Chapter 2
The Origins of Matter,
the Universe and the Earth
Where Did It All Begin?
The Big Bang 15-12 bybp
Formation of Solar System 5.0-4.5 bybp
Cosmogenesis
• Cosmology – the study of the universe
• Origin of the Universe – Big Bang, 13.73 bya
• Matter and energy form and the universe
rapidly expands
• ~200 million years of Dark Ages before any
stars formed and light could be emitted from
them
• After another ~200 million years, stars begin
forming galaxies
The Universe Evolves and the Rate
of Expansion Continues to Increase
Courtesy of NASA/WMAP Science Team.
Figure 01: Big Bang to now
Mathematically, The Universe Is
Actually Flat, But Can Still Expand
There is still a lot to be learned about the origin and nature of the universe
? ?
Figure 02B: Dark Energy
and Dark Matter neither
absorb nor emit light
Some cosmologists argue that
there is a multiverse
Figure 02A: The universe is
made up of atoms
The Future of the Universe
• Density of ordinary matter in the universe is
extraordinarily low, ~six hydrogen atoms per
cubic meter on average
• If the universe had contained much more
matter, it would have collapsed back on itself
• If the universe had contained much less
matter, it would have expanded forever, but
probably never formed stars
Origin of the Solar System
• Interstellar dust and
gases disturbed by a
nearby supernova
• Gravity causes matter
to coalesce into the
sun, planets, moons,
asteroids, comets, etc.
• Formation requires
more than 100 million
years
Origin of the Solar System
• 5-5.6 bya Solar nebula
• 4.6 bya Sun and accretion disc
• 4.5 bya 4 inner terrestrial planets
4 outer gaseous planets
asteroids, comets, dwarf planets
Figure 03D:
Solidification of
planets
Early Earth Is Molten
Origin of the Moon
•
•
•
•
Big Whack
Earth collides with Mars-sized object
Ejected matter coalesces to form the Moon
Oldest Moon rocks are dated to 4.5 bya
The Moon Forms ―
A Major Influence on Living Systems
Theia makes a Big Splash; 30–50 million
years after the origin of the Solar System
What Makes Earth So Special?
• Size of the Sun
• Orbital distance from the
earth to the sun
• Mixture of atomic elements
• Liquid water
• Ozone layer
• Magnetic field
The Earth’s Structure
Figure 04: Section through Earth, which has a radius of 6,357 km
Early Earth Atmosphere
• First Atmosphere ― a reducing atmosphere
– Probably H2 and Helium which were lost to space
early in Earth's history because Earth's gravity is not
strong enough to hold these lighter gases
– Once the earth’s core differentiated, the heavier gases
could be retained
• Second Atmosphere ― a reducing atmosphere
– Produced by volcanic out gassing
– Gases produced were probably similar to those
created by modern volcanoes (H2O, CO2, SO2, CO, S2,
Cl2, N2, H2) and NH3 (ammonia) and CH4 (methane)
– No free O2 at this time (not found in volcanic gases)
Earth's Early Atmosphere and Oceans
• Volcanic eruptions spewed gases from Earth's
interior to the atmosphere, a process called
outgassing that continues today
• Most of the gas was carbon dioxide and water
vapor
• The water vapor condensed to form part of
Earth's oceans as the surface cooled
• Comets may also have contributed water and
complex organic molecules to the Earth's
environment
Earth's Early Atmosphere and Ocea
Second Atmosphere ― a reducing atmosp
H2O, CO2, SO2, CO, S2, Cl2, N2, H2 and
NH3 (ammonia) and CH4 (methane)
No free O2
Earth Evolves
• Hadean Era (from Hades, hell) is the first ~500
million years of earth’s life history
• 4.4 Bya - old zircon crystals required liquid
water and low temperatures to form
• 4.1 – 3.8 Bya - intense bombardment by
meteorites and comets would have sterilized
the planet’s surface
The Earth’s Crust Cools
• The oldest surviving rocks on Earth are dated
to ~4.28 Bya* and are found near Hudson’s
Bay in Canada (2010) [*controversial date]
• So all of the activity of Earth's birth was
already ancient history (except for a possible
"late bombardment" of the last stray
planetessimals around 4 Bya ago)
• Slightly younger rocks, dated by the uraniumlead method at ~3.96 Bya, show that there
were volcanoes, continents, oceans, crustal
plates, and life on Earth by then
Hadean Lasts ~0.5 Billion Years
The Formation of Rocks in the
Lithosphere of the Earth’s Crust
Figure 05: Rock cycle
Adapted from Hawkesworth, C.J. and A.I.A. Kemp, Nature 443 (2006): 811-817.
