cvl423 exam review

small earthquakes that often occur before major earthquakes by days or even by as much as several years

foreshocks

earthquakes of lesser magnitude that occur after a strong earthquake

aftershocks

limited success in predicting an upcoming major earthquake

what’s the outcome of monitoring foreshocks?

they help geologists to determine the size and area of the slippage

what’s the outcome of monitoring aftershocks?

point of where rock slippage occurs. Also called the focus.

hypocentre

location on the earth’s surface, directly above the hypocenter

epicentre

waves that travel through the earth’s interior; arrive at a seismic station before surface waves

body waves

are the waves that travel in the rock layers just below the earth’s surface i.e. travel only through the crust; mainly responsible for the damage and destruction associated with earthquakes

Surface waves

push-pull waves: compressing and expanding the rocks in the direction of waves travel

P or primary waves

when the rocks shake perpendicular to the direction of wave travel

Secondary waves

1\.7 times as fast as S waves

how fast do p waves travel

1\.1 times as fast as S waves

how fast do s waves travel

have slightly greater amplitudes than P waves.

fact about s waves

even greater amplitudes than S waves and retain their maximum amplitude for much longer

fact about surface waves

destruction may not be a true measure of the earthquakes’ actual severity because it depends only on the ground shaking and the building destruction; does not take into consideration the population intensity, building design, and the nature of surface materials

what’s the drawback of intensity or mercalli scales?

• Magnitude

• Duration of shaking

• Local geology

• Population density where the earthquake occurs

• Distance from the epicenter

• Construction practices

• Disaster response planning

• Time: earthquakes during working hours in populated urban areas are the most destructive and cause most injuries.

factors affecting earthquake destruction

• Seismic vibrations

• Liquefaction

• Tsunami

• Fire

• Landslides and subsidence

Major destructive forces that earthquake vibrations can trigger

causes most injuries

what’s the effect of seismic vibration

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they resist ground shaking better than those built on poorly consolidated or water-saturated material

what’s good about structures built on bedrock

to resist the maximum horizontal ground shear (base shear) expected

how should buildings be designed

height of tsunami in an open ocean?

the velocity and wavelength decrease, thus the height of the waves increase and can reach 30 m

how are tsunamis in shallow water in coastal areas?

800km/hr

how fast do tsunamis cross the ocean?

flat shore

does a tsunami have more effect on a flat shore or steep shore

• The best defense is an effective early warning system

• Buildings to be constructed with their narrowest dimension oriented towards the wave

• Lower levels of waterfront buildings comprise open parking to allow water to flow through Tsunami

Minimizing the tsunami’s destruction effect

• Circum-Pacific belt

• Convergent plate boundaries around megathrust faults

• Alpine-Himalayan belt

• Collision of the African and Indian subcontinents with the Eurasian plate

• Thrust and strike-slip faults

• Transform faults

• San Andreas Fault (California)

• Alpine’s Fault (New Zealand)

• North Anatolian Fault (Turkey)

• Intraplate earthquakes (e.g. East of the Rockies, Missouri)

• Ancient fault systems

• Fracking

Where do most destructive earthquakes occur?

the unending circulation of water through the earth’s different spheres – hydrosphere, atmosphere, geosphere, and biosphere.

what is the hydrological cycle?

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evaporation and transpiration involve water going into the atmosphere

What is evapotranspiration?

the land area drained by a stream and its tributaries. (Also called a watershed)

Drainage basin

the imaginary line that bounds a drainage basin

divide

largest particles are carried in suspension. Depends on flow velocity and particle settling velocity \*settling velocity must be less than flow velocity to be carried

define suspended load

Portion of stream load too large to be carried in suspension. Move along the bottom of the bed by sliding, rolling and saltation

define bed load

maximum load a stream can carry per unit time

define capacity

Ability to transport particles based on size

define competence

dendritic, radial, rectangular, trellis

what are the 4 types of drainage patterns?

