updated March 16, 2014
Selected geology notes. These notes have been amalgamated during use of several books, so not all topics listed below were covered in class. Additional contributions courtesy of Celia Nightengale and others.
Disclaimer – This is not intended to be an exhaustive list of everything that will be on tests. It is a general outline of the primary areas you will be tested on. Questions related to other information presented in lectures, labs, or in the books may also be on tests.
Table of Contents
1. Read over the chapter contents on the first page of each chapter—this gives you an overview of what’s in the chapter and also shows you how it’s broken down into parts.
2. Look through all the graphics, the pictures and diagrams and read the captions. This helps you visualize while you are reading and also gives you some snap shots of what the author is presenting.
3. Read the brief reviews that summarize individual sections and the summary of the entire chapter.
4. Scan the list of terms. Do you really know what each term means? If you are not sure of the precise meaning, dig into the chapter and glossary to find out. Remember to use the index at the end of the book to help you find terms.
5. Be able to answer the questions for review.
6. Read the chapter and take notes as you read.
7. Go over your notes from class.
What is the difference between a hypothesis and a scientific theory?
You should be able to define both words. The scientific process is often called the empirical method because it is based on measurements and/or observations.
Scientific method—no single method
hypothesis—a possible explanation for a phenomenon or problem that accounts for existing data and predicts phenomena that should exist IF the hypothesis is correct
A hypothesis is always testable!
principles = laws: refer to statement or mathematical formulas that always succeed in generalizing data and observations about data without necessarily offering explanations.
Theory –a widely applicable and generally accepted explanation for natural phenomena that explains all of the relevant data.
What is geology? The study of the Earth, it’s history, materials, structure, and processes
Why study geology: curiousity—to better understand the Earth system and its processes and history; to learn about hazards and find resources while protecting the environment.
Resources: renewable vs. nonrenewable
Energy trends, energy consumption, future energy needs, and sources of energy over time
Fossil fuels; different kinds; where located; how detected; how obtainedWhat is an ore? Pollution from extraction, mining, and disposal of waste
Early idea and studies of geology
Eratosthenes estimated Earth's circumference more than 2000 yr ago
uniformitarianism – a product of the work of James Hutton, a Scottish physician and farmer (late 1700s). Uniformitarianism concept formalized by Charles Lyell, who wrote the first physical geology text in 3 volumes 1830-35—but term uniformitarianism not used until 1875. Rival concept was catastrophism
-A modern view of uniformitarianism, called actualism, accommodates episodic events (e.g. meteor impacts) over great periods of time and allows for changing rates and conditions for processes.
In many cases geologists observe the result (e.g. ripple marks) of process but not the process in action. To better interpret ancient features, we observe modern processes that can more easily be studied.
Uniformitarianism can be used to make forecasts, in a general sense, but not specific predictions.
History of thought about tectonics:
Alfred Wegener: 1929 book about drifting of continents: continents have shapes that "fit together"; fossils and similar rocks found across the ocean
Harry Hess, pioneering thinker
Tharp and Heezen map of ocean floor
Vine and Matthews, 1963, magnetic "stripes" on ocean floor, how "recorded"?
Mid Atlantic Ridge, East Pacific Rise, etc.seafloor spreading; ring of fire; speed of plate motion
This theory explains a wide array of geologic processes via the motion of lithospheric plates. The plates are ~100 km thick slabs.
The plates contain both continental and oceanic crust and part of the upper mantle.
Lithospheric plates are rigid and strong compared to underlying weaker asthenosphere.
Study of plate motions and rock deformation is called tectonics.
What is Cascadia?
Types of plate boundaries: divergent, convergent, transform: know examples of each
Accreted terranes and tectonic accretion. What's the drift on this?
Age of the ocean floor vs. age of continents
Pangaea the supercontinent.
Mantle convection; hot spots (mantle plume)
Surficial processes: uplift, weathering and erosion, deposition
boundaries separate plates moving apart. Ex:
At convergent plate boundaries one plunges under another where they converge. The overridden plate gets pulled down into the asthenosphere in process called subduction: Cascadia is an example.
Plates slide past each other at transform plate boundaries and lithosphere is not destroyed or created: ex: San Andreas Fault.
