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How does the sun brighten through time

The helium "ashes" left behind are denser than hydrogen, so the hydrogen/helium mix in the Sun's core is very slowly becoming denser, thus raising the pressure. This causes the nuclear reactions to run a little hotter.

Chronostratigraphic vs chronometrictime divisions

Chronostratigraphic- strictly dated material in rock record- uses stratigraphic record and roc

Chronometric- doesnt have any specifc in rock record we can leverage a standard measurement of time

Precambrian Time

Time period before the Phanerozoic eon

Origin of Earth

The process by which the Earth formed

Geologic Time

The division of Earth's history into time intervals

Geologic Time Scale

A scale that represents the divisions of geologic time

Phanerozoic timescale

The most recent eon of Earth's history

Precambrian Timescale

The time period before the Phanerozoic eon

Challenges to studying Early Earth (PNRI)

-pausity of rock record

-no observable life/fossils

-Rocks may have undergone multiple episodes of

Alteration, deformation, metamorphism

-isthe principle of uniforms valid for all points of

Earth history → rates of processes could be different earth is hotter todays age

Archean

The time period from 4 to 2.5 billion years ago

Rock Record

The preserved evidence of Earth's history in rocks

Fossils

Remains or traces of ancient life

Alteration

Changes in rocks due to heat and pressure

Metamorphism

The process of rocks changing form due to heat and pressure

Time-line for Earth Evolution

A chronological sequence of events in Earth's history

Solar Nebular Hypothesis

The theory that the solar system formed from a rotating disk of gas and dust

Terrestrial Planets

Rocky planets like Earth, Mars, Venus, and Mercury

Jovian Planets

Gas giant planets like Jupiter and Saturn

Condensation

The process of a substance changing from a gas to a solid

Coplanar Orbits

Planets orbiting the sun in the same plane

Composition

The chemical makeup of a substance

Asteroids

Rocky objects that orbit the sun, smaller than planets

Planetesimals

Small bodies that formed from the dust and gas in the early solar system

Meteorites

Rocks that have fallen to Earth from space

CI Chondrites

A type of meteorite with solar elemental abundances

Cosmic Heritage

The history and origins of the universe

Claire C. Patterson

A geochemist who determined the age of the Earth

Lead-Lead Dating

A method of dating rocks using the decay of uranium to lead

Pb-Pb Isochron

A graph used to determine the age of meteorites

Meteorite-Lead Isochron

A graph showing the relationship between lead isotopes in meteorites

Radioisotope Dating

A method of dating rocks using the decay of radioactive isotopes

Allende CV3 Carbonaceous Chondrite Meteorite

A type of meteorite used for radioisotope dating

Solar System Formation

The process by which the solar system formed from a rotating disk of gas and dust

Proto-planetary Disc

A rotating disk of gas and dust from which planets form

Differential Accretion

The process by which different elements accumulate in different regions

Compositional Variations

Differences in the chemical makeup of different objects

Chondritic Meteorites

Undifferentiated meteorites from the asteroid belt

Most primitive

Similiar composition to sun (similar origin)

Primitive Materials

Substances that have not undergone significant change or differentiation

Isotopic Compositions

The ratio of different isotopes of an element

Accretionary Process

The process of particles coming together to form larger objects

Average Terrestrial Pb Isotopic Compositions

The ratio of different lead isotopes on Earth

Evidence in support of solar nebular hypothesis

Coplanar orbits of all planets

All planets revolve around son in same direction

All planets except Venus & Uranus rotate in same direction

Can explain the difference between composition oft terrestrial d joulan planets

GSSP (Global boundary Stratotype Section and Point)}

Marks the lower boundary of a geologic time I'm rock record

Chondritic Meteorites

Undifferentiated meteorites from the asteroid beltMost primitiveSimiliar composition to sun (similar origin)

Evidence in support of solar nebular hypothesis

Coplanar orbit of all planets-All planets revolve around the sun in the same direction -All planets except venus and uranus rotate in the same direction-Can explain the difference between the composition of terrestrial and Jovian planets

Explain the solar nebular hypothesis

The molecular cloud underwent some sort of gravitational contraction, and that contraction was triggered by a ex

plosion of massive star by the nebula ( mass of gas and dust ). A supernova (explosion massive star) triggered a gravitational contraction which will make the solar nebula spin out in the form of a disk with most of the mass gravitationationally accreding towards the centre of propplanetary disk to form the sun and all the planet form in the protoplanetary disk.

