Earth Science Final Study

What evidence shows us that our universe is expanding?

The Doppler Effect is what shows us that the universe is expanding. Relative to motion, the waves of sound or light can be compressed or relaxed. The Doppler Effect can be heard when cars whiz past you. The light that is coming from a source that is moving away is relaxed and has a redshift, light that is coming from a source that is moving toward the observer is compressed and has a blue shift. Light from galaxies is observed to be red-shifted which means our universe is expanding.

What is the ‘Big Bang Theory’ and is an explosion the best analogy for the formation of our universe?

The Big Bang Theory is a model of the observable universe that explains the large-scale structure and evolution through time. In the beginning, everything (I mean EVERYTHING) was in a single point. The best analogy for the formation of our universe is not an explosion but rather expansion. Some may describe this as a balloon expanding but others describe it as a raisin bread rising, the raisins separate away from each other as the scale of the bread increases. Everything is getting farther away from each other

How are the timing and ways that Earth and our Moon formed different?

The way our Earth formed is from planetestimals clumping into a lumpy protoplanet which the interior heats, sotens, and forms sphere and the interior differentiates due to density. The moon used to be a mars-sized protoplanet that collided with Earth \~4.53 Ga which disintegrated part of Earth’s mantle and the planet. Collision debris then formed a ring around Earth and this debris coalesced and formed the moon

What does Earth’s magnetic field look like and how does it benefit us?

Earth’s magnetic field is like a giant dipole bar magnet which has north and south ends and grows weaker with distance. Magnetic force is directionally and flows from S pole to the N pole along the bar magnet (so the center of the field), and north to south along field lines outside the bar. The N compass arrow points to the bar magnet S pole which is Geographic North. The magnetosphere is a shield formed by the magnetic field lines around the Earth. It is shaped like a teardrop and can deflect most of solar winds. The Van Allen belts intercept dangerous cosmic radiation. The magnetic field can be revealed by the aurorae, just charged particles that made it past the Van Allen belts that are channeled. 

Draw a diagram of the Earth’s layers (crust, mantle, inner core, outer core, and lithosphere) and label each with its main elements and its state (liquid or solid). Explain why certain elements are partitioned (or organized) into different layers.

The density of the elements will determine where it will be in the Earth’s layers, more dense materials will be closer to the core and lighter elements will be near the surface.

How do the different properties of ocean lithosphere and continental lithosphere help drive plate tectonics?

The continental crust is thicker than oceanic but is less dense which makes it more buoyant than the oceanic crust. This makes it to where the continental lithosphere is not dense enough to subduct which is what causes mountains to form when continental lithosphere plates collide with oceanic plates.

What evidence exists for Plate Tectonics? Describe how earthquakes and paleomagnetism support this theory.

Earthquakes happen when plates move, tend to happen at active margins (where plates are moving). If you have a rift zone/mid ocean ridge, when you pull those two apart the rock has to drop down to let that spread, the plates pulling apart cause earthquakes. Volcanoes and magnetism are common at active margins 

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Relates back to oceanic crust and ripping it apart, ripping apart two plates deep in the ocean, magma comes up in between those plates. The iron grains in the magma as they cool will align with the north. When it is ripped again, when the magnetic field is flipped, the new iron will point towards the magnetic north. Essentially, get down on the ocean floor and walk across and can watch a compass change to where it points north. **Either side of the rift (plate boundary) the patterns for iron alignment are symmetrical.** 

What happens at divergent ocean-ocean boundary?

Tectonic plates are moving apart, this creates mid-ocean ridges as the lithosphere thickens away from the ridge axis. This generates new lithosphere.  

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The aging ocean crust moves away from the heat from the asthenosphere at the base of the mid-ocean ridge. 

What happens at divergent continent-continent boundary?

Occurs in weak spots in the continental lithospheric plate. These boundaries rip apart continents and create new ocean basin. 

What happens at convergent ocean-ocean boundary?