Plate tectonics explains belts of earthquakes, volcanic arcs, and deformation, all of which of which are commonly located near plate boundaries.
occur where molten rock ascend from deep in the mantle below the moving
lithosphere. Plate tectonics does not explain hot spots. Examples are
All around the Earth is evidence of work, from movement of sand grains to rupture of faults, movement of plates, and slow deformation of mountains. It all requires energy, which is a measure of the ability to do work.
Heat is the most important energy source for geological processes.
Solar energy drives process on Earth’s surface like wind, waves, etc.
Natural radioactivity continues to generate heat in the Earth’s interior.
Equilibrium is the balance that can exist in any system
Radiation is energy transferred as waves.
Convection is the simultaneous transfer of energy and mass. Expanded hot liquid is less dense than colder liquid, therefore, the hotter liquid rises. Convection causes the motions of Earth’s tectonic plates.
Potential energy is the stored energy that an object has because of its weight and elevation. It is converted to motion when masses or material move from higher to lower elevations.
Geologic time and the geologic time scale
Primary objectives: 1) to understand that each mineral has a definitive chemical composition and internal atomic structure; these determine physical properties and relate to where and how the minerals form, and 2) to learn the names, compositions, and properties of an important handful of the more than 4,000 known minerals.
Questions related to the objectives:
Properties: luster, hardness, color, diapheneity, specific gravity, paramagnetic, odor, crystal habit, reaction with dilute HCl, etc
What is a mineral?
Density: mass/vol [specific gravity: mass of object in air/mass of equal volume of water]
Hardness: resistance of a mineral to scratching [Mohs hardness scale—a relative scale]
Cleavage: [present in some minerals] the flat, smooth planes along which some minerals break; fracture is nonuniform breakage
Luster: the nature of the light reflection from a mineral’s surface. Depends on smoothness at the atomic scale of mobility of electrons (for example: metallic luster)
Streak: the residue of powered mineral produced by scratching on a porcelain plate; Color results from the interaction of the mineral with light; the color of a mineral may vary depending on the presence of trace amounts of ions of other elements
Ionic- exchange of electron(s)
Covalent - sharing electron(s)—stronger than ionic bonds.
Metallic - electrons move freely
van der Waals force – weak attaction of neutrally charged particles
Water is polar—has slight positive charge at one end which attracts anions of ionically bonded minerals, thus it can dissolve some ionic compounds such as halite (NaCl or salt).
Ion – a charged atom resulting from the gain or loss of one of more electrons so that the number of protons and electrons is unequal. Anion—negatively charged; cation—positively charged
Isotope- a variety of an element that has the same number of protons but a different number of neutrons.
Physical properties of minerals are the result of chemical composition and internal structure of the mineral.
Trace amounts of some elements can affect color: ex: iron, Fe3+, and titanium Ti4+ ions are larger than silicon, Si4+, but iron and titanium can fit between 4 oxygen atoms in place of silicon, thus giving color.
Cleavage plane form where bonds are weakest
Silica has covalent and ionic properties: the silicon and oxygen atoms share electrons, but each Si atom shares electrons with 4 adjacent oxygen atoms, thus resulting in a linked framework that is very strong. P. 34
The big eight: Oxygen, silicon, aluminum, iron, calcium, magnesium, sodium, potassium. (then sulfur and nickel)
> 4,000 minerals in all
Silicate minerals dominate the Earth’s crust: ex: feldspars are most common group of rock-forming minerals in the crust. It is no surprise that they are dominant, because silicon and oxygen are the two most abundant elements in the Earth’s crust.
Nonsilicate minerals include the oxides, sulfides, carbonates, and metallics.
Polymorphs—minerals that have the same composition but different molecular structure.
Learn the basics of rock formation and the basics of rock types (ROCK CYCLE!!!)
Learn how to classify rocks and learn the factors that contribute to the geologic classification systems.
1) How and where do rocks form? [environments]
2) Can rocks be classified according to the processes that form them?
3) How do we know…how to determine rock origins?
4) Are the rock classes related to one another?
1) How and where do rocks form? [environments]
Most rocks are aggregates of mineral grains.
