Earth Science: Exam 1 (Cumulative)
Sharing of Electrons
Carbon: 6 protons, 6 electrons, 6 neutrons; 4 electrons in outer shell, wants 8. 5 carbons share electrons, bond together; creates a strong bond (e.g. diamond)
The closest active plate boundary to us is...
Caribbean, Mexico
Why do nebulae flatten?
Centrifugal acceleration
Precipitation from aqueous solution.
Chemical Sedimentary Rock
Basalt definition
a fine-grained, mafic, igneous rock
What is the viscosity of the mantle, and how do we know?
-almost like window glass -We know from rebound of surface after removal of mass, such as glacier melting
The geomagnetic field is generated by ________ of the outer core around the inner core. Two conductive metals moving in the Sun's electrical field, with high energy (heat). We call this a "________".
-convection -dynamo
Minerals are also ____ based on both _______. A change in either means that it's a new mineral.
-defined -chemical and atomic structure
Mantle is solid, but _______ (i.e. easily flows and deforms); It's ________
-ductile -soft, flows over time
Melting point of iron alloy _______ with pressure; _____ increases with ______.
-increases -pressure -depth
Crystals grow from _____________; a crystal face was the active growing surface where crystal growth happened to stop.
-inside out
Geoscience is/is not...
-is not narrow, it's not just looking at rocks. -is not esoteric or descriptive. -is multidisciplinary and integrative.
By the Doppler Effect
-means that all the galaxies are moving away from earth and each other equal EXPANSION
How did the moon form?
-moon is younger than earth -giant impact theory
Cut Gemstone
-must gems used are these, meaning that they are not raw crystals right from the ground, but have been facets
inorganic
-not consisting of or deriving from living matter. -without organized physical structure.
Dynamo Theory/Geomagnetic Theory
-proposes a mechanism by which a celestial body such as Earth or a star generates a magnetic field -geophysical theory that explains the origin of Earth's main magnetic field in terms of a self-exciting (or self-sustaining) dynamo. In this dynamo mechanism, fluid motion in Earth's outer core moves conducting material (liquid iron) across an already existing weak magnetic field and generates an electric current. (Heat from radioactive decay in the core is thought to induce the convective motion.) The electric current, in turn, produces a magnetic field that also interacts with the fluid motion to create a secondary magnetic field. Together, the two fields are stronger than the original and lie essentially along the axis of Earth's rotation.
Is the magnetic field good? If so, why?
-protects earth from solar winds (which are dangerous) -fish use it to navigate their way around bodies of water
Some matter (gas, dust) is not pulled into the center, but accretes in rings that orbit around it; ___________ made of ________.
-protoplanetary disk -planetessimals
____________ in nucleus; releases energy (radioactivity), involves loss of ___________. Leaves a stable product (a different isotope or element).
-spontaneous natural change -sub-atomic particles
Protoplanetary Disk
-the portion of the accretionary disk outside of the proto-Sun -the matter within it ultimately becomes planets, moons, and other objects
The earth's magnetic field drifts, and reverses (flips) approximately every _______
1 million years
What's missing from Alfred Wegner's picture?
1) Any idea about creation and destruction of the sea floor (age of oceanic crust), or much about sea floor topography, variation of oceanic crust. 2) Any concept of where motion occurs (nature of plate boundaries) 3) No mechanical explanation of how and why it occurs
What was Wegner's evidence for continental drift?
1) Geography- the shapes of the continents 2) When the continents are fit together, rocks, mountains, and unique fossil groups line up like a puzzle 3) Distribution of volcanoes on land 4) Rough idea of difference between continental and oceanic crust. 5) Local climate change on continents that fits better with continent motion than global change.
Mid-Ocean Ridges Characteristics & Features
1) basaltic magmatism, sea-floor spreading 2) ridge in sea-floor (buoyant) 3) age of oceanic crust 4) Extension: divergent motion on faults; like fissures 5) Cold seawater interacts with magma; "hydrothermal circulation". Entire ocean passes through ridges ~10 m.y.; 25% of Earth cooling.
