INTRODUCTION     Geology - study of Earth and other bodies in space   I. VITAL STATISTICS ABOUT THE EARTH A. 149,000,000 Km between the Sun and the Earth B. 1 revolution = 365 days C. 1 rotation = 24 hours D. Diameter = 12,756 Km E. Density = mass/volume Average density ~ 5.5 gms/cm3 F. Mass = 6x1021 metric tons G. Average surface temperature = 59 oF or 15 oC oF = 9/5(oC) + 32 oF H. > 90 % of people live between 0 - 300 m II. FOUR PHILOSOPHICAL QUESTIONS A. How and when did the Earth form? 1. Planetary differentiation--dense elements sink toward gravitational center 2. 4.6 billion years old B. How and where did Earth acquire its four spheres? 1. hydrosphere--watery portion 2. atmosphere--gaseous portion 3. biosphere--living portion 4. lithosphere--rocky portion C. What factors modify the Earth? D. How long might we expect the Earth to last? 1. Moon--4.6 billion years and 2.0 b.y. 2. Earth--3.99 b.y. -----------> today   III. SCIENTIFIC METHOD - Systematic, Logical Approach to Address a Problem A. Define the problem B. Collect and evaluate data C. Hypothesize (produce a scientific explanation) D. Test of time--a theory may become a natural law   IV. LATE 1700's A. Law of Original Horizontality B. Law of Superposition--in an undisturbed sedimentary sequence, the oldest rxs are at the bottom and the youngest are at the top.   V. GEOLOGICAL TIME A. Relative vs. absolute time 1. Absolute time--approximate time of a geological event (measured in years, thousands of years, etc.) 2. Relative time--something happened before or after something else a. Law of Superposition b. 2 is older than 3; 2 is younger than 1 3. Combining absolute and relative times a. 14 m.y. K-Ar B. Uniformitarianism--"Present is the key to the past" 1. James Hutton (1726-1797) "Father of Geology" excerpt from Hutton's Investigations of the Principles of Knowledge