Many rocks originate from observable processes that take place at Earth’s surface
Not all rocks can be related to processes visible at the surface—this suggests they relate to processes active within the Earth
2) Can rocks be classified according to the processes that form them? [this is a GENETIC way of classifying them, and the rock cycle is the sequence of processes and products that links the different types to each other]
Sedimentary rocks form from the products of the breakdown of preexisting rocks.
Igneous rocks form from the solidification of molten rock (magma).
Metamorphic rocks form by the solid-state transformation of minerals in a preexisting rock under the influence of elevated temperature, pressure, hot fluids, or all three.
Weathering, the deterioration of rocks results in smaller rocks and mineral grains. [clastic]
Chemical sedimentary rocks form via the precipitation
Lithification – the process by which lose sediments form sedimentary rock via compaction and/or cementation
Bedding –the distinctive layering of sedimentary rocks as sediments are laid down through time.
Magma – molten rock
Volcanic rocks solidify at the surface [extrusive]
Plutonic rocks solidify beneath the surface [intrusive]
Plutonic rocks typically have a massive appearance because they lack layering.
Metamorphic rocks have been changed by conditions inside Earth.
Regional metamorphic rocks have been squeezed and heated by overlying rocks and/or tectonic processes. They usually exhibit layering. This type is common at convergent plate boundaries.
Contact metamorphic rocks have been cooked and/or stewed, typically near igneous intrusions.
Hydrothermal metamorphic rocks form due to hot-fluid reactions with rock.
A link between processes and rock products that emphasizes the genetic nature of rock classification.
The rock cycle, the processes and the relationships, are related to processes at plate boundaries, and hence plate tectonics is a driving force in the rock cycle.
Chapter 4 –igneous rocks and volcanism
A. Magma vs. Lava: Intrusive (plutonic) versus extrusive (volcanic) –think about how texture of the rock tells the story of what it’s environment of cooling was like
B. Bowen’s Reaction Series, felsic versus mafic—the order in which the minerals crystallize depending on their melting points.
C. Igneous rock textures (fine-grained = aphanitic, coarse-grained = phaneritic, porphyritic is a type of aphanitic that indicates a compound cooling history (phenocryst, ground mass [matrix], pegmatitic, vesicular, fragmental, glassy)
D. Causes of changes in magma composition or differentiation: (“SPAM” – settling crystals, partial melting, assimilation, magma mixing)
E. Igneous rocks (rhyolite, andesite, basalt, granite, diorite, gabbro, pumice, obsidian)
F. Plutonic structures (dikes, sills, stocks, batholiths, laccoliths, pipes)
Volcanic & Plutonic Activity
A. Relationship between tectonic plates and volcanics/plutonics (divergent, convergent, transform)
B. Types of volcanoes (shield, composite cone/stratovolcano, cinder cone, maar, caldera), their compositions, features, associated events, and examples on Earth
C. Craters and calderas
D. Fissure eruptions & flood (“plateau”) basalts
E. Formation of columns, pillows, lava tubes
F. Pyroclastic eruptions
G. Relationship between magma silica content and viscosity
H. Relationship between magma gas and silica content and explosivity
I. Volcanic hazards (lahars, debris avalanches, tephra and ash, pyroclastic flows (nuee ardentes), earthquakes, tsunamis, etc.)
J. Volcanic Monitoring: earthquakes, deformation, gases; forecasting vs. prediction;
Weathering & Soil and Sedimentary Rocks
A. Mechanical vs. chemical weathering
B. Mechanical weathering processes: frost wedging, unloading/sheeting, insolation (thermal expansion), salt crystallization, biologic activity (tree roots, animal activity--including humans), spalling
why frost wedging => water expands by 9% to form ice
C. Talus slopes
D. Chemical weathering processes: dissolution (and impact of increased acidity), oxidation, hydrolysis (know basic process and basic minerals types and/or elements affected – don’t need to know precise chemical reaction)
E. Chemical weathering processes that decompose iron-rich minerals, feldspars and quartz and the products weathering of these minerals creates
F. Relationship between Bowen’s Reaction Series and weathering rates (those minerals that crystallize at the highest temperatures are most susceptible to weathering.
