SCI Test Prep Two

Charles Lyell

Proposed the concept of uniformitarianism to understand gradual change

Natural processes

Constant through time and space

Intrusive Rocks

Thousands to million of years to solidify

Extrusive Rocks

Minimum to days to solidify

Relative Age

Apply stratigraphic principles to know this age

Absolute Age

Measure this by measuring radioactive decay in certain rocks

Radioactive Decay

Some atoms unstable (exceptional particles or energy become stable)

Constant and measurable for particular

Possible to calculate how many half lives passed

Measure in a lab

Parent vs daughter

Parent daughter combos

Half life- the amount of time it takes for ½ of remaining parent particles to decay

Radiocarbon dating

Date archeological finds

Not always good to measure

Radiocarbon dating, Carbon 14

Produced at a constant rate in the atmosphere

Incorporated into organisms during life but not after death

After 8000 years not enough c 14 to measure *not always good to measure

Radioactive atoms

Longer half needs to date rocks

Age of rock formations

Problem with Radiometric dating

Can only be used on igneous rocks

Sediment are older than the rock that contains them

Index fossils only formed in sedimentary rocks

Solution to radiometric dating

Combine relative and absolute age dating (steno’s laws)

Volcanic Ash

Can travel farther than a lava flow

Extrusive igneous rock

Can be used with Radioactive dating techniques

Absolute age of index fossils can be determined

Geologic timescale

Reference to age history

Understanding the time period

Time based on appearance of certain fossils

Assigning ages to certain fossils

Geologic Eons

Eons, Hadean, Archean, Proterozoic, and Phanerozoic

Earliest Eon

4.6 - 4.0 billion years

Earth’s surface still molten

Hades - Greek underworld

Before continents formed

Archea

Earth’s surface cooled and solified

Formation of continent

State of place tectonics

Ocean form

Likely first life

Proterozoic

Protero = 1st zoic life

Singular cellular life common

Oxygenerated atmosphere forms

First multicellular life

Phanerozoic Eon

Today

Phanerozoic = visible, zoic - life

Multi cellular life

Phanerozoic

The Paleozoic era “old life”

Mesozoic era “middle life”

Cenozoic “new life/today”

The Precambrian

Majority of the fossil record found in rocks that are from Phanerozoic eon

The Cambrian - 1st period of Phanerozoic eon

Earth history before the Cambrian referred to as the Precambrian

Hadean Eon

Events of the Hadean

Earth forming out of stellar nebula

Formulation of Moon

Differentiating Earth’s layers

Start of the magnetic field

End of the heavy bombardment stage

Archean Eon

4.0 to 2.5 billion years ago

Oldest rocks

Oldest Continents

Formulation of Solar System

Dust and gas from stellular nebula under gravity

Most mass spins to center (our sun)

Remaining dust cloud coalescence into plants and moons

Age of the Solar System

Known from using radiometic age dating on meterorites

4.53 to 4.58 billion years ago

Meteorites

Leftovers of solar system life

Rock that hasn’t been incoporated into planets or moons

Forming the Earth

Solar system formed from stellar nebula

Cloud of dust and gases

Object with mass attract with other objects with mass

Earth is one of the four inner planets (rocky planets)

Earth mostly comprised of

Felsic rocks, metals/malfic rocks, solid with gases with solid fraction of mass

Earth’s layers

Energy with heat in the center

Denser elements sunk to the center and lighter elements floated to the top

Earth’s magnetic field extends from the poles into the space around the earth

Protects earth’s surface from electrically charged solar radiation

Though to be produced by the spinning of earth’s liquid outer core

Age of the Earth

4.5 billion

Age of Moon Rock

4.4 billion

Oldest Rocks on Earth

3.3-4.28 billion, 4.4 billion

Forming the moon

Collision ejected mantle material into space around earth

Material into new astronomical body the moon

Composed mostly felsic minerals

Moon has very little heavier elements that other inner planets have

Earths orbital plane and moon’s orbital plane are aligned

Heavy bombardment phase

Leftover littered the solar system

Craters not removed from the moon (from weathering)

Earth’s crust

Molten rock, continental rock (felsic), oceanic crust (mafic), oceanic crust subducted due to the process of plate tectonics

Continuously being recycled in mantle

No older crust (than 300 million years)

Cartons

The “cores” of the modern continents

Made of Archean crust

Stable but not tectonically active

No current place boundaries

Formulation of the oceans

70% of Earth’s surface covered by oceans

Ocean today

Saline, dissolved ions, continental weathering, chemical erosion of rocks on continents, carried to oceans by rivers

Sources of Water

Vaporized during Hadean

Terrestrial sources

Terrestrial sources

H2O molecules chemically bonded to mantle materials

As earth coooled, H2O came out of early volcanoes as water vapor

H2O component of gas today

50-60% of volcanic gas is water vapor

Extraterrestrial Sources

“Icy” comets formed at the edges of the solar system

Heavy bombardment stage at end of Hadean

Godlilocks zone hypothesis

Not to cool for liquid water

Mars is too cold for liquid water

Venus is too hot for liquid water

Not too hot to vaporize water away

Respiration

Metabolic process that burns O2 to produce energy

Waste product is O2

Photosynthesis

Metabolic process that burns CO2 to produce energy

Waste product is O2

Early atmosphere

Hydrogen and helium gases formation

Thought to be lost at Hadean for being “too light”

Terrestrial Source

Volcanic Gas

Where did nitrogen come from?

Built over the years from volcanic gas

Where did oxygen come from?

Photosynthesis (produces oxygen)

Evidence of Oxygen

Free oxygen

Evidence for Carbon Dioxide

Photosynthesis “consumes” CO2

Archean CO2 sources from volcanic gas

Faint Young Sun Paradox

Young sun

No liquid water in Archean

Weather

The state of the atmpsphere at any given time

Constantly changing due to complex character of the atmosphere on short timescales

Climate Change

Energy in and out

When more energy leaves the system, temperature rises

Energy in

Solar luminosity: how much energy is emitted from sun; energy output of sun has changed over time

Energy out

“Black body radiation” head radiated into space as infrared radiation

Some energy is trapped by gases in atmosphere

• water vapor

• Methane

• Carbon dioxide

Green House effect

How much energy is kept on Earth

Icehouse

When there is stable ice sheets at the poles

Last year round

Greenhouse

There is no stable ice at the poles

Fractionation

When chemical doscriminate between isotopes

Evaporation of H2O causes fractionation between oxygen isotopes

Evaporation

H2O causes fractionation between oxygen isotopes

This takes away 16O and leaves 18) behind

Takes 16O and “locks” away ice

Temperature Proxies

Can’t sample water directly in most cases

Snowball Earth

Late Proterozoic

Global Ice sheets = cut off from the atmosphere

End of snowball earth would trigger the formations from the atmpshere

Glacial and sea ice reached the equator

Evidence for glaciers

Glacial erratics

Poorly sorted glacial deposits