Geology 102 - Between Midterms 1 and 2

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98 Terms

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felsic - phaneritic

granite

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felsic - aphanitic

rhyolite

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intermediate - phaneritic

diorite

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intermediate - aphanitic

andesite

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mafic - phaneritic

gabbro

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mafic - aphanitic

basalt

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ultramafic - phaneritic

peridotite

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equigranular

texture in igneous rocks where the crystals are of similar size

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porphyritic

texture in igneous rocks characterized by large crystals embedded in a finer-grained matrix

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felsic

igneous rocks that are rich in silica and light-colored minerals

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intermediate

igneous rocks that have a composition between felsic and mafic, containing a mix of light and dark minerals

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mafic

igneous rocks that are rich in magnesium and iron, typically darker in color

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Where do we find felsic rocks?

continental hot spots, associated with volcanic activity, particularly in areas of subduction and continental rifting

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Where do we find mafic rocks?

oceanic crust, commonly found in mid-ocean ridges and volcanic islands, ocean hot spots

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Where do we find intermediate rocks?

subduction zones, volcanic arcs, and continental margins

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Phenocrysts

form in the magma and are brought up in the magma

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Xenocrysts/xenoliths

didn’t form in the magma, brought along by the magma

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bedrock

rock that is attached to Earth’s crustand is the solid foundation beneath soil and loose material

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outcrop

exposure of bedrock at the surface

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weathering

the process of breaking down rocks and minerals through physical, chemical, or biological means

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erosion

the process by which rocks and soil are worn away and transported by natural forces such as water, wind, or ice

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What are sedimentary rocks formed from?

the accumulation and compaction of mineral and organic particles over time or salts that have dried out of a solution

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deposition

the process by which sediments, soil, and rocks are added to a landform or land mass, often through water, wind, or ice

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lithification

the process of turning sediments into solid rock through compaction and cementation.

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What are the steps in producing a sedimentary rock?

weathering, erosion, transportation geomorphological processes, deposition, compaction and lithification

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strata/beds

layers of sedimentary rock

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clastic

sedimentary rocks formed from fragments of pre-existing rocks

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biochemical, organic

sedimentary rocks formed from the remains of living organisms or biological processes.

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chemical

sedimentary rocks composed of ions that have precipitated out of solution

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conglomerate

a coarse-grained sedimentary rock composed of rounded fragments within a matrix of finer grained material

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breccia

a sedimentary rock made up of sharp-angled fragments of minerals or rocks that are cemented together by a fine-grained matrix

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epicenter

a location on the Earth’s surface directly above the focus

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Fault surface (plane)

the fracture surface between one block and another along which movement occurs.

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Focus

‘origin’ of the earthquake

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Seismic waves

waves of energy that travel like shock waves from the focus to the surrounding area

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P-wave

primary, compression wave

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S-wave

secondary, shear wave

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Types of Faults

strike-slip, normal, thrust, and reverse

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Main shock

biggest earthquake in the cluster

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Foreshock

occurs before the main shock

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Aftershock

occur after the main shock

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What is the scale we use to measure earthquakes?

Moment magnitude scale (Mw)

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Quantitative

property of something that is a measurement

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Qualitative

property of something that is descriptive. A subjective measure

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Causes of earthquakes: natural events

creation of a new fault, movement along an old fault, movement of magma below the surface or a volcanic explosion, huge landslide

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Causes of earthquakes: anthropogenic

underground nuclear explosive tests, fracking, wastewater injection

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Elastic Rebound Theory

Energy is stored in the form of elastically deformed rock. When strain exceeds rock strength, the rock fractures and energy is released

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Body waves

P and S-waves, travel through the Earth’s interior

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Surface waves

love and rayleigh waves, travel along the surface of the lithosphere

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Layers of the Earth

Crust, Upper Mantle, Aesthenosphere, Lower Mantle, Outer Core, Inner Core

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Love Wave

cause horizontal shifting at the surface of the Earth

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Rayleigh wave

rotating waves along surfaces, create vertical displacement (movement), like ripples on water

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Divergent Boundaries

Shallow earthquakes within ocean basins, foci are located:

• Along mid-ocean ridges

• Along transform faults

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Transform-Fault Boundaries

Strike-slip fault mechanism due to shearing forces from tectonic plate movement, Can produce large, destructive earthquakes

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Convergent Boundaries

Largest earthquakes occur at subduction zones called megathrust earthquakes

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Earthquakes cause damage in what ways?

Faulting and shaking – primary hazards, Landslides, Liquefaction, Tsunamis, Fires

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Ordovician Period

505 to 440 Ma. First vertebrates, fish appear, Evidence of glaciation, sea level lower, Mass extinction at the end

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Silurian Period

440 to 410 Ma. Age of corals and reefs. • Sharks, toothed fish • First primitive land plants and insects

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Devonian Period

410 to 360 Ma - ‘Potash’ evaporite sedimentary deposits, deposited in shallow saline seas. • Land plants (e.g., trees) and insects thrive • Evidence of glaciation • Mass extinction at end. Pangaea supercontinent begins to form

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Carboniferous Period

360 to 286 Ma First reptiles. • Huge swamps and the first global coal forming period. • Coal forming in area that would become Estevan, SK • Appalachian Mountains beginning to form.

