geo exam 3

isotopes: how many daughter atoms are produced for every parent that decays

1

isotopes: a sample has been shown to have only 1/4 of the original parent atoms. How many half lives has it undergone

2

oceans: how does landward migration occur

2 ways - storms wash sand landward during storms (overwash deposits) And tidal currents preferentially move sand from the beach into the back lagoon

history: Proterozoic Eon

2.5-.541 protero-first zoic - life formation and breakup of several large super contintents rodinia turned into pannotia snowball earth episodes evolution of prokaryotic/eukaryotic cell first eukaryote fossil grypania atmospheric oxygen skyrocketed as a result of cyanobacteria (blue green algae)-aerobic respiration formation of ozone layer,blocked UV rays late proterozoic 640-540 Ma earliest animals

history: phanerozoic eon

541 Ma Phaneros = visible Zoic = life cambrian explosion Three Phanerozoic Eras Paleozoic - ancient life -diverse life with hard parts -silurian and devonian life, first land animals 360Ma Mesozoic - middle life -dinosaurs evolved Cretaceous (late Mesozoic)-high sea levels and shallow continental sea -unusual volcanic activity lead to hotspots that released huge CO2 -warmed atmosphere -expanded ocean crust -continental flooding -sierran arc grew from subduction along west coast Cretaceous tertiary -meteorites ended this period -iridium enrichment in K-T boundary clay Cenozoic - recent life -expansion of mammals -uplift of mountain ranges -pronounced cooling and formation of polar ice sheets -ape/human like primates

groundwater: potentiometric surface

A hypothetical surface representing the level to which groundwater would rise if not trapped in a confined aquifer equates to the water table of the unconfined aquifer

oceans: gyres

An ocean gyre is a large system of circular ocean currents formed by global WIND PATTERNS and forces created by EARTHS ROTATION The movement of the world's major ocean gyres helps drive the "ocean conveyor belt." south pacific gyer is massive, bound by australia, south america and equator indian ocean gyre is much smaller horn of africa, sri lanka, indonesia

isotopes: half life

As a parent disappears, the daughter "grows in" or increases. After one half-life, one-half of the original parent remains. After three half-lives, one-eighth of the original parent remains.

energy: fractional distillation

At the refinery, the crude oil, which also contains a lot of gas, is processed. This involves separating out all the different hydrocarbons in the crude oil. To do this, the crude oil is heated in a furnace and then passed through a cooling tower. The method relies on the fact that different hydrocarbons have different boiling points. Consequently the heavy hydrocarbons like bitumen with high boiling points accumulate at the bottom of the cooling tower. Light hydrocarbons like paraffin with low boiling points accumulate near the top of the top. This process is known as fractional distillation.

strat: stratigraphic correlation

Earth history is recorded in sedimentary strata. layers of strata include time gaps formations: rock units that can be mapped over a region. Often, formations can be correlated over long distances. Stratigraphic columns depict the strata present in a region. They are drawn to scale to accurately portray relative thicknesses. The different rock types are depicted by graphical fill patterns. Lithologic correlation is based on rock type in a particular region.

plate tectonics: felsic and mafic

Earthquake (seismic) waves allowed geologists to refine the model of Earth's interior. Here, the mantle and the core are subdivided. Mafic is used for silicate minerals, magmas, and rocks which are relatively high in the heavier elements. mafic magmas also are relatively enriched in calcium and sodium. (Ca, Na) Mafic minerals are usually dark in color Felsic, on the other hand, is used for silicate minerals, magmas, and rocks enriched in the lighter elements silicon (Si)and oxygen(O), aluminum, (Al)and potassium.(K) Felsic minerals are usually light in color

groundwater: flow rate

Groundwater flow rate is governed by the PERMEABILITY of the porous material multiplied by the hydraulic gradient. G = P x HG High permeability increases the rate of flow. Low permeability decreases it.