Tectonic plates move together toward one another, subduction happens here. The subducting plate is always oceanic lithosphere. Subduction recycles oceanic lithosphere which helps balance the sea-floor spreading. Causes deep-ocean trenches, accretionary prisms, volcanic arcs, back-arc basins

What happens at convergent continent-continent boundary?

One of the plates will subduct, these often cause folded mountains, and earthquakes.

What happens at convergent ocean-continent boundary?

The oceanic lithosphere will subduct under the continental crust.

What happens at transform boundary?

Tectonic plates slide sideways, nothing is created nor destroyed. This offset-spreading ridge segment is characterized by earthquakes and the absence of volcanism. 

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Oceanic transforms offset the mid-ocean ridge axis and create fracture zones that cause active slips (earthquakes).

What processes form each family of rocks (sedimentary, igneous, and metamorphic)?

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1. Igneous forms through the solidification of melt or other materials extruded from the mantle. Melt could be magma (below the surface) or lava (above the surface) Ash or dust as well


1. Requires a way to melt rock
2. Can happen from the melting of other rocks, input of new melt into the crust from the mantle, and the constant heating and remelting from old igneous rock
2. Sedimentary forms through the burial and lithification of sediment. Sediments are the eroded pieces of any other kind of rock. 


1. Requires water (wind or ice) and topography \\
2. Can happen from erosion, transportation, and deposition of other rocks (and sedimentary rocks). 
3. Metamorphic rock forms through the burial and heating rock. Pressure and temperatures are not high enough to melt the rock, but they do change the shape of the pieces within the rock


1. Requires a way to move rock (create pressure) and/or heat


1. Can happen from burial, heating, and remetamorphism from other rocks (and metamorphic rocks) 

Define a mineral and give examples of things that are and aren’t minerals

A mineral is something that is naturally occurring, formed geologically, solid, crystalline in structure, definite chemical composition, and inorganic (few exceptions) (synthetic minerals can be made by man). Living organisms can create minerals (called biogenic minerals, things like bones, shells, and other skeletal types). Minerals also must be a state of matter that can maintain its shape indefinitely, minerals are solids, not liquids or gases.

Minerals 

* Diamonds
* Graphite
* Quartz
* Halite

Not minerals

* Glass
* Water
* Blood
* Wood

How do minerals grow? How can they be destroyed?

Solidification from a melt, crystals grow when the melt cools.

Precipitation from a solution, seeds form when a solution becomes saturated.

Solid-state diffusion, atomic migration from one point to another in a solid.

Biomineralization, minerals produced by a living organisms.

Precipitating directly from a gas.

(Seed crystals are tiny early crystal acts as a seed for further growth, atoms migrate to the seed and attach to the outer face, growth moves outward from the center. Unique shape reflects the crystal’s internal atomic order.

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Minerals can be destroyed by melting, dissolving, or chemical reactions.

What are the properties used to identify a mineral?

Color, streak, luster, hardness, specific gravity, crystal habit, fracture or cleavage, and special physical properties (effervescence, magnetism, taste)

How do you test for color, streak, and luster?

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1. Color


1. The part of visible light that is not absorbed by a mineral. Diagnostic for some minerals but some minerals also exhibit a broad color range. Color varieties often reflect trace impurities
2. Streak


1. The color of a powder is produced by crushing a mineral, obtained by scraping a mineral on unglazed porcelain. Less variable than crystal color
3. Luster


1. The way a mineral scatters light. Has two subdivisions, metallic and nonmetallic (silky, glassy, satiny, resinous, pearly, earthy) 

How do you test for hardness, specific gravity, and crystal habit?

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1. Hardness


1. The scratching resistance of a mineral. This derives from the strength of atomic bonds. 
2. Specific gravity


1. Represents the density of a mineral, mineral weight over the weight of an equal water volume. Imagine it’s about heavy it feels, like how Galena “feels” heavier than quartz. 
3. Crystal habit


1. How a crystal grows through time, well-formed faces, aggregate of many well-formed crystals, or arrangement of faces reflects internal atomic structure. Variation is in directional growth rates. Block or equant (equal growth rate in three dimensions), bladed (shaped like a knife blade), needle-like (rapid growth in one dimension, slow in others) 

How do you test fracture or cleave and special physical properties?

