Geology Reviewer: Introduction, Branches, Minerals & Rocks - PDF

**GEOLOGY REVIEWER** **1: Introduction to Geology** **Geology** is the scientific study of the earth's structure, composition, and processes that shape its surface. Geologists investigate the formation of rocks, minerals, and the earth's interior through systematic methods like field work, laborat...

**GEOLOGY REVIEWER** **1: Introduction to Geology** **Geology** is the scientific study of the earth's structure, composition, and processes that shape its surface. Geologists investigate the formation of rocks, minerals, and the earth's interior through systematic methods like field work, laboratory analysis, and technology. By examining rocks, fossils, and landscapes, geologists reconstruct earth's history, understand natural hazards, and contribute insights crucial for resource exploration and environmental management. **Branches of Geology** 1. **Physical Geology** - Physical geology is the scientific discipline that is concerned with all aspects of the Earth's structure, composition, physical properties, constituent rocks and minerals, and surficial features. 2. **Crystallography** - Crystallography is the branch of science that deals with discerning the arrangement and bonding of atoms in crystalline solids and with the geometric structure of crystal lattices. 3. **Mineralogy** - Mineralogy is the scientific discipline that is concerned with all aspects of minerals, including their physical properties, chemical composition, internal crystal structure, and occurrence and distribution in nature and their origins in terms of the physicochemical conditions of formation. - **Crystals vs Minerals** - Minerals are naturally occurring, inorganic substances with a definite chemical composition and a crystalline structure. - Crystals are solids with a regular, repeating arrangement of atoms, molecules, or ions. They can form from minerals, but they can also form from other substances, such as organic materials (e.g., sugar crystals) or synthetic materials (e.g., silicon crystals). 4. **Petrology** - Petrology is the study of rocks - igneous, metamorphic, and sedimentary - and the processes that form and transform them. - **Rocks vs Soils** - **Rocks** - Aggregation of minerals found in the earth's crust. - Aggregate of one or more minerals. - **Soils** - Unconsolidated materials consisted of solids from disintegration of different rock types. - Mixture of minerals, organic matter, gases, liquids and countless organisms.  5. **Structural Geology** - Structural geology is the branch of geology that deals with the form, arrangement, and internal structure of rocks, and especially with the description, representation, and analysis of structures, chiefly on a moderate to small scale. 6. **Stratigraphy** - Stratigraphy is the scientific discipline concerned with the description of rock successions and their interpretation in terms of a general time scale. It provides a basis for historical geology, and its principles and methods have found application in such fields as petroleum geology and archaeology 7. **Paleontology** - Paleontology is the scientific study of life of the geologic past that involves the analysis of plant and animal fossils, including those of microscopic size, preserved in rocks 8. **Historical Geology** - Historical geology is the discipline that uses the principles and methods of geology to reconstruct the geological history of Earth. 9. **Economic Geology** - Economic geology is the scientific discipline concerned with the distribution of mineral deposits, the economic considerations involved in their recovery, and an assessment of the reserves available. 10. **Hydrogeology** - Hydrogeology is the science of the occurrence, distribution, and movement of water below the Earth\'s surface. 11. **Engineering Geology** - Engineering geology is the application of geologic information to aid in realistic characterization of construction sites for the design of suitable foundations, and support thereof, which can reasonably be expected to withstand all the probable loads to which said structures might someday be dealt. **Geotechnical engineering** is an area of civil engineering that focuses on the engineering behavior of earth materials. Using the principles of soil and rock mechanics, this subdiscipline of geological engineering uses knowledge of geology, geophysics, hydrology and more. **Rock mechanics** is the study of the fundamental principles governing the behavior of all rock and rock masses. **Soil mechanics** is the study of the fundamental principles governing the behavior of all soil and soil masses. **Geotechnical engineering** is an area of civil engineering that focuses on the engineering behavior of earth materials. Using the principles of soil and rock mechanics, this subdiscipline of geological engineering uses knowledge of geology, geophysics, hydrology and more. Foundation engineering applies geology, soil mechanics, rock mechanics and structural engineering to the design and construction of foundations for civil engineering and other structures. *Other allied fields:* earthquake engineering, ground improvement engineering, geosynthetics, slope stabilization engineering, tunnel design, offshore geotechnical engineering **GEOLOGY** **2 -- Historical Geology** **Historical Geology** is the study of changes to earth and life in time and space. **Types of ages:** - Relative time (relative age) -- measurement of time using comparison methods. - Absolute time (absolute age) -- measurement of time using actual numbers **Measuring Earth's Relative Age** - Use of rock layers - Use of faults to determine relative rock age layers and the order in which events happened **Measuring Earth's Absolute