Historical Geology

1. Historical Geology 460:102:01

2. Jim Wright Wright Laboratories, Room 233D 732-445-5722 email: jdwright@rci.rutgers.edu Office Hours: 12:30-1:30 T-Th

3. Historical Geology Text: S. Stanley, 2005. Earth System History (Freeman). Web Site: http://rockbox.rutgers.edu/~jdwright/Historical/Syllabus.htm http://www.iclicker.com

4. 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."

6. Chapter 6

7. I. Exploring the Earth’s System Themes: A. Immensity of Time B. Plate Tectonics C. Organic Evolution

8. 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.

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

10. I. Exploring the Earth’s 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

11. 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.

12. Actualism • Modern ripples provide clues to ancient systems

13. 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.

14. 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'.

15. 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.

17. 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)

18. 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 sun’s rays was about 7.2°. With these measurements he computed the diameter and circumference of the earth as we will do.

19. III. The Founders of Historical Geology Eratosthenes also measured the tilt of the Earth axis as 23.5 degrees, which gives us the seasons.

20. 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.

21. 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,

22. III. The Founders of Historical Geology Pliny the Elder wanted to study the eruption of Vesuvius but died trying to rescue people (August 25).

23. 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.

24. 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).

25. 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.

26. 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.

27. III. The Founders of Historical Geology • 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. • He concurred with Aristotle's view that fossils were the remains of ancient life.

28. 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."

29. 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.

30. 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.

31. 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

32. 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.

35. 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.

37. 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

39. 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

40. Steno’s 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

43. 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.

44. 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

45. 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 Earth’s crust, regardless of composition were precipitates of the world encompassing primeval ocean.

46. 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.

47. 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. D’Aubisson de Voisins proved volcanic origin of basalts

48. 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.

49. 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.

50. 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.”