GEOL 1330 Exam 3

runoff formula

(rainfall) - (infiltration) V(f)=A(db) * (runoff)

oceanic crust

-.16% volume -3 density -basalt/gabbro composition

continental crust

-.44% volume -2.7 density -granitic composition

core

-16.4% volume -10-13 density -Iron w/Nickel composition

mantle

-83% volume -3.3-5.7 density -peridotite composition

F.Y.I.

-U.S. production of oil had been decreasing since 1970. >has since increased to similar levels due to fracking -U.S. consumption has been largely increasing since at least 1949

uranium

-Uranium-235 is the only naturally occurring isotope that is ready fissionable >primarily fuel used in nuclear power plants >rare element in earth's crust

oil traps

-a geologic environment that allows for economically significant amounts of oil and gas to accumulate underground -all oil traps consist of a reservoir rock and a cap rock -reservoir rock - HIGH porosity and permeability -cap rock -LOW porosity and permeability

hydraulic conductivity (K)

-a measure of how efficiently an aquifer transmits water -a function of both permeability and porosity

plate tectonics

-a model explaining how the Earth works -a set of ideas explaining the observed motion of the Earth's lithosphere through the mechanisms of subduction and sea floor spreading, which in turn, generate earth's major features including continents and ocean basins

Groundwater contamination sites

-agriculture -landfills -industrial runoff

What determines the volume of floodwaters at a specific location?

-amount of rainfall (inches or cm.) -area of the drainage basin (miles square or km square)

recurrence interval

-average number of years between events of similar or greater magnitude (n+1)/m -the annual recurrence interval (RI) of an event of a particular magnitude is the average number of years between events of similar or greater magnitude -a better way of defining it is a flood that has a 1% chance of occurring every year

global climate change

-based on current models -earth's average surface temperature will continue to warm by 2-4 degrees Celsius in the next century -concentrations of carbon dioxide, methane, and other greenhouses gases are building up at faster rates than the previous 50 years

Rodinia

-before Pangea -Rodinia split apart betweeen 750 and 550 million years ago -some fragments eventually formed Gondwana while others became continental landmasses in the Northern Hemisphere -most of these landmasses were reassembled into Pangaea

petroleum and natural gas

-biological products derived from the remains of organisms in a marine environment -hydrocarbon compounds (H,C)

The core-mantle boundary

-characterized by bending (refracting) of the P-WAVES -the fact that S waves do not travel through the core provides evidence for a liquid layer beneath the rocky mantle as S Waves only move through solid rock and NOT a liquid medium

types of fossil fuels

-coal -oil -natural gas -oil shales -tar sands -gas hydrates

Use of Groundwater in Texas

-constitutes 57% of all water used in state -Agricultural (mainly irrigation) - 80% -Municipal - 15% -Industrial - 5%

oil shale

-contains enormous amounts of untapped "oil" -currently not worth mining because of world markets and current technologies

hydrocarbon generation

-continued burial of organic-rich sediment -temperatures ad pressures reach a critical point where organic matter is transformed to liquid and gaseous hydrocarbons -petroleum forms at T= 100-200 C, Gas at T=> 120 C

immature stage

-continued rifting creates new oceanic crust -cooling and subsidence of rifted margin allows sediments to be deposited

wind energy

-converting the kinetic energy of a moving air mass (wind) into others forms of energy to perform work -increase in the number of wind turbines installed >wind speed is crucial in determining suitability of installing a wind-energy facility

How can you increase the velocity of water in a channel?