Continental crust is rich in Si, O2, but little Fe/Mg. Representative rock is ________; more variable than oceanic crust.
granite/diorite
What drives the formation of nebulae?
gravity
Convection
heat transfer that results when warmer, less dense material rises while cooler, denser material sinks (lava lamp)
Lithosphere
the relatively rigid, nonflowable, outer 100- to 150-km-thick layer of Earth, constituting the crust and the top part of the mantle
How is mantle convection possible (if it's solid)?
t's a viscous solid; it flows
Mantle
From 3500 to 6350 km radius (83% volume), solid, silicate (Si, O, Fe, Mg) composition, 3000 °C.
Arab Formation
Jurassic; shelf carbonate
High Viscosity
doesn't flow well (sap)
Mineral or no: coal
no
Viscosity
resistance of material to flow
Mantle Rock
"peridotite", made of Fe and Mg rich silicate minerals (Si and O2) olivine and pyroxene.
Radiation
(physics) electromagnetic energy traveling away from a source through a medium or space
Evidence of such impacts are ________ of crystalline iron, formed ________
-"iron meteorites" -deep in the interior of a large asteroid or mini-planets
When did we get the data (much of which was global information about the oceans) to change his hypothesis to a theory?
-Data collected during oceanographic exploration during the Civil War????
1. Elemental abundancies/ Big Bang nucleosynthesis:
-First few seconds: hydrogen forms -After 3 minutes: hydrogens can fuse into helium atoms -By 5 minutes: process complete; first 5 elements exist (H2, He, Li, Be, Bo)
Why did nebulae form, and continue to grow in size and density as they spiral away? What caused the order to emerge from expanding universe?
-Gravitational Attraction -G = g (M1)(M2)/r2 -Gravity overcomes inertia of expansion locally. As mass comes together, gravitational force increases; it become a runaway process.
Why is this important for the Periodic Table?
-Heavy elements form by fusion inside of stars or during supernovas -There is a cycle of star formation and destruction, from 1st generation stars onwards.
Large bodies (even the ______ are spheres because they are ___ (___) when they form (and gravity).
-Moon -soft (hot)
Earth's Surface
-Ocean -Atmosphere -Landscape -Systems/cycles (hydro, climate, & chemical)
Why is half life used to characterize an isotope's decay rate
-Physicists can't specify how long an individual radioactive atom will survive before it decays, but they can measure how long it takes for half of a group of parent isotopes to decay
Rock vs. Mineral
-Rock= a coherent, naturally occurring solid, consisting of an aggregate of minerals or a mass of glass -Mineral= a single, homogeneous substance
How and why does the oceanic crust get made?
-Solid (hot/ductile) mantle rises due to convection; depressurizes, melting temperature decreases, it partially melts -This forms magma chambers beneath the ridges. Lighter magma rises to the surface. -The light magma is extruded to make the sea-floor, which is oceanic crust.
Why is it that we date minerals?
-The internal clock we use is based on systematic change produced by radioactive decay of atoms bound inside minerals. -A mineral becomes a chemically closed system when it forms.
What determines which elements join to form certain minerals?
-What's available and chemical affinity based on charge (ions; electron gain/loss, achieving equilibrium)
So what new evidence was added in the 1960s (and since) that took Wegener's hypothesis to the level of an accepted theory?
1) seafloor bathymetry- ridges at sea-floor spreading centers; trenches at subduction zones 2) Global distribution of large earthquakes defining plate boundaries 3) The motions involved in earthquakes themselves; rupture of plate boundaries 4) Motion of the crust surface observed from space; GPS, radar 5) Plate motions based on "hot spot" tracks. 6) Age of the oceanic crust
Consequences of convection:
1) the Earth cools 2) plate tectonics
Subduction Zones: Characteristics & Features
1) volcanoes in overlying plate 2) sea-floor trench; 10 km 3) Earthquakes in the subducting plate; define its geometry (also imaged with seismic tomography). 4) Largest earthquakes occur between the plates; "Great Earthquakes". 90% of all seismic energy on Earth • Combination of earthquakes and volcanoes around the Pacific Plate = "Ring of Fire". 5) Distillation of continental crust at volcanic arcs.