How many stony meteorites and iron meterorites dif patterson use to construct a meteorite-lead isochron and what was the determined age?

Three stony and two iron and the age was determined to be 4540

Is a chondrite meteorite undiffrentiated or diffrentiated?

Undiffrentiated

Precambrian time is chronometric

No specifics in rock record that we can leverage

Refractory elements

Condense out of the nebula at high temp

What are diffrentiated asteroids

(larger asteroids) have internally melted and in the process have developed a core (Sometimes they are broken up by other collisions and then the fragments that reach us come form differentiated asteroids which we call differentiated meteroties)

How is earth unique among terrestrial planets

Earth is the only planet with plate techtonics

Accretionary wedges

Formed through accretion of sediments on the edge of over riding plate in subduction zone

Linear volcanic mountain

forms volcanic arc

Ophiolite section

chunks of oceanic lithosphere obducted on top of continents, the become dense and then subduct in oman

blueschits eclogites

Metamorphic rocks formed in high pressure and low temperature

Theory of archean earth techtonic plates isss

That there were smaller and faster plates

Petrotechtonic indicators of seaflorr speading

rock type that preserves signatures of modern style plate techtonics

Physical traits that make plate techtonics in early earth questionable

Archean, earth was much more hotter than today

more radioactive heat production

TTG stand for

Tonalite- trondhjemite- granodiorite

TTG are

Felsic plutonic rocks

- earliest coherent fragments of felsic continental crust

- represent the transition from a mafic to felsic crust

Where can a TTG rock be foud

ACASTA GNEISS 4.03 GA

Constraints from experiemtns of TTG (3)

Formation of archean TTG require 20% wt of garnet in region

- for morb-type metabasalts this requires depth >48km

-stabilization of eclogite assemblage requires depth> 55km

How does water affect techtonic styles

Water cools down hot magma when it reacts with water and also affects and facilitates the bending of plates which creates the subduction and oceanic lithosphere

Where is most of earths water traced in?

trace amounts of hydrogen that is incorporated in rock forming siliciate minerals

Where do we have direct evidence of water in rocks

Isua supracrustal belt in greenland

Explain how the pillow lava structures in the isua supracrustal belt show water

formed through the eruption of basalts in deep water columns or when basaltic magmas interact with water

Explain how the banded iron structures in the isua supracrustal belt show water

chemical sedimentary rock formed in ocean basins

Explain how the METACARBONATES structures in the isua supracrustal belt show water

also precipitate from ocean-> sed carbonates from ocean

Explain how the g beddingraded structures in the isua supracrustal belt show water

indicates flucial deposition

Explain how conglomerate structures in the isua supracrustal belt show water

rounded which implies they were deposited by fluvial processes

Why are the hadean zircons important

detrital zircons, zircons are preserved in younger sediments - 4.4 billion years old

Venus is always hot because

There is high c02 in the atmosphere and very thick in atmosphere it is 92atm

earth is at a comfortable temperatur because

of low c02 in the atmosphere

Mars is very cool because

thin atmosphere and doesnt produce very much greenhouse gase

What are constraints from the solar evolution model

-the sun was 30 percent less bright in the archean

-if earth has some atmospheric composition as present atmosphere the surface water before the MESOPROTEROZOIC would have been below freezing

How do you get large angular cobbles in fine-grained marine rocks?

drop stones from glaciers

Consequences of rise in atmospheric Oxygen

-"Snowball Earth" because of less effective greenhouse

-caused banded iron formations

-weathering of sulfate into oceans leading to a partially euxinic (sulfidic) ocean

-precipitation with HS, caused removal of essential trace elements stalling the biological pump