-decrease resistance to flow -increase channel efficiency -increase slope

solar energy

-direct use of the Sun's rays to supply energy -passive solar collectors a) south-facing windows -active solar collectors a) photovoltaic (solar) cells convert the Sun's energy directly to electricity -stirling dish converts thermal energy to electricity

The Moho (Mohorovicic discontinuity)

-discovered in 1909 by Andrija Mohorovicic -observed that the average velocity of P waves increases ~200 km from earthquake source -concluded that at ~50 km there is a change in physical property in the earth

The Core - Mantle Boundary

-discovered in 1914 by Beno Gutenberg -there is an extensive zone where direct S waves are not observed -there is a smaller zone where direct P waves are not observed -concluded that there is a boundary separating the solid mantle from a liquid core

The Inner Core

-discovered in 1936 by Inge Lehmann -observed that some P-waves are strongly refracted as they pass through the inner portions of the core -seismic wave reflections from nuclear tests in 1960's confirmed the presence of the inner core

heat flow in the crust

-dominated by conduction -rates of heat flow in the crust are low

types of Earth resources

-energy -mineral -water

processes involved

-evaporation -precipitation -infiltration -runoff -transpiration

suture stage

-ex. Himalayan Mountains

remnant stage

-ex. Mediterranean stage

unconfined aquifer

-exposed at the land surface

The Wilson Cycle

-formation and destruction of ocean basins

coal

-formed mostly from plant material -along with oil and natural gas, coal is commonly called a fossil fuel -the major fuel used in power plants to genreate electricity -problems: environmental damage from mining and air pollution

non-renewable energy resources

-fossil fuels -nuclear fuels

gas hydrates - a fuel from ocean floor sediments

-gas hydrates are an unusual compact chemicals structure made of water and natural gas -(methane hydrates are the most common) -resembles ice but ignites when lit by a flame

geothermal energy

-geothermal energy is power generated by steam and hot water used for heating and to generate electricity -three factors determine if a geothermal reservoir has commercial value >a potent source of heat >large and porous reservoirs >a cap of low-permeability rocks

infiltration is affected by--

-ground slope -soil type -rainfall intensity -soil saturation -vegetation/land use

Sources of Earth's internal heat

-heat emitted by radioactive decay of isotopes of uranium (U), thorium (Th), and potassium (K) -heat released as iron crystallizes to form the solid inner core -heat released by colliding particles during the formation of the Earth

current levels of carbon dioxide

-highest in more than 800,000 years -other greenhouse gas concentrations also raising rapidly

current levels of methane

-highest in more than 800,000 years (almost 3x)

the average temperature of the Earth --

-hotter now than it has been any time during the last 2000 years

hydroelectric power

-hydroelectric power is power generated by falling water used to drive turbines to produce electricity -most energy is produced at large dams >dams have finite lifetimes >limited sites to construct dams

one aspect of the last 10,000 years

-i.e. rise of civilization -the remarkable stability of global climate

mantle convection

-important process in earth's interior -provides the force that propels the rigid lithospheric plates across the globe -because the mantle transmits S waves and at the same time flows, it is referred to as exhibiting plastic (both solid and fluid) behavior

In order to increase V to decrease A we:

-increase hydraulic radius (R) -increase slope (S) ; decrease sinuosity -decrease roughness (n)

Question: how can you reduce flooding without reducing discharge?

-lower the stage by reducing cross-sectional area (A) -to do that without reducing discharge (Q), you must INCREASE VELOCITY (V) (hint: remember the continuity equation)

magnetic reversals

-magnetic reversals are reversals in the polarity of the earth's magnetic field -we call north polarity normal and south polarity reversed -a period of time in which magnetism is dominantly of one polarity is called a magnetic epoch

other energy resources

-many other energy resources exist and are currently utilized -many have various drawbacks that make them difficult to rapidly replace fossil fuels

flow velocity

-measured by a current meter at several places across the stream channel -the newest meters use Doppler radar -older meters use a propeller that spins in response to the moving water

what we want to happen to hydrocarbons

-migration out of the source rock into a permeable reservoir rock (e.g. porous and permeable sandstone or limestone) -trapping of fluids by an impermeable seal called a cap rock (e.g. impermeable shale, limestone, or evaporite)

Tar sands

-mixtures of clay and sand combined with water and bitumen (a viscous tar) -several substantial deposits around the world -obtaining oil from tar sands has significant environmental drawbacks

