Geology of the Pacific Northwest Study Outline

updated June 8, 2013

Selected geology notes, many from the book How the Earth Works by Gary Smith and Aurora Pun and from Essential Earth, by Jordan and Grotzinger and other sources. Additional contributions courtesy of Celia Nightengale and others.

NOTE: And...in addition to the topics listeed below, there could be questions based on our lab exercises or any assigned videos. For example, you should know how to calculate the velocity of a tectonic plate given the appropriate data.

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.

Contents


Online resources

Main topics 
Detailed topics 
Contents of Detailed Topics section:
Why we study the Earth    How do we study the Earth   Plate Tectonics    How do energy and work apply to Earth?   Minerals, Earth's building blocks  
  Rocks, rock cycle, and rock-forming processes    Igneous rocks and volcanism    Weathering, soils, and sedimentary rocks    Metamorphic rocks 
Geologic time    Earthquakes    Mass wasting (mass movement)—Earth materials moving downslope    Groundwater    Running water 
Glaciers, glaciation, ice ages, and changing climate    Crustal deformation and geologic structures    
Study guide to tectonics and terranes of the Pacific Northwest  
Jack Powell’s 11-stage overview of Washington Geology      Ancient Rocks of the Pacific Northwest       
Terranes of the Pacific NW       North Cascades and Insular Superterrane      Eocene sedimentary rocks and the Olympic Mountains  
Early volcanism in the Pacific Northwest      Columbia River Basalt Group        CRBs and the Yellowstone Hot Spot   


Studies of recent geologic history



Online Resources


online resource for Physical Geography by Micheal Ritter  See "contents"; contains info on a number of physical geology concepts and, in each chapter, see "topic outline".

DLESE - Digital Library of Earth System Education

USGS simplified geologic glossary

Resources for Earth Sciences and Geography Instruction by Mark Francek

Geoman's glossary of Earth science terms 

Annenberg Earth Revealed video series    Mike Strickler's guides for Earth Revealed videos  Suggestion: read through Mike's questions on a pertinent video and use these as a guide when viewing the video!

Pacific Northwest geology:
WA Division of Geology and Earth Resources (DGER)           DGER "Geology of Washington"  
Northwest Origins by Townsend and Figge    John Figge's Introduction to the historical geology of WA State and southern BC  
Burke Museum at the Univ. of WA 

Ralph Dawes Geology of the Pacific NW pages  

Main topics

Test 1

Overview of Geology
-Intro to what geology and earth sciences are all about; see Earth science literacy and the "big ideas" about Earth science 
-Geologic materials (rocks and sediments), scale differences—microscopic to planetary, geologic time and geologic history, geologic processes (rock cycle, weathering, erosion, glaciers, rivers, mass movements, etc), Earth systems are interconnected: geosphere, hydrosphere, atmosphere biosphere, "cosmosphere"); structure of the Earth, Earth's heat energy: external (solar) vs. internal (radioactive isotopes, etc)
-History of thought about geology: some early big names: Nicholas Steno (basic principles about interpreting layers), James Hutton and uniformitarianism, Charles Lyell (first geology text)
-Scientific method: hypothesis, scientific theory, etc
-internal structure of the Earth (inner and outer core, mantle and crust) as related to density and composition: e.g. mafic vs felsic and continental crust vs. oceanic crust
-layers of the Earth based on physical properties (e.g. brittle vs. plastic): lithosphere, asthenosphere, etc
-basic plate tectonics: tectonic boundaries (convergent, divergent, transform), seafloor spreading, relationship of earthquakes, volcanoes, and topography to tectonics

Minerals
-Definition of a mineral
-mineral formation processes and structure of a mineral; made of elements (atoms)
-physical properties of minerals: form, fracture/cleavage, color, streak, luster, optical properties, density, taste, smell, feel magnetism, striations, fluorescence, optical properties, etc
-mineral families: silicates, oxides, sulfides, sulfates, native elements, carbonates [what defines these? examples]

Rocks and rock cycle
-definition of a rock
-be able to draw the rock cycle including the three major types of rocks plus the processes that connect or form each type
-rock: composition vs. texture
-know terms including clastic, outcrop, etc