Crystals (and minerals) can form on Earth by:
1. Crystallize from a liquid (i.e. magma). 2. Precipitation from aqueous solution. 3. Solid state - atoms rearrange via diffusion.
The Earth should have cooled in about __________ years by _______ but it's obviously still hot (e.g. the core), and therefore ________.
100 million/conduction/dynamic
The half-life of Iodine-123, a common radio-isotope tracer in medicine, is (8/24)
13 hours
How long has it been this way? (the closest plate boundary)
180 million years, since supercontinent Pangaea rifted apart
2. Observed Expansion; "Red Shift"
1920s, Edwin Hubble observed distant galaxies emit light that is shifted to red wavelength (lower frequency); nine are shifted blue.
How old are the oldest Earth rocks (minerals)?
4.4 b.y.
Oldest Mineral
4.4 billion years
Moon
4.5 billion years
Earth's Age
4.53 b.y. or 4.53 Ga
Meteorite
4.57-4.54 billion years
Collisions continue until everything left is in stable orbit. What is the result?
8 major planets (4 rocky, 4 gaseous). Rocky planets are too close to the sun to retain Volatile (H, He has) envelope.
Inner Core
A dense sphere of solid iron and nickel at the center of Earth (1% volume)
Outer Core
A layer of liquid iron and nickel that surrounds the inner core of Earth (16% volume)
Big Bang
A sudden "explosion" from a single, infinitely dense point (energy only, no atoms) at the center of the Universe approximately 13.7 billion years ago
So how do Plate tectonics work?
A. The plates are called "lithosphere". They are strong, riding over weak "asthenosphere". Part of the mantle is strong; it is included in the lithosphere. B. Plate motion is driven by mantle (asthenosphere) convection C. There's about a dozen major plates; many minor ones. D. The plates move at inches per year (~2-10 cm/yr). E. One type of plate boundary is a mid-ocean ridge: where hot, buoyant asthenosphere rises to make new oceanic ridge F. The second type of plate boundary is the subduction zone: where cold, oceanic lithosphere sinks back into the asthenosphere Oceanic plates subduct, continents do not G. Incidental motions occur at the edges of plates; lateral or transform boundaries. When a subducting oceanic plate causes continent to join, collision (mountain building) results.
Why did it take until the 1960s to develop this theory?
Alfred Wegner's concept (1915) of continental drift was not accepted.
What did all of this heat do to the Earth?
All of this heat softens and melts the Earth
Aurora Borealis
Also known as the Northern Lights, the magnetic fields are visible from Earth. It's not pure magnetism, but solar particles coming into earth's atmosphere and ionizing produces color
How do we know our solar system was created the same way?
Another star from a past generation which was destroyed produced the elements found in our solar system. (These elements came from somewhere else, before our solar system.)
Which of the following is an Archean Craton?
Appalachian Mountains???
The first continental crust forms by about 4.0-3.5 billion years ago. This is still locally preserved in some places known as ________.
Archean "cratons"
How Bathymetry affects the two main types of plate boundaries:
Bathymetry=variation of depth. When oceanic plates push together upwards, ridges are created along the ocean floor similar to mountains. In a subduction zone, two plates push downwards into the mantle, creating trenches and cliffs, where the sea floor is deeper. Think about the top of a mountain and a valley
Why did fusion occur?
Because of massive amounts of heat and pressure
Why is the hotter inner core solid, while the outer core is liquid?
Because of the phase relationship of iron alloy (state of phase versus temperature & pressure)
Our Universe evolved after this
Big Bang
Mid-Ocean Ridges
Create new oceanic crust/lithosphere. Made by partial melting of mantle asthenosphere as it rises due to convection.
Geoscience is diverse & broad example
Curiosity Rover- on Mars for like 5 years and offshore research
What did we call this early Earth?