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1. Fracture or cleavage 


1. How a mineral breaks in ways that reflect atomic bonding. Fracturing implies equal bond strength in all directions. Cleavage describes a tendency to break along planes of weaker atomic bonds, produces flat shiny surfaces. Cleavage can be in one direction, two directions at 90 degrees, two directions not at 90 degrees, three directions at 90 degrees, three directions not at 90 degrees. 
2. Special physical properties


1. Effervescence (reactivity with acid)
2. Magnetism (magnetic attraction)
3. Taste ( :) ) 

Compare and contrast crust vs lithosphere?

Crust is a compositional layer, if you crack it the “froth” and “beer” are the same composition of the crust but break and stuff are different. Crust is a compositional layer with light less dense elements with more dense elements under. The top part of the mantle behaves the same as the top layer of the crust. The lithosphere is a much thicker layer as it describes how it behaves, below lithosphere the mantle bends. How the material/layer behaves is the lithosphere, how it is composed of is crust.

What is the difference between lava and magma?

Magma—melted rock below ground Lava—melted rock once it has reached the surface

Phaneritic

Individual grains are visible to the eye Slow cooling, generally intrusive

Aphanitic

Individual grains need a microscope to be seen Rapid cooling; generally extrusive

Porphyritic

A few large grains (phenocryst) set in a finer-grained groundmass

Two cooling rates; slow at first to form phenocryst; then more rapid to form groundmass

Vesicular (Porous)

Spongy, filled with large or small holes Rapid cooling accompanied by the release of gases

Glassy

Smooth, shiny, looks like glass, no individual grains present Extremely rapid cooling; generally extrusive

Pyroclastic (Fragmental)

Mineral grains, rock fragments, and glass shards welded together Explosive eruption of ash and rock into the air.

heat transfer

Rising magma carries mantle heat with it. This raises the T in nearby crustal rock, which then melts.

volatile addition

volatiles lower the melting temperature of rock. Volatiles – substance easily evaporated at room temperature, often exists as a vapor under normal conditions

pressure release

a decrease in pressure (P) allows atoms to change phase

Melting will occur if P is decreased and atoms are allowed to change phase.

P drops when hot rock is carried to shallower depths.

Mantle Plumes, Rift Valley, Mid-Ocean Ridge

Felsic

66-76% silica 

(feldspar and silica) quartz, feldspars, micas

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refers to a predominance of the light-colored (felsic) minerals feldspar and silica in the form of quartz. These light-colored minerals have more silica as a proportion of their overall chemical formula. Minor amounts of dark-colored (mafic) minerals like amphibole and biotite mica may be present as well. Felsic igneous rocks are rich in silica (in the 65-75% range, meaning the rock would be 65-75% weight percent SiO2) and poor in iron and magnesium.

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Phaneritic (Coarse-grained), Aphanitic (Fine-grained), Porphyritic, Vesicular (Porous), 

Glassy,

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Pyroclastic (Fragmental)

Intermediate

52-66% silica

feldspars, amphibole (hornblende) \\n

a composition between felsic and mafic.  It usually contains roughly-equal amounts of light and dark minerals, including light grains of plagioclase feldspar and dark minerals like amphibole.  It is intermediate in silica in the 55-60% range.

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Phaneritic, Aphanitic, Porphyritic, Pyroclastic

Mafic

45-52% silica

(Mg- and Fe-rich) olivine, pyroxene (augite), feldspars

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refers to a abundance of ferromagnesian minerals (with magnesium and iron, chemical symbols Mg and Fe) plus plagioclase feldspar. It is mostly made of dark minerals like pyroxene and olivine, which are rich in iron and magnesium and relatively poor in silica. Mafic rocks are low in silica, in the 45-50% range.