G. Understand spheroidal weathering
H. Effects on weathering rates of climate, parent, fractures, topography
I. Controls on soil formation(temperature, rainfall, parent, slope, fractures, vegetation, orientation)
J. Composition of soil and basic concept of soil profile (humus at top, unaltered parent material on bottom, gradational zones between)
A. Sedimentary rock abundance on earth
B. Detrital (or clastic) versus chemical sedimentary rocks & how named: particle size and comp for clastic; and for chemical, method of extraction (materials removed by org vs. inorganic process) and mineralogy
C. Distinction between inorganic chemical and biochemical (organic) sedimentary rocks; examples thereof
D. Lithification processes – compaction, cementation, intergrown crystals
E. Three main cementing materials:
F. Transport distance and time – interpretation of presence of feldspars and other rock fragments, poor sorting, angular grains
G. Identify and know depositional environments, major mineral component(s) and symbols of mud-stone/shale, sandstone, conglomerate, breccia, limestone, chert, coal and
rock salt, rock gypsum
H. Interpretation of sedimentary structures, such as bedding, laminae, cross beds, ripple marks (symmetric and asymmetric), mud cracks, graded beds, fossils
I. Know generally what is necessary for fossilization to occur
J. Interpretation of bedding and facies diagrams
Chapter 6 Metamorphic Rocks
Metamorphism, from the Greek:
Meta(to change) morph (form)
What is metamorphism?
Changes that take place in a rock in response to a change in its environment. These changes can be mineralogical, chemical, and textural (usually usually in the solid state) and result from changes in temperature, pressure, and/or addition or subtraction of fluids. The parent rock is called the protolith.
Metamorphic rocks have been changed by conditions inside Earth.
What is the role of temperature in metamorphism?
Heat drives away water and gases. The geothermal gradient is about 25-30 deg. C/km depth beneath continents and 60 deg C/km beneath oceans. Rocks also experience higher temperatures near igneous intrusions.
What is the role of pressure in metamorphism?
Stress = force on a given area; normal stress is perpendicular to a surface, whereas shear stress is parallel to a surface. Strain is the deformation of a rock in response to the applied stress.
What is the role of fluid in metamorphism?
Fluids from the original rock or from magma delivers and removes minerals and ions and allow reactions to take place faster than in dry conditions.
Why do metamorphic rocks exist at the surface?
Mountain building processes uplift rocks and expose them at the surface. Temperature, pressure, and fluid content are not enough to allow rocks to revert to their protolith rocks in the short amount of time they are uplifted.
How do we know…how to determine the stability of minerals?
Minerals are stable only within a range of temperatures and pressures. Laboratory experiments conducted on different minerals at controlled conditions reveal the ranges of temperature and pressures at which they are stable.
What were the conditions of metamorphism?
These are revealed by “index minerals”.
How are metamorphic rocks classified?
Metamorphic rocks are classified by texture (foliation and grain size) and mineral content. Foliated rocks display a preferred orientation of mineral grains or banding. Foliated rocks crystallize under lithostatic pressure. Nonfoliated rocks crystallize under hydrostatic pressure.
They are also classified by grade. Increasing temperature and pressure yields a higher grade of metamorphic rock. Compare figure 6.2 in Smith and Pun with fig. 6.23.
What was the rock before it was metamorphosed?
Protolith or parent rock is interpreted from the mineral composition of the rock, so long as fluids have not extensively changed the composition during metamorphism. Major elements such as Fe and Mg found in the constituent metamorphic rocks are similar to those found in the minerals of the parent rock.
If a parent rock contains mainly one mineral its metamorphosed equivalent can often contain mainly the same mineral but recrystallized. (e.g. limestone => marble; quartz sandstone => quartzite). See fig. 6.23 in Smith and Pun.
Protolith increasing metamorphic grade=>
One example: shale => slate => phyllite => schist => gneiss
Where does metamorphism occur?
Regional metamorphic rocks have been squeezed and heated by overlying rocks and/or tectonic processes. They usually exhibit layering or foliation This type is common at convergent plate boundaries.
Contact metamorphic rocks have been cooked and/or stewed, typically near igneous intrusions.
Hydrothermal metamorphic rocks form due to hot-fluid reactions with rock.
