1. Chapter 3 – Section 2 Igneous Rocks Open your books to page 62 AND take notes over the yellow slides!

2. Igneous rock (from the Latin ignis meaning born of fire)

3. Formation of Igneous Rocks Igneous rocks are created when hot magma OR lava cools and hardens

4. Rocks
Igneous Rocks – created when hot magma or lava cools and hardens

5. Magma – molten rock material located underneath the Earth’s surface Lava – magma that reaches Earth’s surface – it comes out of volcanoes (see pg. 62, figure 5)

6. Magma – below the Earth’s surface
Lava – above the Earth’s surface

7. Where does Magma come from
Where does Magma come from? In certain places within the Earth, the temperature and pressure are just right for rocks to melt and form magma.

8. Most magma comes from deep below the Earth’s surface From near the surface to about 150 km below the surface (this is 90 miles) Temperatures from about 650 degrees C (1,202 F)to 1200 degrees C (2,192 F)

9. Where does the heat come from to cause rocks to melt
Where does the heat come from to cause rocks to melt? The decay of radioactive elements within Earth Some heat was left over from when Earth was formed, which originally was molten

10. Magma is less dense than the surrounding rock and forced upward towards the surface (volcano)

11. Intrusive vs. Extrusive Igneous rocks are either intrusive or extrusive, depending on how they were formed.

12. Intrusive – igneous rocks that form from magma below the Earth’s surface (see pg. 63, figure 6) - Takes a long time for these to cool, so they rock crystals are larger and can be easily seen. - Found at the Earth’s surface only after layers of rock and soil have eroded away Erosion takes place as these rocks are pushed up towards the surface.

13. Intrusive – igneous rock forms from magma below the Earth’s surface
Intrusive – igneous rock forms from magma below the Earth’s surface. (They cool slowly so crystals are large)
* Think IN – Inside the Earth

14. Extrusive – igneous rocks that form as lava cools on the surface of the Earth (see pg. 63, figure 6) - When lava flows on Earth’s surface, it is exposed to air and water - Lava cools very quickly - Quick cooling does not allow the atoms time to arrange themselves so the crystals are very small.

16. Extrusive – igneous rocks that form from lava on top of Earth’s surface (they cool quickly so crystals are small)
* Think EX – Exit the Earth

18. Volcanic Glass – cool very quickly so few or no mineral grains are formed Exp: obsidian, pumice, scoria In pumice and scoria, gases become trapped in the molten material as it cools. Some of these gases escape and leave behind holes in the rock.

19. Volcanic Glass – cools very quickly so few minerals grains are formed Ex: obsidian, pumice, scoria

20. Classifying Igneous Rocks Igneous rocks are first classified by whether they are intrusive or extrusive. Then they are further classified by what their magma is composed of

21. Basaltic Rock – dense, dark-colored rock
Basaltic Rock – dense, dark-colored rock. Form from magma that is rich in iron and magnesium (this gives the rock its dark color) Basaltic lava is fluid and flows freely from volcano

22. Basalt (an extrusive igneous rock in this case); light colored tracks show the direction of lava flow.

23. Basaltic Rock – dense, dark
colored rock. Made of iron (Fe) &
Magnesium (Mg)
(Iron gives the rock its dark color)

24. Granitic Rock – light colored rocks – contains a lot of silica – magma is thick and stiff Because magma is stiff, it can build up great pressure under Earth’s surface, which is released violently during volcanic explosions

25. Granitic Rock – light colored
rock (contains a lot of silica
magma)
- It’s stiff and thick

26. Andesitic Rock – have mineral compositions between granitic and basaltic These volcanoes can erupt violently REVIEW TABLE 1 ON PG. 64

27. Andesitic Rock – has mineral compositions of both granite &
basaltic rock

28. Here’s a short video about igneous rock