history: Hadean

Hadean: 4.54 and 4Ga formed earth by planetismal accretion -earth was heated and partially melted -gravity pulled iron into center -ultramafic mantle remained as thick outer shell formation of moon Earth was smashed by a Mars-sized protoplanet that blasted a part of Earth's mantle into space. The debris from the collision formed a ring around Earth that coalesced into the Moon. Thus, the Moon has the same composition as Earth's mantle. volcanic outgassing created deadly atmosphere meteorites bombarded surface -no crustal rocks survived first evidence of oceans from marine sediments

groundwater: hydraulic head

Hydraulic head - the level to which water rises in a drillhole A piezometer is a small device used to measure hydraulic head. Flow always moves from high to low hydraulic head. pressure gradient force: water flows from high to low pressure

energy: where does plankton come from

In certain parts of the world's oceans, plankton occurs in enormous quantities, or blooms. Exactly where those plankton blooms occur is controlled by OCEAN CURRENTS The richest sites are where cold, nutrient rich waters rise to the surface from the deepest parts of the ocean. The nutrients found in these 'upwelling zones' feed plankton and allow them to reproduce quickly most oil and gas starts life as microscopic plants and animals that live in the ocean

strat: principle of fossil succession

Index fossils are diagnostic of a particular geologic time.

strat: isotopic dating

Isotopic dating provides the ages of minerals (grains or crystals) within a rock. Igneous rocks form at the same time as their composite minerals and thus are datable. Sedimentary rock grains, such as sand, mud, and gravel, are derived from the physical and chemical weathering of preexisting rocks at relatively low temperatures. The mineral components within sedimentary rocks are generally much older than the rocks themselves (principle of inclusions).

energy: main producers of oil

OPEC: 36% of worlds oil biggest producer is Saudi Arabia Iran, Venezuela, UAE OECD: 24$ USA biggest producer Mexico, Canada, UK soviet union contributes 15% china shows biggest year to year increase in usage global oil production will peak year 2000 and trigger an energy crisis with power blackouts and rising cost of energy

energy: unconventional resources

Oil and gas that is trapped within its source rock, or in a "tight" reservoir that does not permit easy flow, is becoming increasingly accessible. The principal techniques are horizontal drilling and "fracking", or hydraulically inducing fractures. The success of these techniques is such US just re-surpassed Saudi Arabia and Russia as the world's leading oil producer in August 2018, according to the Department of Energy. By as soon as 2022 the US may produce more hydrocarbons than we consume.

oceans: passive and active margins

Passive margins occur on both sides of the Atlantic. -wide shelf -gentle slope -continental rise -older, higher sediment supply -lowlying coastal plains Active margins border the Caribbean and the western coast of South America. also border north pacific ocean -little to no shelf -steep slope -trench, no rise -rocky coast

stratigraphy: relative vs numerical

Relative ages are based upon the order of formation and permit determination of older vs. younger relationships. -qualitative Numerical ages are the actual number of years since an event occurred. -quantitative

groundwater: recharge vs discharge

Replenishment of infiltrating groundwater is known as recharge. Discharge of groundwater occurs when water emerges from the ground. groundwater infiltrates at recharge areas at higher elevations and exists discharge areas at lower elevations

energy: reservoirs and traps

Reservoir: a rock with sufficient porosity and permeability to allow for hydrocarbon accumulation reservoir rock: permeable trata in an oil trap -have pores that absorb the oil Trap: a structural or stratigraphic feature that allows hydrocarbons to accumulate in the subsurface. structural trap - anticline trap stratigraphic - unconformity One of the most common ways that oil and gas becomes trapped in pockets in the rock is where it is rises into a structural dome capped by impermeable rocks. The cap rocks prevent the oil and gas escaping upwards. The buoyancy of the less dense hydrocarbons in the pore waters prevent them from sinking back down. This is an example of an Oil Trap.

stratigraphy: what is it

STRATIGRAPHY: science of interpreting spatial and temporal relationships among rock bodies

energy: seismic surveys

Seismic surveys are used to locate likely rock structures underground in which oil and gas might be found Shock waves are fired into the ground. These bounce off layers of rock and reveal any structural domes that might contain oil

isotopes: atoms

The number of protons in an atom determines which element it is. If you change the # of protons, the element changes & the mass changes. If you change the # of neutrons, the element stays the same, but the mass changes

strat: unconformities

Unconformities represent periods of nondeposition or erosion in the rock record disconformities: two packages of flat lying rock, no tilting, just erosion nonconformities: has igneous or metamorphic rock at the bottom angular unconformities: includes tilted beds

groundwater: the ogallala problem

Water level declines of 2-3 feet per year in some regions are drawing concern of the aquifer drying up - first one in the U.S. This is due to pumping more water than is replaced through recharge, and only 10% is restored by rainfall.

