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Geologic Time Scale

Divisions are determined by geological or paleontological events, many are based on mass extinctions.  see "Extinctions".  Strata are described in Eon, Era, Period, Epoch, Stage, then by layers of geological series and formations.  Major divisions are world wide.  Most series and formations are regional.  No place on Earth has layers of all the divisions.  It is like a 3D mosaic.  Because of regional discrepancy's in nomenclature, geologists often use Upper (Late), Middle, or Lower (Early).

Why do dates of time periods change from list to list?

When scientists first started studying astronomy, geologic layers and , they believed the Earth as the center of the universe, the world could not be more than a few thousand years old, and the continents were static.  Universities were religious institutions, so knowledge was molded by religious traditions.  Challenging religious concepts is very dangerous.  A tremendous amount of data had to be collected and presented to change commonly held beliefs.

Each generation's understanding is built on previous experiences and should not be ridiculed for what they did not know.  The man who proposed a creation date of over 10,000 years was laughed at, but the evidence supported him.  Now we believe the Earth is 4.6 billion years old and the universe is 11 to 20 billion.  Each year, new studies refine our understanding.

Beginning of Time

Then till now

Big Bang

between 11.2  & 20 billion years ago

The sudden existence of all matter and energy of our universe spreading out from a singularity.  Everything was evenly spaced with a common temperature.  Light was ubiquitous.

1 second later

First growth spurt of the universe, inflation factor of 10⁴³.

Formation of protons and neutrons as the universe expanded.

3 minutes later

Formation of the first helium and lithium atoms.

CMB

380,000 years old

The universe expands and cools enough to form neutral hydrogen.

Formation of the Cosmic Microwave Background.

Cosmic Dark Ages

200 million years old

Lasts about 1 billion years

Neutral hydrogen naturally traps visible and UV light making the universe dark.  This Dark Matter does not dissipate its own energy.  (Even today, 80% of all the mater in the universe still consists of Dark Matter.)

CMB currents clump together Dark Matter.  When the mass of Dark Matter became larger than 1000 Suns then the mass was cool enough to let hydrogen clump.

The expansion of the universe kept gravity from collapsing matter back into a singularity.  Currents in the CBM created eddies that kept expansion from tearing matter apart.

600 million years old

Gravity pulled Normal Matter (baryons) together, to the center of Dark Matter clumps that were the size of small galaxies.  More matter means more density.  Enough density allows nuclear fusion and the first stars form.

These stars were larger then any today.  Heavy elements (created inside current stars), which dissipate heat efficiently, did not existed at this time. So these massive suns burned very hot, producing UV photons that ionized the hydrogen and unbound other Normal Matter 1000 light years around them.

These first stars were more than 100 times larger than our sun.  They may have become supernovas within 1 million years.  That explosion would have formed a bubble of Normal Matter within the surrounding Dark Matter cluster (which astronomers still see around galaxies).  Normal Matter clumps together to form more stars.

If a star was over 300 times larger than our sun then it would have imploded to become a large black hole.

The universe was still filled with neutral hydrogen so it still would have appeared dark to a human.

Age of Re-ionization

about 1 billion years old

Enough mater pulls together to re-ionize the universe.  This allows for visible light to be transmitted.

Precambrian

4.5 billion to 500 million years ago

Hadean Eon

4.5  to

3.8 bya

Our solar system forms, possibly from a supernova cloud.

Archaean Eon

3.8 to

2.5 bya

Earth's crust cools and oldest terrestrial rocks form (3.8 bya)

Atmosphere of methane and ammonia

Oldest fossil at 3.5 billion ya is stromatolite

Proterozoic Eon

2.5 bya to

543 mya

First true continents

Abundant fossils of bacteria and archaeans

eukaryotic cells are possibly 1.8 billion years old

Atmospheric oxygen pollution from photosynthetic organisms like stromatolite - First mass extinction

First "red bed" layers from iron oxide

Llano uplift of Texas contains rocks from this age

*Vendian Period

650 to

543 mya

First fossils of soft-bodied multi-cellular organisms

Super-continent of Rodinia

Phanerozoic Eon

544 mya to today

Paleozoic Era

543 to 248 mya

*Cambrian Period

543 to

490 mya

Cambrian Explosion - in a few million years almost all known animal phyla appear and diversify

Breakup of the super-continent of Rodinia

The largest land mass is called proto-Gondwana

No glaciation - mild climate

*Ordovician Period

490 to

443 mya

Super-continent of Gondwana shifted to the southern hemisphere and much of it sunk underwater.  mild climate.

