The Solid Earth - Chapter 1: Igneous Rocks Flashcards
Igneous rocks form when ____ cools and crystallizes
Magma
Igneous (molten) rock consists primary of the elements found in ____ material
Silicate
Because the magma body is ____ dense than the surrounding rocks, it works its way toward the surface
Less
When magma occasionally breaks through the surface, it produces a ______ _______
Volcanic eruption
Spectacular explosions that sometimes accompany an eruption are produced by the gases or _____ that escape as the confining pressure lessens near the surface
Volatiles
This is similar to magma, except that most of the gaseous component has escaped
Lava
What are the two types of rocks that result from magma or lava?
Extrusive or volcanic
Intrusive or plutonic
These types of igneous rocks form when lava solidifies
Extrusive
These types of rock form when magma crystallizes at depth
Intrusive
Magma may contain suspended _____ and a gaseous component
Crystals
The liquid portion of a magma body is composed of (ions/atoms) that move freely
Ions
What happens to the ions as magma cools and they being to crystallize?
The ions arrange themselves into patterns
What is a primary influence on the size of crystals?
The cooling rate
When magma cools slowly, relatively ___ centers of crystal growth develops
Few
Slow cooling allows ions to ____ over distance
Migrate
Slow cooling results in the formation of rather ____ crystals. (large/small)
Large
When cooling occurs rapidly, the ions lose their motion and readily ___
combine
Quick cooling results in a large number of tiny crystals that all compete for the available _____
ions
The outcome of rapid cooling is the formation of a solid mass composed of _____ intergrown crystalls
small
Rocks that consist of unordered atoms are referred to as ___
glass
This is used to describe the overall appearance of the rock based on the size and arrangement of its interlocking crystals
Texture
The rate of cooling is (quick/slow) in magma chambers deep within the crust
Slow
The rate of cooling is (quick/slow) for a thin layer of lava upon the earth’s surface
Quick
Igneous rocks that form at the earth’s surface or as small masses within the upper crust have a very _________ texture
fine grained
The spherical or elongated openings left my gas bubbles trapped as magma solidifies
vesicles
In the ____ (upper/lower) zone of a lava flow, cooling occurs rapidly enough to “freeze” the lava and preserve the openings produced by expanding gas bubbles
Upper
A name for rocks that form in the upper zone of a lava flow and have preserved openings
Scoria
When large masses of magma solidify far below the surface, they form igneous rocks that exhibit a _______ texture
coarse-grained
Do all minerals within a magma crystallize at the same rate?
No
A rock that has large crystals embedded in a matrix of smaller crystals, probably from a partially cooled eruption has a ______ texture
Porphyritic
Rapid cooling may generate rock with a ____ texture when the ions do not have sufficient time to unite
glassy
An example of a volcanic rock that often exhibits a glassy texture (often found in obsidian)
Pumice
Because of the large percentage of voids, many samples of pumice will (float/sink) when placed in water
Float
The mineral makeup of igneous rock is determined by the _____ composition of the magma from which it crystallized
Chemical
True or false: a singular magma might produce rocks of varying mineral content
True
An arrangement of minerals that take place in order based on cooling rates from one magma
Bowen’s reaction series
Olivine forms at a (higher/lower temperature)
Higher
What four types of igneous rock would form in order from highest temperature (first to crystallize) to lowest temperature (last to crystallize)?
Ultramafic
Basaltic
Andesitic
Granitic
Name a mineral formed in ultramafic rock
Olivine
What are two names for basaltic rock?
Basalt
Gabbro
What type of rock will biotite mica form? (Basaltic or Andesitic)?
Andesitic
Name two types of granitic rock
Rhyolite
Granite
Name three common minerals for granitic rock in the last stage of cooling
Potassium feldspar
Muscovite Mica
Quartz
The remaining (last) melt of crystallization will have a high ____ content, which eventually crystallizes as quartz
Silica
True or false: at one or more stages of the crystallization process, a separation of the solid and liquid components of a magma can occur
True
If the earlier formed materials are denser (heavier) than the liquid portion and settle to the bottom of the magma chamber (happens often with dark silicates like olivine and pyroxene)
Crystal setting
The process of developing more than one rock type from a common magma
Magmatic differentiation
The first minerals to crystallize form rocks that are higher in iron (Fe) and Magnesium (Mg) and are lower in _____.
Silica
The iron content of ultramafic rocks and mafic rocks makes them appear ____
Darker
The term _____ is derived from Mg and Fe
Mafic
Another term used to describe mafic rocks, named after one of the common resulting rocks
Basaltic
_____ is the most common extrusive igneous rock
Basalt
The upper layers of the oceanic crust consist primary of ____
basalt
The first minerals to crystallize produce rocks that are mainly consisting of ____
feldspar and silica
The term ____ is applied to granitic rocks
Felsic
_____ is the best known igneous rock
Granite
Because ____ is tough to erode, it is often the core of eroded mountains
Granite
The fine-grained volcanic equivalent of granite
Rhyolite
