Igneous Rocks Flashcards

Terms Definitions
Strato Volcano
-cone shaped
-intermediate felsic comp.
- explosive eruptions
- 2nd largest
EX: Mt. St. Helen's
PERIDOTITE- igneous rock containing mostly olivine and pyroxene. OPPOSITE to Felsic(GRANITIC) rocks. RARE on surface, but main component of upper mantle. Very low silica content (45%)
Medium grained dark igneous rock
Light, Lightweight, Coarse Crystals, Igneous RockFound at Destructive Plate Boundries
- From Formation of Earth
-From radioactive decay.
Intrusive rocks
Magma that crystallizes at depth
olivine present, fine grained, flat black color
Acts as a flux to promote melting.
dark green to black, can see crystals
Heat, Pressure, and Volatiles.
Three factors that generate Magma
Vesicular texture
Rocks with voids left by gas bubbles at escape as lava solidifies
These rocks cool fast, and have small crystals, thus having fine grains. These rocks are mafic and include basalt and gabbro.
RATE at which magma cools, amount of SILICA present , amount of dissolved GASES in the magma
Three factors that affect crystal size.
Volcanic Breccia
-Underground intermediate rock
-Eruption Point is 900 degrees celcius
cuts across preexisting layering
vesicular, felsic and holey
Olivine rich, orthopyroxene peridotite. Spinel, garnet accessory
pyroclastic particles that measure less than 2 mm
separation of different ingredients from an originally homogeneous mixture
converts sediment into rock. Compaction caused by pressure generated from weight of overlying sediment. Cementation is binding of sediment by mineral agents. Common cementing agents hematite, limonite, calcite and silica
volcanic. above ground. small no crystals. pumice, obsian
forms first in fractional crystallization
mafic minerals
a rock made up of groundmass
magma chambers
large pools of molten rock
Degrees of crystallinity
- Holocrystalline
o Totally crystalline
- Hypocrystalline
o Part crystal/part glassy
- Holohyaline
o Wholly glassy
igneous rocks that form at depth
The process by which atoms are arranged to form a material with a crystal structure
Fractional crystallization
The process where different minerals COOL at different temperatures,
What type of volcanism is associated with Plinian eruptions?
a small discordant pluton with an areal extent at earth's surface of less than 100 square km
crystal settling
earlier formed minerals are denser than the liquid portion and sink to bottom of magma chamber
Fissure Eruptions
Volcanic material erupts through an elongated crack
Magma that flows out onto Earth's surface
Partial Melting
Process in which different minerals melt into magma at different temperatures, changing its composition
An igneous rock created below the surface of the earth. They have larger crystals (1mm-10+mm in diameter) than extrusive rocks.
pillow lava
Lava that cools underwater, taking on a distinctive pillow-like shape as it hardens (basalt)
intrusive rock
rock that appears to have crystallized from magma emplaced in surrounding rock
Rock made out of ash, crystals, rock fragments, pumice, etc...
extrusive rock
igneous rock formed from lava that erupted onto Earth's surface.
The loss of electrons from a substance involved in a redox reaction.
geothermal gradient
the fradual increase in tempature with depth in the crust
describe felsic magma
>65% silica rich, lots of sodium, potassium and aluminum but little calcium, iron and magnesium, high viscosity (slow moving, very sticky), aa, nuee ardente, ash,
very explosive
cinder cones, stratovolcanoes (composite)
ex. Mt. St. helens
a body of molten rock found at depth, including any dissolved gases and crystals
How is igneous rock formed?
extrusive rocks=lava cools at surface
intrusive rocks=magma cools inside earth
Igneous Rocks
Form when lava or magma cools and crystallizes
Early nomenclatures
- little to no agreement on criteria
- every unfamiliar rock gets a new name
- names were often associated with type localities
o problems
- non unique
- non descriptive
- hard to remember
- difficult to get a type specimen
rough because of large crystals
intrusive rocks are rough or smooth
Upwelling at spreading centers
Most melting of mantle occurs where pressure have been lowered by ________.
fine grained or glassy
what type of texture do extrusive rocks such as basalt have
Igneous rock comes from where?
inside the earth (magma). outside the earth (lava)
Melting of wall rock, fractional crystallization, magma mixing
Magmatic differentiation is made up of three processes.
How do igneous rocks form
by the cooling of molten rock. as the magma or lava cools, minerals crystallize to form igneous rocks.
mafic compositon
aphanitic mafic
describes granitic igneous rocks
Intermediate Ig
Volcanic: Andesite
Plutonic: Diorite
cool too fast to crystallize
Mt. Rushmore
South Dakota
Formed by subduction
Other-George Washington, Thomas Jefferson, Abraham Lincoln, Theodore Roosevelt, made in 1920s-1930s by Gutzon Borglum
Remaining melt during freezing becomes more
Porphyritic Trachyte
porphyritic aphantic, felsic, large grains and scratches glass
Magma bends the overlying layers upward
Ex) Abajos, La Sals, and Henrys(southeast Utah)
(chemistry) a substance formed by chemical union of two or more elements or ingredients in definite proportion by weight
gaseous components of magma dissolved in the melt; readily vaporize at surface pressures
have gas pockets and are extrusive
vesicular rocks
igneous rock that cools slowly below the surface causing the rock to be coarse grained.
