Geology 104 Midterm #1 Review Sheet PDF

# Geology 104 Review sheet for Midterm #1 on Feb. 19, 2025 You are expected to understand the following topics and answer related questions. ## Ch 1 An Introduction to Geology 1. Difference between physical geology and historical geology. Physical geology examines materials composing earth...

# Geology 104 Review sheet for Midterm #1 on Feb. 19, 2025 You are expected to understand the following topics and answer related questions. ## Ch 1 An Introduction to Geology 1. Difference between physical geology and historical geology. Physical geology examines materials composing earth and seeks to understand the many processes that operate beneath and on the surface of earth. Historical geology seeks understanding of the origin of earth and its development through time. 2. Catastrophism vs. Uniformitarianism. How do these two views think about the age of Earth? * Catastrophism – earth's landscapes shaped primarily by catastrophes: sudden process; young earth (mid 1600s) * Uniformitarianism – the physical, chemical, and the biologic laws that operate today have operated throughout the geological past; old earth, process is slow and spans over a long time (1795) 3. How are a scientific hypothesis and a scientific theory defined, respectively? Based on making observations and developing explanations. Assumes the natural world behaves consistently and predictably. * Hypothesis a tentative (or untested) explanation * Theory – a well-tested and widely accepted view that the scientific community agrees best explains certain observable facts 4. Doppler effect, red shift, and big bang theory of Universe formation. Doppler effect is the basis for big bang theory of universe formation. Apply to different types of waves: sound and light waves. Red Shift (lower frequency): moving away. The universe is always expanding 5. Theory for solar system formation. How did the solar system form? The Nebular theory – the sun and all other objects in the system formed from material in nebulae Solar system - The ball at the center grows dense and hot, Fusion reactions begin: the Sun was born, Dust in the rings condenses into particles, Particles coalesce to form planetesimals, then forming planets 6. Ages of the Universe, the solar system, and Earth. Earth - Planetesimals accumulate into a large mass, An irregularly-shaped proto-Earth develops, The interior heats and becomes melting, Gravity shapes the Earth into a sphere, Differentiation: internal layering, e.g., metal sank, A primitive atmosphere evolved from volcanic gases. 7. What are spheres and cycles in the Earth system? Are they independent or interacting? Earth is a dynamic body with many separate, but interacting, parts: 4 spheres * Hydrosphere - global ocean and fresh water * Atmosphere - gaseous envelope * Geosphere - the solid Earth * Biosphere - all plant and animal life * cycles in the system: Hydrologic cycle, Carbon cycle, Rock cycle 8. Earth's layered structure by chemical composition and physical properties. * Crust - Earth's thin, rocky outer skin, divided into the continental and oceanic crust. Oceanic crust is approximately 7 kilometers thick and composed of basalt. * Continental crust is 35–70 kilometers thick and composed primarily of granite. Mantle approximately 2900 kilometers thick and composed of peridotite. Upper mantle. Lower mantle * Core - composed of an iron-nickel alloy. Outer core: liquid. Inner core: solid Earth's interior is divided into different zones based on physical properties: * Lithosphere - the rigid outer layer of Earth that consists of the crust and part of the upper mantle: strong, brittle. Average 100 km thick, up to 250 km * Asthenosphere - the soft, weak layer below the lithosphere: weak, plastic (solid, but mobile). Up to 410 km depth * Transition zone - a zone marked by a sharp increase in density below the asthenosphere. From 410 km to 660 km depth * Lower Mantle a zone of strong, very hot rocks subjected to gradual flow below the transition zone * Outer core - liquid outer layer of the core, 2250km think * Inner core - solid inner layer of the core, 1221km radius 9. Basic types of rocks. What does rock cycle tell us? What are major geological processes that transform one type of rocks to another? Igneous, Sedimentary, Metamorphic Rock cycle allows us to visualize interrelationships among different parts of the earth system. 