geol105 - exam 1

geosphere components

• core

• mantle

• crust

core

• inner core = solid

• outer core = liquid

mantle

• upper mantle = atmosphere

• the rocks here are weak and able to slowly flow in response to the uneven distribution of heat deep within Earth.

crust

• lithosphere

• rigid outer layer that includes the crust and the uppermost mantle

soureces of energy

• renewable

• nonrenewable

renewable resources

can be replenished over a relatively short time spans

ex) plants and animals food, natural fibers for clothing, forest products for lumber and paper, and energy from flowing water, wind, and the sun

non renewable

these resources cannot be easily replenished

ex) metals such as iron, aluminum, and copper. As do our most important fuels: oil, natural gas, and coa

environmental issues

• greenhouse effect

• global warming

• climate change

greenhouse effect

carbon dioxide as well as other gases trap the heat reflected back from earth’s surface, this retention of heat reflected back

scientific method

the process described, in which researchers gather data through observations and formulate scientific hypotheses and theories

hypothesis

a tentative/untested explanation, meant to be answered through investigation trying to explain how or why things happen

theory

a well-tested and widely accepted view that the scientific community agrees best explains certain observable facts

steps of scientific method

• observation

• question

• hypothesis

• results

• conclusion

universe theories

• big bang

• doppler effect

big bang

the universe started in a dense, hot state, followed by expansion, cooling, and a less dense state. Therefore, there is no “before the Big Bang”, only what occurred after it

doppler effect

which is a change in the frequency of a sound, light, or other wave caused by movement of the wave’s source relative to the observer

terrestrial planets

• composed of rock and metallic elements that condensed at high temperatures

• Mercury, Venus, Earth, Mars

jovian planets

• small rock cores compared with their overall size and are composed mostly of hydrogen, helium, ammonia, methane, which condense at lower temperatures

• Jupiter, Saturn, Uranus, Neptune

earth components

• crust

• mantle

• liquid outer core

• solid inner core

rock cycle

pictorial representation of events leading to the origin, destruction or changes, and reformation of rocks as a consequence of Earth’s internal and surface processes

organic evolution

states that all present-day organisms are related and that they have descended with modification from organisms that lived in the past

geologic time scale

divided into a hierarchy of increasingly shorter time intervals, each of which has a specific name and duration

continential drift

all land masses were originally united in a single supercontinent

alfred wegener

German meteorologist is generally credited with developing the hypothesis of continental drift. He proposed that all land masses were originally united in a single supercontinent that he named Pangaea, from the Greek meaning “all land”

supercontinents

• Pangaea – supercontinent proposed by Wegener

• Laurasia - northern supercontinent containing North America and Asia (excluding India)

• Gondwanaland - southern supercontinent containing South America, Africa, India, Antarctica, and Australia

continental drift evidence

• Puzzle-piece fit of coastlines of Africa and South America has long been known, connecting continents allowed plants and animals to roam different lands without crossing oceans

• Wegener noted South America, Africa, India, Antarctica, and Australia have almost identical late Paleozoic rocks and fossils in early 1900s

• Glossopteris (plant), Lystrosaurus and Cynognathus (animals) fossils found on all five continents.

• Mesosaurus (reptile) fossils found in Brazil and South Africa only

continential drift evidence

Fitting of Continents and the matching of rock types: Redefined the edge of each continent as the middle of the continental slope greatly improved the fit.

Rock matches show when the continents were together, paleomagnetic data indicate the direction and rate of movement.

glacial continential drift evidence

During the late Plaeozoic Era, massive glaciers covered large continental areas of the Southern Hemisphere

Evidence for the glaciation include:

• Layers of till (sediments deposited by glaciers)

• Glacial striations (scratch marks from glaciers sliding downslope)

paleomagnetism

is the remnant magnetism in ancient rocks recording the direction and intensity of Earth’s magnetic poles at the time of the rocks formation

• When magma rocks cool, the magnetic ironbearing minerals align themselves with Earth’s magnetic field, recording both direction and strength.

• The temperature at which iron-bearing minerals gain their magnetization is called the Curie Point.

• Uses mineral magnetic properties to determine direction and distance to the magnetic pole when rocks formed.

plate boundaries

1. divergent

2. convergent

3. transform

divergent boundary

• plates move apart

• Can occur in the middle of the ocean or within a continent.

• Marked by rifting, basaltic volcanism, and eventual ridge uplift.