The Third Atmosphere (Current)
• Organic molecules
• Nitrogen, Oxygen
• O2 from cyanobacterial photosynthesis
• Autotrophs consume CO2
• Ozone (O3) layer forms gradually
• Ozone blocks uv radiation which reduces
mutation rates in DNA
Stromatolites – Colonial Cyanobacteria
O2 from cyanobacterial photosynthesis
Dating Earth’s Rocks and Fossils
• Igneous rocks
– ~65% of the total crust volume
– 17-20% of the exposed crust
• Sedimentary rocks
– ~8% of the total crust volume
– 50-55% of the exposed crust
• Metamorphic rocks
– ~25% of the total crust volume
– 25-30% of the exposed crust
Radioactive Decay
A Closer Look at Radiometric Dating
Parent and Daughter Isotopes Used in
Radiometric Dating
Carbon Isotopes
• While alive, organisms
accumulate both ordinary
carbon (C12) and its unstable
isotope carbon-14 (C14)into
their tissues in proportion to
their availability in the
atmosphere
• During its lifetime, an organism
continually replenishes its
supply of C14 by photosynthesis,
respiration and absorbing or
ingesting nutrients
Radiocarbon
Dating
• When the organism dies, stable C12 persists, but unstable
C14 decays to N14 at a constant rate and is slowly lost from
the fossil
• To measure the amount of radiocarbon left in a fossil,
scientists burn a small piece to convert it into carbon
dioxide gas
• Radiation counters are used to detect the electrons given
off by decaying C14 as it turns into nitrogen
Radiocarbon (C14) Dating
• The more time that passes, the
more C14 is lost from the fossil,
thereby changing the
proportion of C14 to C12 with
the passage of time
• Consequently by measuring
the proportion of C12 to the
remaining C14, scientists are
able to calculate the geologic
age of the fossil
C14 / C12
The History of Life Now Runs Some
4.6 Billion Years
Abiogenesis
Brief History of Geology
• Greek Natural Philosophers were interested in
the nature of matter and the age of the Earth
• Xenophanes of Colophon (570-480 B.C.E.)
recognized that some fossil shells were
remains of shellfish, and, therefore, that sea
floors had risen over time
• Aristotle (384 – 322 B.C.E.) observed a slow
rate for geological change, undetectable in the
lifetime of a human being
Brief History of Geology
• Shen Kuo (1031 - 1095) of the Song Dynasty in
China used the evidence of uplifted marine
fossils found in neighboring mountains to
propose gradual climatic and geological
change
• Many Islamic Natural Philophers also
contributed to the developing principles of
earth science
Brief History of Geology
• Ibn Sina (981-1037), a
Persian, known to later
Europeans as “Avicenna,”
elaborated concepts related
to earthquakes, mountain
building, rock strata
formation, and an
understanding of what we
would call the Theories of
Catastrophism and
Uniformitarianism in
Geology
Brief History of Geology
• Isaac Newton (16431727) calculated that an
Earth-sized sphere
would require 50,000
years to cool to its
present temperature
• As a pious Christian, he
felt obliged to reject his
own calculations
Brief History of Geology
• Georges-Louis Leclerc, Comte
de Buffon (1707-1788)
• Buffon calculated that the
age of the earth was 75,000
years, basing his figures on
the cooling rate of iron
• The Sorbonne (Paris Faculty
of Theology) forced him to
issue a retraction
Brief History of Geology
• James Hutton, MD (17261797), a Scot, is the Father
of modern Geology, though
his “uniformitarian”
proposals were obscured by
his difficult writing style
• He recognized both
sedimentation and
vulcanism as sources for
rock strata
Brief History of Geology
• Alexandre Brongniart (1770 –
1847) was an colleague of Cuvier’s
and made important contributions
to geology and paleontology
• 18th century Neptunists (founder
the German Abraham Werner
(1749-1817)) advocated that the
Noachian Flood formed all rock
strata
Brief History of Geology
• James Hutton proposed Plutonism
which advocated that volcanic
activity formed most rock strata
formation with sedimentation as a
secondary process
• John Playfair (1748-1819) restated
Hutton’s ideas in Illustrations of the
Huttonian Theory of the Earth
(1802)
The Principle of Faunal Succession
• William Smith noted that
different rock strata
contain particular types of
fossilized flora and fauna,
and that these fossil forms
and communities succeed
each other in a specific
and predictable order that
can be identified over
wide distances
Geologist William Smith
(1769-1839)
Baron Georges Cuvier (1769-1832)
• Accepted some fossils as
evidence of extinctions, in
opposition to Buffon
• Recognized evidence of
