Exam I Review Flashcards
What is the difference between hypothesis, theory, and scientific law?
Hypothesis: An explanation for observations to be tested (may be supported, not confirmed)
Theory: An explanation for observations that have been tested numerous times and is supported by evidence
Scientific Law: An equation or principle that precisely predicts behavior (not an explanation)
Which are bigger, eras or eons?
Eons
What is the order of the eras?
(youngest to oldest) Cenozoic, Mesozoic, Paleozoic
Meaning of ka, Ma, Ga
(in years) Thousands, Millions, Billions
When was the Big Bang?
13.8 Ga
Difference between inner and outer planets
Inner: terrestrial, smaller, metallic core, rock mantle
Outer: larger, mostly gas/ice
How old is the Earth?
4.565 Ga
Origin of the moon
Protoplanet crashed into baby Earth, was destroyed, and formed rings of debris around Earth. Gravity pulled debris together to form the moon.
Order of compositional and mechanical layers of the Earth
Compositional:
Crust- stone made of oxygen, silicon, aluminum
Mantle- stone made of oxygen, silicon, magnesium
Core- metal made of Iron alloy (nitrogen, nickel, oxygen)
Mechanical:
Lithosphere: crust and uppermost mantle, rigid solid
Asthenosphere: mid-low mantle, weak solid
Outer core: liquid metal
Inner core: solid metal
What is the most abundant element in the core? Three most abundant in the crust and mantle?
Iron is the most abundant element in the core.
Oxygen, silicon, and aluminum/magnesium are most abundant in the crust and mantle.
What is isostasy, and what are the implications for erosion of mountain ranges (discussed later in book, but in this section in lecture)?
The floating of the lithosphere atop the asthenosphere bc it is less dense/more buoyant.
As mountain ranges erode, the lithosphere will float up and establish a new balance (essentially replacing the mountain range with new mountains).
Origin of heavy elements in the Earth (heavier than He, lighter than Fe)
Fusion reactions in stars (stellar nucleosynthesis)….created elements like carbon, sulfur, silicon, gold, uranium
What distinguishes the mechanical layers? How do they relate to the compositional layers?
Mechanical layers are defined by their physical characteristics, not their components (i.e., soft layers, rigid layers, liquid layers). The lithosphere is primarily oxygen/silicon/aluminum/magnesium, the asthenosphere is primarily oxygen/silicon/magnesium, the outer core is mostly liquid iron, and the inner core is mostly solid iron.
What are differences between continental and oceanic crust?
Continental: less dense, thicker, more buoyant, plagioclase feldspar (must abundant mineral)
Oceanic: thinner, more dense, made of basalt and gabbro
How did the compositional layers form? (which two separated first, and which formed later and are still being formed)
Internal melting caused denser iron metal to sink to center of planet while lighter rock remained and formed the surround layers of shell (differentiation).
Metal and mantle separated first; crust cooled and formed later and is still being formed at plate boundaries.
Difference between continental drift and seafloor spreading?
Continental drift proposes no true explanation for continental movement and plate but seafloor spreading does and backs up plate tectonics.
magnetic evidence for continental drift vs magnetic evidence for seafloor spreading
Continental drift: apparent polar wander (it turns out pole stayed fix while continents drifted)
Seafloor spreading: stripes of magnetic anomalies as seafloor formed at different periods of earth’s magnetic polarity (positive stripes formed when magnetic field was like today’s, negative stripes formed when polarity was reversed)
About how many plates?
15
In general, how fast do plates move? (cm/yr, m/yr, or km/yr)
1-15 cm per year
Sources of heat in the Earth
1) ongoing radioactive decay
2) heat remaining from Earth formation (rocks are good insulators)
Four heat transfer mechanisms; which is associated with tectonics?
1) conduction
2) radiation
3) convection
4) advection
Convection associated with plate tectonics.
