Rocks, Rocks and More Rocks!

1
Rocks, Rocks and More Rocks!

• Igneous FIRE ROCKS
• (for now)

2
Extrusive Igneous Rocks

• Notes Extrusive Igneous Rocks
• form when lava erupts from a volcano or bubbles
  up from tectonic plates moving apart - onto
  Earths surface.
• Ex Basalt the most common extrusive rock on
  Earth forms most of Earths ocean floor.
• Ex Obsidian black volcanic glass

3
Igneous Rocks

• Earth's Most Abundant Bedrock Basalt
• Basalt forms more of Earth's surface than any
  other rock type. Most areas in ocean basins are
  basalt.
• May be on land from lava flows, too.

4
Igneous Rock - Obsidian
Obsidian was used to make knives, arrow heads,
spear points, scrapers and many other weapons and
tools
5
How igneous rocks form
Extrusive When a volcano erupts or when magma
bubbles to the surface
Intrusive when magma cools slowly inside earth
6
Intrusive Igneous Rocks

• Notes forms when magma hardens beneath Earths
  surface (INSIDE).
• Ex Granite the most abundant intrusive rock on
  Earths continents.
• Forms the core of many mountain ranges.
• Ex Porphyry- looks like jello w/fruit inside it

7
Intrusive Igneous Rocks

• Granite
• is used to make many objects
• Granite is also well-known from its many
  world-famous natural exposures.
• These include Stone Mountain, GA Mount
  Rushmore, SD

8
Intrusive Igneous Rock
Porphyry
9
Igneous Rocks

• Notes Texture fine grained
• Rapidly cooling lava forms a fine-grained rock
  with small crystals.
• Ex Basalt - crystals too small to be seen
  without a microscope.
• Ex Obsidian smooth, shiny texture like thick
  glass cooled without forming crystals Volcanic
  Glass

10
Igneous Rocks

• Obsidian

Obsidian on the side of a volcano
11
Igneous Rocks

• Notes Texture coarse-grained
• Slowly cooling magma forms coarse-grained rock
  with large crystals
• Ex granite and porphyry

12
Igneous Rocks Mineral Composition

• Notes
• When magma is high in silica light-colored rocks
  form - like granite.
• When lava is low in silica dark-colored rocks
  form - like basalt

13
High Silica vs. Low Silica
14
Uses of Igneous Rock

• Notes
• Granite Statues, Bridges and old public
  buildings, Paving streets with cobblestone,
  floors, kitchen countertops (thin polished sheets
  of Granite)

15
Uses of Igneous Rock

• Basalt - Gravel for construction
• Obsidian - Sharp tools for cutting and scraping
  (Native Am!), Starting vegetable gardens
  (fertilizer) its called Perlite, which is
  formed from heating Obsidian

16
Pumice is cool! It can float!

• Pumice used for cleaning and polishing

17
Uses of Igneous Rock

• Statues, Public Buildings - Granite

18
Uses of Igneous Rocks

• Cobblestone streets, kitchen countertops
  Granite

19
Questions

• What processes form Igneous Rocks?
• How are the 2 types of Igneous Rock different?
• How can we use Igneous Rocks? How have they been
  used in the past?
• Can you describe the most common Intrusive Ign.
  Rock? Where is it commonly found?
• Can you describe the most abundant Extrusive Ign.
  Rock? What area on Earth is mostly made of this
  type?

20
Project reminder

• Please make sure you are working on your Igneous
  Rock Paper and Illustration. Directions are on my
  webpage. Make sure you turn in your copy of the
  directions with your project! Thanks!
• I will take questions in class everyday until
  Tues. because it is due on Wed when you come in
  class. ?