Igneous rocks
-intrusive (plutonic) vs extrusive (volcanic)
-ultramafic, mafic, intermediate, felsic
-coarse vs. fine grained texture; porphyritic texture (groundmass; phenocrysts)
-glassy, vesicular, fragmental (volcaniclastic, aka pyroclastic)
-magma source and relation to plate tectonics; seafloor spreading, subduction, volcano types
-partial melting, differentiation (how and where different magmas form)
-Bowens reaction series and mineral melting points
-features and structures of intrusive igneous rocks: plutons, batholith, stock, dike, sill, laccolith

Sedimentary rocks
-mechanical (physical) and chemical weathering processes --> particles and solutions
-types of mechanical weathering
-chemical weathering processes
-stability differences of minerals
-products of weathering
-erosion and transportation
-depositional environments: terrestrial vs. marine
-lithification
-clastic (aka detrital) vs. chemical sedimentary rocks
-examples of detrital and chemical sedimentary rocks
-detrital rock texture: grain size, sorting, roundness, sediment maturity
-sandstones

-chemical sedimentary rocks
-textures of chemical sedimentary rocks
-minerals that compose chemical sedimentary rocks and their respective rock names (ex: calcite: limestone, silica: chert, etc; evaporites)
-What do sedimentary rocks record?  grain size, composition, environment, color, high vs. low energy
-examples of sedimentary rock processes and environments: glaciers, rivers, lakes, landslides, deserts, coastal areas deep sea etc

Sedimentary rocks structures and features
-beds, crossbeds, ripple marks, graded beds, mudcracks, raindrop imprints, preferred orientation, fossils    how formed, significance of, etc?
-formation, contact

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Detailed topics

Why we study earth? 


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, reduce hazards, find resources

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 obtained
What is an ore?  Pollution from extraction, mining, and disposal of waste
Water as a resource; use of...; irrigation;  the hydrologic cycle
Impacts from outer space: meteors and comets
Natural hazards: examples: hurricanes, earthquakes, volcanoes, landslides (mass movement), impacts from space

climate change and greenhouse gases—Earth systems are interconnected, so geosphere, atmosphere, hydrosphere, biosphere, and "cosmos-sphere" are linked!

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How do we study Earth?

From space: remote sensing; ocean exploration, drilling, measuring
Geologic record found in rocks
Eratosthenes estimated Earth's circumference more than 2000 yr ago
Field work is combined with lab work.

Earth's major layers: the crust, mantle, and core, differ in composition; other layers like lithosphere and asthenosphere differ in physical properties such as strength
Info about the Earth inferred from meteorites.
Open vs. closed systems;
ocean crust vs. continental crust; density differences
Earth systems: geosphere (lithosphere), atmosphere, hydrosphere (and cryosphere), biosphere, cosmosphere
heat transfer: conduction, radiation, convection
Earth's magnetic field.
Geologic time scale

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; some term this an "educated guess", but that does not count as a complete answer!~

A hypothesis should always be 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.

 uniformitarianism – a product of the work of James Hutton, a Scottish physician and farmer. Concept formalized by Charles Lyell, who wrote the first physical geology text in 3 volumes 1830-35, but term uniformitarianism not used until 1875; uniformitarianism is sometimes referred to by the statement "the present is the key to the past".  

 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.

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Theory of plate tectonics


History of thought about tectonics:

Sir Francis Bacon noticed that shape of the

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"?

Chrons

Mid Atlantic Ridge, East Pacific Rise, etc.seafloor spreading; ring of fire; speed aof 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?

GPS velocities

Age of the ocean floor vs. age of continents

Pangaea the supercontinent.

Mantle convection; hot spots (mantle plume)

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Web:

http://www.scotese.com/newpage13.htm

Plate tectonics section in Ritter's online book   see also his link Tectonics and landforms 

Plate Tectonics links in Mark Francek's Geo Resource pages

 

 


 
Plate boundaries

Divergent boundaries separate plates moving apart. Ex: Atlantic Ocean expands by ~5 mm/yr. Material from asthenosphere moves up into the gash as plates separate.

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.
Hot spots

These occur where molten rock ascend from deep in the mantle below the moving lithosphere. Plate tectonics does not explain hot spots. Examples are Hawaii and Yellowstone.

Hot spots

These occur where molten rock ascend from deep in the mantle below the moving lithosphere. Plate tectonics does not explain hot spots. Examples are Hawaii and Yellowstone.