• Eventually creates a new ocean basin.

convergent boundary

• plates move together

• Ocean-ocean plate convergence – marked by ocean trench, Benioff zone, and volcanic island arc

• Ocean-continent plate convergence – marked by ocean trench, Benioff zone, volcanic arc, and mountain belt

• Continent-continent plate convergence – marked by mountain belts and thrust faults

• Ophiolites- equences of rock on land consisting of deep-sea sediments, oceanic crust, and upper mantle. Ophiolites are one feature used to recognize ancient convergent plate boundaries.

transform boundary

• plates slide horizontally past one another

• lithosphere is neither created nor destroyed along a transform boundary, the movement between plates results in a zone of intensely shattered rock and numerous shallow-depth earthquakes

• ex) San Andreas Fault in California

seafloor spreading

the concept that the seafloor is moving like a conveyor belt away from the crest of the mid-oceanic ridge until it disappears by plunging beneath a continent or island arc. Proposed in 1962 by Harry Hess

deep mantle convection

circulation pattern driven by rising of hot material (hot mantle rock) and/or the sinking of cold material (oceanic crust)

marine magnetic anomalies

alternating positive and negative magnetic anomalies that form a stripe- like pattern parallel to the mid-oceanic ridges, which allows us to measure the rate of movement and to predict the age of the sea floor

intraplate activity

• mantle plume - narrow columns of hot mantle rock that rise through the mantle. Stationary with respect to moving plates; large mantle plumes may spread out and tear apart the overlying plate forming a Hot Spot at the Earth’s surface (examples include Hawaii, Yellowstone and Iceland

• hot spot volcanism - Mantle plume hot spots in the interior of a plate produce volcanic chains

mineral

• building blocks of rocks

• is any naturally occurring inorganic solid that possesses an orderly crystalline structure and a definite chemical composition that allows for some variation

defining a mineral

1. naturally occurring

2. generally inorganic

3. solid substance

4. orderly crystalline structure

5. definite chemical composition that allows for some variation

mineral?

• wood - no

• table salt - yes

• water - no

• ice - yes

• ice cube - yes

• bone - no

• dirt - no

• synthetic diamonds - no

• gold - yes

atoms

the smallest particles that cannot be chemically split. They do contain even smaller particles: protons, and neutrons located in a central nucleus that is surrounded by electrons.

protons

positive charge

electrons

negative charge

neutrons

neutral charge

valance electrons

can be transferred or shared with other atoms to form chemical bonds

ionic bonds

valence electrons transferred

covalent bonds

valence electrons shared

metallic bonds

electrons free to move; resulting in high electrical conductivity

diagnostic properties

useful in identifying an unknown mineral.

ambiguous properties

properties of certain minerals varying among different specimen of the same mineral

properties of minerals

1. color

2. streak

3. luster

4. cleavage and fracture

5. hardness

6. crystal shape

7. density

color

the most conspicuous characteristic of any mineral, it is considered a diagnostic property of only a few minerals

streak

color of the mineral in powdered form

luster

• appearance or quality of light reflected from the surface of a mineral

• Minerals that have an appearance of of metal, regardless of color, are said to have metallic luster.

• Minerals with a dull coating or tarnish exhibit a submetallic luster

• Most minerals have a nonmetallic luster

• ○Vitreous/glassy

  ○Earthy/dull - soil like

  ○Pearly

  Silky/greasy

cleavage

• is the tendency of a mineral to break (cleave) along planes of weak bonding

cleavage directions

• 1 direction (plane)

• 2 directions (planes) = 90%

• 2 directions (planes) (different angle) ≠ 90%

• 3 directions (planes) = 90% intersect

• 3 directions (planes) ≠ 90% intersect

• 4 directions (planes)

hardness

measure of the resistance of a mineral to abrasion or scratching

crystal shape

refer to the common or characteristic shape of individual crystals or aggregates of crystals.

density

mass per unit volume

fracture

minerals do not break along planes of cleavage, they fracture

• Irregular fracture- produce uneven surfaces

• Conchoidal fracture- break into smooth curved surfaces resembling broken glass

• Splintery/Fibrous fracture

silicates

Made up of the two most common elements in Earth’s crust, Oxygen and Silicon, combine to form the basic “building block” for the most common  group.

silicate-oxygen tetrahedron

consisting of four oxygen ions that are covalently bonded to a comparatively smaller silicon ion, forming a tetrahedron- a pyramidal shape with four identical faces

silicate structures

●Isolated Silicate

●Chain Silicates

○Single

○Double

●Sheet Silicates

●3D Framework Silicates.

non silicates

●Carbonates – contains C O₃ in their structures (calcite – C a C O₃).

●Halides - contains Cl, F, Br in their structures (halite - NaCl)

●Sulfates – contains S O₄ in their structures (gypsum – C a S O₄. 2H₂O).

●Sulfides – contains S (but no O) in their structures (pyrite – F e S₂).

●Oxides – contains O, but not bonded to S i, C or S (hematite – F e₂O₃).

