Utah's "Little Grand Canyon" in the San Rafael Swell area of Utah as photographed from the Wedge Overlook (photo by E. L. Crisp, May 2001).  The sedimentary rock layers here are Triassic and Jurassic in age and record much of the geologic history of this region during a large portion of the Mesozoic Era.  The sedimentary strata here are like the pages in a history book and geologist can read the information recorded in these rock layers to help unravel the geologic history of this region.

 

Introduction to Historical Geology

(related to Chapter 1 in Wicander and Monroe, 2004)
 

I.  Introduction:  A view of the changing and dynamic Earth through time.  The interwoven themes of Historical Geology are evident here: 1) Plate Tectonics, 2) Organic Evolution and 3) long periods of time (Deep Time).

II. Earth Systems:  Earth acts as a system (combination of related parts that interact in an organized manner) and is divided into several interconnected subsystems: 1) solid Earth, 2) the atmosphere, the biosphere, and the hydrosphere.  Earth is not isolated from the rest of the Universe and is affected by extraterrestrial phenomena, thus we also speak of the Earth-Universe system.

III.  Geology: From Geos (meaning Earth) and logos (meaning to study).  Geology is study of Earth, its composition, struture, internal and external processes, origin, and evolution (both physical and organic).  Geology is divided into Physical Geology and Historical Geology (and each of these into many subdisciplines).  Physical Geology is the study of Earth materials (minerals and rocks) and with the external and internal processes that affect Earth.  Historical Geology studies the origin and evolution of Earth and tries to explain the cause of past events using present Earth processes as a key to interpreting the past (Uniformitarianism or Actualism).

IV.  Historical Geology and the Scientific Method: Facts, Hypotheses, Theories, Prinicples, and Laws - these are the products of science.  In Historical Geology we must use the scientific method to determine what happened in the past (we can never go back in time to observe the events in Earth History).  But just as forensic investigators gather evidence and formulate hypotheses to explain past events (for crimes such as murder, rapes, robberies, etc), geologists gather data from the rocks to explain past events in the history of Earth.  Scientific explanations must be testable and have the potential to be proven false.  Science cannot appeal to the supernatural for explanations of nature because these explanations are not testable.  Science does not say that supernatural beliefs are untrue (or true), just that they are outside the realm of scientific testing.

V.  Origin of the Universe and Solar System - Big Bang Theory and the Solar Nebula Theory  (see Lecture Origin and Evolution of the Universe and Solar System (to go with Chapter 1)

VI.  Earth Materials: Minerals and rocks.

VII. The Dynamic Earth:  Earth is constantly changing and has been in a state of dynamic change since its origin 4.6 billion years ago. VIII. Plate Tectonics: Continetal Drift (Alfred Wegener, 1912), Plate Tectonic Theory (1960s), Mantle Convection and Heat Flow, Plate Boundaries (divergent, convergent, transform fault), Sea Floor Spreading, Subduction, Earthquakes, Volcanoes, Mountain Building Orogenies, Continental Accretion, Exotic Terranes, etc. IX.  Organic Evolution: FACT - LIFE ON EARTH HAS CHANGED OVER TIME (THE BIOTA HAS EVOLVED)!!!  Darwin (1859) - On the Origin of Species by Means of Natural Selection. Alfred Russell Wallace.
Descent with Modification.  Survival of the Fittest. All life on Earth has a common ancestor (all life on Earth is monophyletic).  Many lines of evidence of evolution: how organism are classified (based on comparable traits), embryology, comparative anatomy, biogeography (the distribution of organisms), the fossil record, molecular biology, etc. Sexual reproduction and the various combinations of genes gives rise to changes in populations. Mutations as one source of variations in populations.  Paleontology and the study of fossils as a record of the changes in life that have occurred on Earth during the past.  The principle of fossil succession and the relative dating of of the rock record (the relative geologic time scale).

X.  Geologic Time and Uniformitarianism: Deep Time. Earth is 4.6 billion year old (based primarily on dating meteorites).  Oldest Earth rocks date at about 4 billion years.  Oldest moon rocks date at about 4.4 billion years.  The Present is the Key to the Past (Principle of Uniformitarianism).  Relative time versus absolute time (based on relative dating {primarily using fossils and principles of relative dating of rock layers} and absolute dating {primarily using radiometric dating to put absolute numbers on the geologic time scale}.  Catastrophic events do occur and the rates of geologic change may have been different in the past than today.

MEMORIZE THE RELATIVE GEOLOGIC TIME SCALE (as presented on page 14 in Wicander and Monroe)!!! We will use this constantly throughout the course.