How do the concepts of energy and work apply to Earth?

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 generates heat in the Earth’s interior.

Equilibrium is the balance that can exist in any system

How heat causes motion

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.


Minerals: building blocks of rocks, and the planet

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?

 

Mineral characteristics:

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

Crystal habit: the arrangement of the crystal faces reflects atomic arrangement and crystal structure during growth of crystal.

Chemical bonds

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.

 

WEB

 

Atlas of igneous & metamorphic rocks, textures, and minerals

Minerals links from Mark Francek's Geo Resource pages

 


Rocks and rock-forming processes

Learning objectives:

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.

Questions:

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] p. 54

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.

 

Rock classes:

(See more details on the different rock classes farther down)

Sedimentary (summary)

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.

 

Igneous Rocks (summary)

Magma – molten rock p. 55.

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 (summary)

Metamorphic rocks have been changed by conditions inside Earth. P. 56

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.

 

Rock cycle

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.

 


Igneous rocks and volcanism

Igneous Rocks

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;



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Weathering, soil, and sedimentary rocks

 

Weathering:

 

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)

 

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Sedimentary rocks

 

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

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Metamorphism and 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.

Metamorphic volcabulary words

protolith, foliation, metamorphic grade, regional metamorphism, contact metamorphism, hydrothermal metamorphism, index mineral, metamorphic facies (zones), slate, phyllite, gneiss, quartzite, marble
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Geologic Time: 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, James 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, inclusions, 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 [half life = t1/2]; dendrochronology): (Bequerel, Curie, Rutherford, Boltwood [1905-1910; dated rocks 410 m.y. – 2.2 b.y.]); Claire Patterson  4.5 Ga

H. Unconformities (hiatus or loss of record) : angular unconformity, disconformity, nonconformity



Geologic time volcabulary words

relative dating, absolute dating, half life, parent element (radioactive nuclide), daughter element (stable), radiocarbon dating, geologic time scale

Web tools


Smithsonian Institution—Geologic Time  

UC Berkeley—Geologic Time Scale 


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Earthquakes

 

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

Q.     Western Washington earthquake causes and hazards, and evidence for BIG quakes

R.     Basis of earthquake forecasting (NOT prediction)

 

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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

 

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Groundwater

 

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

H.     Hot springs – source of heat (magma, cooling plutons, geothermal gradient)

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).





 

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Running Water

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 Mississippi River flood); channelization

 

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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

K.      Ice age impacts on the U.S., Washington State and Thurston County

L.      Possible causes of ice ages (plate tectonics, dust & gases in atmosphere, variations in Earth’s orbit)


 

Terms
ice sheet, continental glacier, alpine glacier, valley glacier, ice cap
arete, col, horn, hanging valley, U-shaped valley, cirque and cirque glacier, tarn, striations
moraine (lateral, terminal, medial, ground), kame, kettle,
outwash, till, varves, erratics, stratified vs. unstratified glacial drift, drumlins and drumliniodal terrane, flutes, esker
Missoula floods (when, how, how many, effects)
Milankovitch cycles: what are they and what have they influenced?
paleoclimate, ice cores, dendrochronology, isotopes

Web links
Pat's links to earthscience textbooks and other aids online   
Michael Ritter's Chapter on Glacial systems  See "topic outline" to go to the list of topics for this chapter. This is nice review!

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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


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Study guide to tectonics and terranes of the Pacific Northwest


This Dynamic Earth, Bob Tilling  

This Dynamic Planet, Smithsonian   

 
Maps

Map Scales   (types: bar, verbal, fraction; implications for area covered and detail?)

Projections  (ex: conic, plane, cylindrical, interrupted, Mercator; equivalence vs. conformality)

Isolines and contour maps  (contour interval, index contour; rule of v’s; how made—historically vs. today?, magnetic north vs. true north and declination)

Remote sensing: aerial photos, orthophotos, georeferencing, color/infrared, microwave, multispectral (LANDSAT), LIDAR; radar interfereometry)

Global Positioning Systems (GPS)

Geophysical imaging: gravity, seismic, magnetics

GIS—Geographic Information Systems
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Jack Powell’s 11-stage overview of Washington Geology


1)      Rodinia and Belt Supergroup (1.5–1 Ga)

2)      Rifting of Rodinia (750 Ma)

3)      Kootenai coastal sediments (750–200 Ma)  (Snowball Earth in NW?)

