GEOL 113- Exam 1

A'a

-slow flowing lava
-"stony rough lava"
-forms thick chunks
-clinky sound

active volanoes

erupting, recently erupted or likely to erupt

apharitic (finely crystalline)

-crystals not seen under naked eye
-rapid cooling
-crystals do not have enough time to grow

assimilation

-magma pushing upward causes fractures
-injected magma can dislodge rock
-displaced rock is then melted and incorporated into the melt
-overall chemical composition of the magma has changed

basaltic lava flows

-very hot, low silica, and low viscosity
-90% of lava that erupts on earth

basaltic, andesitic, rhyolitic

types of lava flows

biomineralization

some organisms can use their surroundings to create minerals that exist inside their bodies or as protective shells

burial lithification

more sediments is added onto previous layers and becomes compacted, reduces pore spaces between clasts

caldera

- a gigantic depression formed after a massive eruption
-form from massive eruptions
-the volcano collapses as magma is erupted from the magma chamber

carbon cycle

-plants absorb CO2 through photosynthesis
-when plants die, some CO2 is deposited in sediments
-over geologic time, a small amount of CO2 is deposited as sediment, but considerable amounts is converted into fossil fuels

carbon sequestration

the process of trapping CO2 gas in a solid phase e.g. limestone

cementation lithification

minerals grow in pores, "gluing" sediments

chemical sedimentary rocks

minerals that crystallize directly from water

chemical weathering

-the chemical transformation of rock into one of more new compounds
-the most important agent is water
-dissolution and oxidation

clastic sedimentary rocks

made from weathered rock fragments (clasts)

composistion

tells us important information about where the magma orginated

composition (silica content), temperature, gas content, crystal content

what does viscosity depend on?

craters

-a bowl-shaped depression atop of volcano formed during an explosive eruption
-vent: conduit that lava erupts from

Crystal settling

earlier-formed minerals are denser than the liquid portion of the magma and sink to the base of the magma chamber

crystal shape aka habit

characteristic shape of crystal or aggregate of crystals

crystallization (minerals)

-solidification from a liquid
-crystals grow when a magma or lava cools
-liquid H20 Freezes to form solid

crystallization (rocks)

The cooling of magma, which results in the systematic arrangement of ions into ordered crystalline structure

density, specific gravity, taste, feel, stinky streak, magnetism, double refraction, effervescence

other properties of minerals

depositional enviornments

-locations where sediment accumulates
-differ in sediment delivery, transport, and depositional conditions, chemical, physical, and biological characteristics
-environments range from terrestrial to marine

differential stress

applies to a rock that are stronger in some directions compared to others

dikes

sub-horizontal to vertical cooling of magma chambers

dissolution

the process of dissolving minerals/rocks into a homogenous solution, small amounts of acid increase the corrosive force of water

dormant volcanoes

has not erupted in hundreds to thousands of years

dunes (sedimentary)

similar to ripples except much larger

effusive eruptions

-produce "gentle" lava flows
-lava flows stream away from vents
-low viscosity lavas
-can produce large lava fountains

erosion

the removal and transport of weathered rock by wind, water, or ice

explosive eruptions

-blow up
-produce explosive ash clouds
-caused by gas pressure buildup in the more viscous magma
-blanket the landscape with tephra

extinct volcanoes

not capable of erupting

Extrusive (volcanic) igneous rocks

magma cooled quickly at the surface

felsic

-lighter in color
-lack iron and magnesium
-lower density and melting temperatures
-common in earth's continental crust

ferromagnesian

-dark color silicate minerals
-contain iron and/or magnesium
-higher density and temp.
-common in oceanic crust and mantle

foliated

preferred layering resulting from differential stress

fossils (sedimentary)

the altered remains of once living organisms

fracture

minerals with equally strong bonds have an absence of cleavage but produce an uneven surface

fragmental igneous rock textures

-solidified fragments from an explosive volcanic eruption
-the still hot volcanic rock pieces fall and are cemented together

gems

crystals of rare minerals with the exceptional quality/ clarity: emerald, diamond, ruby

glassy igneous rock textures

-from very rapid cooling of lava in water or air
-no time for crystals to form

hardness, cleavage, fracture, tenacity

strength properties of minerals

heat (metamorphism)

-metamorphism occurs as the result of heat
-the upper temperature limit is melting. Once melting occurs, this becomes ingenious
-heat energy breaks and reforms atomic bonds
-from geothermal gradient and magnetic intrusions

hydrolysis

the reaction of any substance with water, silicates primarily decompose by hydroplysis

hydrothermal metamorphic enviornments

-alteration by hot-water leaching
-alteration by hot, chemically aggressive water
-a dominant process near mid-ocean ridge magma

