geology chapter 4
felsic
freezing of the magma that remains after much fractional crystallization has occurred, _______ igneous rock
Vesicles
gas bubbles open holes where glassy rocks form
magma
molten rock (melt) beneath the earth's surface
lava
molten rock (melt) that has emerged onto earths surface
in a NON orderly pattern, they are in clusters or chains
molten rock molecules lie _______
mantle plum and mid ocean ridges
where does decompression melting happen
1. hot spots 2. midocean ridges/ rifts
where does decompression melting take place
subduction zone
where does flux melting occur
laccoth
A blister-shaped igneous intrusion that forms when magma injects between layers underground in a manner that pushes overlying layers upward to form a dome.
volcanic arc
A curving chain of active volcanoes formed adjacent to a convergent plate boundary.
sills
A nearly horizontal tabletop-shaped tabular intrusion that occurs between the layers of country rock.
stoping
A process by which magma intrudes; blocks of wall rock break off and then sink into the magma.
large igenous province
A region in which huge volumes of lava and/or ash erupted over a relatively short interval of geologic time.
fragmental igneous rocks
A rock consisting of igneous chunks and/or shards that are packed together, welded together, or cemented together after having solidified.
magma chamber
A space below ground filled with magma.
dike
A tabular (wall-shaped) intrusion of rock that cuts across the layering of country rock.
crystalline igenous rocks
An igneous rock that consists of minerals that grew when a melt solidified, and eventually interlock like pieces of a jigsaw puzzle.
pluton
An irregular or blob-shaped intrusion; can range in size from tens of m across to tens of km across.
pyroclastic debris
Fragmented material that sprayed out of a volcano and landed on the ground or sea floor in solid form.
glassy
If a melt cools very rapidly, it can become solid before seeds have grown into crystals, it forms a _______ rock
mafic
If an originally mafic magma freezes before much fractional crystallization has occurred a ______ igneous rock forms
Glassy igenous rocks
Igneous rock consisting entirely of glass, or of tiny crystals surrounded by a glass matrix.
igneous rock
Rock that forms when hot molten rock (magma or lava) cools and freezes solid.
source-rock composition
The composition of a melt reflects the composition of the solid from which it was derived.
fractional crystallization
The process by which a magma becomes progressively more silicic as it cools, because early-formed crystals settle out.
viscosity
The resistance of material to flow.
volcanic ash
Tiny glass shards formed when a fine spray of exploded lava freezes instantly upon contact with the atmosphere.
Obsidian
Volcanic glass used in tools, mirrors, and knives
aphanetic
a melt that cools rapidly, but not glass rapidly
large crystals
a melt that cools slowly
xenolith
a stoped rock that does not fully melt and becomes surrounded by new igneous rock
lava flow
a syrupy red-yellow stream
Silica (SiO2)
all molten rocks contain
rocks with crystals too small to see with the naked eye
aphaneritic
aphanetic
crystals so small you cant see them
phaneretic
crystals you can see with your eyes
very hot magma rises from the mantle to the crust
describe heat transfer melting
Lava is above Earth's surface and magma is below Earth's surface
difference between magma and lava
volatile
evaporates easily, H20 CO2
- hot mantle rock rises slowly -pressure decreases -temperature remains unchanged
explain decompression melting
-volatiles mix with hot mantle rock -that breaks the chemical bond
explain flux melting
volcanic
extrusive rocks are aka
pumice
felsic rock with a ton of tiny vesicles that can float like strofoam
a vent from which melt that originates inside the earth emerges into the planet's surface
first part of volcano definition
Porphyritic
have larger crystals (called phenocrysts) surrounded by a mass of fine crystals (called groundmass).
they form in dikes, BUT they are not cooled slowly and still have large crystals
how are pegmatites the exception to the cooling-texture rate
silica composition
how do geologists classify magma
freezing of magma underground after it has intruded into wall rock
how does an igenous rock form
by the solidifying (freezing) of a melt
how does an igneous rock form
650-1,100ºC
igneous rocks freezing point
oceanic crust
igneous rocks make up the entire __________ _______
melt
incandescent molten rock
plutonic
intrusive rocks are aka
phenocrysts
larger crystals are called
Fine-grained (aphanitic)
lava flows, dikes, and sills are made up of ________ textured rock
intermediate
melt that composition is partway between that of mafic and felsic melts.
mafic
melts that contain a relatively high proportion of magnesium oxide and iron oxide compared to silica
felsic
melts that have a fairly high proportion of silica, compared to magnesium oxide and iron oxide
ultramafic
melts that have an even higher proportion of magnesium oxide and iron oxide, relative to silica
mafic magma
partial melting of an ultramafic rock results in _______
rocks with crystals large enough to see with the naked eye
phaneritic
Coarse grained
plutons tend to be made of ________ textured rock
pyroclastic rock
rock made from fragments that were blown out of a volcano during an explosion and were then packed or welded together
intrusive
rocks with larger crystals are intrusive or extrusive
extrusive
rocks with smaller crystals are intrusive or extrusive
a hill or mountain built from the products of an eruption
second part of volcano definition
lava flow
the area covered by lava as it pours out of a volcano's vent
solid
the crust and mantle are _______
pegmatities
the exception to the cooling-texture rate
partial melting
the process by which different minerals in rock melt at different temperatures
Assimilation
the process of magma contamination in which blocks of wall rock fall into the magma chamber and dissolve
Bowen's Reaction Series
the sequence in which different silicate minerals crystallize during the progressive cooling of a melt
upward
the temperature of the earth decreases as you go ______
ultramafic
type of igenous rock with less than 45% Sio2
mafic
type of igneous rock with 45-50% SiO2
intermediate
type of igneous rock with 50-65% SIO2
felsic
type of igneous rock with 65-75% SiO2
15%
wet melts include _____ volitiles
flux melting
what causes volcanism at convergent boundaries
the plume itself does not consist of magma, it is composed of solid rock that is hot enough to be relatively soft so that it can flow
what does the plume hypothesis say
obsidian
what example of glassy rock is used
continental volcanic arc
what happens when oceanic lithosphere subducts beneath continental lithosphere
volcanic island arc
what happens when one oceanic crust subducts underneath another
explosive
what kind of magma is felsic magma
interlocking crystals
what texture does a crystalline rock have
no crystalline structure
what texture does a glassy rock have
fragmental
what texture does a pyroclastic rock have
pyroclastic, volcanic ash
what type of rock is tuff and what is it made of
the freezing of lava above ground, in contact with air/water, after it extrudes/erupts
when does extrusive rock form
they form from water rich melts so atoms can diffuse rapidly
why do pegmatites form differently