Hadean Earth
What does this accretion process involve or look like?
High energy collisions, impacts (meteors)
an educated guess that attempts to explain a phenomenon or set of observations, derived from existing knowledge.
Hypothesis
Where can you stand on a mid-ocean ridge?
Iceland (Mid-Atlantic Ridge) = localized heat source where there is extra magnetism where the magma hardens and forms above sea-level
Crystallize from a liquid (i.e. magma).
Igneous Rock
How do we know the structure of the mantle?
Imaging seismic velocity structure; global "tomography" (3D image)
Scientific Method
a sequence of steps for systematically analyzing scientific problems in a way that leads to verifiable results
What object is smaller than Pluto?
Makemake (2/3 the size of Pluto)
Solid state - atoms rearrange via diffusion.
Metamorphic Rock
We talk about the chemical composition of the Solar System, as well as its age. How do we know these things?
Meteorites that have hit Earth, which have consistent chemistry and age, known as chondrite meteorites (stony meteorites).
Where does oceanic crust get made?
Mid-ocean ridges (a type of active plate boundary)
Crystal
a single, continuous piece of a mineral bounded by flat surfaces that formed naturally as the mineral grew
How do proto-planetary discs and planetesimals accumulate in nebulae and how can we explain why the Solar System has eight major planets, associated dwarf planets and moons, and other debris?
Planets form out of cosmic dust grains that collide and stick to form larger and larger bodies. When the bodies reach sizes of approximately one kilometer, then they can attract each other directly through their mutual gravity, aiding further growth into moon-sized proto-planets. Planetesimals may form in a very dense layer of dust grains that undergoes a collective gravitational instability in the mid-plane of a proto-planetary disk A proto-planetary disk is a disk of matter, including gas and dust, from which planets may eventually form or be in the process of forming.
P-Waves Shadow
P-waves can go through liquid, but they bend as they go down (as velocity increases; this is called refraction). Since velocity decreases in the liquid core, they bend the opposite way, leaving another shadow zone.
How'd they get the age of the sea floor
Paleomagnetism
Doppler Effect
Phenomenon in which the frequency of wave energy appears to change when a moving source of wave energy passes an observer
Two minerals with same atomic structure (cubic), different composition
Pyrite - FeS2 Galena - PbS2
How do we know the structure of the core?
Radius of earth = 6370 km Deepest well = only 15 km deep 1) Earth has a magnetic field emanating from the core
S-Waves Shadow
S-waves cannot go through liquid, and so cannot penetrate outer core and define where outer core starts.
Understand how rocks record magnetic signature of the Earth (paleomagnetism), how this reverses with time, and how this can be used to determine the age of rocks in the ocean.
Scientists can study the history of Earth's magnetic field by using Earth's rocks as records. Paleomagnetism is the study of magnetic rocks and sediments to record the history of the magnetic field. Some rocks and materials contain minerals that respond to the magnetic field. So, when rocks form, the minerals align with the magnetic field preserving its position. It's called rock magnetism when rocks record the position of the magnetic field. The magnetic signature of the rocks allows Paleomagnetists to date the rocks and map the position of the field at the time of their formation. Because the ocean floor is mostly composed of basalt, an iron-rich substance containing minerals that align with the magnetic field, they record the alignment of the magnetic fields surrounding oceanic ridges. Scientists studied the magnetic signatures of the rocks on the ocean floor and noticed some recorded opposite directions for magnetic field lines even though they were side by side. This likely occurred because magma rose from the ridges in the ocean floor and formed new rock recording a more recent alignment of the magnetic field while pushing old rock with more outdated magnetic records further from the ridge.
Solar System forms in the same way. The ________ begins condensing ~5 billion years ago, collapsing to form the Sun. The Sun is likely a 2nd, 3rd, or 4th generation star.
Solar Nebula
Age (4.54-4.57 billion years) represents initial formation of _________, composition represents average Solar System (except H/He).
Solar System
What does the stellar nucleosynthesis process, along with the original composition of the universe, mean for stars and star systems that have heavy elements, dust, and rocky material?
