The Theory of the Ancient Earth

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The Theory of the Ancient Earth

• The Earth in Time

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Bishop Ussher Leonardo da Vinci Nicholas
Steno Robert Hooke Werner (the Neptunists) James
Hutton (the Plutonists) James Hutton
(Uniformitarianism) William Strata
Smith Georges Cuvier (Catastrophism) Charles
Lyell (Principles of Geology) Sedgwick and
Murchison Darwin Lord Kelvin (Deduction vs.
Induction) Alfred Wegener
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Anglican Archishop Ussher (1664) Calculated the
age of the Earth counting the begats in the
Bible. His estimate was that the Earth was 6000
years old, and put a birthdate on it October
23, 4004 B.C. Intellectual thought was
preserved in the church through the Dark Ages, so
most thinking, including the birth of science,
was intially rooted in church doctrine.
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• Some thinking Outside the Box
• Leonardo da Vinci 1500
• Described fossil shells in Northern Italy and
  correctly interpreted them as representing
  ancient life.
• The fossils were grouped into living
  communities.
• Shells were to fragile to be washed in by the
  Deluge, and 40 kilometers was too far for clams
  to migrate in 40 days.
• Fossils changed in successive strata, with
  strata in between that represented other
  geological events.

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Sedimentary Rock Terms Bed a layer of sediment
1 cm or more in thickness lamina(e) a layer of
sediment less than 1 cm. in thickness. (adj.
laminated). Bedding (Plane) The surface upon
which sediment was deposited. The surfaces
separating layers of sediment. Stratum a layer
of sedimentary rock (may be comprised of several
beds or laminae). Strata a set of layered
sedimentary rock.
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• Nicholas Steno in 1669
• 3 laws of superposition
• Principle of Superposition In a succession of
  strata, the oldest stratum is at the bottom with
  successively younger strata on top.
• Principle of Original Horizontality Sediment
  accumulated by gravity layering such that most
  strata was originally horizontal
• Principle of Lateral Continuity Strata
  originally continued laterally until they either
  thinned to 0 or terminated against the edges of a
  basin of deposition

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Fig. a.1
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• Nicholas Steno in 1669
• 3 laws of superposition
• Principle of Superposition In a succession of
  strata, the oldest stratum is at the bottom with
  successively younger strata on top.
• Principle of Original Horizontality Sediment
  accumulated by gravity layering such that most
  strata was originally horizontal
• Principle of Lateral Continuity Strata
  originally continued laterally until they either
  thinned to 0 or terminated against the edges of a
  basin of deposition

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Fig. 2.11
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• Nicholas Steno in 1669
• 3 laws of superposition
• Principle of Superposition In a succession of
  strata, the oldest stratum is at the bottom with
  successively younger strata on top.
• Principle of Original Horizontality Sediment
  accumulated by gravity layering such that most
  strata was originally horizontal
• Principle of Lateral Continuity Strata
  originally continued laterally until they either
  thinned to 0 or terminated against the edges of a
  basin of deposition

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Fig. a.6
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Fig. 2.11
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• Robert Hooke 1703
• 1. Fossils have fixed lifespans in the rock
  record (See William Smith and Georges Cuvier 100
  years later!!)
• They may be useful in making chronological
  comparisons of rocks the same age.
• These shells are the greatest and most lasting
  monuments of antiquity which in all probability,
  will far antedate all the most ancient momuments
  of the world, even the pyramids, obelisks,
  mummys, hieroglyphicks, and coins. Nor will
  there be wanting media or criteria of chronology
  which may give us some account even of the time
  when they formed. Robert Hooke, 1703

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Fig. 2.4
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Noahs Flood Like Bishop Usshers proclamation
for the Earths birthday, the Great Deluge was
dated November 18, 2349 B.C. With intellectual
thought still rooted in church doctrine, Noahs
flood concept gave rise to the first Earth origin
theory Neptunism
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Abraham Werner (the Neptunists), late 1700s
early 1800s Recognizes 3 rock types primitive
(primary), secondary, and tertiary, all deriving
from the Deluge (Noahs flood) ocean. Primitive
rocks are primary precipitates from
ocean Secondary are sedimentary flat lying
rocks. Tertiary are re-worked (weathered,
eroded, and re-deposited) rockshe recognized
older rocks in younger.
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Fig. 2.11
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Fig. 3.19
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James Hutton (the Plutonists), 1785 Recognizes
the igneous rock types as forming from melts
(magmas and lavas), not Werners primary
precipitates.
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James Hutton and the angular unconformity At
Siccar point in Scotland, Hutton observes an
angular unconformity in the Old Red Sandstone.
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Fig. a.2
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Fig. 2.14
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Fig. 2.16
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James Hutton and the angular unconformity At
Siccar Point in Scotland, Hutton observes an
angular unconformity in the Old Red Sandstone.
No vestige of a beginning, no prospect of an
end. -James Hutton The mind seemed to grow
giddy looking so far into the abyss of
time. -John Playfair (1805, at Siccar Point)
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• James Hutton, 1785 (uniformitarianism)
• Proposes that gradual processes acting today are
  the keys to understanding the past (interpreting
  the rock record), which becomes known as
  uniformitarianism.
• Uniformitarian view sharply contrasted with
  catastrophism
• Which is true, gradual processes or catastrophic
  processes? Becomes center of debate in 1800s,
  and echoes of the debate last to this day, but we
  recognize both processes have a role in Earths
  history.
• Our thinking now is called actualism the
  assumption that present laws of science would
  apply at all times thus presently known
  processes are presumed to have always acted in
  the same way but with greatly varying intensities.