stratification of rock layers,
examples of sedimentation,
uplift and subsidence
• Recognized a Principle of
Faunal Succession used to
assign times to geologic
strata
Cuvier’s Theory of Catastrophism
• Cuvier proposed a Theory of Catastrophism to
explain extinct organisms
• Cuvier and other catastrophists were scientists and,
in accord with expanding data, proposed an
increasing number of natural catastrophes to
explain the many extinct faunal assemblages
• Cuvier was a harsh critic of theories of
transmutation of species (“evolution”) but did not
advocate special creation as did some of his fellow
catastrophists and the Natural Theologians
19th Century Geologists
Baron Georges Léopold
Chrétien Frédéric Dagobert Cuvier
(1769-1832)
Catastrophism
The Animal Kingdom, Distributed According
to Its Organization (1817) made major
improvements to the Linnaean system of
classification of the living world.
19th Century Catastrophists
Accepted that the Earth Was
Many Thousands of Years Old
Richard Owen (1804-1892)
Louis Agassiz (1807-1873)
19th Century Geologists
Sir Charles Lyell (1797-1875)
3 vols.
1830-1833
Uniformitarianism
A mentor to Darwin
Sir Charles Lyell (1797-1875)
• Uniformitarianism: “the
present is the key to the past”
• Modest observable processes
acting today (rain, wind,
earthquakes, sedimentation,
erosion) explain the changes in
the earth’s surface when they
act over very long periods of
time
• Lyell accepted Darwinism, but
uncomfortably, because of
Lyell‘s own religious beliefs
Lyell Observed Sea Level Changes Through
Time on Roman Columns in Naples, Italy
Figure 06: Frontispiece of Lyell’s 1830 Principles of Geology
© maurizio grimaldi/age fotostock
The Age of the Earth
• The conflict between Catastrophism and
Uniformitarianism intensified the interest in
determining the age of the earth
• [Both terms coined by William Whewell
(1794-1866)]
• Recall Bishop Usher proposed ~6000 years
• Lyell initially thought of hundreds of
thousands of years; eventually he thought of
millions of years
19th Century’s Best Estimate of the Age
of the Earth
• William Thomson, Lord Kelvin (1824-1907), the
foremost Victorian era physicist estimated the
age of the earth at 15-20 mybp maximum; too
young for Darwin’s hypotheses of gradual
macroevolution
• Based his calculations of thermodynamic
properties, comparing the size and temperature
of the sun and earth, and estimating the rate of
cooling of the earth
• The 20th century discovery of radioactive isotope
decay in the Earth’s core as the heat source
which refuted Kelvin’s calculations
Darwin’s Contributions to Geology and
Paleontology
• Darwin had training as a geologist
• Darwin made extensive observations and
collections of strata and their fossils while on
excursion from the Beagle
• Darwin studied coral reefs and atolls and
explained their formation by incremental
growth
• Darwin linked geographical distribution of
organisms to the geology of their locations
Darwin’s Evidence
for Evolution
• Darwin’s The Origin of Species (1859)
– documents that fact that evolution has occurred
– gives examples of artificial and natural selection to
explain the mechanism of evolution
– includes considerable evidence from comparative
anatomy and comparative embryology
– invokes Uniformitarianism to give time for gradual
change
– relies very little on the fossil record, a record still quite
meager in the 1850s
The Great Exhibition of 1851
in Hyde Park, London
 Sponsored by Queen Victoria and Prince Albert, included
the famous Crystal Palace and elaborate outdoor displays
including the first life-sized restorations of dinosaurs, which
brought home the fact of extinction to the common people
 By the time of Darwin’s publication of The Origin of Species,
in 1859, the list of extinct species would have only been in
the hundreds
Crystal Palace
Now there are tens
of thousands of fossil
forms known from
the Fossil Record
Crystal Palace Dinosaurs
Important Principles of Geology
• Uniformitarianism – the central principle
• Original Horizontality - sediments form horizontal
layers; volcanic/igneous material may or may not;
any tipping or bending must have occurred later
• Superposition - strata, if undisturbed, form a
vertical time line, whether sedimentary or
volcanic/igneous or a mixture; younger rocks are on
top of older
Important Principles of Geology
• Intrusive Relationships - when volcanic/igneous
material penetrates into sedimentary strata, it is
younger
• Inclusions - newly formed strata (sediments or
igneous flows) may surround older material such as