Stellar nucleosynthesis is the process by which elements are created within stars by combining the protons and neutrons together from the nuclei of lighter elements. All of the atoms in the universe began as hydrogen. Fusion inside stars transforms hydrogen into helium, heat, and radiation. Heavier elements are created in different types of stars as they die or explode.
A meteorite traveling 20 km/s produces same energy as an equal mass of ___.
TNT
Nebulae
The Universe, 13.5 billion years ago (200 million years after Big Bang): lots of empty space, with expanding concentrations of light matter was known as this
Why is the Earth so hot? Where does the heat come from?
The decay of radioactive elements; mainly (^40 )K and (^238) U
Red Shift
The phenomenon in which a source of light moving away from you very rapidly shifts to a lower frequency; that is, toward the red end of the spectrum
Stellar Nucleosynthesis
The production of new, larger atoms by fusion reaction in stars; the process generates more massive elements that were not produced by the Big Bang
Plat tectonics
The theory that the outer layer of the Earth (lithosphere) consists of separate plates that move with respect to one another
a major idea that began as a hypothesis but has survived repeated challenges and accumulated support. It is predictive, supported by most data and scientists (99%).
Theory
Radiometric Dating
To date a mineral, we need a closed chemical system that contains a radioactive element (or isotope)
Seismic Waves
Waves produced by earthquakes transmit through the earth. By recording them on the other side (whether they show up, how fast they travel), we can tell about the nature of the layers at depth (i.e. liquid, solid, how soft it is, etc.).
What kind of plate boundary occurs along eastern North America? (***Test Question***)
Western Atlantic Ocean is part of the North American Plate. The boundary between the continent and ocean is a "passive margin".
Are there any planetessimals left?
Yes, asteroids (asteroid belt). Some are in stable orbit, but this changes automatically. We still have collisions today.
Is there anything older than earth's rocks?
Yes, the moon. Moon rocks from Apollo are 4.5 b.y.
nebulae
a cloud of gas or dust in space
Rock definition
a coherent, naturally occurring solid, consisting of an aggregate of minerals or a mass of glass
Craton
a long-lived block of durable continental crust commonly found in the stable interior of a continent.
Giant Impact Theory
a mars-sized body impacts the Earth, causing an equal mass to be ejected; the moon.
differentiation (of a planet)
a process early in a planet's history during which dense iron alloy melted and sank downward to form the core, leaving less-dense mantle behind
Conduction
a process of heat transfer involving progressive migration of thermal energy from cooler to warmer regions in a material, without the physical flow of the material itself
Mafic
a term used in reference to magmas or igneous rocks that are relatively poor in silica and rich in iron and magnesium
Ultramafic
a term used to describe igneous rocks or magmas that are rich in iron and magnesium and very poor in silica
Plate Tectonics
a theory that the outer layer of Earth is divided into ~12 rigid plates that slowly move against one another (i.e. continental drift), active for last 3 billion years
Rules of Subduction Zones
a) Oceanic lithosphere subducts (sinks) once cold (dense); recycled. b) Balances what is produced by mid-ocean ridges (all <200 million years old). c) Continental lithosphere does not subduct because it is more buoyant
Which of the following is the name of the super continent that existed prior to Pangaea?
a.) Rodinia
Magnetic lineation's (+/-) of sea floor indicate _____ of oceanic crust, define _______
age/plate motions
Felsic
an adjective used in reference to igneous rocks that are rich in elements forming feldspar and quartz
Chondrite Meteorites
any stony meteorite characterized by the presence of chondrules
what are nebulae like and what are they made of?
are not only massive clouds of dust, hydrogen and helium gas, and plasma; they are also often "stellar nurseries" - i.e. the place where stars are born
Which of the following plates is subducting beneath Washington and Oregon state?
b.) Juan de Fuca
Oceanic Crust
basalt composition; Si, O, minor Fe/Mg (but less than the mantle; oceanic crust is less dense than mantle).
