4.6 billion years ago

Q: From what materials is our solar system made?

Solar System FormationSolar System Formation

Long goneLong gone

Orogens and other topographical elevations are removed - a window into the Earth.

Paleomagnetic polar wanderingPaleomagnetic polar wandering

The rocks point to magnetic poles over time - the relative movement of the apparent poles on different plates indicates movement

Remember these?

Meteorites called carbonaceous chondrites

The juxtaposition of very high temperature components (chondrules and inclusions made of silicates) and very low temperature components (complex carbon compounds).

Building blocksBuilding blocks

SegregationSegregation

Taylor, 2005

Density variation between stable phases in a gravitational field-

The Fe alloys head down, the silicates float.

Note solidification of silicates with depth.

Two types of materials?

Ballentine, Science 296, 2002, 1247-1248

Then and nowThen and now

The dense stuff is at the center.

We have an atmosphere made of the light stuff (but not really light stuff).

How?

The Moon shows evidence of heavy bombardment up to 3.8 Ga

Undoubtedly, the Earth is being impacted simultaneously – the impacts would make the surface of the Earth unsuitable for liquid water. Life is not likely to arise until frequent impacts cease.

Early EarthEarly Earth

Recent evidence shows that the oldest materials on earth, Jack Hills Zircons, are 4.4 biliion years old.

These record crystallization temperatures in the 600-750 ºC range - implying wet magmatic conditions and the possible establishment of the hydrosphere.

NASA’s Earth Observatory

Or not…Or not…

But prior to 4.4 Ga, there are a number of problems with the early Earth.

•Very hot

•Frequent inputs of high kinetic energy

•Weak atmosphere

•Sunlight reduced at surface

•No liquid water at surface (and little fluid water at depth)

•No complex organic molecules

All except last are reduced through gravitation and kinetics. The last is trickier although helped by cooling temperatures.

HotHot

The upper mantle has a “depleted” composition. Crust + depleted mantle is roughly that of the lower mantle and chondrites

The lanthanides (La-Lu) are also known as the rare earth elements.The lanthanides (La-Lu) are also known as the rare earth elements.

ridge

ContinentsContinents

CratonsCratons

North American StructureNorth American Structure

The shield is the oldest part of the continent

Primary continental material - it’s mostly metamorphosed or igneous.

Platform - largely the locus of layered sediments.

Orogenic belts - mountain building deformation

CratonCraton

Assembly of the shield and sub-platform over a sequence of time

Analyses of DNA make it suggest that all of life on Earth is related back to one single organism.

Chemically, we’re all very similar.

Domains of LifeDomains of Life

24-515Figure 24.24

In 1953, Miller and Urey conducted an experiment in which methane, ammonium, hydrogen, and water were subjected to an electrical discharge. After a week, 10-15% of C formed organic compounds, 2% as amino acids.

Suggests that a primitive atmosphere could produce life compounds.

Life chemistryLife chemistry

Amino acids are a long way from proteins and nucleic acid

The next step is the subject of ongoing investigations.

One current theory: the RNA world

RNA has the ability to copy itself, modify as an enzyme, and bond with amino acids.

Many viruses proliferate with nothing more than RNA and protein (although few think viruses were the first life – too dependant on cellular life)

Secondary stepsSecondary steps

Clay surfacesClay surfaces

James Ferris (RPI) has been able to assemble complex polymers (primitive RNA) compounds by activating simpler monomers on the surface of clays.

RNA (Ribonucleic acid) is present in all life forms, aids protein encoding, and can carry genetic information.

Cyanobacteria from the Bitter Springs chert of central Australia, a site dating to the Late Proterozoic, about 850 million years old.

Early life: Cyanobacteria [P]Early life: Cyanobacteria [P]Early life: Cyanobacteria [P]Early life: Cyanobacteria [P]

Stromatolites - shallow marine algal mounds from the Cambrian as seen in Lester Park, near Saratoga Springs, NY.

The first fossils of bacteria are 3.2 Ga.

Rock is 2.5 billion years old (found world wide from 3 - 1.8 Ga)

Dark: Hematite (Fe2O3)Red: Quartz (with iron)Yellow: Crocidolite (blue asbestosform)

The accumulation of iron as seafloor sediments is thought to result from early photosynthesis on the ocean surface

under N2 – CO2 rich conditions.

A lack of atmospheric O2 permits Fe ions in surface seawater – these bond with O2 produced by photosynthesis.

Meet BIF (Banded Iron Formation)Meet BIF (Banded Iron Formation)

Oxygen and complex lifeOxygen and complex life

24-507Figure 24.4

Scientists think that the first organisms (producers) depleted an initially CO2 rich atmosphere, enriching it in oxygen

Q: what process may have enriched O2 in the atmosphere?