gravels, cobbles, or boulders
• Cross-Cutting Relationships - when strata break and
faults develop, the faults are younger than the
surrounding strata and any material which fills into
a fault is younger still
Important Principles of Geology
• Faunal Succession – fossil organisms change
through time and may be used to give relative ages
to strata in different locations
• Faunal Succession - earlier fossil life forms are
simpler than more recent forms, and more recent
forms are more similar to existing forms
– [We now recognize that earlier fossil life forms are not
always simpler than more recent forms.]
A Geologic Column is a vertical diagram of the layers of rock strata at a
particular location. No column at any location on earth contains all the strata
from the entire geologic record. For decades, study of relationships among
sedimentary strata
columns was the only way to establish relative dates.
Stratigraphy
• Sediment settling out of water
collects at the bottom of lakes
• As more sediment collects, the
deeper layers are compacted by
the ones above until they harden
and become rock
• Animal remains become
embedded in these various layers
• Deeper rock forms first and is
older than rock near the surface
• Logically, fossils in deeper rock
are older than those above, and
their position within these rock
layers gives them a chronological
age relative to older (deeper) or
younger (surface) fossils
Stratigraphy
• Fossil animals and plants occur in sedimentary rocks
deposited on oceanic shorelines, one atop the other
• Subsequent cracks in the Earth’s surface, weathering,
or erosion by a river open these ancient sedimentary
deposits, exposing their cache of fossils
Making Fossils
• The remains of extinct animals that
persist have escaped the appetites of
scavengers, decomposers, and later
tectonic shifting of the Earth’s crustal
plates in which they reside
• Most surviving fossils are of dead
animals that quickly became covered by
water and escaped the notice of
marauding scavengers
• As more and more silt is deposited over
time, the fossil becomes even more
deeply buried in soil compacted into
hardened rock
• For the fossil held in the rock to be
exposed, the Earth must open either by
fracture or by the eroding action of a
river
Fossil Dig in Wyoming
• (a) Partially exposed dinosaur bones.
The work crew prepares the site and
notes the location of each excavated
part
• (b) This Triceratops femur is
wrapped in a plastic jacket to
prevent disintegration or damage
during transport back to the
museum
Restoration of a Fossil
a) This skeleton of the extinct short-faced
bear, Arctodus simus, is positioned in a
likely posture in life
b) Scars on the bones from muscular
attachments and knowledge of general
muscle anatomy from living bears
allow paleontologists to restore
muscles and create the basic body
shape
c) Hair added to the surface completes
the picture and gives us an idea of
what this bear might have looked like
in its Alaskan habitat 20,000 years ago
Index Fossils
• After careful study at many well-dated sites, paleontologists can confirm
that certain fossils occur only at restricted time horizons (in specific rock
layers)
• These distinctive index fossils are diagnostic fossil species used to date
rocks in new exposures
• In this example, the absence of index fossils confirms that layer B does not
exist at the third location
• Perhaps rock-forming processes never reached the area during this time
period, or the layer was eroded away before layer C formed
Building a Chronology of Fossils
• Each exposure of rocks
can be of a different age
from other exposures
• To build up an overall
sequence of fossils,
various exposures can be
matched where they
share similar sedimentary
1
2
3
4
layers (layers of the same
ages) Data from five sites in the southwest United States:
5
overlapping time intervals allow paleontologists to build a
chronology of fossils greater than that at any single site
Geological Time Intervals
• The Earth’s history, from its
beginnings ~4.6 billion years
ago, is divided into four
major eons of unequal
length—Hadean, Archean,
Proterozoic, and
Phanerozoic
• Each eon is divided into
periods, and periods into
epochs
• Only epochs of the Cenozoic
are listed in this figure
Index Fossils for Major Epochs
Figure T02:
Geological Ages
and Associate
Organic Events
Note: Dates derived mostly from Gradstein et al. A
Geological Time Scale. Cambridge University Press,
2004 and Geologic Time Scale, available from
http://www.stratigraphy.org, Accessed January
2010.