We can't directly date the Earth, but we can ______ its age between these events.
bracket
Minerals form via _________ to make compounds with unique properties
chemical reactions
Ring of Fire
combination of earthquakes and volcanoes around the Pacific Plate
Convergent
coming closer together, especially in characteristics or idea o Convergent Plate Boundary- a boundary at which two plates move toward each other so that one plate sinks (subducts) beneath the other; only oceanic lithosphere can subduct
P-Waves definition
compressional seismic waves that move through the body of the Earth
Distillation
concentration of a by-product of some process (in this case, melting) due to difference in density
Crystalline
containing a crystal lattice; having the structure and form of a crystal; composed of crystals; material in which atoms are fixed in an orderly pattern
Continents stick up higher because....
continental crust is less dense
Theories are not proven, but
continually tested an evaluated and left open to change.
Subduction Zones
convergent (coming together)
Gravitational accretion by meteorite impact ....
converted potential energy into kinetic energy (heat)
Differentiation: Earth differentiates by gravity by ~4.4 billion years ago. This means what?
dense liquid sinks to center, light floats near surface
Continental crust then grows ____________. Continents are assembled from the _________ by piecemeal accretion.
gradually for 1.5 billion years/inside-out
The moon ______ due to heat, becomes smooth due to gravity
differentiated (transformed)
Crust was made through a much slower process (slower than differentiation of core and mantle) of _______, from repeated ____________ of the mantle, which continues today.
distillation/partial melting
Big Bang Theory
does not explain why the bang occurred, but was constructed to explain observed consequences
Material Science
experiments at high temperature and pressure
Low Viscosity
flows easily (water)
Alfred Wegner
formed hypothesis of continental drift well before 1960s
G =
g (M1)(M2)/r^2
Paleomagnetism
geomagnetic field reverses every ~1 million years, providing a way to map age of the sea floor without sampling rocks
Isostasy
height of surface depends on density underneath; maintain gravitational equilibrium at any point in the ductile mantle.
Plate Tectonics theory
important and explains a lot -unifying theory of geology
The crossover point is at the ...
inner-outer core boundary
lattice
interlaced structure or pattern
Fabrication
is making up data or results and recording or reporting them
Falsification
is manipulating research materials, equipment, or processes, or changing or omitting data or results such that the research is not accurately represented in the research record
Gravitational Attraction
is proportional to the product of the mass of 2 bodies
Continental Crust density
less dense (2.7 g/cm3)
Basalt
mafic rock (meaning dark). It is the most common rock in Earth's crust.
Earth has a _____ field emanating from the _____
magnetic/core
Fusion
the process by which the nuclei of atoms fuse together, thereby creating new, larger atoms
What is the nature of difference between asthenosphere and lithosphere?
mechanical difference
Partial Melting
melting in a rock of the minerals with the lowest melting temperatures, while other minerals remain solid
Heat Transfer (melting)
melting that results from the transfer of heat from a hotter magma to a cooler rock
Oceanic Crust density
more dense (3.0g/cm3)
Mantle density
most dense (3.3 g/cm3)
hydrothermal circulation
most general sense is the circulation of hot water; occurs most often in the vicinity of sources of heat within the Earth's crust. In general, this occurs near volcanic activity, but can occur in the deep crust related to the intrusion of granite, or as the result of orogeny or metamorphism.
Mineral definition
naturally occurring (vs. synthetic), solid, crystalline, inorganic, specific chemical composition and atomic arrangement (lattice). Homogenous; cannot be mechanically divided.
Mineral or no: sugar
no
Mineral or no: synthetic diamonds
no
Mineral or no: window glass
no
Mineral or no: clam shell
no?
Scientific Method Steps
o Recognizing the Problem o Collecting Data o Proposing Hypothesis o Testing Hypothesis o Organizing Results o Forming a Possible Theory
Geoscience is relevant example
oil in the Middle East because of geologic history
Atomic structure means that bonded atoms are arranged in an ___________, that defines the crystal form of the mineral.
organized, repeating framework (lattice)
By about 2.5 billion years ago, we have continental and oceanic crust, and normal _______
plate tectonics.