Chapter 7 – Earth Materials as time keepers
A. History of thought regarding the age of the Earth.
B. Catastrophism and Uniformitarianism: Archbishop Ussher-1654, Buffon (Iron balls), Joly (salt), Cuvier (fossils), Werner, Hutton (“Deep time”; the present is the key to the past); Lyell (1830-first textbook of geology)
C. Geologic Time Scale
D. Age of beginning of Paleozoic Era (or Phanerozoic Eon) and significance; Age of beginning of Mesozoic and significance; age of beginning of Cenozoic and significance; age of Quaternary period
E. Principles of relative dating (laws of stratigraphy—Nicholas Steno): superposition; original horizontality; lateral continuity, law of faunal succession (index fossils), cross-cutting relations, inclusion, uniformitarianism
F. Estimates for age of the Earth: Ussher (6000 yr), Buffon (75,000), Joly (salt; 90 m.y.), Lord Kelvin (24-40 m.y.), others (e.g. sedimentation: 3 m.y. – 1.58 b.y.);
G. Basic understanding of absolute dating techniques (radiometric dating [t1/2]; dendrochronology): (Bequerel, Curie, Rutherford, Boltwood [1905-1910; dated rocks 410 m.y. – 2.2 b.y.])
H. Unconformities (hiatus or loss of record) : angular unconformity, disconformity, nonconformity
Web tools Smithsonian Institution--Geologic Time
A. Know what causes earthquakes
B. Association between plate tectonics and earthquakes
C. Focus versus epicenter
D. Seismic waves – distinguish body waves, P&S, and surface waves (motion, relative speed, materials they travel through, and how density and rigidity of materials vary speed)
E. Know how seismic waves have aided understanding of earth’s interior – concept of shadow zones
F. Seismographs – basically how they work and what they record
G. Know how to determine distance from epicenter and how to locate epicenter
H. Deep versus shallow quakes – related to plate tectonics and damage caused
I. Know potential causes of earthquakes away from plate boundaries (intraplate)
J. Magnitude versus intensity – Mercalli scale versus Richter scale
K. Energy & amplitude differences between levels of magnitude
L. Foreshocks & aftershocks
M. Movement along faults – stick-slip, regular slip, fault creep
N. Effects of the following on earthquake destruction – magnitude, depth, duration of vibrations, nature of material
O. Earthquake hazards and causes of earthquake destruction (e.g., mass wasting, fires, subsidence, liquefaction, seiches, buildings and other human-made structures breaking, tsunamis, etc.)
P. Tsunamis – wave speed, wave length & wave height (at sea and near shore), ability to detect
R. Basis of earthquake forecasting (NOT prediction)
Mass Wasting—the downslope movement of geologic material under the direct influence of gravity
G. Classification of events (material involved and nature and rate of movement)
H. Types of material involved (mud, debris, rock & earth)
I. Types and relative speeds of movement (falls, avalanches, slides, slumps, flows, creep and solifluction)
J. Evidence of mass wasting on the landscape
K. Impacts of water, vegetation, oversteepening, undercutting, orientation of bedding, “rock quality”, and fracturing on mass wasting
L. Mass wasting “triggers”: examples: saturation and increased pore water pressures, timber harvesting and loss of root strength as cause of shallow, rapid (‘translational”) landslides; earthquakes; overloading
M. Turbidity currents
A. Importance as fresh water supply see
B. Distribution (soil moisture, zone of aeration, zone of saturation, water table)
C. Water table in relation to land, streams, lakes, swamps
D. Rate of flow, porosity and permeability; aquifers and aquitards
E. Confined versus unconfined aquifers
F. Springs, wells, artesian conditions
G. Concepts of recharge and renewability
I. Basics of limestone cavern formation and karst topography
J. Wells: drawdown; cone of depression:
K. Problems associated with groundwater (recharge rates, pollution, subsidence,
salt contamination, political issues).