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Permian Period

286 to 245 Ma • Formation of Pangaea – a super continent. • Glaciation in the Southern Hemisphere - Extinction! 300 mile crater found in Antarctica (2006) • Volcanic activity in Siberia, dust >CO2 in atmosphere, warming. • End of the Paleozoic

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Triassic Period

245 to 208 Ma • Pangea starts to breakup. Mid-Atlantic ridge forms, • Deserts. Warm climate. • First small dinosaurs & first primitive mammals

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Jurassic Period

208 to 146 Ma • Dinosaurs rule! Large & diverse dinosaurs and marine vertebrates. • First birds. Eosinopteryx in Chinese forests 150 Ma

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Cretaceous Period

146 to 65 Ma • Global climate MUCH warmer • First flowering plants • Tyrannosaurus rex dominates the plains.

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Tertiary Period

65 to 2.6 Ma • Giant beavers (60-100 kg), giant bears, mastodons, giant sloths • Last wooly mammoths

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Quaternary period

2.6 Ma to the present • First hominids • 20 Ma human-like primates • Homo 2.4 Ma, Homo erectus 1.6 Ma - Ice Age (again), at least 4 major glacial and interglacial periods (ice retreat of continental glaciers)

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Holocene Epoch

the current geological epoch, beginning around 11,700 years ago and continuing to the present day. It's also known as the "Age of Man" because of the significant impact humans have had on the planet during this time

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Magma

originates deep within the Earth’s lithosphere / upper mantle due to the melting of rock and associated minerals

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Lava

the name given to molten rock when it reaches the Earth’s surface from volcanic activity

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extrusive

Igneous rocks that reach the Earth’s surface cool, solidify, and crystallize relatively quickly. aphanitic texture

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How do metamorphic rocks form?

Transformation of pre-existing rock due to: high temperature, high pressure, and (sometimes) chemically active hot fluids.

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At what temperature and depth does a rock start to metamorphose?

around 250°C, typically at depths > 8 km

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Foliation

planar or wavy structure that results from the flattened growth of minerals in a metamorphic rock

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Foliation develops through:

rotation of minerals, change in mineral shape, and recrystallization

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Non-foliated rocks occur when:

the pressure is low or equal from all directions (contact metamorphism), or the composition of the rock does not include platy minerals such as mica

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Contact metamorphism

hot magma chambers ‘bake’ the relatively cooler ‘host rock’ (country rock) where they come in contact

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Seafloor metamorphism

Only takes place in the ocean, Common around mid ocean ridges, mafic rocks, greenschist

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Regional metamorphism

associated with mountain building and plate tectonics occurs over a large area

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Burial metamorphism

temperature increases with depth and the geothermal gradient • No directed pressure acting on the rocks, just weight of overlying rocks

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Shock Metamorphism

Results from meteorite impacts, Leaves evidence in the mineral grains, e.g., planar fractures in quartz grains

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Hot spots

Mantle plume: upwelling of hot rocks in convectional cells in the mantle to the base of the lithosphere. Heat from the plume melts overlying rocks and magma seeps up to surface creating a volcano.

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pyroclastic material

solid rock fragments ejected during an eruption

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Tephra

Air-borne pyroclastic material

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Pahoehoe

basaltic flow of lower viscosity (more fluid), ropy structure

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Aa lava

sharp, spiny, surface, basaltic deposit of higher viscosity (less fluid)

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Shield volcano

The largest conical volcanoes. Formed from basalt. Gentle slopes (5o - 12o). Eruptions via fissures and vents, often form lava lakes in a large vent. Lava flows quickly and over great distances. Lava rivers and lava tubes common

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Cinder cones

A small volcano cone (a few 100 m in diameter) • The slope angle is approximately 24-32o on average from the horizontal (angle of repose). Smaller in size and shorter life span • Often form on the sides of shield volcanoes

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Composite cones (stratovolcanoes)

Intermediate in size and average composition •Variable slope angles but often have a distinctive conical shape •Located along subduction zones, Can be inactive for long periods of time before eruptions

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Flood basalt

• Basaltic lava flow, very fluid, ejected from a fissure (crack) and flooding a large area • Fed from mantle plumes

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Caldera volcano

A volcanic crater that develops from the explosion and collapse of a composite volcano. • some of the largest features (20 to 40 kms wide) and form from violent, often infrequent eruptions (10,000 yr frequency).

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Mid ocean ridges

Have earthquakes, hot water emissions • Basaltic magma

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Lava Domes

lava too viscous to flow and piles up at vent. Cools quickly generating glassy high silica obsidians

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Spatter cones

very small basaltic cones, build up around vents where magma is splattered by bubbles of gasses

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Fumarole

vents that emit hot gases, can be 1000ºC.

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Gases

CO2 and H2 S are invisible, but can asphyxiate or poison people. can also dissolve in water droplets in the air and lead to acid rain

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Pyroclastic flow

Avalanche of hot gas and pyroclastic material. • E.g., Mt Vesuvius, Italy (79 AD)

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Lahar

volcanic debris flow (hot mud flow)

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Phreatic explosions

Occur when magma comes in contact with water or ice • Occurs in subterranean volcanoes or island arc volcanoes