4)      Pangaea  (300–200 Ma)

5)      Docking of Intermontane Superterrane—rocks of Okanagan Highlands: (What is terrane?   …superterrane?   see next lecture (180–170 Ma); new volcanic arc forms

6)      Docking of Insular Superterrane (rocks of North Cascades (100–60 Ma)

7)      Eocene-to-Miocene Sandstones and volcanics (55–20 Ma)

8)      Docking of Olympia Peninsula (50–30 Ma)

9)      Eruption of Columbia River Basalts (17–6 Ma)

10)  Ice Ages (1.6 Ma–11,500 yr B.P.)

11)  Modern Cascades Volanoes, 2 Ma to today
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Ancient Rocks of the Pacific Northwest

Geologic Time Scale (GSA)     USGS Geologic Time Scale 2010 (pdf file)   Smithsonian version     Berkeley edition  

Age of Earth

First life  3.8–3.5 Ga? (Prokaryotes)

Oxygen revolution ~2.4 Ga  Stromatolite fossils, cyanobacteria, Prokaryotes vs. Eukaryotes; Snowball Earth #1;

Eukaryotes? 2.1–1.5 Ga?,

Precambrian rocks—where? Craton, basement rocks? How to study basement rocks? Rb87-Sr87

Parent vs. daughter product> 0.706 line for Sr87.

How to study basement?  (windows, cores, inclusions, geophysics).

Thickness of Belt rocks (15–20 km)

Belt rock types (Ss, Sltstn, Ls, Sh);  Structures (ripple marks, raindrop imprints; fossils (stromatolites)

Environment of deposition?
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 Terranes of the Pacific NW (including Intermontane Superterrane)


How to grow a continent?  Sedimentation, subduction, collision??

What are terranes?     …superterranes?

Major types of terranes: hot spot, island arc, oceanic spreading ridges, microcontinents.

Guess which of the four types of terrane noted above based the following geology: felsic volcanics and plutonic, metamorphic; conglomerate, sandstone, and coal?
Which based on this geology? intermediate or felsic volcanics. graded beds; limestone, graywacke (from eroded volcanoes)
Which based on these rocks? basalt, limestone, sandstone, siltstone, shale
And finally which of the terrane types is characterized by these rocks? shale, chert, limestone, basalt (pillows), gabbro, serpentinite, maybe peridotite or dunite?


Where did terrane originate? (How do we know?) rock types, microcontinents, fossils, sediment provenance, and paleomagnetics

      Paleomagnetics (inclination vs. declination)

When did terrane dock? age of terrance, stitching pluton, overlap sequences, timing of regional metamorphism

Major terranes of WA: (see Jack Powell's 11 major episodes...)
Intermontane Superterrane: Okanogan highlands have some of these rocks
Insular Superterrane: North Cascades rocks: Terrane groupings! 95 Ma. Some were “exotic terranes”; melange

Intermontane Superterrane
...after rifting of Rodinia: probably passive margin (like east coast North America) then...
Kootenay Arc (what caused it?)
Intermontane accretion: when did this occur?
What evidence tell us where some of the terranes in the Intermontane Superterrane came from?
What is the significance of Tethyan fossils? What was the Tethys?
Rocks of the Methow Basin? What is deposited there? What do the deposits show?
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North Cascades and Insular Superterrane

When did the terranes dock?
How extensive are the terranes, for example, Wrangellia (how far to the north and south?) What about the paleomagnetics--what can this show?
Any clues as to the style of terrane docking based on distribution of the terrane such as Wrangellia north and south?
Major faults cut the North Cascades and separate major terrane groups.
    Skagit Crystalline core, melanges, NW Cascades and San Juan thrust system


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Eocene sedimentary rocks and the Olympic Mountains

From 55 to at least 20 Ma sediment accumulated in basins to form widespread sedimentary rock units such as the Cowlitz, Blakely, Skookumchuck, Lincoln Creek, Tukwilla, and other formations. Basins opening up along strike-slip faults like the Straight Creek Fault may have been responsible. The rocks accumulated sediments, including volcanic sediments at times of volcanism.