Wells

-most common method of removing ground water -to ensure a continuous supply of water, a well must penetrate below the water table -pumping of wells can cause a) drawdown (lowering) of the water table b) cone of depression in the water table

hydrocarbon migration

-newly created petroleum and natural gas is mobile and flows (migrates) into adjacent permeable rock -because oil and gas are less dense than water, they will flow to the surface-unless something stops it

nuclear energy

-nuclear energy in an important part of U.S. energy needs -fuel comes from energy released by nuclear fission (splitting atoms) -resulting controlled chain reaction releases heat used to drive steam turbines

Springs

-occur where the water table intersects earth's surface -natural outflow of groundwater -can be caused by an aquitard creating a localized zone of saturation which is called a perched water table

tidal power

-ocean's energy potential remains largely untapped -tidal power is harnessed by constructing a dam across the mouth of a bay or estuary in a coastal area

carbon dioxide

-only 50% of emitted carbon dioxide ends up in the atmosphere -~25% ends up dissolved in the oceans which increases the acidity

marine environment

-organic-rich sediment is buried -sediment experiences elevated temperature and pressures due to burial

drainage pattern

-pattern of the interconnected network of streams in an area -often influenced by bedrock structures -common drainage patterns a) dendritic b) radial c) trellis d) rectangular (less common)

obstacles to development

-plant safety -example: Fukushima nuclear power plant, 2011

water mining

-problem associated with groundwater withdrawal -consists of treating groundwater as a nonrenewable source -in many places the water available to recharge the aquifer falls significantly short of the amount of being withdrawn

Saltwater contamination

-problem associated with groundwater withdrawal -excessive groundwater withdrawal causes saltwater to be drawn into wells, thus contaminating the freshwater supply -primarily a problem in coastal areas

subsidence

-problem associated with groundwater withdrawal -ground sinks when water is pumped from wells faster than natural recharge processes can replace it -ex. San Joaquin Valley of California

Groundwater contamination

-problems associated with groundwater withdrawal -sewage- although groundwater can be purified by traveling though certain rock types (e.x. sands and sandstone), high flow rates though other aquifers (e.g. limestone, coarse gravel) can transmit contaminants long distances -heavy pumping can also redirect contaminated water towards wells

opening and closing basins: the super continent cycle

-rifting and dispersal of one supercontinent results in creation of new oceans -closure of ocean basins results in reassembly of continental fragments -SUPERCONTINENT CYCLE

losing stream

-river water flows into (recharges) groundwater -connected -disconnected

seismic tomography

-signals from many different earthquakes and seismic stations are collected -allows seismologists to identify faster (colder) and slower (warmer) parts of earths interior -similar to CT scan

What happens to channel slope when you decrease channel sinuosity?

-slope INCREASES as sinuosity DECREASES -explains why we straighten rivers to try to mitigate flooding hazards

rates of groundwater movement

-slow to very slow (depending on permeability) -generally within the range of 10 to 100 cm per day -energy for the movement in provided by the force of gravity

renewable energy resources

-solar -wind -geothermal (?)

seismic refraction

-speeds up and bends up -slows down and bends down

lithosphere

-sphere of rock, rigid -100-250 km thick -includes crust + the uppermost solid mantle

bedrock streams

-streams that cut within hard bedrock -bedrock - a general term for the rock, usually solid, that underlies the soil or other unconsolidated material -the pattern of such streams generally reflects the structure of the underlying bedrock in the drainage basin

lower mantle

-strong -located in lower mantle -more rigid because increase in pressure

lower mantle

-strong -located in lower mantle -weak due to high temperatures

permeability

-the ability of a material to transmit a fluid -it is a measure of how fast water can travel through a rock or sediment

What makes a good aquifer?