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• William Strata Smith, early 1800s
• As a canal engineer, he realizes he can recognize
  strata across the countryside based on rock type
  similarities.
• Learns to identify strata across the countryside
  based on fossils.
• Produces first geologic map in 1815, which helps
  in locating coal.

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Fig. 2.8
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Georges Cuvier, 1820s 1.) Working in France
about the same time as Smith in England, he also
produces one of the first geologic maps. 2.)
First to recognize EXTINCTION for what it was. A
radical concept at the time, it paves the way for
evolutionary thinking. 3.) 27 separate creation
and extinction events, each separated by a
catastrophe. 4) Results in the catastophism
movement in geology.
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Fig. 2.5
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Charles Lyell (Principles of Geology),
1830 First geology textbook, formalizes
Huttons uniformitarian concepts. Apparently,
Lyell could writeHutton could not write so well.
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Adam Sedgwick and Roderick Murchison 1830s Forma
lly named 1st geologic time periods from
representative rocks in their area.
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Fig. 4.4
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Table. a.1
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Darwin (1859 1872) I think youve heard about
this guy before. More on him later, but he had
two books on his 1830s voyage on the HMS Beagle
where he formulated the Theory of Evolution 1.)
Charles Lyell, Principles of Geology 2.) Rev.
Thomas Malthus, Essay on Population Interesting
side note Darwin, Lyell, Newton, James Clerk
Maxwell, and others are buried side-by-side in
Westminster Abbey.
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• Lord Kelvin, late 1800s
• (20 million year age estimate for Earth)
• Deduces a 20 million year age estimate for Earth
  using rates of Earths heat loss from an
  originally molten-Earth origin to todays
  geothermal gradient.
• His estimate troubles Darwin immensely. Darwin
  knows he needs at least 300 my for his theory of
  evolution to work. Darwin dies not knowing the
  solution to this problem.
• Theory of Ancient Earth at this point is almost
  entirely from Induction
• At the time, Lord Kelvin was scientific royalty

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Lord Kelvin late 1800s (20 million year age
estimate for Earth) and he was WRONG! 1.)
Discovery of radioactivity Earth has its own
heat source. 2.) Discovery of radioactivity
Absolute age dating methods yield 4.5 billion
year old Earth.
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• Rate-based Age Dating
• Any estimate of the age of the Earth, or some
  span of geologic time represented by rocks,
  relies on an assumption that some rate is
  constant through time. This parsimonious
  assumption is a part of actualism.
• Examples
• Estimates of ages, or spans of time, from
  sedimentation rates (an age-of-Earth estimate
  came up short by neglecting periods of
  non-deposition and erosion).
• John Joly Age of Earth by rate of addition of
  salt to oceans (came up short neglected removal
  of salt from oceans in ocean sediments).
• Kelvin Age of Earth by rate of Earths heat
  loss (came up short neglected Earths
  radiogenic heat gains).
• Modern methods for calculating the age of Earth
  (or rock) based on rates of radioactive decay
  (known as absolute age dating).

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Fig. a.7
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Relative Age Dating Rate-based age dating relies
on deduction, starting from a principle or
assumption. To a geologist, the age of the Earth
is known largely by induction. One of the most
powerful inductive tools is relative age dating,
i.e. putting events (processes) in order, and
realizing the time associated with these events.
Relative Age dating tools 1.) Stenos laws
(already discussed). 2.) Correlation and lateral
tracing (already discussed). 3.) Cross-cutting
relationships (whatever is cutting is younger
than whats cut). 4.) Inclusions A rock
included in a host rock is older than the host.
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Fig. a.3
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Fig. a.5
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Fig. 5.1
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Fig. a.4
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Fig. a.8
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• Alfred Wegener, early 1900s
• Proposes continental drift to explain alignment
  of coastlines and rocks / fossil assemblages
  across the Atlantic.
• Hypothesis rejected as preposterous, What does a
  meteorologist know anyway?

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Fig. 2-1, p.13
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Fig. 3.14
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Fig. 3.13