Types of plate margins and highlighted examples of each (some used again and again)
Convergent: north american plate meeting pacific plate
Divergent: mid atlantic ridge, east african rift
Transform: fracture zones around mid atlantic ridge
Volcanism, earthquakes, and mountains at different kinds of plate margins (info in the table)
see table screenshot bc good lord i’m not typing all that
Direction of plate motion related to hotspot volcano ages
Volcanoes grow more older in the direction of plate motion (so joh wherever the oldest volcano in the chain is is where the plate is currently at)
What process is thought to cause hotspots?
Mantle plumes
Where are volcanic arcs formed?
Subduction zones (either oceanic subducts continental or oceanic subducts oceanic)
What is the Moho?
Border between crust and mantle, above the border between lithosphere and asthenosphere
What is the Wadati-Benioff zone?
band of seismic activity defined by earthquakes occurring on down-going slab of convergent plate boundary (subduction zone)
What defines a specific element?
material consisting entirely of one kind of atom, cannot be subdivided or changed by chemical reactions
Ions and isotopes
Ions: when there isn’t an equal amount of protons and electrons (cation: positive ion, anion: negative ion)
isotope: variations of an element that have same number of protons but different number of neutrons
What are the four components of the definition of a mineral used in lecture?
1) solid
2) naturally occurring
3) crystalline structure
4) definable composition
What are the four bond types? How do they work? Which is strongest? Which is weakest? Which is associated with high conductivity? Which is associated with ease of dissolution?
1) covalent: shares electron
2) ionic: transfers electron
3) metallic: sharing sea of electrons
4) Van der Waals: weak bonds based on transient charges within structure
Strongest: covalent
Weakest: Van der Waals
High conductivity: metallic
Ease of dissolution: ionic
Cleavage vs crystal form (how are they different?) Why is one more useful than the other?
Cleavage: a mineral breaking on planes of atomic weakness
Crystal form: how a mineral grows unimpeded (has crystal faces)
Cleavage is more useful bc most minerals don’t have a perfect environment to grow unimpeded in
List the basics of the physical properties of a mineral
color luster streak crystal form cleavage hardness (mohs) density taste reaction with acid striations magnetic
How are the basic structures of silicate minerals built?
with one silicon and four oxygen (silicon-oxygen tetrahedron)
Two distinct ways to deal with the extra charge (-4) of the silicon tetrahedron in making minerals (all silicate minerals use one, the other, or a combination)
1) stacked sheets (aka framework) of tetrahedron (where all four corners of oxygen are shared)
2) introduce a second element
How many tetrahedron corner oxygens are shared in a single chain, sheet, and framework silicates?
single chain: two corners
sheet: three corners
framework: four corners
How are the silicate structures of the micas (biotite and muscovite) reflected in their physical properties?
Micas have sheet silicate structures, and bc these sheets are stacked onto each other, they break in single horizontal cleavage
What controls which minerals will form in a rock?
1) what elements are present
2) physical conditions (temp, pressure)
What property of a gem is described by carats?
physical weight
About how many minerals have been recognized?
4,000
What are the three rock types, what differentiates them, and what are their rock forming processes?
1) Igneous: made from magma
2) Metamorphic: recrystallizing in solid state
3) sedimentary: rock fragments/dissolved rock components compacted on surface
What is the rock cycle?
Igneous erodes into sediment
Sediment has lithification into sedimentary rock
Sedimentary has metamorphism to become metamorphic
Metamorphic melts, then re-solidifies into igneous
(or some version of this)
Origin of mafic versus felsic magma
Mafic magma comes from mantle (50% SiO2)
Felsic magma comes from crust (75% SiO2)
Three ways to make intermediate magmas
1) mix felsic and mafic magma
2) assimilation of country rock
3) fractional crystallization (distillation by crystal setting)
How do we interpret grain size in igneous rocks? (cooling rate and depth)
Larger grains form at a slower cooling rate deeper w/in earth
Small grains form at fast cooling rate at or near surface of earth.