when the flow of a stream exceeds the capacity of its channel and overflows its banks

when does a flood happen?

natural phenomena, but the magnitude and frequency are influenced by human activities like forest clearing, cities, flood control structures

what are floods?

regional, flash, ice-jam, dam-failure

name some types of floods

• Steepness of slope

• Nature of the surface materials

• Intensity of the rainfall

• Type and amount of vegetation

what are factors effecting run-off, evaporation, infiltration?

soil water for plants

what is the zone of soil moisture

Water held by surface tension (capillary)

what is capillary fringe

Pores are filled with air and water, water can not be pumped from this zone

what is zone of aeration (Vadose)

All the open spaces of sediments and rocks are entirely filled with water, this water is the groundwater The upper limit of the saturation zone is the water table

what is Zone of saturation (Phreatic)

Impermeable layer that hinders or prevents water movement (such as clay)

define aquitard(confining layers)

Permeable rock layer or sediment that transmits groundwater freely (such as sand and gravels)

define aquifier

• Plants

• Animals for food

• Trees for lumber

• Energy from flowing water, sun, wind

What are examples of renewable resources?

• Fuels (coal, oil, natural gas)

• Metals (iron, copper, uranium, gold)

what are examples of non-renewable resources?

A geologic environment that allows economically significant amounts of oil and gas to accumulate underground

define oil trap

porous and permeable rock that contains petroleum and natural gas

define reservoir rock

impermeable to oil and gas, prevents it from escaping

define cap rock

an unconventional but significant source of oil

• Mixture of clay, sand, water and bitumen (black, highly viscous material)

• Extracting and refining require almost half of the energy from the end product

what are oil sands?

• Huge quantities of oil can be trapped in impermeable rock

• Fluids (mixture of water, sand, and chemicals) are pumped into the impermeable rock at high pressures • Opens cracks and keeps them open for gas and oil to flow up to the surface

• Can trigger minor earthquakes and cause groundwater contamination

what is hydraulic fracturing (fracking)?

Uranium-235

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• Readily fissionable

• Only naturally occurring isotope

• Clean source; doesn’t emit carbon dioxide

• Cleaning up nuclear power plant accidents is difficult and costly e.g. Chornobyl plant Energy Resources – Nuclear Energy

What’s the primary fuel for most nuclear power plants?

useful minerals that are available commercially

What are mineral resources?

already identified deposits from which minerals can be extracted profitably

What are reserves?

a deposit that has naturally occurring concentration of one or more metallic minerals that can be extracted for economic goods

what’s an ore?

• Magmatic Differentiation

• Hydrothermal Deposits

• Metamorphic Deposits

• Weathering Deposits

• Placer Deposits

What are main minerals deposits?

• Very abundant, little intrinsic value until after extraction and processing

• Natural aggregate - Crushed stone, sand, and gravel. Used to make concrete and asphalt.

• Solid stone used for building facings, walkways, countertops

• Gypsum for plaster and wallboard

• Clay for tile and bricks

• Limestone and shale for cement Building Materials

Building Materials

• These are sources of specific chemical elements or compounds

• May also be sourced for the physical property e.g. garnet which can be used as an abrasive

• Fertilizer – mainly phosphate and potassium are from sedimentary and evaporite deposits

• Sulfur – Found in salt domes and volcanic areas

• Salt – found in evaporite deposits Industrial minerals

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• Clays

• Carbonate Minerals

• Evaporite Salts (mined in Saskatchewan and New Brunswick)

• Phosphate

• Sulphur (most extracted from fossil fuels)

• Talc, graphite, asbestos, garnet, corundum

Industrial Materials

changing in rock composition or texture due to heat, pressure, and the action of fluids.

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• Changes happen in solid state

• Physical and chemical changes

• Degree of change depends on the type and intensity of metamorphic processes

What is metamorphism?

Magmas: contact metamorphism

Earth’s internal heat

What are the sources of heat?

