Chapter Three

1
Chapter Three

• ROCKS

2
Section 3-1 Classifying Rocks

• When studying a rock sample, geologists observe
  the rocks color and texture and determine its
  mineral composition.
• Using color and texture, geologists can classify
  a rock according to its origin.
• Texture is the look that results from the size,
  shape, and pattern of the rocks grains.

3
3-1

• Coarse-grained the grains are large and easy to
  see.
• Fined-grained the grains are small and can been
  seen under a microscope or hand-lens.
• Some rocks grains results from the shape of the
  crystals that form the rock.
• In other rocks, the grain shapes result from
  fragments of other rock.

4
Texture
5
Texture
6
3-1

• The three major groups of rock are
• Igneous forms from the cooling of molten rock.
• Sedimentary forms when particles of other rocks
  of 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.

7
3-2 Igneous Rock

• Igneous rock is any rock that forms from magma or
  lava. Most igneous rocks are made of mineral
  crystals. Igneous rocks are classified according
  to their origin, texture, and mineral
  composition.

8
Classification of Igneous Rock
9
Extrusive Rock

• Extrusive rock is igneous rock formed from lava
  that erupted onto Earths surface.
• Basalt is the most common extrusive rock.

10
Samples of Extrusive Rock
11
3-2

• Intrusive rock Igneous rock that formed when
  magma hardened beneath the Earths surface.
• Granite is the most abundant intrusive rock.
• The texture of an igneous rock depends on the
  size and shape of its mineral crystals.

12

• Texture may be fine-grained, coarse-grained,
  porphyritic, or glassy.
• Fined-grained rapid cooling lava forms
  fined-grained.
• Coarse-grained slow cooling lava forms
  coarse-grained.
• Porphyritic large crystals scattered on top of
  small crystals. This occurs when magma cools in
  two stages, first slow, and then rapidly as magma
  moves near to the surface.

13
Samples of Intrusive RockGranite
14
Samples of Intrusive RockGabbros
15
Samples of Intrusive RockDiorite
16
3-2

• Lava low in silica forms dark-colored rocks, such
  as basalt.
• Magma that is high in silica usually forms light
  colored rocks, such as granite.
• Many igneous rocks are hard, dense, and durable.
  People use igneous rock for tools and building
  materials.

17
3-3 Sedimentary Rock

• Sedimentary rocks form from particles deposited
  by water and wind. Sand, mud, and pebbles.
  Sediment is small, solid pieces of material that
  come from rocks or living things.
• Erosion running water or wind loosen and carry
  fragments of rock.
• Deposition the process by which sediment settles
  out of the water or wind.
• Compaction the process that presses sediments
  together.
• Cementation the process in which dissolved
  minerals crystallize and glue particles of
  sediment together.

18
3-3

• There are three major groups of sedimentary
  rocks
• Clastic rock sedimentary rock that forms when
  rock fragments are squeezed together. Sandstone
  is a clastic rock formed from the compaction and
  cementation of sand.
• Organic Rock forms where the remains of plants
  and animals are deposited in thick layers. Coal
  is formed from the remains of swamp plants and
  limestone is formed from the hard shells of
  living things seashells.
• Chemical Rock when minerals that are dissolved
  in a solution crystallize. Chemical rocks also
  form from mineral deposits left when seas or
  lakes evaporate.

19
Samples of Sedimentary Rock

• Sandstone

20
Samples of Sedimentary Rock

• Gypsum

21
Samples of Sedimentary Rock

• Shale

22
3-4 Rocks from Reefs

• Coral animals are tiny relatives of jellyfish
  that live together in vast numbers. They build
  skeletons that grow together to form a structure
  called a coral reef.
• Coral reefs only form in warm, shallow tropical
  waters.
• When coral animals die, their skeletons remain,
  and new corals build on top of them.
• There are three types of coral reefs fringing
  reefs, barrier reefs, and atolls.
• A coral reef is really organic limestone.

23
Fringing Reef
24
Barrier Reef
25
Atoll Reef
26
Coral Reefs
27
Coral Reefs
28
3-5 Metamorphic Rock

• Every metamorphic rock is a rock that has changed
  its form. Heat and pressure deep beneath Earths
  surface can change any rock into metamorphic
  rock. Metamorphic rock can form out of igneous,
  sedimentary, or other metamorphic rock.
• Geologists classify metamorphic rocks by the
  arrangement of the grains that make up the rocks.
• Metamorphic rocks that have their grains arranged
  in parallel layers or bands are said to be
  foliated slate is the most common.
• Metamorphic rocks that have grains arranged
  randomly. Marble and Quartz.

29
Metamorphic Rock Samples
30
Metamorphic Rock Samples

• Marble

31
Metamorphic Rock Sample

• Quartz

32
3-6 Rock Cycle

• Forces inside Earth and at the surface produce a
  rock cycle that builds, destroys, and changes the
  rocks in the crust.
• The rock cycle is a series of processes on and
  beneath Earths surface that slowly change rocks
  from one kind to another.

33
The Rock Cycle
34
Rock Pictures - Lava

• http//www.hoho.co.uk/html/lanzarote_lava_and_rock
  s.html