Download Assignment 3 (IGNEUS ROCKS) Solution (1)

Assignment - 3 (Igneous Rocks) (10%)
Please answer practice questions 4.1, 4.3, 4.9 and 4.11 at the end of the text book.
4.1. If an igneous rock has phenaritic texture, what origin can be presumed for the rock?
They are of volcanic origin. Due to the slow process of cooling they have large crystals of various
minerals.
4.3. What criteria are used to classify the igneous rocks?
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Composition (mineral content)
Texture
Color
Chemical structure
4.9. What factors will determine whether a dike or a sill will form?
The main difference between the dike and sill is their orientation. If the fractures in the crust are
horizontal, they get filled by magma and sill form. The vertical fractures in the crust allow vertical
migration of magma and dikes form.
4.11. Contrast the general conditions relative to engineering projects that would be encountered in
intrusive and extrusive rock terrains.
Igneous rocks make good engineering material. Their high strength and low permeability are favorable
properties from engineering perspective. Extrusive rocks are less uniform compared to intrusive rocks and
are likely to have less favorable properties relative to their intrusive counterparts.
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