10. What are major surface features of the Earth? * Ocean basins and continents * Continental margins: shelf, slope, rise * Deep ocean basins: abyssal plains, deep ocean trenches, seamounts * Ocean ridges ## Ch 2. Plate Tectonics 1. Evidence for the continental drift hypothesis. Why was it not widely accepted before 1960s? Continental jigsaw puzzle, fossil matching across the sea, rock types, geological features, ancient climates Wegener's inability to identify a credible physical mechanism for continental drift 2. What does apparent polar wandering mean? Curves for North America and Europe have similar paths but are separated by about the width of the North Atlantic Ocean (3000 mi) 3. How can one use the seafloor spreading hypothesis and the observations of magnetic reversals to explain the pattern in marine magnetic anomalies? * Magnetic reversals: Paleomagnetic measurements of lava layers on land reveal magnetic north/south poles flip periodically * Magnetic anomalies: caused by near-surface objects (detect submarines, find metal mineral resources,...) * Normal polarity rocks enhance the current magnetic Field - Positive anomalies * Reverse polarity rocks weaken - Negative anomalies * Seafloor spreading + magnetic reversals => marine magnetic anomaly pattern * By 1968: continental drift + seafloor spreading united => plate tectonics 4. How does Earth's layered structure support plate tectonics? Earth's Outer Shell made of Cold, Stiff “Lithosphere” (~100 km thick on average - made up of Crust and uppermostMantle ) Below Lithosphere, Hot, Soft, Convecting Asthenosphere (Mantle) Lithosphere made up of some number Rigid Plates Most Displacements/Deformation at Plate Boundaries (i.e. Faulting, Earthquakes, Subduction, Mountain Building ), Not much Tectonics in Plate Interiors 5. Types of plate boundaries. How can they be identified? * Divergent – constructive margins, plates move apart * Convergent – destructive margins, plates move together * Transform – conservative margins, plates grind past each other without production or destruction of lithosphere 6. Divergent plate boundaries & continental rifting: where? examples? What happen there? What is the typical spreading rate? * Along the crest of the ridge is a canyon-like feature called a rift valley * Seafloor spreading is the mechanism that operates along the ridge system to create new ocean floor. * Average rate is 5 cm/year * Continental rifting – 2 plates split, continental crust sinks and a new ocean basin is formed 7. Convergent plate boundaries: different types, examples, & features. Two plates move toward each other and leading edge of one slides beneath the other Where lithosphere descends (subducts) into the mantle: subduction zones Deep-ocean trenches are the surface manifestations produced at subduction zones Oceanic-continental, oceanic-oceanic, continental-continental 8. Transform plate boundaries: where? examples? what happen? Plates slide horizontally past one another, without production or destruction of lithosphere. Most occur on the seafloor joining two spreading center 9. Plate boundaries along the west coast. * San Andreas fault (SAF): a transform fault * Cascadia subduction zone: Juan de Fuca plate subducts beneath North America plate 10. How do ocean drilling's results and hot spots observations support the plate tectonics theory? Hundreds of holes were drilled through layers of sediments that blanket the ocean floor and the basaltic crust Sediments increase in age with distance from the ridge crest Sediments are almost absent on the ridge crest and thickest furthest from the spreading center 11. Forces that drive plate motion and relative importance. convection in the mantle is the ultimate driver of plate tectonics The subduction of cold, dense oceanic lithosphere is as slab-pull force. Elevated lithosphere at oceanic ridges will slide down due to gravity, causing the ridge-push force. 