Mid-ocean ridges are a type of active plate boundary in _______. They are considered ________.
plate tectonics/extensional
What is a feature produced by abrasion in a river? (8/20)
pothole
Plagiarism
practice of taking someone else's work or ideas and passing them off as one's own
Unifying Theory
puts everything (rocks, geography, motions) in a context
How do we determine the age of a rock?
radioactive dating (newer term: isotopic dating)
As a result, we can calculate the mineral's age based on the counts of parent and daughter atoms and known as________
rates of decay
Conflict of Interest
refers to situations in which financial or other personal considerations may compromise, or have the appearance of compromising a researcher's professional judgment in conducting or reporting research
Oceanic crust makes up the ______, thus explaining about _____ of the Earth's surface (or outer layer).
sea-floor/70%
Short term variations in Earth's magnetic field are called?
secular variation
The process of magmatism at mid-ocean ridges results in new crust. This pushes the old crust apart...
see-floor spreading
S-Waves Definition
seismic shear waves that pass through the body of the Earth
Radioactive decay rates can be measured precisely by the radiation produced, and (for short-lived isotopes) by the amount lost over time. Decay rates are systematic; each isotope has a __________ (that vary from days to billions of years); rates do not change with time.
specific rate
radioactive decay
spontaneous, natural change in nucleus; releases energy (radioactivity), involves loss of sub-atomic particles. Leaves a stable product (a different isotope or element).
Matter collects at the center, compressing due to gravity (protostars). Eventually, it is dense enough that it "ignites" as a star; _________, or "hydrogen burning".
stellar nucleosynthesis
Mantle convection can be simulated by ______
supercomputers
Isostasy Definition
the condition that exists when the buoyancy force pushing lithosphere up equals the gravitational force pulling lithosphere down
Decompression Melting
the kind of melting that occurs when hot mantle rock rises to shallower depths in the Earth so that pressure decreases while the temperature remains unchanged
Asthenosphere
the layer of the mantle that lies between 100-150 km and 350 km deep; it is relatively soft and can flow when acted on by force
What time period does "Archean" refer to on the geologic timescale?
the middle Precambrian eon (4.0-2.5 Ga)
Crust
the outer layer of the solid Earth, 10-40 km thick. There are two types; oceanic and continental crust.
Half Life
the time it takes for half of a group of a radioactive element's isotope to decay
As nebulae continue to grow...
they collapse due to mass, spin faster, and then collapse into a disc
Planetessimals
tiny, solid pieces of rock and metal that collect in a planetary nebula and eventually accumulate to form a planet
Esoteric
unimportant
Bathymetry
variation in depth
Magmatism
volcanism; key process in partial melting????
Mineral or no: graphite
yes
Mineral or no: ice
yes
Mineral or no: salt
yes
Mineral or no: copper
yes?
Mineral or no: lead
yes?
As a result of sea-floor spreading, _______________; it gets older away from ridge in either direction.
young oceanic crust is found at the ridges
what are some different properties of minerals that help identify them and result from composition and atomic structure.
• Color • Streak • Luster • Hardness • Specific gravity • Crystal habit • Specific properties • Fracture & cleavage
What about the continents? Why are they higher?
• Density • Oceanic crust and the mantle are thicker and therefore denser than the continental crust. A larger quantity of less dense material (continental crust) rises higher above the ocean's bottom than the denser material (oceanic crust)
The oldest oceanic crust is also <200 million years old, meaning that it is getting destroyed somewhere. Where?
• Oceanic crust sinks back into the mantle at what's called a subduction zones after it cools, contracts, and densifies
So, what about making that continental crust?
• Subduction causes melting of oceanic crust at island arc volcanoes; separate the lighter magma (distillation) = continental crust
What would it mean if there was no way of destroying the sea-floor made at mid-ocean ridges?
• The Earth would have to expand. It's not.
What is meant by "active" plate boundary?
• fault rupture, motion of plates, earthquakes