1. Chapter 3.2
Based on Readings /29

2. Abundance and Distribution of Plutonic Rocks
Granite is the most abundant plutonic igneous rock in mountain ranges (erosion and weathering expose this)
Metamorphic and Plutonic are similar in age.
Exposed in the grand canyon otherwise covered by sediment (Great Plains)

3. Abundance and Distribution of Plutonic Rocks
Basalt and Gabbro make up the ocean floor.
Andestine=Volcanoes
Ultramfic rocks make up the mantle

4. How Magma Forms The mantle is not just a giant pool of Magma
The heat required to melt rock comes from the core (5000 Degrees Celsius)
Conducted

5. How Magma Forms
Geothermal Gradient…Heat increases as you go deeper into the earth (3 Degrees every 100 meters)
Rocks melt at all different ranges (because they are made up of so many different minerals)
Two factors create magma (liquid rock) Heat and pressure.
Minerals require more heat to melt at higher pressures.

6. Decomrpession Metling and Addition of Water
Decompression Melting occurs when hot mantle rock rises to a lower pressure.
This allows it to become liquid.
Water breaks silicone and oxygen bonds
Greatly lowers the melting point click here

7. How Magmas of different Compositions Evolve
Why are the oceans made of basalt and continents made of granite?
It depends on how these minerals cooled…
Bowens reaction series
Certain Minerals Crystallize at higher temperatures.
Calcium to sodium more silica at the end

8. Explaining Igneous Activity
Plate Tectonics explains the huge variety of igneous rocks.
Divergent= Basalt, Gabbro
Convergent= Andestine and Granite

9. Explaining Igneous Activity
Igneous Processes at Convergent Boundaries
Water pushed down into the asthenosphere.
Lowers the melting point of ultramafic rock
Creates Granite and Andestine
Igneous Processes at Divergent Boundaries
Crust beneath the worlds oceans is mafic (contains less sliica)
Due to partial melting of the asthenosphere
Closer to the surface in the oceanic crust
Decomrpression Melting (Silica melts first and is removed)
Ultramafic