What is a combination of cooling environments?
a rock's appearance with respect to the size, shape and arrangement of its grains or other constituents
Porphyritic texture
large, well formed crystals surrounded by finer grained crystals of the same mineral
Intermediate rock; has water in it; Intermediate in composition between mafic basalt and felsic rhyolite
the process of becoming hard or solid by cooling Ex: magma into an igneous rock
lava dome
a bulbous mass associated with an old-age volcano produced when thick lava is slowly squeezed from the vent, lava domes may act as plugs to deflect subsequent gaseous eruptions
viscous felsic magma, sometimes intermediate
extrusive igneous rocks
rapid cooling at Earth's surface produces the fine-grained texture or glassy appearance
marine sedimentary rocks
Deposits of sediment from the ocean
Sheeted dikes
- Intrusive igneous features caused by repeated shallow intrustions of basalt into just-intruded basalts
- Fine grained
- Chilled margins
scoria and pumice
are two porous vesicular igneous rocks
organic sedimentary rocks
rocks made of particle produced by plants and animals
ground mass
matrix of finer grained minerals in a porphyritic composition
Rocks formed from lava are called?
extrusive, or volcanic rocks
mineral composition
the texture of an igneous rock depends on its
Fine -grained texture & small grains is formed by what kind of magma?
rapid cooling of magma
subduction of water-laden sediments
Most melting of mantle occurs where fluid content has been increased by ___________.
diorite gets its coarse grain because
of its fast cooling rate
grain size
the size of the grains that make up a rock, which helps to classify the type of rock
What are the properties of intermediate magma?
It is andesitic, cooler with higher viscosity (less liquidy) and more gas rich than basalts. More explosive eruptions and construct steep sided cones or stratovolcanoes (E.g. Mt st helens, Mt Ruapehu)
Describe the relationship between the cooling rate of magma/lava and the size of the crystals in an igneous rock.
The longer the cooling time the bigger the crystals.
aphanitic--ultra mafic
corse grained texture
large crystals in rocks
granitic and no crystals
Intrusive igneous rocks crystallized from
rich in iron and magneseum
rocks made by precipitation and evaporation ex. limestone
rocks that consist of unordered ions
Made of explosively ejected particles that are compressed and cemented, or welded.
Shattered glassy deposit formed by cracking and alteration of glass during quenching under water
- Typical for mid-ocean ridge basalts
Volcanic tuff
felsic, pyroclastic, extrusive, sandy, tap on table and ash falls out
process by which solid sediments or clast are "glued" together by precipitated minerals form a sedimentary rocks
rocks with holes created by expanding gas as magma rose to earths surface
the measure of a liquid's resistance to flow
Rhyolitic Tuff
Pyroclastic, light colored ash, felsic (ligth gray to red in color) composition
carbonate rock
made up primarily of carbonate materials (ex: limestone & dolomite)
Welded tuff
• Glass fragments are fused together
• Visible in thin section
basaltic composition:
rich in iron, magnesium - darker, denser
examples: gabbro. basalt
Cooling Rate
When magma cools down quickly, the resulting rock consists of very small crystals which are invisible to the unaided eye- just below the surface (shallow intrusive) magma slowly cools, resulting in large crystals since they have time to form
metamorphic rock
Rock changed in structure by heat, moisture, and pressure.
Pyroclastic grain sizes
1. Bombs >64mm, molten
• Agglomerate - rounded clasts >64mm
o Rounded during transport
2. Blocks >64mm, broken, angular
• Pyroclastic Breccia - Angular clasts >64mm
o Minimal transport, near vent
3. Lapilli 2-64mm
4. Ash grains <2mm
• Coarse >.0625
• Fine<.0625
• Rock or consolidated ash = tuff
5. Shards: glass fragments
A _____ is an igneous body that crystalized deep underground.
large grains
If rock cools slowly are grains large or small
mafic rock or magma
silica-deficient igneous rock with a relatively high content of magnesium, iron, and calcium.
pyroclastic rocks
Any rock make up to material ejected explosively from a volcanic vent
the soft layer of the mantle on which the tectonic plates move
_____ ______ is a process during the crystallization of magma in which the earlier-formed, metal-rich minerals are denser than the liquid portion they are surrounded by and settle to the bottom of the magma chamber.
Crystal settling
Intrusive igneous rocks
What type of rocks are formed when magmas cool and crystallize within the crust?
What are some primary volcanic hazards?
Lava flows, pyroclastic flows, pyroclastic falls, lateral blasts,
large or very large crystals such as gabbro
coarse texture igneous rocks
Olivine Amphibole and Biotite
Contain FE and MG in their chemical formula
True or false: Different minerals are present in both volcanic and plutonic igneous rocks that form from the same magma.
False. Despite the difference in mineral grain sizes, THE SAME minerals are present in both volcanic and plutonic igneous rocks that form from the same magma.
True of false: The size of the mineral crystals that form depends on how fast the magma cools and solidifies.
Grain sizes in (volcanic, plutonic) rocks are too small to be seen without a microscope.
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