Evidence of Environmental Change
The Grand Canyon in Arizona:
The Strata Date From 0.25 to 1.7 Billions Years Ago
Different Fossil Organisms in Different Strata of Sedimentary Rock
Document Different Climate and Environmental Conditions Through Time
The Geologic Time Scale
Youngest
Students: You should become familiar with
The Eons, Eras, Periods, and Epochs by name;
I don’t expect you to remember the # of m years
Oldest
Correspondence Among Data Sets
• When several independent lines of evidence are in
agreement, the confidence in the results is greatly
increased
• Today geologists can use evidence from fossils and
transitions between fossil types and even fossil
communities, evidence from the study of geologic
columns and rock strata, evidence from Radiometric
and Geomagnetic Dating, and from Tectonic Plate
Movements to document the evolution of species
and communities through time
Geomagnetic Dating
Geomagnetic Dating
Paleomagnetism in volcanic strata
Paleomagnetism in volcanic sea floor
spreading
Continental Drift
• Alfred Wegener (1880 – 1930), a
German meteorologist, proposed
continental drift in 1912 based on
fossil and mineral distributions
and continental coast lines
• He proposed that all the
continents were once joined in a
single landmass, which he called
Pangea
• Plate Tectonics was not accepted
as the explanatory theory until the
1960s
Continental Drift
Alexander du Toit (1878-1948), South African geologist, was the only
major supporter of Wegener at the time Wegener first advocated
for continental drift
du Toit pioneered this theory in his book Our Wandering Continents
(1937) in which he provided considerable evidence of correlations
between the Atlantic coasts of South America and Africa, using
bio- and lithostratigraphy
Continental
Laurasia &
Drift
Gondwana
Pangaea
• Changing continental positions through most of the
Phanerozoic era. Time, in millions of years, is approximate.
Evidences for Continental Drift
• Fit of Continental
Margins
• Paleomagnetism
• Sea Floor Spreading
• Plate Tectonics
Figure 08: An oceanic ridge showing how
sea-floor spreading produces differently
magnetized belts
Supercontinent Pangea
Figure 07: Offshore continental shelves at 500 fathoms deep
on opposite sides of the Atlantic Ocean
Plate Tectonics
• Plate tectonics describes the large scale motions of Earth's lithosphere
• The theory encompasses the older concepts of continental drift, developed during
the first half of the 20th century, and seafloor spreading, understood during the
1960s
Plate Tectonics
Asthenosphere
• The outermost part of the Earth's
interior is made up of two layers:
above is the lithosphere,
comprising the crust and the rigid
uppermost part of the mantle
• Below the lithosphere lies the
asthenosphere
• Although solid, the asthenosphere
has relatively low viscosity and can
flow like a liquid on geological time
scales
• The deeper mantle below the
asthenosphere is more rigid again
due to the higher pressure
Plate Tectonics
• The lithosphere is broken up
into what are called tectonic
plates — in the case of
Earth, there are seven major
and many minor plates
• The lithospheric plates ride
on the asthenosphere
• Earthquakes, volcanic
activity, mountain-building,
and oceanic trench
formation occur along plate
boundaries
Tectonic Plates
Proponents of Continental Drift
• Alfred Wegener (1880 –
1930): proposed
continental drift based on
fossil and mineral
distributions and
continental coast lines
• Léon Croizat (1894 – 1982):
proposed continental drift
based on living organism
distributions
Léon Croizat (1894 – 1982)
• Léon Croizat was an Italian biologist,
whose career included time in the
USA (1936-47) and later in
Venezuela, also proposed
continental drift, more or less
independently, based on distribution
of communities of living organisms
• Croizat lived to see continental drift,
explained by Plate Tectonics,
accepted as a Theory in the 1960s
• He was still writing scientific papers
when he died at age 88!
