Galcium-rich píagiocfasě
Reaction
Biotíte mica			Sodium-nch 'piagiociase	
				
	Potassium feldspar (orthoelase)			
				
	Muscovite-mica			
				
	Quartz.			
£> FIGURE 3-6 Bowen's reaction series. Note that it consists of a discontinuous branch and a continuous branch.
Country rock
nclusion
Assimilated pieces of country rock
ř> FIGURE 3-9  A s magma moves upward, fragments of country rock are dislodged and settle into the magma. If they have a lower melting temperature than the magma, they may b incorporated into the magma by assinulation. Incompletely assimilated pieces of country rock are inclusions.
Magma chambe
X.   ^B jest >v=«i    ďtt
*35&5
^ FIGURE 3-8  Differentiation bv crystal settling.
v                    v                                                         CTÍ
Early-formed ŕerromagnesían minerals have a specific gravity greater than that of the magma so they settle and accumulate in the lower part of the magma chamber.
Ě> FIGURCE 3-11   Magma mixing. Two rising magmas mix and produce a magma with a composition diíFerent from either of the parent magmas.
^ FIGURE 3-2O  Block diagram showing che various types of plutons. Notice that some of these plutons cut across the layering in the country rock and are thus discordant, whereas others parallel the layering and are concordant.
Lava flow
Volcanic neck
Composite volcano
Volcanic pipe
Stock
Batholith
......."■1I  '                                                      -----------------.....                                         ______
TABLE 3-í The Most Common Types of Magmas
Type of Magma                              Silica Content (%)
Mafic                                                         45-52
Intermediate                                              53 — 65
Felsic                                                         >65

£> figure 3-12 classification of
igneous rocks. The diagram illustrates the relative proportions of the chief mineral components of common igneous rocks.
Type of Magma
Felsic
Aphanitic:   Rhyolite Phaneritic:   Granite
Intermediate
Mafic
Andesite
Diorite
Basalt Gabbro
Peridotite
- 100
Silica increases
FIGURE 4-21  Most volcanoes are at or near plate boundaries. Two major volcano belts arc agnized: the circum-Pacific belt contains about 60% of all active volcanoes, about 20% are in Mediterranean belt, and most of the rest are located along mid-oceanic ridges.
J-------L
Spreading ridges
Convergent plate margins
Volcanoes
^* FIGURE 4-12 The sequence of events leading to the origin of Crater Lake, Oregon, (a—b) Ash clouds and ash flows partly drain the magma chamber beneath Mount Mazama.
(c)  The collapse of the summit and formation of the caldera.
(d)  Post-caldera eruptions partly cover the caldera floor, and the small volcano known as Wizard Island forms, (e) View from the rim of Crater Lake showing Wizard Island.
n it 1
P 1. b o
s 1; ť t t C t S
t
■\ c
Distance measurement points
rm^       -__J~__   c
D
Horizontal and vertical distances increase from Stage 1   ■••
Volcano shape at peak inflation
Magma
reservoir
nflated
(a) Stage 1
(b) Stage 2
Eruption    -   .,?,
Distances decrease from Stage 2
Volcano shape returns to normal
^> FIGURE I  Volcano monitoring. These diagrams show three stages in a typical eruption of a Hawaiian volcano: (a) The volcano begins to inflate; (b) inflation reaches its peak; (c) the volcano erupts and then deflates, returning to its normal shape.
(c) Stage 3