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Phaneritic, Aphanitic, Porphyritic, Vesicular, Pyroclastic

Ultramafic

38-45% silica

olivine

Intrusive, 

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refers to the extremely mafic rocks composed of mostly olivine and some pyroxene which have even more magnesium and iron and even less silica. These rocks are rare on the surface, but make up peridotite, the rock of the upper mantle. It is poor in silica, in the 40% or less range.

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Phaneritic 

Why does magma rise toward Earth’s surface?

Magma doesn’t stay put; it is buoyant and rises upward in the crust. Fluid magma is less dense than surrounding solid rocks. This transfers mass from deep to shallow parts of Earth

What is a volcano?

a location where magma has breached the surface.

How do temperature, volatile content, and silica content affect magma viscosity?

Temperature: hot \= lower viscosity; cooler \= higher viscosity Volatile content: More volatiles—higher viscosity Less volatiles—lower viscosity Silica (SiO2) content: Less SiO2 (mafic)—lower viscosity. More SiO2 (felsic)—higher viscosity.

What is viscosity?

Viscosity – a materials resistance to flow; it’s “stickiness”

Contrast the eruption of a basalt (low viscosity) and andesitic (high viscosity) eruption.

Mafic lava—very hot, low silica, and low viscosity •Basalt flows are often thin and fluid (\=effusive). Andesitic flows have higher SiO2 content which makes andesitic lavas viscous. Unlike basalt, they do not flow rapidly. Instead, they mound around the vent and flow slowly. The crust fractures into rubble, called blocky lava. Andesitic lava flows remain close to the vent. Rhyolitic Rhyolite has the highest SiO2 and the most viscous lava. Rhyolitic lava rarely flows. Rather, lava plugs the vent as a lava dome. Low viscosity tend produce vast outpouring of lava, more viscous eruptions tend to be explosive and create pyroclastic flows and tephra.

What is a Pahoehoe?

•a Hawaiian word describing basalt with a glassy, ropy texture •Pahoehoe forms when extremely hot basalt forms a skin. •With flow, the skin is rolled into ropy ridges and furrows.

What is a A’a’?

•a Hawaiian word describing basalt that solidifies with a jagged, sharp, angular texture. •A’a’ forms when hot flowing basalt cools and thickens. •With flow, lava crumbles into shards and fragments.

What is columnar jointing?

solidified flows may contract with vertical fractures, creating polygonal columns.

What is pillow basalt?

•round blobs of basalt cooled underwater •The pillow surface is cracked, quenched glass. •Lava pressure ruptures a pillow to form the next blob. •The process repeats to form a mound of pillow basalts. •Common on the mid

What mineral melts first (when a magma first starts to heat up?)

Quartz, Muscovite, Feldspar, Plagioclase (Na-rich)

What mineral melts last (when a magma is as hot as it gets)?

Olivine, Pyroxene, Plagioclase (Ca-rich)

What mineral crystallizes first (as a magma starts to cool down)?

Olivine, Pyroxene, Plagioclase (Ca-rich)

What mineral crystallizes last (once a magma is very cold)?

Quartz, Muscovite, Feldspar, Plagioclase (Na-rich)

What is a sill?

injected parallels to rock layering (Trinidad)

What is a dike?

cuts across rock layering (Ship Rock)

What is a laccolith?

pushes up the surrounding rock and comes in from a batholith

What is a large igneous province? (LIP)

unusually large outpourings of magma Mostly mafic, include some felsic examples Mantle plume first reaches the base of the lithosphere. Erupts huge volumes of mafic magma as flood basalts. Low viscosity Can flow tens to hundreds of kms

What are the important features of a volcano?

fissure, vent (flank vent), caldera, magma chamber.

What is a fissure?

Some magma rises via a conduit to the surface. Magma may erupt along a linear tear called a fissure. eruptions may display a “curtain of fire.” evolve into discrete vents and craters.

What is a vent?

•Crater—a bowl

\*Form as erupted lava piles up around the vent

•Summit eruptions—located within the summit crater

•Flank eruption—located along the side of a volcano

What is a caldera?

giant volcanic depression (steep sidewalls and flat floors) develops from a magma chamber that emptied and then collapsed

What is a magma chamber?

located in the upper crust.