-the ability to store large amounts of water which can be removed easily, as measured by a) porosity b) permeability

discharge

-the amount of water flowing past a certain point over a period of time -the rate of flow=volume/unit time Q=VA (V=average flow velocity A=cross sectional area of water (channel)) -conductivity * area * gradient

drainage basin

-the area drained by a river at a particular point -also referred to as the "watershed"

The continent cycle - before Pangaea

-the earliest documented supercontinent, Rodinia, formed about one billion years ago

porosity

-the percent void space in a rock or sediment -it is a measure of the potential volume of water than can be stored in a rock

peak oil

-the point in time when the maximum rate of global petroleum extraction is reached, after which the rate of production enters terminal decline

infiltration

-the portion of precipitation that soaks into the ground

paleomagnetism

-the study of the earth's past magnetic field as preserved by magnetic minerals in rocks -the most convincing evidence set forth to support the concepts of continental drift and sea-floor spreading

water table

-the top of the saturated zone of groundwater -the level to which water will rise in a hole -the level to which water will rise in an unconfined aquifer

Greenhouse Effect

-the trapping of energy (heat) by a planet's surface -specific gases in the atmosphere are responsible for the effect

hydraulic gradient

-the water table slope -determined by dividing the vertical difference between the recharge and discharge points by the length of flow between these points

heat flow in the mantle

-there is not a large change in temperature with depth in the mantle -mantle must have an effective method of transmitting heat from the core outward: convection

effect of urbanization

-urbanization prevents infiltration and increases rate of runoff -causes higher peak discharge (and stage) after rain

embryonic stage

-volcanic and non-marine sediments are deposited in rift valleys -as the crust is puled apart, large slabs of rocks sink, generating a rift valley -ex. East African Rift Valley

asthenosphere

-weak sphere -located in the upper mantle -weak due to high temperatures

formation of magnetic

-when new basaltic rocks form at mid-ocean ridges, they magnetize according to earth's existing magnetic field -hence, oceanic crust provides a permanent record of each reversal of our planet's magnetic field over the past 200 million years

Artesian well

-where groundwater under pressure rises above the level of the aquifer -two types of artesian wells a) nonflowing b) flowing

Greenhouse Gases (exluding H20)

1) Carbon Dioxide - 49% 2) methane - 18% 3) "CFC's" - 14% 4) nitrous oxides - 6% 5) others - 13%

top 10 proven crude oil reserves

1) Venezuela 2) Saudi Arabia 3) Canada 4) Iran 5) Iraq 6) Kuwait 7) United Arab Emirates 8)Russia 9) Libya 10) Nigeria

where does added carbon dioxide come from

1) burning of fossil fuels - 75% 2) land clearing - 15% 3) manufacturing - 7% 4) fuel wood -3%

What we know--

1) concentrations of carbon dioxide, methane, and other greenhouse gases have built up over the last 100+ years due to human activities 2) Earth's average surface temperature has armed by 0.9 degrees Celsius in the last century, a conclusion based on direct measurements

layering by chemical composition

1) core 2) mantle 3) crust

Frequency is measured by:

1) recurrence interval 2) exceedence probability

resources are classified as--

1) renewable 2) nonrenewable

Heating the Atmosphere

1) short-wave solar radiation passes through the atmosphere and is absorbed by Earth's surface 2) Earth's surface emits longwave radiation which is absorbed greenhouse gases 3) greenhouse gases radiate some energy Earthward, thus trapping heat in the lower atmosphere

layering by physical properties

1) solid inner core 2) liquid outer core 3) solid lower mantle 4) solid but mobile upper mantle (asthenosphere) 5) lithosphere

per capita consumption of resources in the United States

1) stone 2) sand/gravel 3) cement 4) other nonmetals 5) salt etc.

20% of the carbon dioxide emitted today will still be in the atmosphere 300 years from now

10% will still be there in 10,000 years

What was the warmest year on record?

2016

P-Wave Shadow Zone

An area between ~100 and ~140 degrees from an earthquake focus where little P-wave energy is recorded by seismographs.

