Historical Geology

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Historical Geology

• 46010201

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• Jim Wright
• Wright Laboratories, Room 233D
• 732-445-5722
• email jdwright_at_rci.rutgers.edu
• Office Hours 1230-130 T-Th

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Historical Geology

• Text
• S. Stanley, 2005.
• Earth System History (Freeman).
• Web Site
• http//rockbox.rutgers.edu/jdwright/Historical/Sy
  llabus.htm
• http//www.iclicker.com

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Historical Geology

• Grading
• Three exams will count for 30 each of the final
  grade.
• Pop quizzes will count for 10. Will be
  administered using Iclicker.
• Final Exam is NOT cumulative
• "No make-up exams will be given without WRITTEN
  documentation from a Rutgers University
  official."

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Chapter 6
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I. Exploring the Earths System

• Themes
• A. Immensity of Time
• B. Plate Tectonics
• C. Organic Evolution

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Important Point

• Appreciate the Earth as a system comprising both
  physio-chemical and biological components and
  begin to see how this perspective provides
  important insights into how current and future
  environmental changes may affect us.

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Earth System History

• Study of the inter- connected physiochemical and
  biological changes that our planet has
  experienced over the course of geologic time

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I. Exploring the Earths System

• A. Physical
• 1. Plate Tectonics, mountains, the rock cycle,
  chemical reactions, climate
• B. Biological
• 1. Bacteria ? the origin of plants and animals
• C. Physical and biological components are
  intertwined
• 1. Must study system as a whole - not individual
  components
• 2. Physical environments influence life??creates
  niches for evolutions, hostile environments
• 3. Biology can influence physical environment
  ??facilitate erosion, change the atmosphere CO2

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Foundations of Geology

• Principle of Uniformitarianism
• There are inviolable laws of nature that have not
  changed in the course of time
• First founding principle of geology
• James Hutton
• Actualism
• Application of modern processes to ancient system
• The Present is the Key to the past.

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Actualism

• Modern ripples provide clues to ancient systems

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II. The Principle of Uniformitarianism

• Exceptions
• Rocks formed under conditions that no longer
  exist ??Banded Iron Formations
• b. Conditions exist but cannot be observed
  ??Depth, metamorphism - Lab results may simulate
  these conditions.
• c. Conditions exist at present, but require long
  time periods to form.

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III. The Founders of Historical Geology

• A. Greeks
• Herodotus, a Greek historian, concluded in 400 BC
  that the Med. was at one time more widespread and
  that the Nile delta was constructed from great
  volumes of sediment that had been transported and
  deposited by the Nile River. (Modern
  sedimentology?) But, he believed most features
  were the result of sudden, violent processes.
• Herodotus is the first writer to make a conscious
  attempt to discover and explain past events. He
  is rightly known as the 'father of history'.

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III. The Founders of Historical Geology

• Aristotle (384-322 BC) recognized river deposits
  and realized that fossil seashells from rocks
  were similar to those found on the beach,
  indicating the fossils were once living animals.
  He deduced that the positions of land and sea had
  changed and thought these changes occurred over
  long periods of time.

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III. The Founders of Historical Geology

• 3. Eratosthenes (250 BC) calculated the
  circumference of the Earth by measuring noontime
  shadows at two localities of different latitude.
  He extrapolated the distance from his reference
  points at Syene and Alexandria in Egypt and
  determined Earth's circumference to be 40,000
  km, a remarkably accurate estimate and major
  scientific accomplishment.

(40,045km)
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III. The Founders of Historical Geology
Eratosthenes knew that at the summer solstice the
sun shone directly into a well at Syene at noon.
He found that at the same time, in Alexandria,
Egypt, approximately 787 km due north of Syene
(now Aswan), the angle of inclination of the
suns rays was about 7.2. With these
measurements he computed the diameter and
circumference of the earth as we will do.
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III. The Founders of Historical Geology
Eratosthenes also measured the tilt of the Earth
axis as 23.5 degrees, which gives us the seasons.
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III. The Founders of Historical Geology

• B. Romans - Grecian theories of scientific
  inquiry transcended time and culture and were
  inherited by Roman scholars.
• Pliny the Elder (23-79 AD)
• Or Caius Plinius Secundus (23-79)
• Roman officer and encyclopedist,
• author of the Natural history.

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III. The Founders of Historical Geology

• Pliny the Elder (23-79 AD) reached similar
  conclusions as those of the Greeks concerning the
  distribution of land and sea modern and fossil
  shell comparisons,

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III. The Founders of Historical Geology

• Pliny the Elder wanted to study the eruption of
  Vesuvius but died trying to rescue people (August
  25).

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III. The Founders of Historical Geology

• An Italian monk, Dionysius Exiguus, was
  commissioned by the pope in AD 525 to work out a
  Christian chronology. Using earlier tables, he
  concludes that Jesus Christ was born in the Roman
  year 753 AUC. He therefore proposes that the
  Christian era begins at the start of the
  following year. 1 January 754 AUC (Roman
  calendar) becomes 1 January AD 1.