Oxygenation of the atmosphereOxygenation of the atmosphere

The existence of life deep in the ocean at extreme conditions has led many to conclude that early life may have used the heat of the Earth for energy

We are still a long way from understanding how life chemistry came together initially.

ExtremeExtreme

http://projects.edtech.sandi.net/miramesa/Organelles/fossilbact.html

Cellular life

The oldest fossils – not much to look at, but appears to be a filamentous bacteria from 3.5 billion years ago.

It’s life, as we know itIt’s life, as we know it

Archaea [D] (Archaea [D] (extremophilesextremophiles))Archaea [D] (Archaea [D] (extremophilesextremophiles))

Changes in ice coverageChanges in ice coverage

End of Proterozic evidence suggests a very cold Earth surface.

Snowball Earth starts with ice on continents extending into the oceans

SequencesSequences

There is more or less a global response to sea level (as a function of ice cover). Sedimentary layers show how the water covers inland (transgression) and recedes (regression)

North AmericaNorth America

Sea levelSea level

Keep in mind that the sea level fluctuation is best recorded by rises (more shelf). The rises are the result of less ice - therefore warmer global systems

Making-closing and oceanMaking-closing and ocean

20-424Figure 20.50

Oldest humanoid fossil 4.3 Ma

Oldest fossil plants 440 Ma

Oldest chordates 510 Ma

Oldest fossil green algea 530 Ma

Oldest shelled invertebrates 570 Ma

Oldest animal fossils (Vendian) Oldest fossil fungi 650 Ma

Oxygenated atmosphere 1.7 Ga

Oldest fossil organism 3.5 Ga

Oldest rock 3.9 Ga

Q: what is the significance of plants with respect to environment?

Geologic Time ScaleGeologic Time Scale

The fossil record not only tells of the development of life, it speaks to the termination of organisms.

Extinction is when a type of organism (species) fails to appear past a certain time horizon in the fossil record, or ceases to exist in modern ecosystems.

Extinctions happen throughout time, but there have been six to seven points in earth history when a significant number of organism types became extinct.

650, 540, 510, 440, 340, 248, 65 million years

The cause of mass extinctions is not known, but most theories point to global catastrophe

Bolide impacts (likely for the K-T)

Large-scale volcanism

Rapid climate change

Slow magnetic reversals

1.1 Ga1.1 Ga

Recall the mountain building event we called the Grenville Orogeny. The assembly of the super continent known as Rodinia formed these mountains.

Grenville in North AmericaGrenville in North America

650 Ma650 Ma

Very little land. However, all of the organisms are likely marine dwelling.

Specialized cells apparently arose by 650 Ma, with the Vendian organisms. They look like casts of soft parts – but not much is known about these critters.

Fungi also arise at the same time. Fungi can be monocellular, colonial, or multicellular.

The one in the picture (right) is only 360 Ma from the Rhynie Chert, Scotland.

VendianVendian

EventsEvents

PaleozoicPaleozoic

Starting at 570 and leading to 540 million years ago, life diversified. The number of fossils increases in the rocks, and they organisms have different morphologies. Many of these organisms have some relatives alive today

Segmented arthropods: trilobitesSpongesBryozoaCoralsBrachiopods

The reason is the source of serious scientific debate, but obviously linked to emerging (and possibly stabilized) thermal and chemical conditions in the ocean.

Cambrian explosionCambrian explosion

514 Ma514 Ma

Eukaryotes can be single cellular or multicellular. Specialized cells developed. Some cells in complex organisms can be quite complicated.

Sponges (poriphera) are animals

Note, sponges, are extensive in the fossil record, beginning 540 Ma – a hard skeleton made of calcite or quartz makes them incredibly durable.

Multicellular and skeletalMulticellular and skeletal

458 Ma458 Ma

Taconic orogenyTaconic orogeny

Iapetus seafloorIapetus seafloor

Plants are very close to algae in genetic structure

Algae are another organism that has its oldest fossils in the Cambrian.

Plants occur much higher in the record – 440 million years ago, and are found in rocks that formed on land.

Plants are simple to complex multicellular autotrophs. Key is the development of specialized cells to extract moisture, amino acids, nitrates, phophates, and minerals from soils (roots).

Some of the earliest fossils are fern-like in morphology

Note: modern land plant height is limited by gravitational constraints of lifting water.

Early PlantsEarly Plants

Animals are heterotrophs – they need to eat autotrophs to get carbohydrates.

Until recently, fossil land animals were found to be all younger than fossil plants

However, a 470 Ma fossil of a millipede, discovered in 2004, is now thought to be the oldest land fossil. Either older land autotrophs existed or this millipede stayed close to the water.

