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geo directory

Some of these questions must be answered by consulting your textbook which correlates with the video series.  Consult: "Physical Geology -Earth Revealed" by Carlson, Plummer and McGeary; published by McGraw Hill, New York City, NY


 14. Intrusive Igneous Rocks 
 Most magma does not extrude onto Earth’s surface but cools slowly deep inside Earth. This magma seeps into crevices in existing rock to form intrusive igneous rocks. Experts provide a graphic illustration of this process and explain the types and textures of rocks such as granite, obsidian, and quartz. Once again, plate tectonics is shown to be involved in the process.

Episode 14: Intrusive Igneous Rocks

What factors contribute to the formation of magmas?


Discuss in detail the differences between mafic, intermediate, and felsic magmas.


How does cooling history relate to the texture of the resulting rock?


How do textural variations within the dike illustrate the effect of cooling history?


Discuss cooling and the formation of phaneritic, aphanitic, and glassy textures.


What is Bowen's Reaction Series and how does it describe magma crystallization?


How does differentiation relate to the evolution of magmas?


How does magma composition relate to plate boundaries?


Describe the formation of intermediate (andesitic) magmas in subduction zones.


Describe granitic (felsic) rocks.


What are xenoliths and what do they represent?


Describe the formation of a batholith.


How does the study of igneous rocks help in our interpretation of earth history?


Compare and contrast igneous rocks found on the continents and ocean floor.


link to answers  (this will not be an active link until after the assignment due date!)