What, in an abstract sense, causes rocks to melt? (explain on PT diagram)
Increase in temperature, decrease in pressure, and/or addition of water.
What tectonic processes drive melting in each of the three ways from the previous point?
Adding heat: hotspots
Reducing pressure: mid-ocean ridge, continental rifts, hotspots too lol
Adding water: subduction zones
Intrusions: know batholiths, dikes, volcanic necks, laccoliths, and sills as discussed or show in pictures.
Batholiths: >100 km2, made up of separate magma bodies called plutons
Dikes: tabular, discordant, usually vertical
Sills: tabular, concordant, usually horizontal
laccoliths: blister shaped, magma injected in between layers that pushes upwards to form dome
volcanic neck: eroded core of volcano
How are mafic, intermediate, and felsic magmas different in SiO2?
Mafic: 50% SiO2
Felsic: 75% SiO2
Intermediate: 55-65% SiO2
Names of fine and course grained rocks crystallized from each of the three magma types?
look at table
Explain what drives explosive eruptions (e.g., what do volcanoes and beer have in common)
Low viscosity magma: Gas bubbles float up easily, expanding as pressure drops, arrive at surface at atmospheric pressure w/ little fanfare
High viscosity magma: bubbles are trapped within magma and react slower to pressure decrease, bubbles arrive at surface at greater pressure than atmosphere which causes them to suddenly expand and boom!
How are aphanitic rocks formally named?
Through chemistry, specifically a plot showing sodium + potassium versus SiO2
About what temperature (C) is basalt lava? Is it the hottest or coolest?
Temp: >1200 degrees C
-It is the hottest of all magmas
What are the differences in viscosity and gas content of basalt and rhyolite magma? How does this relate to the propensity for explosive eruption?
Basalt: low viscosity, low dissolved gas content
Rhyolitic: high viscosity, high dissolved gas content
The higher the viscosity and the dissolved gas content, the more likely to be explosive.
What kinds of volcanoes are created by effusive eruptions of basaltic, andesitic, and rhyolitic lava?
Basaltic: shields
Andesitic: composite
Rhyolite: domes
Recognize the difference between aa and pahoehoe lava
Aa: rough, chunky
Pahoehoe: smooth, ropey surface
(in that one photo, aa was on top bank, and pahoehoe covered ground)
Recognize volcano types (domes, shields, composite)
Shield: broad, gently sloping
Domes: steep, domal, formed by super viscous lava
Composite: alternate between lava flows and pyroclastic eruptions (super steep and mountain-esque looking)
What are very large volume basaltic lava sequences called?
flood basalts
What does pyroclastic refer to?
fragmented material that sprayed out of volcano and landed on ground/seafloor in solid form
Where do pillow lavas form?
in underwater eruptions (hot spot or mid ocean ridges)
Where is the largest volcanic mountain in the solar system? (reading)
Mars (Olympus Mons, extinct shield volcano, 600 km across base)
What is a xenolith? (reading)
Relict of wall rock surrounded by intrusive rock when the intrusive rock freezes
Where was the largest eruption of the ‘common era’? (volcano and country) (reading
Mt Tambora, 1815, Indonesia, ejected 145 km3 of debris (remember, to be super-volcano, must eject at least 1,000 km3 of debris)
Aphanitic, phaneritic, porphyritic, pegmatite
Aphanitic: grains not visibile
phaneritic: grains visible, less than 2.5 cm
porphyritic: bimodal grains (groundmass and phenocrysts)
pegmatite: grains visible, bigger than 2.5 cm
difference between pyroclastic rocks and porphyritic rocks
Pyroclastic: ash with rock fragments (rocks w/in rocks)
porphyritic: groundmass crystals with phenocryst crystals
polymorphs?
minerals w/ same composition but different structure (diamond and graphite)
vesicles
gas pockets in rocks
