Geography 11-12

Most igneous rocks contain
Silica

Fast cooling =
Fine grained or glassy (rhyolite)

Slow cooling =
Coarse grained (granite)

Tabular
Igneous body has a flat shape

Massive
Large and somewhat irregularly shaped

Discordant
Cut across existing structures

Concordant
From parallel to existing structures

Pluton
Any intrusive igneous structure

Batholiths
The largest form of a pluton- an irregular shaped mass with a surface exposure. Mountain ranges

Sills
Plutons that form parallel to layers of sedimentary rocks. Tabular and generally concordant less viscous magma

Dikes
Plugins that cross layers of country rock. Discordant and tabular.

Laccoliths
Lens shaped plutonium in a country rock. Generally concordant more viscous magma, lifts (arches) overlying strata

All intrusive structures can be exposed by
Weathering actions of air, water, and ice

What are igneous rocks are categorized by what?
Texture and composition

Felsic
Igneous rocks derived from feldspar and silica (minerals) are high in silica, aluminum, potassium and sodium. Low melting points, light color, and less dense than mafic rocks

Mafic
Igneous rock derived from magnesium and iron are darker color and more dense than Felsic rocks

Basalt
A fine grained, extrusive cooled quickly

Crystallization
The formation and growth of a crystalline solid from a liquid or gas

Magma
A body of molten rock found at depth. The liquid portion is compromised of freely moving ions

Crystal growth is called
Embryo crystals

With slow cooling
Larger crystals

With fast cooling
Small, sometimes micro crystals

Igneous rock texture
Describes overall appearance

Aphanitic texture
Fine grained

Phaneritic texture
coarse grained

Porphyritic texture
Rocks with large and small crystals

Basaltic rock type
Feldzpar

Andesitic type
Fine grained. Diorite coarse grain

Granite type igneous rocks
Felsic rock. Thy have feldspar and Quartz

Rhyolite
Volcanic equivalent of granite. Uncommon compare to granite

Determination of the nature of eruptions
Magma composition, magma temperature, amount of dissolved gases

Hawaiian volcanos
70% water vapor

Volcano
A landform at the end of a conduit or pipes which rises from below the crust and vents to the surface

Crater
a circular surface depression formed by volcanism , located at a volcanic vent or pipe

lava(molton rock)
the magma which issues from the volcano

tephra
pulverized rock and clastic material ejected violently during the volcanic eruption

cinder cone
a landform compromised of tephra and scoria. usually small and cone shaped

magma
originates from solid rock in the crust and the mantle

Hawaiian islands
a hot spot

oceanic plate-cont. plate
Mt. St. Helens

oceanic plate-oceanic plate
japan

sea floor spreading centers and location
iceland and east africa

sedimentary rocks
you must weather pre-existing rocks then transport then deposition

weathering
the disintegration and decomposition

mechanical weathering
breaking up materials, small pieces

chemical weathering
dissolved material by either organic or inorganic

erosion
transported by wind, water, gravity, and ice

Delta, glaciers, dunes, beach
places thing are dumped

Shale
most known sedimentary rock, comprised of silk and clay, fine grained

sandstone
2nd most known sedimentary rock, sand-sized grains. Quartz

congiomerate
3rd known sedimentary rock, largely of gravels

rock salt
an example of sedimentary rocks

Two types of Sed.rocks are
detrital/physical and chemical

Detrital/physical sed rocks
solid particles derived from chemical and physical weathering

Chemical sedimentary rocks
soluble material produced by chemical weathering

sedimentary rocks sometimes contain
evidence of past environments and of the mechanisms involved in their formations

precipitations can occur in two ways
inorganic or biochemical process

inorganic process for precipitation
evaporation, chemical reactions

biochemical process for precipitation
sea dwelling organisms extract calcite and silica from seawater to build their shells

Strata(beds)
sedimentary rocks are laid down in layers

bedding planes
a nearly flat surface separating two beds of sedimentary rocks

cross bedding
when sediments do not accumulate in a horizontal fashion

what provide clues to the past environments
fossils, ripple marks, and mud cracks

metamorphism
changes existing rocks in size, shape, texture, and minerals they contain
*remember heat, pressure, and chemically

regional metamorphism
produces the greatest volume of metamorphic rocks. occurs during mountain building when great are subjected to the intense stresses and high temps

contact metamorphism
occurs when rock is in contact with or near a mass of magma “bake”

common foliated rocks
slate, schists, gnesis

common nonfoliated rocks
marble and quartzile

slate
a very fine grained foliated rock comprised of minute mica flakes. mica flakes are small and not visibile

schists
strongly foliated rocks, formed by regional metamorphism..platy

gnesis
banded metamorphic rocks. high grade of metamorphism

marble
a coarse, crystalline rock, parent rock limestone. Large crystals

quartzite
a very hard metamorphic rock formed from quartz sandstone.

Igneous rock originates when hot, molten material called __________ cools and crystallizes.
magma

Which one of the following is NOT a possible product of a volcanic eruption?
marble

Igneous rocks that form when lava solidifies are classified as extrusive or volcanic igneous rocks.
true

Which one of the following greatly affects both the size and arrangement of mineral crystals in an igneous rock?
rate of cooling of the magma or lava

In a rock with a porphyritic texture, the large crystals are referred to as __________.
phenocrysts

Igneous rocks rich in dark silicate minerals with about 50 percent silica are said to have a(n) __________ composition.
basaltic

Igneous rocks that form from the last minerals to crystallize from magma will have a(n) __________ composition consisting of quartz, potassium feldspar, and sodium-rich plagioclase feldspar.
granitic (felsic)

When the minerals in an igneous rock cannot be identified, the composition can be estimated based on the percentage of phenocrysts present in the rock.
false

An igneous rock with less than 15 percent dark minerals would have a(n) __________ composition.
granitic (felsic)

Rocks that contain voids left by gases that escape as lava solidifies are said to exhibit a(n) __________ texture.
vesicular

Basalt makes up the ocean crust as well as lava flows and volcanic structures on land.
true

Sedimentary rocks form when the products of __________ are transported to a new location where they are deposited and eventually __________ into solid rock.
weathering; lithified

Compaction and cementation are examples of this process.
lithification

Detrital sedimentary rocks are made primarily of the products of mechanical weathering.
false

The most common minerals in detrital sedimentary rocks are __________.
clay and quartz

Geologists use __________ to distinguish among detrital sedimentary rocks.
particle size

Angular pieces in a detrital sedimentary rock indicates the particles were not transported very far from their source prior to deposition.
true

The common name for sediment consisting of particles between 1/16 mm and 2 mm is __________.
sand

The presence of abundant feldspar in a sedimentary rock suggests that advanced stages of chemical weathering have taken place.
false

Precipitation of dissolved material by the life processes of water-dwelling organisms produces material called __________ sediment.
biochemical

The most abundant chemical sedimentary rock is __________.
None of the above

Which sedimentary rock listed below has a biochemical origin?
coquina

Which one of the following is NOT a sedimentary structure or feature that helps geologists interpret past geological conditions?
vesicles

Detrital sediments would predominate in all of the following environments except:
salt flat

Compaction is a very important lithification process for which sediment?
mud

Rock salt and rock gypsum are examples of __________ sedimentary rocks.
evaporite

Which sedimentary rock consists of materials that originated and were transported as solid particles?
sandstone

Which one of the following is NOT a variety of limestone?
chert

Sediments precipitated by processes such as temperature change, evaporation, and chemical activity are called biochemical sediments.
false

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