Usually, an open cavity or area of highly fractured rock

May contain a large quantity of magma

Most magma cools here to form intrusive igneous rock. Some magma may rise to the surface to form a volcano.

What are the three main types of volcanoes?

shield, stratovolcano, and scoria cone.

What is a shield volcano?

broad, slightly dome-shaped (like an inverted shield)

Constructed by lateral flow of low-viscosity basaltic lava.

Examples: Mauna Loa, Olympus Mons

What is a scoria cone?

Conical piles of tephra; the smallest type of volcano Built of ejected lapilli and blocks piled up at a vent Typically from a single eruption event There can be a lot of scoria cones in one area

What is a stratovolcano?

Large, cone-shaped volcanoes with steeper slopes

Made of alternating layers of lava, tephra, and debris

Examples include Mount Fuji, Mount Rainier, Mount Vesuvius

How can volcanic gases be dangerous?

•Aerosols can cause respiratory problems in people.

•Volcanic gases can be poisonous (H2S, CO2).

Contrast effusive and explosive eruptions.

Effusive eruptions— produce a vast outpouring of lava

• Lava flows stream away from vents.

• Lava lakes can form near, or inside, the vent.

• Can produce huge lava fountains.

• Common with mafic magma (basalt)

• Very hot

• Low viscosity

Explosive eruptions— release pressure catastrophically

• High gas pressure is from more viscous SiO2-rich magma

• Create pyroclastic flows and cover the land with tephra

• Can eject many cubic kilometers of debris skyward

• Mostly andesitic and rhyolitic compositions

How do we mitigate volcanic hazards?

Planning

Danger assessment maps

Delineate danger areas

Pyroclastic flows

Lahars

Landslides

Used for planning, zoning

Mitigating Volcanic Hazards Evacuation—moving those at high risk saves lives.

• Mount St. Helens—timely evacuation saved hundreds.

• Even if eruptions don’t occur, there are large expenses. Diverting flows—flowing lava can be diverted.

• Explosives

• Heavy equipment.

• Seawater

What is clastic rock?

loose rock fragments (clasts) cemented together

What is biochemical rock?

cemented shells of organisms

What are the four classes of sedimentary rocks?

Clastic, biochemical, organic, chemical

What is organic rock?

carbon-rich remains of once living organisms

Usually dark

What is chemical rock?

minerals that crystallize directly from water Plastic texture

How are clastic rocks made?

Weathering—generation of detritus via rock disintegration.

Erosion—removal of sediment grains from parent rock.

Transportation—dispersal by gravity, wind, water, and ice.

Deposition—settling out of the transporting fluid.

Lithification—transformation into solid rock.

What two processes are important for sedimentary lithification?

Compaction, Cementation

What is compaction in terms of sedimentary lithification?

burial adds pressure to sediment. Squeezes out air and water. Compresses sediment grains.

What is cementation in terms of sedimentary lithification?

minerals grow in pore spaces. Often quartz or calcite. Precipitate from groundwater. Glue sediments together

We can describe clastic sedimentary rocks by the size, sorting, and composition of their clasts. Describe how these properties relate to the processes of erosion and deposition. How do they reflect the ENERGY of deposition?

Clast size: the more fine-grained or smaller it is the more energy used in deposition (i.e. more distance traveled)

Clast composition: composition yields clues about the original rock

Angularity: the less angular means more energy of deposition

Sphericity: well-rounded = more energy of deposition

Sorting: uniformity = more energy of deposition

What are the types of terrestrial deposition?

Glacial, mountain stream, alluvial fan, sand-dune environments, river, lake, lake delta

What is the glacial environment?

due to movement of ice. Ice carries and dumps every grain size. Creates glacial till; poorly sorted gravel, sand, silt, and clay.

What is the mountain stream environment?

fast-flowing water carries large clasts during floods.

During low flow, these cobbles and boulders are immobile.