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III. The Founders of Historical Geology

• From other sources of evidence it later becomes
  clear that Jesus must have been born before 4 BC
  - the date of the death of Herod, from whose
  massacre the infant Jesus is supposed to have
  escaped. But this does not make the new
  chronology any less useful for dating subsequent
  events, once the chronology is widely used (a
  process which takes some time to achieve).

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III. The Founders of Historical Geology

• C. --- The Dark Ages (500-1100 AD) ---
• Decline of the Roman Empire - Principle of
  uniformity of nature's processes, along with
  scientific inquiry suffered a critical blow -
• The DARK AND MIDDLE AGES. For 1000 years,
  Religious dogma held sway and any departures from
  the structures of the time was considered a
  serious offense.

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III. The Founders of Historical Geology

• D. --- Printing Press invented (1450)
  Renaissance begins ---
• The Renaissance - advance in many scientific
  fields - development of scientific principles -
  Copernicus, Kepler and Galileo put the Earth in a
  new cosmic context (Astronomy).
• Geology - another story - religious climate still
  limited advances in geology - the science of the
  Earth itself. Genesis portrayed an Earth that
  was 6000 yrs. old. Creationists considered the
  Earth as stable since the Noachian flood
  catastrophe.

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III. The Founders of Historical Geology

1. Leonardo da Vinci (1452-1519) recognized that
   material carried by rivers to the sea was
   eventually compacted into sedimentary rock and
   later uplifted to form mountains.
2. He concurred with Aristotle's view that fossils
   were the remains of ancient life.

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III. The Founders of Historical Geology

• Doubted the Great Flood
• "if the shells had been carried by the muddy
  deluge they would have been mixed up, and
  separated from each other amidst the mud, and not
  in regular steps and layers -- as we see them now
  in our time."

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III. The Founders of Historical Geology

• Leonardo's answer
• "it must be presumed that in those places there
  were sea coasts, where all the shells were thrown
  up, broken, and divided. . ." Where there is now
  land, there was once ocean.

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III. The Founders of Historical Geology

• 2. James Ussher (1581-1665) was the first to
  estimate the age of the Earth using genealogies
  of the Bible. Ussher stated in 1650 that the
  Earth was created on October 22, 4004 BC. This
  date was later reproduced in many editions of the
  Bible and was incorporated into the dogma of the
  Christian church. For nearly a century
  thereafter, it was considered heresy to assume
  that Earth and its puzzling geologic features
  were more than 6000 years old. Thus, a very
  young Earth provided a basis for most
  chronologies until the 18th century.

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III. The Founders of Historical Geology

• 3. Nicholas Steno or Neils Stensen (Danish
  physician, 1638-1687)
• Studies of Italian geology - settled in Florence
  Italy - Physician to the Grand Duke of Tuscany
• - ample time to explore and follow interests

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III. The Founders of Historical Geology

• THE PRINCIPLE OF SUPERPOSITION
• In a sequence of strata, any stratum is younger
  than the sequence of strata on which it rests,
  and is older than the strata that rest upon it.
• "...at the time when any given stratum was being
  formed, all the matter resting upon it was fluid,
  and, therefore, at the time when the lower
  stratum was being formed, none of the upper
  strata existed." Steno, 1669.

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III. The Founders of Historical Geology

• PRINCIPLE OF INITIAL HORIZONTALITY
• Strata are deposited horizontally and then
  deformed to various attitudes later.
• "Strata either perpendicular to the horizon or
  inclined to the horizon were at one time parallel
  to the horizon." Steno, 1669.

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III. The Founders of Historical Geology

• PRINCIPLE OF CROSS CUTTING RELATIONSHIPS
• Things that cross-cut layers probably postdate
  them.
• "If a body or discontinuity cuts across a
  stratum, it must have formed after that stratum."
  Steno, 1669

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III. The Founders of Historical Geology

• PRINCIPLE OF STRATA CONTINUITY
• Strata can be assumed to have continued
  laterally far from where they presently end.
• "Material forming any stratum were continuous
  over the surface of the Earth unless some other
  solid bodies stood in the way." Steno, 1669

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Stenos Principles

• Principle of Superposition
• Oldest strata are at the bottom in an undisturbed
  sequence of strata
• Principle of Original Horizontality
• All strata are horizontal when they form
• Principle of Original Lateral Continuity
• Strata originally are unbroken flat expanses
• Interrupted by erosion

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Figure 1-11 (p. 11)An example of how the
sequence of geologic events can be determined
from cross-cutting relationships and
superposition.
From first to last, the sequence indicated in the
cross-section is first deposition of D, then
faulting to produce fault B, then intrusion of
igneous rock mass C, and finally erosion followed
by deposition of E. Strata labeled D are oldest,
and strata labeled E are youngest.
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Cross-cutting Relationships

• Principle of Intrusive Relationships
• Intrusive igneous rocks are always younger than
  the rock they invade
• Principle of Components
• Fragments within a second body of rock are older
  than the second body of rock

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III. The Founders of Historical Geology

• Abraham Gottlob Werner (German, 1750-1817)
• Professor Mineralogy, Freiberg Mining Academy
• Internationally known - first great synthesizer
  of geologic knowledge - Carried the idea that all
  crystalline rocks formed at one time to an
  extreme. Zealously nurtured the idea that all
  rocks of the Earths crust, regardless of
  composition were precipitates of the world
  encompassing primeval ocean.