The conversion from water to land (or vice versa) is a difficult one

Most (but not all) aquatic heterotrophs organisms extract oxygen from water*, and autotrophs carbon dioxide from water. Most land heterotrphs extract oxygen from air.

Life is largely made of water, and therefore is similar in density. Most organisms are boyant in water (and not in air). Gravity is more of a factor on dry land.

*the attempt to extract oxygen from water in organisms that extract it from air is the phenomena known as drowning.

425 Ma425 Ma

SilurianSilurian

Closing IapetusClosing Iapetus

Recall that the Taconic orogeny slaps an linear string of volcanoes (an island arc) onto the eastern end of Laurentia (proto-North America). The closure of the Iapetus results in the Acadian orogeny.

Acadian-Caledonian orogenyAcadian-Caledonian orogeny

390 Ma390 Ma

Devonian - age of the fishesDevonian - age of the fishes

Fish fossils become abundant and exhibit a diversity - jawless, jawed, and bony.

Sharks are first found here

Forming PangaeaForming Pangaea

Appalachian orogenyAppalachian orogeny

Appalachian sectionAppalachian section

356 Ma - Mississippian356 Ma - Mississippian

Carboniferous forestCarboniferous forest

306 Ma - Pennsylvanian306 Ma - Pennsylvanian

255 Ma255 Ma

PermianPermian

Permian rocks record less swampy environments - in parts of North America, lots of oxidized sandstones.

Large lizard fossils, like Dimetron, date from this time.

The end of the world occurred 248 million years ago - the Permian extinction

Ninety to ninety-five percent of marine species were eliminated as

a result of this Permian event.

Gone:•fusulinid foraminifera•trilobites•rugose and tabulate corals•blastoids

Reduced•bryozoans•brachiopods•ammonoids•Sharks•bony fish•eurypterids•echinoderms

WhyThis was a long time ago - some ideas•Global cooling/sea level drop•Pangea formation•Glaciation - global dehydration•Intense volcanism

Making wayMaking way

MesozoicMesozoic

237 Ma237 Ma

Begin the time of the DinosaursBegin the time of the Dinosaurs

Early dinosaurs - often small like Ceolophysis.

Success at adapting to the variable climates of the mesozoic.

Gondwanaland splitsGondwanaland splits

The dry westThe dry west

Western North America during the Jurassic is very dry.

Navajo sandstone - massive unit with dune x-bedding

195 Ma195 Ma

JurassicJurassic

Dinos get larger - more diverse. An arms race of sorts between the predators and the prey.

152 Ma152 Ma

North America in the late JurassicNorth America in the late Jurassic

94 Ma94 Ma

Exotic terranesExotic terranes

In assembling North America we’ve seen the incoporation of chains of andesitic volcanoes in the Taconic orogeny - and here again in the early K with what will become the Klamath orogeny.

Add-ons to the westAdd-ons to the west

This modification accounts for the extent of continental growth.

How might this compare with continental destruction?

K warm seasK warm seas

66 Ma66 Ma

The K-T boundaryThe K-T boundary

In contrast, the Cretaceous extinction was a mild event

Sixty percent of all species were eliminated as a result of this

Permian event.

Clay layers from this boundary typically include enriched iridium.

The prevailing theory for this extinction involves bolide impact at the Yucatan Peninsula - the Chicxalub

structure.

Earth!

million years without a single mass extinction6 5

50 Ma50 Ma

Orogeny in the modern EarthOrogeny in the modern Earth

Subduction to strike-slipSubduction to strike-slip

Western extensionWestern extension

14 Ma14 Ma

Morphology

DNA deviations

Repetition

Successful changes

Perhaps evolution is best attempt of organisms to find lowest energy form over time (like any chemical phase)?

24-514Figure 24.17

Q: how old is mankind’s direct ancestors? Where did humanoids first develop?

Ancestors of humansAncestors of humans

Spencer Wells

the y-chromosome is a parcel of DNA, passed on from father to son, basically unchanged for generations save random mutations.

By looking at modern individuals y-chromosome DNA, a migration path for H. sapiens is revealed.

Q: What would have prompted this migration at 50,000 years?

Last Glacial MaximumLast Glacial Maximum

PrecessionPrecession

Result of oblate shape and the moon

Axis wobble with a 26,000 year period

Vega will be the North Star in another 12,000 years

Milankovitch Cycles

One potential cause of glaciation – coincidence of earth’s motion variations precession, rotational axis, orbital eccentricity

Milankovitch Cycles

One potential cause of glaciation – coincidence of earth’s motion variations precession, rotational axis, orbital eccentricity

21.5-24.5o 41 kyr Low-high 100 kyr

One precession per 23 kyr

Humans are relative new comers to life on this planet.

Humans are relative new comers to life on this planet.