Algae, graptolites, trilobites, brachiopods, cephalopods, coral, crinoids, gastropods.

First bone teeth in early vertebrates called conodonts

Possible - first plants growing above water.

Late Ordovician - massive glaciers drain shallow seas, and drop sea levels.

Mass Extinctions - 60% of all marine invertebrate genera

*Silurian Period

443 to

417 mya

Stabilization of climate, melting of the glaciers, rise in ocean levels

Rapid spread of jawless fish

First coral reefs, first freshwater fish, first jawed fish

On land, relatives of spiders & centipedes

First vascular plants

*Devonian Period

417 to

354 mya

Two small continents and one large in southern hemisphere

First forests of ferns, horsetails, seed plants, trees

First tetrapods, first terrestrial arthropods and arachnids

Many new fish appear.

Mass Extinctions - 365 mya possibly volcanic - Russia/Asia

Mass Extinctions - 354 mya possibly volcanic - Russia/Asia

*Carboniferous Period

354 to

290 mya

Abundant swamps deposited material that became large coal beds across North America, Europe, and Asia.

First amniotic egg

Mild climate decreased club moss and large insects

Increase in tree ferns

**Mississippian Epoch

360 to

325 mya

in USA mostly limestone, crinoids, algae

**Pennsylvanian Epoch

325 to

290 mya

in USA mostly coal

climate with glaciers alternate land as terrestrial or marine

Collision of Laurussia and Godwanaland produces the Appalachian Mountains, Hercynian Mountains of the UK, and the Ural Mountains of eastern Europe.

*Permian Period

290 to

248 mya

Super-continent of Pangaea, super-ocean of Panthalassa, small sea called Tethys

Interior of Pangaea was a seasonal desert, less glaciation

First gymnosperms

End of the Permian - largest mass extinction, mostly marine

Mass Extinctions - 240 mya possibly volcanic - Russia/Asia

Mass Extinctions - 248 mya possibly volcanic - Russia/Asia

Mesozoic Era

248 to 65 mya - "Age of Dinosaurs"

*Triassic Period

245 to

208 mya

Modern gymnosperms

First dinosaurs

Mass Extinctions - 208 mya

*Jurassic Period

208 to

146 mya

Dinosaurs grow huge

First pterosaurs, first birds

Huge marine reptiles, abundant cephalopods

Break-up of Pangaea begins

Gondwanaland split

large trap splits Antarctica from South Africa

Mass Extinctions - ? mya

Mass Extinctions - ? mya

Mass Extinctions - 146 mya

*Cretaceous Period

146 to

65 mya

Middle Cretaceous

First angiosperms - diversified quickly

First Ceratopsians,

First modern mammal and bird groups

Massive volcano removes India from Africa and slams it into Asia forming the Himalayan Mountains

Mass Extinctions - ? mya

Mass Extinctions - ? mya

Mass Extinctions - 65 mya Massive asteroid hits near Chicxulub and leaves a 300 mile wide crater in the Gulf of Mexico.  Killed all non-avian dinosaurs, ammonites, marine reptiles

Cenozoic Era

65 mya to present - "Age of Mammals"

*Tertiary Period

65 to

1.8 mya

**Paleocene Epoch

65 to

54.8 mya

Mass Extinctions - 54.8 mya

**Eocene Epoch

54.8 to

33.7 mya

Oldest known fossils of many modern orders of mammals, early dear and horses were prevalent

