1. Chapter 5 : Rocks from molten liquids
Including adaptions from Dupre and Copeland (2004)

4. Andesite - granite at the surface
Hand sample-Santiago de Chile
Microscope slide

6. Genetic Classification of Igneous Rocks
Intrusive: crystallized from slowly cooling magma intruded within the Earth’s crust; e.g. granite, gabbro

7. Genetic Classification of Igneous Rocks
Extrusive: crystallized from rapidly cooling magma extruded on the surface of the Earth as lava or erupted as pyroclastic material.

8. Extrusive Igneous Rocks Include:
rocks formed from the cooling of lavas
rocks formed by the cooling of pyroclastic material, i.e. fragmented pieces of magma and material erupted into the air

10. Last Days of Pompeii-Karl Briullov--Copyright © 1999. George Mitrevski
Last Days of Pompeii-Karl Briullov--Copyright © George Mitrevski. Auburn University

11. Mt St Helens crater 08-7-80, 60 mph, 800 deg F-pyroclastic flow- USGS

12. Composition and Classification of Igneous Rocks
Chemistry: e.g. % SiO2
Mineralogy: e.g.
Felsic (Feldspar and Silica)
Intermediate
Mafic (Magnesium and Ferric)
Ultramafic

14. Why Figure 5.4 I so important
The color and mineral distribution indicate an increasing density and melting temperature. Darker igneous rocks generally weigh more and are formed at higher temperatures and pressures. This reflects the density-stratification of the whole Earth!

15. Felsic Igneous Rocks: -Igneous rocks rich in minerals high in silica
Felsic Igneous Rocks: -Igneous rocks rich in minerals high in silica. They include:
Granite
Rhyolite

16. Intermediate Igneous Rocks: -Igneous rocks in between in composition between felsic and mafic igneous rocks. They include:
Granodiorite
Dacite
Diorite
Andesite

17. Mafic Igneous rocks -very low silica content, and consist primarily of mafic minerals. The most common ultramafic rock is:
Peridotite

18. What controls the melting temperatures of minerals?
*External pressure
*and Water content
*Internal composition (including internal water content)

20. Factors Affecting Melting of Minerals (and Rocks)
Pressure: Increased Pressures raises melting points
Water Content (internal and external to the mineral): Increased Water Content lowers melting points
Composition: Felsic minerals melt at lower temperatures than mafic minerals

22. When rocks melt (or partially melt).
How do magmas form?
When rocks melt (or partially melt).
Why do rocks melt?
When the temperature exceeds the melting point of the rock or some minerals within the rock.

23. Partial Melting
--Occurs when some of the minerals forming a rock melt at lower temperatures than other minerals within the same rock

24. If different minerals melt at different pressures that means that different minerals become solid at different temperatures too. What does this imply about the internal composition of a magma body as it cools???

25. Fractional Crystallization!

28. What is Magmatic Differentiation ?
If, during fractional crystallization, the remaining magma were to erupt it would be
(a) more felsic or
(b) more mafic than the original magma????

29. What do we know about the shape of magmatic bodies. Are they sheets
What do we know about the shape of magmatic bodies? Are they sheets? Blobs? Spheres?

31. “Magmatic Pipes -101” Dykes are near-vertical
Sills are horizontal and squeeze in between other layers of rock
Plutons are deep (km) bodies of solidified magma. An example of a plutonic rock is granite or gabbro.

37. www.jemmoore.com/flying/ shiprock.html
Shiprock, NM. It's hard to tell, mainly because I was flying at about 12,000ft when I took this picture, but this massive piece of rock sticks up over 2,000ft from the surrounding plain, and is as big as a small city. It is on Navajo land, and is a significant spiritual site for the Navajo. The hard, volcanic spines radiating out from the main spire are really amazing. From this high up, you couldn't even see an eighteen-wheeler on the ground next to Shiprock, it would be just a speck.

38. Summary of Volcanoes
Subduction volcanoes in continental crustal and oceanic crust at convergent plate margins
Hot spot volcanoes (anywhere)
decompression volcanoes at divergent plate margins

40. IGNEOUS ROCKS-rocks from liquid melts
END of CHAPTER 5
IGNEOUS ROCKS-rocks from liquid melts