My Notes for Unit 3 Flashcards
What does lava help to tell us?
What is down deeper
Composition of meteorites is like that of___.
Earth
Earth is made of___stuff inside, ___stuff outside.
- heavier
- lighter
What is gravitational differentiation?
- iron and nickel
- sink down to the bottom
- density separation of elements
- heavier elements sink down
What percent of Earth’s core is iron? Nickel?
- Iron = 93%
- Nickel = 3%
What is silica?
silicone and oxygen
What is silicate
silica and some other element
What is the mantle almost entirely made out of?
silicate minerals
What happened to the primitive crust?
We don’t have any of the primitive crust left. Buried by geological processes.
What is the continental crust the result of?
Ca, K Na, Al (silicates)
What is the oceanic crust made out of?
Fe, Mg, Ca, Al (silicates)
What is the inner core made out of?
Solid Earth: Fe, Ni
What is the outer Core made out of?
Liquid Earth: Fe, Ni
What is mantle made out of?
Fe, Mg, Ca, Al (silicates)
Solidus?
The temp at which melting begins A mixture of solid and liquid.
What is the solidus controlled by?
controlled by lithosphere and pressure
Why are planetary bodies hot inside?
1) Gravity (accretion pressure and impact of asteroids and comets)
2) Atomic Fission (breakup up of atomic isotopes)
What is isostasy?
The lithosphere-crust and upper mantle is not actually sitting on the mantle–it is floating on it. Rocky crust is floating on lithosphere (floating equilibrium).
What happens when a glacier flows on X-Sections (isostasy)?
When a glacier flows, it is the additional weight added to the crust by the weight of the glacier that creates floating. When a glacier melts, the land surface will come backup. depresses lithosphere into mantle.
What happens after volcanism?
Ground will “rebound” after volcanism ceases for good and erosion strips away the top.
What are the two different ways to discuss the outer part of Earth?
1) Chemical composition (rock type)
2) Physical strength
What are the two crustal parts?
continental and oceanic
What is the depth of the continual crust?
35 km depth (shallows towards ocean)
What is the depth of the oceanic crust?
8 km depth (close to ocean)
4 km depth (rocky depth)
What is the contact between mantle and base of crust called?
Moho
Physical strength of outermost part of mantle is similar to___ ___.
crustal ricks
What is under the lithosphere?
A unit that is physically weak called the asthenosphere.
What is the asthenosphere?
weak sphere
What is the lithosphere?
strong sphere
What makes up the upper mantle?
asthenosphere and lower part of lithosphere
What is the weakest part of the earth system?
asthenosphere.
What is broken into tectonic plates?
lithosphere
What do the tectonic plates move over?
the asthenosphere
What is the material the lithosphere is composed of?
rock
When were the major ice ages (4 of them)?
~600-700 (Paleozoic)
~450 (Paleozoic)
~300-250 (Mesozoic)
~3-now (Cenozoic)
What is planetary magnetism off-set with?
Geographic poles (spin axis), but this is temporary
Magnetic poles___with time.
shift
What is magnetic polar shift?
The fact that magnetic poles shift several km/year (irregular), so their positions move over the globe (mainly polar regions) a considerable amount.
Is the strength of magnetism set or varied?
Varied, but may not drop to zero
Is the strength of magnetism increasing or decreasing at present?
decreasing
What is magnetic polar reversal?
After weakening it becomes chaotic (theory), then builds back up…sometimes in the opposite sense.
Earth’s magnetic field varies in___[___] by perhaps___% over a time scale of decades to ventures. Does___appear to drop to zero.
vaires
- intensity
- 50
- not
What is polar shifting?
the poles “walk”…variable rate (~50 km/year for the past 20 years).
What is the average position of the poles for that past are thousand years?
At the spin axis.
On average, how ofter does the vector reverse with magnetic polar reversal?
3 times per million years
Magnetism of planet Ear is___to what it would be if in the centre of the earth ere was a magnet.
similar
What happens with basalt from volcanoes and Earth’s magnetism?
Basalt lavas always have a small amount of magnetite (FeO4). When basalt is still hot, not affected by magnetic field (1000 degrees C). When it reaches 700 degrees C, it becomes affected –> called Curie Temp.
What are magnetic pole position sin northern hemisphere based on?
The remnant magnetism in igneous rocks for the last 20 ma.
For how long has magnetic polar reversal been going on? How long do we have detailed measurements for?
at least the last 3 Ga – but we have detailed measurements only for the last ~160 Ma
Magnetism will always be appalled with___ ___ ___.
force field lines
What could be the 3 causes of Earth’s magnetism?
1) flowage of Fe material in liquid core (convective flow)
2) differential rotation – spin
- inner solid core spins slightly differently than rest of core because of liquid core.
3) force field follows ~ spin axis (self-exciting organism)