Responsible for changing the physical characteristics of the rock.

Pressure (stress)

\-Confining pressure (uniform)

Pressure is equal (uniform) in all directions

2 types of pressures

The pressure isn’t equal (non-uniform) in all directions.

Direct pressure

\-Squeezing the rock into the smallest possible volume without change in shape.

\-Increases with increasing burial depth.

\-forces mineral grains to crowd together and become compact.

\-Recrystallization but no internal deformation

Confining pressure (uniform stress)

\-Results in distortion of the rock

\-Associated with horizontal shortening and stretching of the earth’s crust

Directed Pressure (Differential Stress)

layers or sheet like shape as a result of high pressure

What is foliation

\-Rotation of mineral grains to a new orientation

\- Changing the shape of equidimensional grains to be elongated along the preferred orientation

\-Recrystallization of minerals to form grains that grow in the direction of the preferred orientation

Factors influencing the development of foliation

• Water originally trapped in pores of sedimentary rocks during formation

• Dehydration of water-bearing minerals such as gypsum (CaSO4.2H2O) which contain water in their crystal structure

• Volatile fluid within the magma

Sources of chemically fluids:

200 degrees celsius

what temp. does metamorphism begin

700 degrees celsius

what temp. does melting begin

• Recrystallization, new minerals

• Segregation of minerals

• Foliation of rock, sheet-like layers

• Reorientation of layers, horizontal layers become inclined or vertical layers

• Bending of sedimentary rock layers

• Increase in grain size

Main changes to metamorphism

the actual number of years that have passed since an event occured

What is numeric dating

rocks are placed in their proper sequence of formation

what is relative dating?

a break/gap in the rock record caused by uplift, erosion, subsidence, and new sedimentation

what is an uncomformity?

William Smith, engineer (1700s) noted that sedimentary strata in widely separated areas could be identified and correlated by their distinctive fossil content.

Fossils and Correlation

a group of fossil that can be used to date rocks more precisely than a single fossil

Fossil assemblage

represents 88% of earth’s history

Precambrian time

they’re closer to the melting point, weaker, and more ductile.

What happens when rocks are in high temps?

Rocks are brittle and prone to fracture

What happens when rocks are in cool environments?

Increased in all directions makes rock less brittle and hard to break

Confining pressure

The way a rock responds to stress is influenced by mineral composition and texture

What is a rock type?

• Stress applied slowly enough can accommodate ductile deformation

• Applied too quickly and the rock will fracture

Time (rate of deformation)

rock salt, gypsum, shale

Weak rocks

True

Crystalline rocks (igneous) have strong internal bonds and will fracture.

True

Sedimentary & Metamorphic rocks that have foliation tend to be ductile and fail by folding.

limestone. schist, marble

Intermediate rocks:

Granite, basalt

Strong rocks:

\-Hanging wall

\-Footwall

\-Fault dip angle

Fault terminology:

vertical displacement along faults

Fault scarp:

Polished striated surface due to crystal blocks sliding against one another

Slickensides:

\-Loosely coherent rock that form near earth’s surface

\-composed of broken rock fragments

Fault Breccia:

• Movement is parallel to the slope of the fault surface

• dominant displacement is vertical

Dip slip

• Normal

• Reverse

• Thrust

Types of Dip-slip Faults

right lateral; left lateral

Types of Strike-slip Faults

\-Hanging wall moves down

\-Tension stress, lengthening

Normal fault

• The hanging wall moves up relative to the footwall

• The dip of the fault plane is > 45 degrees

• Resulted from compression stress, shortening

dip slip Reverse

• Displacement is horizontal

• Caused by shearing stress

Strike-slip Faults

Fractures with no layer displacement. Result of brittle behavior from rock. may range from a few mm (micro joints) to many tens of meters (master joints)

What are joints?

True

Rocks fracture in a plane parallel to the maximum principal stress and perpendicular to the minimum principal stress

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