●Native elements – composed entirely of one element (diamond – C).

igneous rocks

• intrusive igneous

• extrusive igneous

intrusive igneous

• form when magma solidifies underground (plutonic)

• formed deep underground and typically cools slowly

extrusive igneous

• form when magma solidifies at the Earth’s surface (lava) (volcanic rocks)

• formed at or near the Earth’s surface and cools quickly.

classification of igneous rocks

Igneous rock are classified based on their:

• chemical composition

• texture

chemical composition

mineral content indicates origin and evolution of the magma

texture

rock’s appearance with respect to the size, shape and arrangement of grains or other constituents. Crystal size is determined by the rate of cooling of the magma

chemistry of igneous rocks

• felsic

• intermediate

• mafic

• ultramafic

felsic

• >65% silica by weight

• contain light-colored minerals that are abundant in silica, aluminum, sodium and potassium

• more dangerous

• Convergent boundary: Magma at convergent plate boundaries/subduction zone is mostly intermediate (53%-65% silica) or felsic (>65% silica). find rocks like Andesites and Granites

intermediate

• silica contents between 55% and 65% by weight

• Convergent boundary: Magma at convergent plate boundaries/subduction zone is mostly intermediate (53%-65% silica) or felsic (>65% silica). find rocks like Andesites and Granites

mafic

• silica content between 45% and 55% by weight

• contain dark-colored minerals that are abundant in iron, magnesium and calcium

• less dangerous that felsic, effusive

• Divergent boundary: Magma formed beneath the spreading ridge in invariably mafic (45%-52% silica), consisting mostly of ferromagnesian silicates. Therefore we find mainly basaltic types rocks on the ocean floors.

ultramafic

• <45% silica, by weight

• composed almost entirely of darkcolored (black/green) ferromagnesian minerals

textures

• aphanitic

• phaneritic

• pegmatitic

• porphyritic

• glassy

• vesicular

• pyroclastic

aphanitic

• fine grained

• crystals are too small to see easily with the naked eye

• Magma cooled quickly at or near the surface

• extrusive

phaneritic

• coarse grained

• crystals are large enough to see with the naked eye

• Magma cooled slowly/below the surface

• intrusive

pegmatitic

• extremely coarse grained

• formed when magma cools very slowly at depth

• intrusive

porphyritic

• 2 distinct crystal sizes

• phenocrysts - formed first during slow cooling underground

• groundmass - forming during more rapid cooling at the Earth’s surface

glassy

• contains no crystals at all

• formed by extremely rapid cooling of the magma

• extrusive

vesicular

• contains cavities (vesicles) in extrusive rocks resulting from gas bubbles that were in the lava

• ex) pumice

pyroclastic

• fragmental

• consolidated pyroclastic debris such as ash, pumice or crystalline rock

viscosity

resistance to flow

factors that affect visciosity

• heat

• main influence = silica content

• gases, water vapor, and CO₂

• ex) water = low viscosity, honey = high visciosity

bowen’s reaction series

Minerals crystallize in a predictable order, over a large temperature range.

melting

• decompression melting

• flux melting

decompression melting

• occurs when rising mantle rock is subject to lower melting points as the pressure is reduced

• releasing pressure

• deeper you go = temp and pressure increase

• higher you go = temp and pressure decrease

• going from high to low = decompressing, starting to melt

• melts as it rises

flux melting

• adding water

• Water becomes increasingly reactive at higher temperatures.

• At sufficient pressures and temperatures, highly reactive water vapor can reduce the melting point of rocks by over 200°C.

• addition of water = speeding things up

• decreases melting point by 200 degrees

evolution of magma

• differentation

• crystal setting

• partial melting

• assimilation

• mixing

differentation

process by which different ingredients separate from an originally homogenous mixture.

crystal setting

changes the magma composition as the crystals are removed from the melt as they settle downward

partial melting

process by which the magma composition varies as different minerals/rocks melt at different temperatures

assimilation

• process whereby a hot magma composition will change as it melts and assimilates adjacent rocks into the magma

• xenolith - rock fragment within an intrusive igneous body that is unrelated to the igneous body itself

mixing

• magma mixing

• composition of a magma body changes as it mixes with another magma body

intrusive bodies

collectively called plutons, exist in bodies or structures that penetrate or cut through pre-existing country rock

• dike

• sill

• laccolith

• volcanic neck

• volcanic pipe

• batholith

• stocks

dike

shallow, tabular intrusive structure that cuts across any layering in country rock

sill

shallow, tabular intrusive structure that parallels layering in country rock

laccolith

a sill inflates and causes the overlying rock to bow upward, forming an igneous body

volcanic necks

shallow intrusion formed when magma solidifies in throat of volcano. Then the surrounding volcano material erodes away

volcanic pipe

cylindrical conduit that connects the volcano’s throat to the underlying magma chamber