Léon Croizat & Biogeography
• Croizat developed a new biogeographic methodology,
which he named Panbiogeography ― Based on the
metaphor that "life and earth evolve together" ― which
means that geographic barriers and biotas co-evolve
• This method was basically to plot distributions of organisms
on maps and connect the disjunct distribution areas or
collection localities together with lines called tracks
• Croizat found that individual tracks for unrelated groups of
organisms were repetitive, and considered the resulting
summary lines as generalized tracks which indicated the
preexistence of ancestral biotas, subsequently fragmented
by tectonic and/or climatic changes
Croizat’s Panbiogeographic Tracks
Similar taxa or communities of taxa are linked along the panbiogeographic tracks
Dispersal Versus Vicariance
• Darwin,
Wallace,
Simpson, and
most other
biogeographers,
before the
1960s, looked
for dispersal
events to
explain
distributions
Croizat and his disciples offer an alternative: Vicariance
Dinosaur Distribution: Vicariance
• During the middle of the Mesozoic
era, the dinosaur Allosaurus
occupied the large, single
continent of Pangaea
• Subsequently, as this continent
broke apart, populations of
Allosaurus became isolated from
each other and speciated into
other derivative carnivorous
species (Gigantotosaurus,
Carcharodontosaurus,
Acrocanthosaurus)
• The forming continents drifted into
their present positions today
The location of these fossil remains, now carried into
distant locations, are indicated by red dots
The Evolution of the Continents
Had Major Impacts on Life
Figure 10: Fossil animals on Gondwanan continents
Adapted from Colbert, C.H. Wandering Lands and Animals. Hutchinson, 1973.
The History of Life
Now Runs Some
4.6 Billion Years
Geologic Time
• The Universe is ~13-15 billion
years old
• Cosmic gases coalesced under
gravity’s pull to create the solar
system and Earth ~4.6 billion
years ago
• Life remained rare, simple and
small (“microbial”) until the
Cambrian period, or slightly
earlier, when the various
metazoans appeared, 0.54 Bya
> 99% of all
species are
already extinct!
We’ll talk more about the diversity of life in the coming chapters.
Chapter 2
End
The First 100 Seconds Produces the
Subatomic Particles of Matter
Table T01: The first 100 seconds in the life of the universe
Source: Riordan, M. and Zajc, W.A., Scientific American 294 (2006): 24-31.
Origin of the Solar
System
Figure 03C: Condensation of nebular
material
Figure 03A: Fragmentation of an
interstellar cloud
Figure 03B: Contraction and
flattening of the solar nebula
Figure 03D: Solidification of planets
Radiometric
Dating
• (a) Sand flows regularly from one state (upper portion) to another (lower portion)
in an hourglass. The more sand in the bottom, the more time has passed. By
comparing the amount of sand in the bottom with that remaining in the top and by
knowing the rate of flow, we can calculate the amount of time that has elapsed
since the flow in an hourglass was initiated. Similarly, knowing the rate of
transformation and the ratios of product to original isotope, we can calculate the
time that has passed for the radioactive material in rock to be transformed into its
more stable product.
Radiometric
Dating
•
•
(b) Half-life. It is convenient to visualize the rate of radioactive decay in terms of half-life, the
amount of time it takes an unstable isotope to lose half its original material. Shown in this
graph are successive half-lives. The amount remaining in each interval is half the amount
present during the preceding interval.
(c) A radioactive material undergoes decay, or loss of mass, at a regular rate that is
unaffected by most external influences, such as heat and pressure. When new rock is
formed, traces of radioactive materials are captured within the new rock and held along
with the product into which it is transformed over the subsequent course of time. By
measuring the ratio of product to remaining isotope, paleontologists can date the rock and
thus date the fossils it contains.
Figure 09: Tectonic plates
Adapted from Cloud, P. Cosmos, Earth and Man: A Short History of the
Universe. Yale University Press, 1978.