1/2 Earth Scientist/ Formation and age of Earth and Moon Flashcards
Earth Science
- geology, chemistry, physics, biology of our planet
- application of science and math to study aspects of Earth
What was voyager 1?
- launched in 1977
- took a picture of Earth 4 billion miles away
What is geophysics?
the branch of Earth Science dealing with the interior and its connection to the surface
What can we use geology to do?
Study exposed rocks
What is geochemistry?
- a way to study the chemistry of rocks
- helps us understand how climate has changed overtime because we look the sediments deposited in oceans/seas: they record ancient climate conditions like CO2
Paleoclimate
- the ancient climate
- can track its conditions through looking at geochemistry of sediments deposited in oceans/ seas because they trap CO2
What are the origins of our solar system?
- likely born in a large nebula. Formed when a nearby supernova produced a shockwave, which condensed into a pre-solar nebula to form the sun. Further gravitational collapse made the solar nebula
What is a nebula?
a cloud of gas and dust
What is a solar nebula?
a rotating disk of condensing material around the sun
What’s a supernova?
an exploding star
What is the Eagle Nebula?
- a cloud of gas and dust
- home to 500 young stars (5-6 million yrs old), which each house a solar system
- Largest star is 1 mil x size of sun and 80x the mass.
- 7000 light years away from Earth
- home to pillars of creation
What are the pillars of creation?
the densest region of material in the Eagle Nebula where new stars form. It’s 4 light years in length
How old is the Earth?
4.5 Ga (billion yrs old)
Do we know exactly how the sun formed?
Not exactly. But our best guess is a nearby supernova produced a shockwave, which condensed to a pre-solar nebula. Further gravitational collapse created a solar nebula.
What do we think determines the distribution of elements in the solar system?
The size and proximity of supernovas determines which elements are distributed across solar systems.
What can we turn to to understand the bulk composition of our solar system?
- Carbonaceous chrondites, aka primitive stony meteorites
2. the sun, it’s absorption spectrum
How does the sun show us the bulk composition of our solar system?
- it’s 99.8% mass of our solar system, so it’s a good representation
- look at the absorption spectrum of the sun’s atmosphere: we can identify the elements by identifying the different absorption rates of the spectrum
Does the Earth’s composition match the distribution of elements in the solar system? Why or why not?
- No
- Because of differentiation
- the formation of planets had to have reworked the composition of the solar nebula (where the planets condensed)
What is differentiation?
- Separation of different elements through processes like melting
- The Earth’s core, silicate mantle, and crust came to be because of large-scale melting, which occurred when a mars-sized object struck the earth and debris formed the moon
What is large scale melting?
- A type of differentiation
- Separation of different elements
- Occurred when mars -sized objects struck Earth and debris formed moon. Earth melted, forming magma ocean d
What are carbonaceous chrondites?
- primitive stony meteorites that were unaltered from the time the solar nebula was condensing.
- 4.5-4.65 Ga old
- They are undifferentiated (never melted), old, and never condensed into planets or planetessimals! So they represent the building blocks of terrestrial planets like Earth
- Made of chondrules
What are planetessimals?
A body that combined with others via gravitation to form planets.
What are chondrules?
Formers beads of molten rock that compacted into chondrite
- Ex- silicate and metal bits
If 10% of a rock was melted, what type of elements would that melt be mainly comprised of?
Volatile elements- elements that tend to melt or vaporize 1st
What are volatile elements?
Elements that tend to melt or vaporize first
Name and explain the three differentiated meteorites.
- iron-meteorites- came from the core. Because metals rust on surface.
- iron-silicate/ Pallesite meteorites/ stony iron- core-mantle boudaries.
- Silicate meteorites/ Stony achonrites- from mantle or crust of destroyed planetesimals. 1/2 as old as chondrites.
Name the 2 theories about where Earth’s water came from
- coming from the interior through differentiation
2. Delivery via comets
What are the lunar highlands? What is the age?
- the light areas of the moon
- formed when part of magma ocean cooled, crystals buoyed and formed crust
- rock is anthrosite (found on earth) and made of plagioclase feldspar
- 4.5 Ga
What are the dark areas of the moon? What is the age?
- formed when 1) craters formed by bombardment 2) viscous basalt flowed out, filling basins
- basalt also found in Hawaii
- lunar basalt 3.8 Ga
The moon formed within the first _____ years of the solar system.
150 million years
4.65 (Age of solar system) - 4.5 (age of old lunar crust)= 150 Ma
What do we use to measure the age of rocks?
uranium-lead dating
Where are the oldest rocks on Earth found?
cratons- large old thick stable pieces of continental crust.
Found in Canada, Australia, etc.
What are cratons?
- large old thick stable pieces of continental crust
- home to oldest rocks in rock formations
- formed when protoliths heat and are under pressure. Inside protoliths, zircons (crystals of granite)
What are protoliths?
pre-existing rocks that are heated and pressurized to form cratons
Ex- granite
Zircons
surviving crystals from a protolith
Oldest things on Earth’s surface
Canada- 4.2 Ga
Australia- 4.4 Ga
Name and explain the theories of how the moon formed.
- Moon is a captured object- Earth’s gravity brought it in. The moon is too big for this to happen and it would cause an irregular orbit.
- Fission theory- Earth spinning so fast that it spit out the Moon. No- Earth would have to spin full circle in 2 hours.
- Giant impact theory- moon formed from debris left over from collision with Mars-sized object. Problem: impact would mean moon should have very different composition than earth.
Continuation- synestia. When mars sized object collided, formed spinning mass of molten and vaporized rock, forming donut. Moon formed when chunks of molten rock go into the orbit. Moon and Earth condensed from same composition.
Which theory about the moon’s formation is the most reasonable?
Giant impact theory
Radiocarbon dating
- measuring the amount of carbon 14 in a material that was once living
- not used to measure rocks
- carbon 14- decaying radioactive isotope measured
- when living thing stops eating, stop taking in carbon 14
Uranium-lead dating
- use this to measure rock age as old as solar system
- combination of measuring uranium 235 and 238
- 238 decays slowly to form lead 206
- 235 decays fast to form lead 207
- type of radiometric dating
Radiometric dating
uses half life of radiogenic isotopes to measure age
Accretion
- the coming together of solid material
- happened when dust sized particles formed rocks, formed planetesimals, formed planets in solar nebula, which differentiated.
What is synestia
theory of how the earth and moon formed
- a mars sized object collided with earth, forming a spinning mass of molten and vaporized rock, forming a donut.
- moon formed when chunks of molten rock go into orbit