12. Two models of mantle convection. Whole-mantle convection (plume model) Layer Cake Model ## Ch 3. Minerals 1. Definitions of minerals and rocks. * Mineral: naturally occurring, generally inorganic, solid substance, orderly crystalline structure, definite chemical composition * Rock: a solid mass of minerals or mineral-like matter that occurs naturally 2. How do minerals form? Ions dissolved in a solution reach saturation; Minerals can precipitate from slowly moving groundwater filling fractures and voids 3. What are polymorphs? Example. crystal structures that a substance can form while maintaining the same chemical composition 4. Physical properties of minerals. Definite crystalline structure and chemical composition of minerals give them unique physical and chemical properties. Ability to transmit light, color, streak, shape, hardness, cleavage, fracture, density 5. Abundant elements & minerals in crust. * Oxygen-46.6% * silicon-27.7% * aluminum-8.1% * iron-5% 6. Major classes of minerals and common examples. Silicates, carbonates, halides, and sulfates 7. Silicon-oxygen tetrahedron. How can they link to one another? How does the ratio of the two ions differ in each type of silicate structures? Fundamental building block, Four oxygen ions surrounding a much smaller silicon ion 8. What are common two groups of silicate minerals? How do these two types of silicate minerals differ? The feldspars are the most common silicate group: >50% of Earth's crust. Quartz is the second-most abundant mineral in the continental crust. ## Ch 4. Igneous rocks 1. Four igneous compositional groups and corresponding main examples of minerals and rocks. * Liquid portion = melt * Solids, if any, are crystals of silicate minerals * Volatiles are dissolved gases in the melt that vaporize at surface pressure, including Water vapor, Carbon dioxide, & Sulfur dioxide 2. How does silica content affect magma behavior? * Granitic magmas have high silica content: more viscous * Basaltic magmas have much lower silica content: more fluid-like behavior (less viscous) 3. What is igneous texture? How do igneous textures tell about cooling rates? Texture: the overall appearance of a rock based on the size, shape, and arrangement of interlocking minerals * Slow rate = fewer but larger crystals * Fast rate = many small crystals * Very fast rate forms glass 4. Types of igneous textures and their main features. * Aphanitic (fine-grained) texture: Rapid rate of cooling, Microscopic crystals, May contain vesicles (holes from gas bubbles) * Phaneritic (coarse-grained) texture: Slow cooling, Large, visible crystals 5. What is geothermal gradient? What are processes that generate magma, and how? temperatures in the upper crust increase about 25°C per kilometer Tectonic processes trigger melting by reducing the melting point: Decrease in pressure, Addition of water, Increase in temperature of crustal rocks 6. What are processes that change magma's composition? What does Bowen's reaction series tell us? Assimilation Minerals crystallize in a systematic fashion based on their melting points. As minerals crystallize, the composition of the liquid portion of the magma continually changes. 7. How do basaltic, andesitic and granitic magmas form? * Basaltic - partial melting of mantle rocks at oceanic ridges * Andesitic - Magmatic differentiation of mantle-derived basaltic magma, Basaltic magmas assimilating crustal rocks * Granitic - Most form when basaltic magma ponds beneath the continental crust, heating and melting the much-lower melting temperature felsic minerals. Can also form from magmatic differentiation of andesitic magma 8. What are two types of igneous activities? Tabular and Massive 9. What are different types of intrusive igneous bodies? How to differentiate them? * Tabular - dike, still * Massive - batholith, laccoliths ## Ch 5. Volcanoes 1. What determines eruption styles? What determine magma viscosity? Magma viscosity: composition, temperature, and dissolved volatiles 2. Types of extrusive igneous materials & examples. Block lavas, pillow lavas, gases, pyroclastic materials 3. What are conduit, vent, crater, caldera? * Conduit a somewhat circular pathway * Vent - the surface opening of a conduit * Crater a funnel-shaped depression at the summit, less than 1 km in diameter * Caldera - crater with a diameter of >1 kilometer, produced by a collapse following a massive eruption 4. Types of volcanoes, their features, and examples. Shield volcano, cinder cone, composite cone 5. What are three types of calderas? Crater lake-type, Hawaiian-type, Yellowstone-type 6. What are other volcanic landforms? Examples? Fissure eruptions, basalt plateaus, lava domes, volcanic necks and pipes 7. What are the major volcanic hazards? Pyroclastic flows, lahars, tsunamis, ash, gases 8. Where in terms of plate tectonic settings do volcanic activities occur? Along convergent plate boundaries