Introduction to General geology Instructor: Prof. Dr. Boris Natalin
Instructors • Prof. Dr. Boris A. Natalin, • Office – E 502 • Phone – 285 6221, • e-mail: firstname.lastname@example.org • Website: http://web.itu.edu.tr/~natalin/ • Assistant: Cengiz Zabci • e-mail email@example.com
Textbook • Tarbuck, E. J. and Lutgens, F. K., 1996, Earth: an introduction to physical geology, Prentice Hall, Upper Saddle River, New Jersy, 605p. • Brown, G. C., Hawkesworth, C. J.,, and Wilson, R. C. L., 1992, Understanding the Earth, Camridge University Press, New York, 551p. 3) Posted readings
Examinations and control • Two examinations: The midterm examination will be after 8th lecture; the date of the final exam will be appointed later. • Quiz containing 3-5 questions. • 3 home works • One field trip
Grading • Final examination – 45 points • Midterm examination – 30 points. • Quizzes – 10 points • Homeworks – 15 points • I reserve the right to rise or reduce by 10 points the final mark on the basis of my impression about a student overall performance and enthusiasm • Minimal limit for success – 40 point.
Definition • Geology is the study of the Earth, the materials of which it is made, the structure of those materials, and the processes acting upon them. It includes the study of organisms that have inhabited our planet. An important part of geology is the study of how Earth’s materials, structures, processes, and organisms have changed over time
Geologists are “scientists” with unnatural obsessions with xxxxxx and rocks. Often too intelligent to do monotonous sciences like biology, chemistry, or physics, geologists devote their time to mud-worrying, volcano poking, fault finding, bouldering, dust-collecting, and high-risk colouring. One of the main difficulties in communicating with geologists is their belief that a million years is a short amount of time and their heads are harder than rocks. • “We will we will rock you!”
Geology is truly an interdisciplinary science, relying on the knowledge of chemistry, physics, biology and mathematics to fully understand the processes, which are at work on the surface of the earth and its interior. • Geology is also a multidisciplinary science (e.g. mineralogy, geophysics, geochemistry, etc.) and each geological discipline relies on its own method of study and data acquisition. • Geophysics – study of gravity, magnetic and electric fields of the Earth and its internal structure • Geochemistry – study of the chemical composition of the Earth, history of elements, their migration
Main geological disciplines • Mineralogy and crystallography • Petrography and petrology • Paleontology • Sedimentology • Stratigraphy • Geomorphology • Volcanology • Structural geology • Tectonics • Mineral deposits or economic geology
How geology was born? • Palaeolithic hunter-gatherers collected pyrite concretions, quartz and galena crystals, and fossil mussels • Neolithic (onset 10,000 to 8000 years BP) - first true divinities • Myth as explanation of nature • Noah’s flood • Pre-Socratic Greeks explained natural phenomena without involvements of gods. They thought that the universe was governed by unchanging principles and with intelligible and discoverable natural laws.
Historical perspective • Heraclitus, sixth century BC, - ever-changing world • Xenophanes of Colophon (sixth century BC) observed shells on the mountains and infer the sea level changes • Herodotus (fifth century BC) suggested change of shorelines, steady growth of the Nile • Empedocles of Agrigentum (490-430 BC) assumed that the earth is perforated by many channel of various sizes in which water and fire circulate. Importance of the internal heat!