Earth's internal heat engine

Earth's temperature gradually increases with an increase in depth at a rate known as the geothermal gradient

R

Hydraulic Radius

n

Manning's Roughness Coefficient

Discharge formula

Q=vA v= average flow velocity a= cross sectional area of water (channel)

calculating hydraulic radius

R=A/P (A=area P=wetted perimeter)

rate of flow formula

ROF = volume / unit time

convection

The transfer of heat by the movement of a fluid

S-Wave Shadow Zone

Those areas more than ~100 degrees from an earthquake focus where no S-waves are recorded.

Manning's Equation

V = 1.5 R2/3S1/2 n

The Hundred Year Flood

a flood which has a recurrence interval of 100 years

How is discharge plotted?

a hydrograph plots discharge (or stage) at a gauging station over time

drainage divide

a line separating adjacent drainage basins

resource

a naturally occurring material that is of potential economic use

reserve

a resource that can be economically (and legally) used today

chikyu

a state-of-the-start drilling ship designed to drill up to 7,000 meters (more than 4 miles) below the seafloor

meandering stream

a stream having a pattern of successive meanders (bends, sinuous curves, loops or turns)

In humid regions, the water table is-

a subdued replica of the ground surface

Important Phase changes in the Mantle

a) Olivine to Spinel -occurs at a depth of ~410 km b) Spinel to Perovskite -occurs at a depth of ~660 km -defines boundary between asthenosphere and mesosphere

All natural streams can be classified as either-

a) bedrock streams b) alluvial streams

What governs stream morphology?

a) braided streams - form in areas where the sediment is coarse (sand and gravel) an there is flow has high seasonable variability b) meandering streams - form in areas where the sediment load is fine (mud and sand) and stream flow is more constant

mechanisms of heat transfer

a) conduction - heat transfer by atomic or molecular impact b) convection - heat transfer by hot (less dense) material rising and cold (more dense) material sinking

evolution of an ocean basin

a) evolution of an ocean basin -splits landmasses into two or more smaller segments -ex. East African Rift, Baikal rift, Rhine Valley, Rio Grand Rift, and the basin and range -The Red Sea is an example of a rift valley that has lengthened and deepened into a narrow linear sea

What is Simonton's problem?

a) flooding - Simonton was incorporated in 1979. major flooding in 1991 and 1994 caused $4.5 million in damage b) erosion - significant erosion is locally occurring along the Brazos River in the Simonton area

Streams can move by one of the following processes --

a) lateral migration b) meander cutoff

two types of aquifers

a) unconfined b) confined

The single greatest use of groundwater in the US is for ___.

agriculture

braided stream

an anastomosing network of shallow stream channels that branch and reunite ex. Yukon River, Alaska

aquitard

an impermeable layer hat hinders or prevents water movement (such as clay)

V

average water velocity

bbl

billion barrels

Water table levels respond to --

changes in precipitation by falling and rising, affecting well levels and stream flow

mature stage

continental margin continues to grow supplied from erosion of the continent

sampling the age of the oceanic crust

core samples show that the thickness of sediments increase with distance from the ridge crest

Fresh groundwater along the coast floats on top of more ___ salty groundwater.

dense

Seismic ray paths are curved rather than straight because ---

density increases with depth causing refraction

seismology tells us about the ___

density of rocks

the velocity of seismic waves depends on ___ and ___ of the material

density, elasticity

superposed stream

drainage pattern that cuts across bedrock structures

seismic waves propagate from ___

earthquake source

fossil fuels

energy resources that have formed as the result of the burial and subsequent transformation of organic material

paleomagnetic time scale

established by measuring the magnetic polarity of lava flows of known age

declining stage

ex. Pacific ocean

heavy pumping for certain uses can cause-

existing shallow wells to go dry by drawing down the water table

P waves travel (slower/faster) than S waves

faster **P comes before S**

Alfred Wegener

father of continental drift

Harry Hess

father of sea floor spreading

Relatively slow flow in sandstone results in -

filtration and clean water in adjacent well

flooding

flooding along a river occurs when the volume of floodwaters exceeds the volume of the channel that contains those waters