A stratigraphic diagram shows the relationship of the different formations.

Fossils in rocks record details of warmer climate conditions and about the nature of the ecosystems, e.g., petrified wood at Vantage, bivalves (like clams and mussells), leaves and coal, etc.
McIntosh Formation (mostly shale, but includes Tenino Sandstone). (Super. of Public Ed. teachers in one school.
Wilkeson Formation (State Capitol)
volcanoes began to erupt--interbedded with the sandstones (Ohanepecosh and Northcraft volcanoes)! e.g. Northcraft Formation (up Skookumchuck valley)
Skookumchuck Formation--older, late Eocene; few if any volcanics
Blakely Formation--
Rocks in coal mine are Skookumchuck.
*
Olympics "docked" 30–25 Ma??    "horshoe of basalt around east side of Peninsula.   Age of basalts?
How does the age of the Crescent basalts distributed up and down the coasts
Core rocks are green spumoni. What is the spumoni made of--what kind of rocks and where formed?)
What kind of faults cut through the Olympics and how do the faults demonstrate what happened? What kind of sedimentary rocks are be
core rocks of the Olympic Peninsula?  Are they the same age and degree of metamorphism from east to west?
Origin of Crescent Basalts....what kind of tectonic environment? Any modern analogs??
How did Crescent Basalts dock onto coast?
How extensive along the coast are the Crescent-Siletz Basalts?
How do the ages of the basalts vary from North to south?
What is an accretionary wedge? How, and where does it form?
How far north and south does basalt extend?
Note bend in Cascade Range as you go north--earthquakes at depth show subduction zone bends too--northward push along coast causes shortening, but strong crystalline "buttress" to north cause subduction zone to arch upwards.
Basin and Range extension and northwestward push--creates NW-trending fault zones and features
Rotating blocks of coastal rocks

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Early volcanism in the Pacific Northwest

Cascade Range born ~ 40 Ma
early ("west") Cascades 40–15 Ma
high Cascade arc last 5 Ma (USGS Cascades Volcano Observatory)
Age of subducting oceanic crust may determine angle of subduction and location of eruptions
North vs. Southern Cascade Range
Northcraft and Ohanapecosh Formations, Fifes Peaks, Stevens Ridge--many included ash flows
Some eruptions huge--thick deposits, welded tuff--andesite to rhyolite.
-volcanoes shed debris via lahars and river transport; debris collected in sedimentary basins: Lincoln Creek, Blakeley, and Tukwilla Formations for example.
Columbia River Basalts (see more below)

...in Oregon:
John Day Fossil Beds  in eastern Oregon and other deposits--extensive fossil record recorded in volcanic ash
Clarno and John Day Formations --much ash produced by large caldera eruptions (supervolcanoes)
Recent discovery of  calderas near Prineville OR: ~40, 29.5, & 28.5 Ma;

Mascall, Rattlesnake Formations younger
Ellensburg Formation in WA 12–4 Ma: lahars


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Columbia River Basalts

"CRBs" Flood basalts erupted from fissures in ID and eastern WA and OR ~17–6 Ma
Cover > 175,000 sq. km;   >300 flows CVO webpage on CRBs 
interbeds, colonade, entablature, pillows, feeder dikes, Blue Lake rhino, Ginko Forest; diatomite
greenhouse warming,  fossils,

Columbia River Basalt Group (CRBs) and the Yellowstone Hot Spot (YHS)

Mantle plume probably related to both CRBs and YHS
Location of the Sr/Rb "0.706 line" shows a possible explanation that links CRBs and YHS
706 line is at boundary of old craton with younger accreted terranes: flood basalts to west, "supervolcano" eruptions to east
Steens Basalts to south in OR are similar
Locations of older YHS calderas in Snake River Plain (SRP) show movement of North American tectonic plate over YHS
Great volume of the YHS eruptions; Yellowstone's ongoing activity YVO 


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Geography and maps: portraying the Earth

Map scale: know what it is and how to express it; know large vs. small scale
Map projections: what are they?
topographic maps: contour lines/isolines; contour interval;
global positioning systems; GPS
what is radar interfereometry; where has it been used?
what is remote sensing? Give an example.
Geographic information systems, GIS
LiDAR



Studies 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.


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