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Name_______________________________ GG101L Page 1 of 5 Homework Ex. 7. Geologic Time Part 1: Eons, Eras and Periods Directions: How has the earth’s mineralogy changed over the 4.6 billion years of Earth’s history? Refer to the assigned article available on the class website: R.M. Hazen. 2010. Evolution of Minerals. Scientific American (March 2010). 1. Read the article in detail; it outlines the argument that the 4,400 minerals that exist today owe their origins to the dozen or so minerals present when the solar system formed. 2. Complete the table below, summarizing the information discussed in the article. The “Evolution” of Minerals Phase of Earth History Time Making Earth 4.6 billion years ago Earth’s Environment Very high T, shocks from collisions, condensation from gas, some water present Minerals (with Formula)* (at least 2) olivine (formula) zircon (formula) Type of Rock Metamorphic (?) Mineral Characteristics Silicate, high hardness Name_______________________________ GG101L Page 2 of 5 Homework Ex. 7. Geologic Time Part 1: Eons, Eras and Periods The “Evolution” of Minerals Phase of Earth History Black Earth Time 4.4 billion years ago Earth’s Environment Molten rock, repeated partial melting, high T, anoxic atmosphere, liquid water (oceans) at surface, mineral formation under high pressure. Minerals (with Formula)* (at least 4) jadeite (formula) lepidolite (formula) ETC. Type of Rock Igneous (black basalt & granite) Mineral Characteristics Many silicates (network, chain and sheet), cations such as lithium, beryllium, boron. Name_______________________________ GG101L Page 3 of 5 Homework Ex. 7. Geologic Time Part 1: Eons, Eras and Periods The “Evolution” of Minerals Phase of Earth History Red Earth Time 2 billion years ago Earth’s Environment Oxygen in the atmosphere, relatively low pressures at surface, “room” temperatures, single-celled photosynthetic organisms, stromatolites, standing water. Minerals (with Formula)* (at least 4) carbonate (formula) turquoise (formula) ETC. Type of Rock Sedimentary rocks Mineral Characteristics Many oxides (carbonates, iron oxides, etc.), often red because of oxidized iron cations. Name_______________________________ GG101L Page 4 of 5 Homework Ex. 7. Geologic Time Part 1: Eons, Eras and Periods The “Evolution” of Minerals Phase of Earth History White Earth Time 700 million years ago Earth’s Environment Very low temperatures (< freezing) for millions of years, relatively low carbon dioxide in atmosphere, absence of liquid water, ubiquity of ice. Minerals (with Formula)* (at least 3) kaolinite (formula) “cap carbonate” (formula) ice (formula) ETC. Type of Rock Ice and clay (sedimentary rocks) Mineral Characteristics Clays formed by the abrasion of ice against the silicate landscape. Name_______________________________ GG101L Page 5 of 5 Homework Ex. 7. Geologic Time Part 1: Eons, Eras and Periods The “Evolution” of Minerals Phase of Earth History Green Earth Time 400 million years ago Earth’s Environment Range of temperatures, range of environments (some oxygenated, some anoxic), existence of soil, organic matter accumulates, liquid water and ice. Minerals (with Formula)* (at least 3) aragonite (formula) opal (formula) coal (formula) Type of Rock Mineral Characteristics ETC. Sed, Igneous & Metamorphic Oxides, silicates, metamorphosed minerals, cycling of cations, fossilization of organic matter