well-sorted

gravel and sand

gaining streams

groundwater flows into (recharges) River Water

importance of groundwater

groundwater is the largest reservoir of fresh water that is readily available to humans

groundwater flows from __ pressure to __ pressure

high > low

groundwater flows from areas of ___ water table to ___ water table

high > low

Reflected seismic rays are used to ---

image rock layers and their geometry to search for oil and gas

temperature and pressure ___ with depth

increase

the velocity of seismic waves generally ___ with depth for a given layer

increases

carbon dioxide from fossil fuel fuel combustion is--

increasing in the atmosphere each year is the primary cause of climate change

Rainfall is gentle. Favors ___.

infiltration

Soil is porous and sandy. Favors ___.

infiltration

Flooding-how bad is too bad?

it depends on the frequency and magnitude of flooding events, and how and what you (or society) consider an acceptable level of risk

outer core

liquid iron and nickel

porous sand

mainly uniform granules

poorly-sorted sand

many different grain sizes

The Atlantic Ocean is a ___ ocean

mature

confined aquifer

overlain by an aquitard

Wells allow-

people to map the "topography" of the water table and determine which way ground water is flowing

aquifer

permeable rock strata or sediment that transmits groundwater freely (such as sands and gravels)

Rapid flow in Cavernous Limestone (e.g. the Edwards Limestone) results in -

pollution of adjacent well

flowing artesian well

pressure surface is above the ground

nonflowing artesian well

pressure surface is below ground level

When the velocity of seismic waves decreases as they pass from one layer into another, the waves...

refract (bend) away from the boundary separating them

When the velocity of seismic waves increases as they pass from one layer into another, the waves...

refract (bend) toward the boundary separating the layers

when seismic waves pass from one material to another they are ___ as well as ___

refracted (bent), reflected

Persian Gulf

remnant portion of an ocean closed by the convergence between Arabian plate and Asia

nonrenewable resource

resources that are created by processes that take long spans of time to form (millions of years)

renewable resource

resources that can be replenished over short time spans (months, years, decades)

Ground is nearly saturated. Favors ___.

runoff

Surface has steep slope. Favors ___.

runoff

Surface lacks vegetation and is barren. Favors ___.

runoff

Pumping results in ___.

salt water intrusion

Seismic waves tell us about the ---

shape and composition of the interior of the Earth

S

slope of the energy gradient

inner core

solid iron and nickel

S waves can travel though ___ only

solids

What is forming the S-wave Shadow Zone?

something opaque to shear waves -i.e. something liquid!

alluvial streams

streams that cut within reworked stream-deposited material a) braided streams b) meandering streams

physical property layers

strength of earth materials is a function of composition, temperature, and pressure

It's not the VOLUME of flood waters that determines the flood risk but rather-

the RATE at which the water flows past a specific point

Recharge Area (confined aquifers)

the area where rainfall enters (recharges) the aquifer

continental rifting

the birth of a new ocean basin

The Hydrologic Cycle

the circulation of Earth's water supply

stage

the elevator of the floodwaters

When seismic waves encounter a boundary between materials with different properties (such as air and water)...

the energy splits into reflected and refracted (bent) waves

The Hundred Year Floodplain

the hundred year floodplain is the area flooded by a hundred year flood

The Ogallala Formation

the largest aquifer in the U.S.

Pressure Surface (confined aquifers)

the level to which water will rise in wells in confined aquifers

exceedence probability

the probability (p) of an event of a particular magnitude being equaled or exceeded any given year is P=1/(RI)

sinuosity

the sinuosity of a stream is a measure of how much it is meandering channel distance/linear (or valley) distance

Q = V * A

Q= discharge V= average stream velocity A= cross sectional area of the stream