together
• Sediments can range in size
• Ex. shale, sandstone, conglomerate, breccia

24
Sedimentary Rocks Organic

• 8. Organic rock- forms where the remains of
  plants and animals are deposited in thick layers
• Ex. coal, limestone

25
Sedimentary Rocks Chemical

• 1. Chemical- when minerals that are dissolved in
  a solution crystallize
• Ex. rock salt

26
Rocks from Reefs

• 1.These rocks are made from the exoskeletons of
  coral animals.
• 2. Life can only live within the first 40 meters
  because that is where there is enough light.
• 3. The exoskeletons are made from calcium.
• 4. A coral reef forms when the animals die and
  their skeletons remain building up over time.
• 5. Temperatures must be warm.
• 6.Limestone deposits can tell us that there must
  have been on ocean or sea there sometime in the
  past

27
(No Transcript)
28
Metamorphic Rocks

• 1. Heat and pressure beneath the surface of the
  earth can change any rock into a metamorphic
  rock.
• 2. Geologists classify metamorphic rocks
  according to the arrangement of the grains that
  make up the rocks
• Foliated Rocks
• Non-foliated Rocks

29
Metamorphic Rocks

• When a rock becomes a metamorphic rock
• Its appearance changes
• Texture changes
• Crystal structure changes
• Mineral content changes

30
Metamorphic Rocks

• 3. Foliated grains arranged in parallel layers
  or bands
• Ex. slate, schist and gneiss

31
Metamorphic Rock

• 4. Non-foliated mineral grains are arranged
  randomly
• Ex. marble, quartzite

32
Uses of Metamorphic Rocks

• 5. Two of the most used metamorphic rocks
• Marble building and sculptures
• Lincoln Memorial
• Slate flooring, roofing, walkways, chalkboards

33
The Rock Cycle 1. Forces deep within the Earth
and at the surface, produce a slow cycle that
builds, destroys, and changes the rocks in the
crust. The rock cycle is a series of processes
that change rocks from one kind to another.
34
Quartz Sediment Compaction Cementation Sedimentary
Rock (sandstone) Buried Pressure Heat Metamorphic
Rock (quartzite) What next?
35
(No Transcript)
36
(No Transcript)
37
ROCK CYCLE ACTIVITY
38
(No Transcript)