**Oligocene Epoch

33.7 to

23.8 mya

Cool climate

First elephants with trunks

First true horses

Many new grasses

Mass Extinctions - ? mya

**Miocene Epoch

23.8 to

5.3 mya

Warm climate then cooler, dry continental interiors

Antarctica becomes isolated and oceans do not mix so continent becomes covered with glaciers

Africa/Arabic plates join Asia

First kelp forests, First grasslands

Mass Extinctions - ? mya

**Pliocene Epoch

5.3 to

1.8 mya

Cooler climate, polar ice, Antarctic extinctions

Land bridge between North & South America appears

Grassy savannas with herds of grazers (mammal) on most continents

Late Pliocene - ice ages

*Quaternary Period

1.8 mya

to present

**Pleistocene  Epoch

1.8 mya to

11,000 ya

dramatic climate change - Ice ages alternate with warmer periods but don't seem to have caused the extinctions

Very large land mammals

Mammoths, horse, camels

First Homo sapiens - spread across most of the world and may have caused the mass extinction at the end of the Pleistocene

**Holocene Epoch

11,000 ya

to present

Time between the last ice age and now.

Generally warm climate except for "mini-ice age"

"Age of Man" - all of recorded history

Notes on Discovery or Theory

372-287 BC

Theophrastus

Student of Plato and Aristotle and the next great teacher

Father of Taxonomy - first systematic listing of botany including plants brought back by followers of Alexander the Great

Proved the Atlantic Ocean flowed into the Mediterranean Sea

His ideas dominated science until the Scientific Revolution

1088

Meng Xi Bi Tan

Hypothesized that land was formed by erosion and sedimentation, then was uplifted above the ocean

Discovered that compasses do not point to true north

First modern theory of the solar system (Earth not the center)

1556

Georg Agricola

First systematic book on mining, smelting, wind energy, hydrodynamic power, ore extraction

Father of modern theories of astronomy, physics, and science

Laws of planetary motion

1638-1686

Nicolas Steno

Anatomy - showed that contracting muscles changed shape but not volume by using geometry

1667 - determined "tongue stones" found in rocks were ancient shark teeth not that they fell from the sky or grew there.  He argued that compositional differences were altered by the the current idea of corpuscular theory of matter

1669 - Described how minerals could form inside of other rocks.  Steno's Law: for any kind of crystal the face angles will be the same.   Defined the principles of stratigraphy (how strata is formed).

Principles that made possible geologic time scales - rock layers are laid down in succession with older rocks under younger rocks. 

Used Biblical genealogies for the creation of the world

Used mathematics to prove that motion, one Earth or by planets, are governed by the same natural laws

Used Biblical genealogies, Middle Eastern, and Mediterranean histories for the creation of the world

Realized that the comet was a recurring object orbiting the sun, not an atmospheric phenomena

1746

Jean-Etienne Guettard

Wrote on the distribution of minerals and rock, noted erosion of mountains by rain, first to recognize former volcanoes.

1760

Georges-Louis Leclerc,

Comte de Buffon

75,000 year old Earth

Wrote an encyclopedia on all known natural history to date.

Noted regions have distinct plants and animals, that climate changes may have contributed to the spread.  First to conclude that species have improved or degenerated since creation.

By estimating the time it would take for a molten planet to cool

1744-1829

Jean-Baptiste Lamarck

Wrote a series of flora of France. Buffon had him appointed to the Paris National History Museum

He believed in unchanging species until he studied mollusks (he coined the word invertebrate).  The evidence made him realize that transmutations happed over time.

"Law of Use and Disuse" - function precedes form - adaptation

"Inheritance of Acquired Traits" but he believed a non-genetic trait could be passed on to children

1772

James Burnett,

Lord Monboddo

First to associate humans with primates: common ancestor

Developing tools, social structures, and language as an adaptive response to environment: adapt to survive

Understood selective breading

Believed Adam & Eve story as an allegory

1774

Abraham Werner

1774 - first modern book on descriptive mineralogy

Proposed the theory of Neptunism - rocks formed from crystallization of minerals in the early Earth's oceans.  Receding ocean levels exposed the land.  Currently only sedimentary rocks fit this description.