Contribution of Greek • First geographic map: Anaximander (610-546 BC) • Long duration of geologic time: Anaxagoras (500-428 BC), Herodotus (485-425 BC), Strabo (64/63 BC-23AD) • Landscape is formed by erosion: Herodotus (485-425 BC), PubliusOvidius (Ovid) Naso (43 BC – AD 17/18), Pliny the Elder (23-78 AD), Polybius (ca. 200–118 BC) , Strabo (64/63 BC -23 AD) • Sea level changes: Xenophanes of Colophon (570-470- BC), Herodotus (485-425 BC), Aristotle (384-322 BC), Strabo (64/63BC-23AD), Ovid (43 BC – AD 17/18)
Earthquakes are caused by internal motions of air, water, fire, heat, etc.: Anaximander (610-546 BC), Aristotle (384-322 BC), Ovid, Pliny the Elder • Earthquakes are caused by cooling and heating: Anaximenes of Miletus (585-528 BC) • Volcanoes are safety valves reacting on internal motion of air, water, fire, heat, etc.: Anaxagoras (500-428 BC), Strabo (64/63BC-23AD) , Ovid (43 BC – AD 17/18) • Cyclic nature of geologic processes: Anaximander, Xenophanes of Colophon, Aristotle (384-322 BC), Plato (427-347BC), Pliny the Elder, Strabo (64/63BC-23AD)
Links between geologic processes: Anaximenes of Miletus (585-528 BC) • Stable and unstable regions of the Earth: Democritus (460-370 BC), Strabo • Linear shape of mountains: Pythagoras (570-497 BC), Plato (427-347BC) • Contraction of the Earth: Anaximenes of Miletus
Nicolaus Steno (1638-1686) Glossopetrae (tongue stones)
Nicolaus Steno "The prodromus of Nicolaus Steno's dissertation concerning a solid body enclosed by a process of nature within a solid" Steno introduced three principals of spatial and temporal relationships of rocks • Original horizontality • Original continuity • Superposition
Important ideas • Earth’s landscape has been shaped by great catastrophes • Noachian deluge • Neptunism – Abraham Gottlob Werner (1750-1817) • Plutonism – Leopold von Buch (1774-1815)
James Hutton 1726-1797 Royal Society of Edinburgh Friends: Joseph Black (CO2) John Clerk (Naval tactician) John Playfair (mathematician) James Watt Adam Smith
James Hutton • Uniformitarianism - Physical, chemical, and biological laws that operate today have also operated in the geological past - The present is key to the past - The result, therefore, of our present inquiry is that we find no vestige of a beginning, no prospect of an end • Rock cycle
Historical perspective • Charles Lyell (1797-1875) in 1830-1833 published three volumes Principles of Geology • Argued for uniformity of natural laws and processes (actualism) and for uniformity of rates of these processes (gradualism).
The nature of Scientific Inquiry • Assumption – the natural world behaves in a consistent and predictable manner • Goal – 1) to discover the underlying pattern in the natural world 2) to predict what will or will not happened
The nature of Scientific Inquiry • Scientific facts • Hypothesis • Theory • Scientific Law
Geologic Time Scale • Early estimates • Relative dating (early or later, lower or higher) • Evolution of organisms (fossils and plant remnants) • Radioactivity (parent and daughter elements, e.g. 238U decays to 206Pb or 40K decays to 40Ar) • The age of the Solar system (the Sun and planets) is 4.56 billion years • The age of the Universe is 13.75 billion years
Relative dating • Fossils (Fauna) • Fauna succession, William Smith (1769-1839) • Geologic time, Georges Cuvier (1769-1832) Antedeluvian period Many floods Creation of new life forms Pikaia, earliest chordate
The Universe • The region visible from Earth (the observable universe) is a sphere with a radius of about 46 billion light years (1 ly= 9.46 trillion kilometers) • The universe is defined as the totality of everything that exists, including all matter and energy, the planets, stars, galaxies, and the contents of intergalactic space • Galaxy supercluster → galaxy cluster → star → planet → satellites → comet → meteorite • The diameter of a typical galaxy is 30,000 light-years • The typical distance between two neighboring galaxies is 3 million light-years
The Milky Way Galaxy Orion–Cygnus Arm Solar System The Sun The diameter is approximately 100,000 light-years
Origin of the Universe – Big Bang • Big Bang marks the origin of the Universe. It is fast expansion of hot and dense primordial matter • Only hydrogen, helium, and a little lithium and beryllium were produced in the Big Bang • Heavier elements, which comprise only 2% of the Solar System, were produced because of nucleosynthesis during star evolution
Origin of planets • When the core of contracting cloud becomes dense enough, gravitation causes it to collapse upon itself to form a proto-sun • Thermonuclear fusion • Condensation in the disk production of solid dust • Accretion – collision of dust grains • Condensation leads to production of silicate and oxide particles as well as to other compounds.
Mg, Al, Na, O, Si, Fe, Ca, and Ni compound are formed at hotter part of the disk while C, N, O, Ne, S, Ar, and halogens are formed at a cooler part of the disk. • The grains coalesced to form planetesimals • Asteroid-like planetesimals with silicate or rocky composition formed near the Sun • Comet-like planetesimals with an icy composition formed far from the Sun • Jovian and terrestrial planets
Planets • All planets rotate counterclockwise about the Sun (view from the N pole of the Sun) – ecliptic plane • Planets rotate in the same direction (exceptions – Venus, Uranus, and Pluto) • Composition of the Terrestrial planets is similar to the composition of the Earth
The initial temperature • Heat from impacts and rate of impacts • Temperature rise because of compression and heat conservation • Heat from radioactive disintegration
The lowest curve shows the initial temperature due to accretion. • After 500 Ma radioactivity warmed the Earth. • After 1 billion years the interior heated to the melting temperature of iron at depths between 400 and 800 km. • Iron has the high density (sinks!). • Iron catastrophe. Heating of the Earth
The iron catastrophe Planetary differentiation Core and mantle Convection Chemical zonation