Coarse conglomerate is characteristic of this setting.

What is the alluvial fan?

sediments that pile up at a mountain front. Rapid drop in stream velocity creates a cone-shaped wedge.

Sediments become conglomerate and arkose sandstone.

What is sand-dune environments?

wind-blown, well-sorted sand.

Dunes move according to the prevailing winds.

Result in uniform sandstones with gigantic cross beds.

What is river environments?

channelized sediment transport.

Sand and gravel fill concave-up channels.

Fine sand, silt, and clay are deposited on nearby flood plains.

What is lake environments?

large ponded bodies of water.

Gravels and sands trapped near shore.

Well-sorted muds deposited in deeper water.

What is lake delta?

sediment piles up where a river enters a lake.

What are the marine environments?

Marine delta, coastal beaches, shallow-marine clastic depots, most sediments are biochemical, deep marine deposits

What is marine delta?

sediment accumulates where a river enters the sea.

Sediment carried by the river is dumped when velocity drops.

Deltas grow over time, building out into the basin.

Much more complicated than simple lake deltas.

Many sub-environments present.

What is coastal beaches?

sand is moved along the coastline.

Sediments are constantly being processed by wave action.

A common result? Well-sorted, well-rounded medium sand.

What is shallow-marine clastic depots?

finer sands, silts, muds.

Fine sediments deposited offshore where energy is low.

Finer silts and muds turn into siltstones and mudstones..

Shallow marine carbonate (biochemical) environments.

Why are most marine sediment biochemical?

shells of organisms.

Warm, clear, marine water, relatively free of clastic sediments.

Protected lagoons accumulate mud.

Wave-tossed reefs are made of coral and reef debris.

Source of limestones.

What is deep marine deposits?

fines settle out far from land. Skeletons of planktonic organisms make chalk or chert. Fine silt and clay lithifies into shale.

Why are organic sedimentary rocks important to humans?

Fuels industry since the industrial revolution began for coal.

What do geologists mean when they say ‘bed’? ‘formation’?

Beds have a definable thickness that can change.

Bedding forms due to changes in:

Climate

Water depth

Current velocity

Sediment source

Sediment supply

Formations are distinct rock packages.

Formations are able to be mapped.

Formations are named for places they are best exposed.

Starkville has lots of chalk deposits. Describe how these formed.

The chalk was formed by marine sediments deposited along the eastern edge of the Mississippi embayment during the Maastrichtian stage of the Late Cretaceous

What are the clastic sedimentary rocks?

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Usually silicate minerals (Boulders, cobbles, pebbles) Conglomerate (rounded), Breccia (angular),

Diamictite (muddy matrix on outside)

Sandstone (quartz sandstone, arkose, lithic sandstone, graywacke)

siltstone mudstone (blocky pieces),

shale (thin pieces)

What are the biochemical sedimentary rocks?

Calcite Limestone (Fossiliferous limestone, micrite) (0.004 to 2 mm visible shells) Coquina (\>2 mm visible shells) Chalk (grains not visible)

What are the organic sedimentary rocks?

Oil shale (clay and kerogen) Coal (Lignite coal, bituminous coal, anthracite coal) (carbon)

What are the chemical sedimentary rocks?

Halite = Rock salt (Crystal generally >2mm)

Gypsum = Rock gypsum (Crystal generally >2mm)

Calcite = Oolitic limestone (grains appear like tiny balls) Quartz = Chert (Jasper, flint) (grains not visible)

Dolomite = Dolostone (Grains not visible)

Draw the artifacts that currents leave behind. This can be currents of wind or water

What is a metamorphic rock?

solid-state alteration of a rock that changes the chemistry and mineralogy of a protolith. Meta \= change.Morphe \= form.

What is a protolith?

pre-existing rocks that undergo metamorphism

What does metamorphism change about the pre-existing rock/protolith?

Mineralogy, texture, and creates foliation

What is foliation?

a texture defined by the alignment of platy minerals (i.e., micas), or the creation of alternating light/dark bands