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III. The Founders of Historical Geology

• Abraham Gottlob Werner
• Hot and steamy ocean full of dissolved minerals
  needed to form the rocks. As the ocean shrank
  (subsidence and cooling), it left behind the
  precipitated layers arranged in superpositional
  order.
• Each layer was considered to have its own
  composition and be of the same age everywhere.
  "neptunism" because water was the forming agent.

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III. The Founders of Historical Geology

• Neptunism was appealing because it was
  consistent with the biblical account of the
  creation. Young Earth - 6000 yrs. old.
• Problems - where did the water go? Same origin
  for basalt as for shales, limestones etc.
• J.F. DAubisson de Voisins proved volcanic
  origin of basalts

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III. The Founders of Historical Geology

• James Hutton (Scottish, 1726-1797) Physician
  turned geologist. Not bound by the arithmetic of
  the biblical chronology. Demonstrated that rock
  units and relationships were not worldwide, but
  regional. Conflict - origin of basalt in a
  Primitive Series - Neptunist - Ocean ppt.
• Hutton demonstrated that basalt could form as an
  intrusive body. Cross cutting granite dikes
  through stratified rocks led him to igneous
  origin and that they were molten when they forced
  their way into fissures. Plutonists.

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III. The Founders of Historical Geology

• James Hutton
• Dynamic/cyclic concept of earth history -
  recognized that every rock formation no matter
  how old, appeared to have been derived from other
  rocks, still older rocks.
• Earth is always changing.
• Succession of Worlds.
• Destruction through erosion and weathering.

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III. The Founders of Historical Geology

• James Hutton
• Principle of Uniformitarianism (Actualism) -
  Hutton was convinced that the geologic processes
  in the past were no different from the present.
• No powers that are not natural to the globe, no
  action to be admitted of except those of which we
  know the principle, and no extraordinary events
  to be alleged in order to explain a common
  appearance.

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III. The Founders of Historical Geology

• James Hutton
• Hutton never used Uniformitarianism (William
  Whewell). The present is the key to the past
  Sir Archibald Geike.

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III. The Founders of Historical Geology

• James Hutton
• Concept of immense length of geologic time -
  Recognized the importance of unconformities and
  cross-cutting features.
• The result, therefore, of our present inquiry
  is that we find no vestige of a beginning and no
  prospect of an end. Irreconcilable with 6000
  yr. old earth. Hutton credited with idea of Deep
  Time.

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Siccar Point

• This is Siccar Point, Berwickshire, Scotland
  (about 50 kilometers east of Edinburgh). It is a
  place made famous by James Hutton, who came here
  in a boat in the 1780s, accompanied by his
  friends John Playfair and James Hall.

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Figure 1-8 (p. 8)Angular unconformity at Siccar
Point, eastern Scotland. (A) It was here that
James Hutton first realized the historical
significance of an unconformity. The drawings (B)
indicate the sequence of events documented in
this famous exposure.
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III. The Founders of Historical Geology

• Charles Lyell (English, 1797-1875)
• 1. Advocate and author exposing views of ancient
  earth history and Uniformitarianism - collection,
  organized and presentation the data in support of
  Uniformitarianism. Huttons view of the Earth
  and Playfairs clarification were slow to take
  hold.

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III. The Founders of Historical Geology

• Lyells crusade
• a) establishment of uniformitarianism at the
  expense of catastrophism as the acceptable
  philosophy for interpreting the history of the
  Earth
• b) establishment of geology among the sciences as
  a discipline based on inductive principles

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III. The Founders of Historical Geology

• Charles Lyell
• Author of important text Principles of Geology
  (1830)
• Synthesizer of stratigraphy who developed the
  first geologic time scale- Founded Modern
  Historical Geology and reintroduced Unlimited
  time.
• Unlike Hutton, Lyell was a historian who realized
  the primary task of geology was the unraveling of
  the Earth events in time. Used Faunal
  succession. Successive cycles

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Figure 1-12 (p. 11)(A) Granite inclusions in
sandstone indicate that granite is the older
unit.(B) Inclusions of sandstone in granite
indicate that sandstone is the older unit.
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Siccar Point
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Siccar Point
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Unconformity

• Substantial interval of time when erosion
  occurred rather than deposition