Igneous Rocks

What type of rock is created by the solidification of molten rock

intermediate

composition between mafic and felsic

intrusive (plutonic) igneous rocks

magma cooled slowly underground

lava flows

-molten rock that moves over the ground
-lava can be thin and runny or think and sticky
-flow style depends on viscosity

lava

molten material at the surface

lihification

transforms loose sediment into solid rock

luster, color, streak, crystal shape

optical properties of minerals

luster

appearance of mineral in reflected light

Mafic

-dark colored minerals
-contain iron and/or magnesium
-higher density and melting temperatures
-common in earth's oceanic crust and mantle

magma chamber

-located in the upper crust
-some magma cools here to form intrusive rock (plutons)
-some magma. may rise to the surface to form a volcano

magma formation

-high pressure and temperature
-tectonic processes trigger melting
-caused by: decrease in pressure, addition of water or volatiles, heat transfer

magma mixing

-two chemically distinct magma bodies ascend
-the more buoyant mass overtakes the slower rising body
-creates a new magma body that is a blend

magma

- completely or partially molten rock at depth
-consists of liquid, solids, and volatiles

magmatic differentation

the formation of one or more secondary magmas from a single parent magma

mechanical weathering

-the physical breaking of rocks into smaller pieces
-fractures in the rock expose more surface area to weathering agents
-smaller pieces of rock, greater amount of surface area of rock exposed to chemical weathering, thus faster rock with weather

melting, dissolving, chemical reaction

how can a mineral be destroyed?

metamorphic grade

the degree to which the parent rock changes during metamorphism
-low (low T/P)
-high (high T/P)

metamorphic rocks

rocks changed from their original form into a new one without melting or becoming sediment

mineral classification

Classified by their anionic complex. Sometimes this means a single anion of an element that then bonds to positively charged cations to make minerals or it could be a negatively charge molecule that bonds to other cations.

mineral cleavage

tendency to break (cleave) along planes of weak bonding

mineral formation

-a tiny early crystal acts as a seed for further growth
-atoms migrate to the seed and attach to the outer face
-growth moves faces outward from the center
-unique shape reflects the crystal's internal atomic order

mineral hardness

resistance of a mineral to abrasion or scratching

mineral

building block of rocks
-naturally occurring
-generally inorganic
-homogenous solid
-specific chemical composition
-ordered crystalline structure

moisture (weathering)

more water present more weathering occurs (water is most important chemical weathering agent)

neocrystallization

existing minerals react to form new minerals. Initial minerals become unstable and change to new minerals

non-ferromagnesian

-light color silicate minerals
-lack iron and magnesium
-lower density and temp.
-common in continental crust

non-silicate mienrals

- less abundant than silicate minerals, but can be found in high concentrations in specific geologic formations
-sulfide, sulfate, carbonate, halide groups
-elemental minerals

organic sedimentary rocks

the carbon-rich remains of plants

orogenesis

the process that collectively produces a mountain belt. involves deformation

oxidation

the process of turning iron-bearing minerals like pyrite and magnetite to other minerals (forming rust)

oxygen, silicon, aluminum, iron

4 most common elements in earths crust

pahoehoe

-smooth, unbroken lava
-highly fluid flow
-very hot lava

pegmatitic ingenous rock textures

exceptionally coarse-grained

phaneritic (coarsely crystalline)

-crystals seen with naked eye
-slow cooling
-crystals have enough time to grow

phase change

new minerals form with same chemical formula but different crystal structures (polymorphs)

polymorphs

minerals with identical composition but different crystalline structures

porous igneous rock textures

-filled with holes (or vesicles) that formed when lava cooled around vaporizing gas that was originally dissolved in the magma at depth.

porphoryitic

large crystals are embedded in a matrix of smaller crystals

precipitation (mineral)

-from a solution
-as sea-water evaporates, dissolved ions form crystals
-occurs around volcanic gas vents, which are usually sulfur-rich

pressure (metamorphism)

-mineral stability is dependent on pressure
-Changes in T and P lead to changes in minerals
-these minerals will all have the same chemical composition, but their structure varies with P and T conditions.

protoliths

parent rocks

pyroclastic debris

-fragments blown out of a volcano
-avalanches of hot tephra that race downslope
-produces larger quantities of volcanic ash and tephra

recrystallization

minerals change size and shape

regional metamorphic enviornments

-P and T alteration due to orogenesis
-tectonic collision forms "mountain belts"
-differential stress thickens mountains
-creates foliated rocks

reserves

identified ore deposits from which minerals can be extracted profitably

ripples (sedimentary)

water or air flowing over loose sediment creates ripples

rock

a solid mass of minerals or mineral-like matter that occur naturally

rough ingneous textures

means magma cooled slowly

sedimentary coverage

-75% of earth's surface
-sediment cover varies in thickness from 0 to 20 km

sedimentary rock formation

-boundary between two formations is a contact
-geologic maps display the distribution of formations

sedimentary rocks

-built by sediments
-diverse as are the rocks made from them

sedimentary, igneous, and metamorphic parent rocks

3 pathways to become a metamorphic rock

shale, slate, phyllite, schist, gneiss

order of foliated rocks

shield volcanoes

-broad, slightly dome-shaped
-made by lateral flow of low-viscosity basaltc/mafic lava
-have a low slope and cover large geographic areas