Chapter 2 Rocks and the Rock Cycle
What is a mineral?
Are rocks and minerals the same thing?
What are the types of rocks?
How are the formed?
Is there a rock that can float?
Does a rock ever change from form to another?
How do we use minerals?
How do we use rocks?
Are rocks a renewable resource?
Mineral or Rock?
• Minerals are – natural and solid -the
building blocks of rocks.
• Minerals have a definite chemical
composition and a physical structure
• A mineral always forms a crystal ( a
regular geometric shape)
Minerals or Rocks
• Rocks are: mountains, boulders, and sand
• They are usually made of 2 or more
minerals combined.
• Inorganic ( not living)
• Rock is what are Earth is mostly made
from
3 Types of Rocks
Igneous- from the Greek word ignis
which means fire.
They form when magma is pushed up
from the mantle into the cool crust and hardens
Into rock.
Intrusive Igneous Rock- formed inside Earth’s crust
Extrusive igneous Rock formed outside
Extrusive Igneous Rocks
• Forms from magma cooling outside the
crust
• Not many crystals –it cools too quickly
• Obsidian- lava that cools quickly- glassy
appearance
• Pumice-foamy lava cools quickly- air
bubbles- so light it can float in water
Intrusive Igneous Rocks
Magma that hardens within the crust
Intrudes or pushed into the crust
Also called plutonic rock from the Greek god
of the underworld (below the surface)
They cool very slowly because they are under the ground
Crystals have time to form which gives them a coarse
texture
Plutons are underground structures of igneous rock
When these are exposed by erosion they form batholiths
Uses of Igneous Rock
• Building materials to jewelry
• Granite- very durable- used in buildings
• Obsidian is used in many tools because it
breaks with sharp edges
• Pumice can be ground down into a powder
and used in cleaners and soaps.
Sedimentary Rocks
• Weathering breaks the rocks down
through wind, water, and ice
• Erosion moves the sediment to a new
location (transportation)
• Deposition drops the sediment (at the
mouth of rivers for example)
• Sedimentation is the process of sediment
building up over millions of years.
Cementation takes place with all of the
Compaction, or packing down, of the sediment.
2 types of Sedimentary Rocks
Clastic and Chemical
Sedimentary Rocks
• Clastic Rocks
• Chemical Rocks
• Have particles of varying size
in them
• Conglomerate (large)
• Sandstone (medium)
• Shale (Fine)
• Weathering breaks down rocks
into chemicals that can be
dissolved in water.
• Water evaporates and can
leave minerals
• Limestone forms when shells
and skeletons of sea creatures
become compacted- contains
many fossils.
USES of Sedimentary
• Building materials
• Season and preserve food or use on
roads- Halite
• When weather is bad
• Farming- limestone is used for treating soil
• Petroleum and natural gas are found in
sedimentary rocks
Metamorphic Rock
• Form in the earth’s crust
• Intense heat and pressure cause changes
in the make up of the rock
• Foliated metamorphic rocks have layers or
bands you can see
• Nonfoliated, like marble, do not seem to
be layered.
3 Main causes -Metamorphic rock
• Heat and pressure
• Crustal movement can squeeze rock and
bend it
• Mineral rich water that is extremely hot,
can heat the rocks and change their
mineral make up
Uses of Metamorphic rock
• Building materials like Marble and and
slate
• Talc is used in cosmetics and as paints
• Graphite is used in pencils
Rock Cycle
• The process by which are formed and then
changed into other types of rocks.