Snowball Earth Hypothesis

Entirety of Earth's surface (pole to pole) was covered in ice

Major Ice Ages in the Snowball Earth Hypothesis

Sturtian Ice Age: 750Ma

Marinoan Ice Age: 635Ma

Possible third one 2Ga

The Weak Young Sun

Sun had lower energy output in the past than it does now

-early Sun began converting H to He in its core

-Intial [He] was 26%, now its 62%

-Density of Sun's core is increasing which makes it hotter

-In the Proterozoic the Sun was 4-6% less luminous than today

The Continents

-Were clustered into "supercontinents"

-Located at relatively high latitudes which is likely where glaciation originated

Influence of Albedo Effect

-Earth Temperatures get cooler causing further glacial expansion which is a positive feedback of ice albedo

(Snow and ice have high albedo ranging from 45-95%,Seawater albedo is lower at about 10%)

When there isn't a lot of ice, the darker land absorbs more heat therefore causing warmer climates (another positive feedback loop)

Evidence of Snowball Earth

-tillites and striations, dropstones etc... present between 800-630 Mya

Difference in dating for Phanerozoic vs Neoproterozoic

Phanerozoic has floral and faunal fossils which can be dated, but it is harder for Neoproterozoic glacial deposits

Paleo-latitudes

Paleo-latitudes have been determined for many of the glaciated sites, it tells us that many places had glacial evidence in tropical to subtropical latitudes

Paleomagnetic Reconstruction

-Using fine grained sediments that have iron rich minerals that settled in a NO CURRENT environments

-Minerals will orient themselves to the poles

-This reconstruction CANNOT be used as a primary tool since the poles are always moving but is a helpful tool

How can a glacier exist in tropical, near ocean environments?

-Need initial source first, extended cold spell, Faint young sun, low greenhouse effect

-Runaway icehouse begins after you cross 30 degrees latitude, after which albedo can do bulk of the work

Once the Earth was frozen, why didn't it stay like that?

-It was NOT completely frozen up, there was still open water

-Volcanism, plate tectonics, GHGs pumped into oceans and atmosphere from ocean vents etc... can trigger a RUNAWAY GREENHOUSE EFFECT which will warm up the Earth

Runaway greenhouse effect

GHGs that are pumped into the ocean via deep ocean vents, volcanism etc... can't equilibriate with oceans as fast which is why they'll flux into the atmosphere and accumulate which will cause a Runaway Greenhouse Effect

Evidence of Greenhouse conditions after Neoproterozoic glaciations?

There are "cap dolostones" that are deposited abruptly above glacial tillites

>>implies change from frigid to warm

Prokaryotes

-Single celled organism that LACK a nucleus

-Includes Domains Archaea and Bacteria

-Not as organized

Eukaryotes

-Single AND multicellular organisms that have a cell nucleus

-Includes Kingdoms Protista, Fungi, Plantae, Animalia

-have organelles that can perform unique functions, eg:mitochondira, lysosomes, golgi apparatus

How are Archaeans differentiated from Bacteria?

-Genes

-Metabolic pathways

-Lots of other biochemical components

How are Eukaryotes similar to Archaeans?

-Share numerous SYNAPOMORPHIES(ie shared derived characteristics) that are not found in Bacteria

-DNA replication processes carried out by sets of enzymes: initiation, priming of Okazaki fragments, synthesis, unwinding

Leading hypothesis on eukaryote evolution

Leading hypothesis is that Eukaryotes evolved from Archaea which had split off from Bacteria some time before.

Endsymbiotic Hypothesis(Symbiogenesis)

Suggest eukaryotic organelles(eg mitochondria, chloroplasts, Golgi apparatus etc...) were originally free-living Protobacterium that were engulfed by an early eukaryote but avoids digestion and starts living symbiotically.

Acritarchs

-acid resistant organics(wide variety of sources)

-appear during Proterozoic

(Anything with spare carbon floating around, we don't really know what it belongs to, might be an early Eukaryote)

Algae

-Eukaryotic

-photosynthetic

-no complex organs/tissues(ie not plants)

-show up near the end of the Proterozoic

Bitter Springs Formation

-central Australia(0.8 Ga)

-most diverse Proterozoic microfossils assemblage which includes: -cyanobacteria(subgroup of bacteria that are photosynthetic)

-bacteria

-Algae(maybe)