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Unformatted text preview: HISTORICAL GEOLOGY LECTURE, PAGE 1 I. Introduction A. Geology - the study of the Earth 1. Physical Geology - study of the Earth's materials, such as minerals and rocks, and the various physical and chemical changes that occur on its surface and in its interior 2. Historical Geology - history of the planet and its life forms from its origin to the present B. The Birth of Modern Geology 1. James Hutton (1726 - 1797)- Scottish gentleman farmer and geologist; the &quot;Father of Geology&quot;- formulated concept of &quot;Uniformitarianism&quot; a. Uniformitarianism- &quot;the present is the key to the past&quot;- the Earth is shaped by daily, mundane processes- the Earth is very old- believed that &quot;great catastrophes&quot; have only minor influence 2. Charles Lyell (1797 - 1875) - English Geologist, wrote Principles of Geology (the first volume appeared in 1830)- his influential popularization of Hutton's principles influenced generations of geologists 3. More recent studies use the concept of Actualism a. Actualism- apply studies of modern processes to ancient rocks- the processes that now shape the Earth were similar in the geologic past, although the rate of change may vary- recognizes that &quot;catastrophes&quot; can have powerful influence on the Earth 4. Geologic Time Scale- the Earth is 4.6 billion years old- the subdivisions of the time scale are based primarily on the predominant life forms living during specific times II. Minerals and Rocks A. Mineral- naturally occurring, inorganic, homogeneous, crystalline solid; more than 90% of rock-forming minerals are silicates (contain silicon, oxygen and one or more metals) 1. Chemical Composition of Minerals a. Elements- fundamental components, cannot be broken down to simpler substances by ordinary chemical processes- there are 88 naturally occurring elements- the 8 most common are Oxygen (O), Silicon (Si), Aluminum (Al), Iron (Fe), Calcium (Ca), Sodium (Na), Potassium (K) and Magnesium (Mg); comprise 98% of the Earth's Crust b. Atoms- fundamental units of elements Nucleus - positively charged center of mass; includes protons (with mass and a positive charge) and neutrons (with mass and a neutral charge) Electrons - with no mass and a negative charge; the number and orientation of electrons determines chemical behavior c. Chemical Reactions- filling of the outer shells of electrons Ions = charged atoms; atoms with too few or too many electrons; includes cations (positively charged) and anions (with negative electrical charges) 2. Physical Properties of Minerals- use color, streak, hardness, crystal form, cleavage, fracture, luster, specific gravity, magnetism, chemical reactivity, radioactivity, fluorescence, etc. to identify minerals - see lab manual 3. Mineral Classification a. Based on dominant anion present in the Mineral- including silicates, oxides, sulfides, halides, phosphates, carbonates, native elements and hydroxides b. Silicate Minerals- the most abundant chemical group constitute (about 90% of the Earth's crust)- Silicate Bonding with four oxygen for each silicon; bond directions require a tetrahedral...
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- Fall '10