1774

Nicolas Desmarest

Recognize former volcanoes as a series of ancient events, rocks had changed due to weathering, the origin of valleys

1785

James Hutton

Earth is much older than 4004 BC

First modern geologist

Earth must be much older than 4004 BC because mountains erode and sediments turn to stone then rise up to become dry land

late 1700's

First geological time scale had 4 periods.  Primary, Secondary, Tertiary, Quaternary

1811

Georges Cuvier & Alexandre Brongniart

Earth is much older than 4004 BC

Cuvier discovered fossil elephant bones in Paris.  They proposed a theory of stratigraphic succession similar to William Smith's

1815

William Smith

Father of English Geology

As a coal miner, he observed that strata was found in the same relative positions and could be identified by the fossils it contained.

As a canal surveyor and map maker, he drew the first geologic map, showing the strata of England and Wales

1820-1850

A series of detailed maps of European strata and fossils formulated the geological periods we use today. 

1831

Charles Lyell

240 million year old Earth

By estimating the life of fossils of marine mollusks.

Advocate of Uniformitarianism instead of Catastrophism

First to divided Tertiary rocks into three Epochs

Close friend of Charles Darwin, helped to arrange the co-publication of the theory with Alfred Russel Wallace.

Never fully accepted natural selection as driving evolution because it was too slow

1785-1873

Adam Sedgwick

One of the first modern geologists.

Proposed the Devonian and Cambrian periods

Opposed evolution and the book by Chambers - he believed in a succession of Divine Creative acts throughout a long history - man is separate from animals

1844

Robert Chambers

Book - Vestiges of the Natural History of Creation

A working theory tying together many peoples' theories using "natural laws" (some true some not) instead of miracles.  Lamarck had been publicly discredited for belief in non-genetic traits being passed on to offspring.  So Chambers published the book anonymously.

Simple to complex changes (with Caucasian man as ultimate) but realized there is a "shifting as well as advance" (now called extinction)

Transmutation (now called evolution) everything current developed from earlier forms, planets, minerals, plants, animals, man

Believed God set up the process of Natural Laws but did not constantly fiddle with it. An omnipotent creator, who was always with the creation, would know it would succeed.

1809-1882

Charles Darwin

Geological student and friend of Adam Sedgwick

Observations while on the Beagle supported Uniformitarianism of Charles Lyell's

1837 - first - role of earthworms in the formation of soil

1938 - his first thoughts on natural selection theory

1839 - book Voyage of the Beagle

1858 - co-author with Alfred Wallace on the paper that describes natural selection

1859 - book On the Origin of Species

1823-1913

Alfred Russel Wallace

A naturalist who went in search of evidence to prove Robert Chambers' theories.

1853 - Realized geographical barriers separate closely related species.

1858 - co-author with Darwin on the paper that describes natural selection

1867-1878 - with Jenner Weir - theory that conspicuous coloration could be used as a warning to predators - Darwin preferred coloration as only for sexual selection

1889 - book defending natural selection

Early environmentalist and socialist

1896

Henri Becquerel

discovered radioactivity

By estimating the time it would take for a molten planet to cool using improved calculations

Cooling rate of a molten planet

by calculating the rate salt is delivered to oceans

1903

George Darwin & Joly

Realized that radioactivity allowed the Earth and Sun an internal heat source.

Geologist had argued for a much older Earth than 100 million years for generations.

Using radioactive decay of rocks and minerals.

Using the Hubble constant of a uniformly expanding universe

Using the Hubble constant of a uniformly expanding universe but thought "recent" data made it older.

Estimated age of galactic clusters.

using Hubble constant for very distant stars

estimated age of the oldest white dwarfs thought to have been stars 1 billion years after the Big Bang

estimating age of the oldest star clusters.