Age** A. **Radioactive dating** -- the breaking down of atoms to form different isotopes of the same element or a completely new element **Carbon-14 → Carbon-12** **Energy is given off in the form of:** \- gamma rays \- alpha particles \- beta particles **Most common form of radioactive dating techniques:** a. Uranium-lead dating (U-235 to Pb-207) b. Samarium-neodymium dating (Sm-147 to Nd-143) c. Potassium-argon dating (K-40 to Ar-40) d. Rubidium-strontium dating (Rb-87 to Sr-87) e. Uranium-thorium dating (U-234 to Th-230) f. Radioactive carbon dating (C-14 proportions) B. **Half-life** -- the amount of time it takes for half of the original atoms to decay **Fundamental Theories of Historical Geology** **Theory of Uniformitarianism** - The theory of uniformitarianism (gradualism) suggested that the landscape developed over long periods of time through a variety of slow geologic and geomorphic processes. - Originally proposed by James Hutton in 1785, which was based on natural history and not on the Biblical account, which was later expanded by Charles Lyell in the 1830s. - "The present is the key to the past." **Theory of Uniformitarianism** Lyell's uniformitarianism propositions, according to Reijer Hooykaas in 1963): a. Uniformity of law -- laws of nature are constant across time and space b. Uniformity of methodology -- appropriate hypotheses for explaining the geological past are those with analogy today c. Uniformity of kind -- past and present causes are all the same kind, have the same energy, and produce the same effects d. Uniformity of degree -- geological circumstances have remained the same over time **Theory of Catastrophism** - The theory of catastrophism is the idea that the earth has been affected by sudden, short-lived, violent events that were sometimes worldwide in scope. - First popularized by Georges Cuvier in the 19th century, which proposed that new life forms had moved from other areas after local floods. - Geological epochs had ended with violent and sudden natural catastrophes such as great floods, formation of major mountain chains or asteroid impact.  Cretaceous-Paleogene event, formerly Cretaceous-Tertiary (K-T) extinction event, about 66 million years ago **Theory of Catastrophism**  Giant impact hypothesis -- about 4.5 billion years ago, a large planetesimal somehow impacted the early earth, blew out rocky debris, remelted it and formed the moon. **Fundamental Principles of Historical Geology** Terminologies: - Contact -- distinct surface between two unlike bodies of rocks - Stratum -- single layer/bed of rock - Strata -- multiple layers/beds of rocks - Stratigraphy -- study of strata - Formation -- a body of rock with distinctive structure that is bounded by contacts - Outcrop/Exposure -- locations or portions where rocks are exposed at the earth's surface **Fundamental Principles of Historical Geology** Formulated by Nicolaus Steno in 1669, a Danish physician, to help him make sense of the rocks of Tuscany, Italy and the various objects contained within them. - Steno's Law of Superposition - Steno's Law of Original Horizontality - Steno's Law of Lateral Continuity - Steno's Law of Cross-Cutting Relationships **Steno's Law of Superposition** - At the time when any given stratum was being formed, all the matter resting upon it was fluid, and, therefore, at the time when the lower stratum was being formed, none of the upper strata existed." - In any undeformed sequence of sedimentary rocks, each bed is younger than the one below it and older than the one above it. **Steno's Law of Original Horizontality** - \"... strata either perpendicular to the horizon or inclined to it, were at one time parallel to the horizon." - Sedimentary rocks are horizontal because the original sediments were horizontal. - Steeply inclined strata have been moved from their original position. **Steno's Law of Lateral Continuity** - \"Materials forming any stratum were continuous over the surface of the Earth unless some other solid bodies stood in the way." - Strata originally extended in all directions until they thinned to zero at their edges of deposition. Therefore, matching strata on opposite sides of a valley, or continent can be correlated. **Steno's Law of Cross-Cutting Relationships**  - \"If a body or discontinuity cuts across a stratum, it must have formed after that stratum." - Invading igneous rock is always younger than the rock it intrudes. **UNCONFORMITY** - Unconformities are gaps in the geologic record that may indicate episodes of crustal deformation, erosion, and sea level variations. - They are surfaces between two rock bodies that constitute a substantial break in the geologic records. - Unconformities represent times when deposition stopped, an interval of erosion removed some of the previously deposited rock, and finally deposition was resumed. **TYPES OF UNCONFORMITIES:** 1. **Angular Unconformities** 2. **Disconformity**  Disconformities are also an erosion surface between two packages of sediment, but the lower package of sediments was not tilted prior to deposition of the upper sediment package. 3. **Nonconformity** - Nonconformities are unconformities that separate igneous or metamorphic rocks from overlying sedimentary rocks. - They usually indicate that a long period of erosion occurred prior to deposition of the sediments (several km of erosion necessary). **Summarized Geologic Time Scale**  1. **Paleozoic era** -- age of invertebrates a. Cambrian period b. Ordovician period c. Silurian period d. Devonian period e. Carboniferous period f. Permian period 2. **Mesozoic era** -- age of dinosaurs & reptiles a. Triassic period b. Jurassic period c. Cretaceous period 3. **Cenozoic era** -- age of mammals d. Tertiary period e. Quaternary period