Glaciers and climate change
A. Percent of land covered by glaciers today and at peak of ice age glacial period
B. Times of ice age, most recent ice age advance and retreat, and impacts on sea level; concept of rebound (isostasy)
C. Mountain glaciers (alpine/valley/cirque) versus continental glaciers (ice sheets)
D. Glacial flow – basal sliding and plastic flow (zone of plastic flow, location of crevasses, flow rates, surges)
E. Glacial budget – zones of accumulation and ablation (or wastage), and what happens to terminus when out of balance; concept of advancing and retreating
F. Glacial erosion – plucking (or quarrying) and abrasion, erratics & glacial or rock flour
G. Erosional features and how formed – u-shaped valleys/troughs, cirques, aretes, horns, hanging valleys, fiords, striations, polish
H. Drift – till versus stratified drift
I. Depositional features and how formed – moraines (lateral, medial, terminal, recessional, ground), drumlins, outwash, eskers, loess
J. Types of glacial lakes: lakes resulting from glacial dams, kettle lakes, tarns, pluvial lakes
Ice age impacts
L. Possible causes of ice ages (plate tectonics, dust & gases in atmosphere, variations in Earth’s orbit)
The hydrologic cycle
K. Concepts of sheet flow, rills, and streams; laminar, and turbulent flow
L. Relationships between velocity and discharge, gradient, & channel profile
M. Stream erosion – hydraulic action, abrasion and dissolution (chemical weathering)
N. Concepts of base level and temporary base level, and why & how they are changed; example: dams or changing sea level
O. Sediment transport – bed load, suspended load, dissolved load
P. Concepts of competence and capacity
Q. Stream patterns (straight, meandering, braided)
R. Stream deposition – alluvial fans, deltas, bars, flood plains, channel, natural levees
S. Features of meandering streams – lower gradient (slope of stream), lateral cutting, wide valleys, meanders, point bars, cut banks, flood plains, natural levees, oxbows, meander scars, meander migration
T. Features of “straight” streams – steeper gradient, downcutting, narrow v-shaped valleys, waterfalls, rapids
U. Features of braided streams (form where sediment is abundant): anastamosing channels; bars
V. Concept of stages of valley development, and characteristics of early and late stages, plus stream rejuvenation
W. Drainage basins, divides, incised meanders
X. Drainage patterns and their causes (dendritic, radial, rectangular); Impacts of stream management (human-made structures), such as dams, artificial levees and bank armoring
Y. Floods: flash floods, ice-jam floods
Z. Influence of
man: dam-burst floods, artificial levees (ex. 1993
Crustal Deformation-- Geologic structures
A. Concept of pressures/stresses – confining, compressional, tensional, shear
B. Brittle versus ductile/plastic deformation
C. Factors determining how rocks will behave when subjection to stresses (pressure, temperature, strength of materials, time)
D. Plate tectonics – know what types of deformation are typical at the different types of plate boundaries
E. Geologic maps
F. Fold terms and symbols – strike, dip, limbs, axis, plunge
G. Anticlines, synclines, domes, basins, hogbacks – how formed and how they outcrop and show on geologic maps
H. Dip-slip faults (vertical motion) – type of directional pressures which cause, type of movement; know normal versus reverse (and thrust) faults, and relative movement of hanging wall & footwall.
I. Know how thrust faults can lead to older rock over younger rock
J. Monoclines – how formed
K. Strike-slip faults (lateral motion –right or left lateral) – type of stress which causes and evidence on Earth’s surface
L. Joints & fractures – distinguish from faults; know causes of joint formation and the association of joints with weathering, hydrothermal deposits and groundwater movement
M. Development of block fault mountains and fault scarps – know terms horsts & grabens
N. 3. Faults: dip slip: reverse and normal (THRUST FAULT=LOW ANGLE REVERSE: EX. IS ROCKS IN GLACIER NATIONAL Park
O. Rock Behavior:
1. surface zones: brittle deformation: cataclasis, faulting, jointing
2. deeper zones: ductile deformation: folding, foliation, slaty cleavage, pervasive recrytallization
Studied of recent geologic history
A. Buried and submerged forests record landscape disturbances including past earthquakes and volcanic eruptions.
B. Subfossil trees can be dated by a radiocarbon methods, and sometimes by dendrochronology
C. “Light rings” are low density annual growth rings that record cool summers; many of these cool summers were triggered by climatically effective volcanic eruptions
D. Tree rings are the only tool that allow precise dating of ancient events to the year.