ocean: wave refraction

Wave refraction occurs when wave approaches the shore at an oblique angle waves travel fast in deep water, approach coast at an angle waves travel slowly in shallow water, crest nearly parallel to coast wave refraction tends to bend the waves parallel to the beach - this is due to the changes in wave velocity as it approaches the beach - which effects the front edge first, allowing the rest of the wave to "catch up"

oceans: ekman effect

When surface water molecules move by the force of the wind, they, in turn, drag deeper layers of water molecules below them. Each layer of water molecules is moved by friction from the shallower layer, and each deeper layer moves more slowly than the layer above it, until the movement ceases at a depth of about 100 meters (330 feet). Like the surface water, however, the deeper water is deflected by the Coriolis effect —to the right in the Northern Hemisphere -and to the left in the Southern Hemisphere. As a result, each successively deeper layer of water moves more slowly to the right or left, creating a spiral effect. Because the deeper layers of water move more slowly than the shallower layers, they tend to "twist around" and flow opposite to the surface current.

streams: subsidence at deltas

abandoned deltas starved of sediment, slowly compact, dewater and subside

oceans: longshore drift

although refraction straightens waves, they still hit at an angle, perpendicular to the beach Waves that hit the beach at an angle carry sand and gravel up the beach face at an angle. When the water washes back the sediment is carried straight back down the beach face. Individual particles are moved along the beach in a zig zag pattern. This is called longshore drift. generates spits and baymouth bars

groundwater: darcy's law

an equation that predicts the VOLUME OF WATER passing through an area of an aquifer per TIME Q = K(h1-h2/j)A where, Q = Discharge volume K = Hydraulic conductivity (similar to permeability) (h1-h2/j) = Hydraulic gradient A = Cross-sectional area perpendicular to flow Darcy's law states that discharge volume is proportional to the hydraulic gradient multiplied by the permeability.

oceans: wave cut notch

an indent in a cliff when waves attack rocky coasts, resulting in shattering of the cliff and erosional removal of material

groundwater: aquifer and aquitard

aquifer: high porosity, high permeability rock that transmits water easily unconfined: lies at surface, easily contaminated confined: lies beneath aquitard, less susceptible to pollution aquitard: lower permeability rock that hinders water flow

oceans: deadzones

areas lacking in oxygen often called hypoxia

isotopes: what are they

atoms with same element but different number of neutrons

streams: sediment loads

bed loads: pebbles and sand which move along stream bed without being suspended in water suspended load: silts and clay plumes of muddy water form this way dissolved load: material in solution

energy: turning black shale to gas

black shale is buried and heated organic matter is changed by increase in temperature into kerogen 90 - 150c it's a liquid state which we call oil 150C is changed into a gas a rock that has produced oil and gas in this way is known as a source rock

streams: deposition

competence: maximum PARTICLE SIZE a stream can transport depends on stream velocity rivers will deposit their sediment loads when particles can no longer be transported (competence) because of changes in velocity capacity: total quantity of sediment that a stream can carry depends on velocity and discharge

energy: drilling

cost of drilling is 10,000 for each metre potential oil trap is called a prospect only 40-50% of total oil will rise to the surface hole is drilled adjacent and gas is pumped down to push oil out of the rock and into the well

energy: crude oil and gas

crude oil : mix of longer chain hydrocarbons carbon with H around it CnH2n+2 n=8 -can be separated into components with differing number of carbon atoms based on boiling point gas: short chain hydrocarbon with one carbon atom CH4

plate tectonics: earth's interior

crust - least dense felsic and mafic mantle - denser ultra mafic core- most dense iron and nickle (fe, ni)

Streams: Thalweg

deepest part of the channel (usually highest current velocity)water moves fastest

isotopes: chemical element

defined by the number of protons in the nucleus isotope refers to proton-neutron combination ex: nucleus of lead (Pb) contains 82 protons if nucleus contains 124 neutrons, the isotope is 206

STREAMS: Drainage networks

dendritic - most common, delevop on land surface where underlying rock is resistant to erosion radial - develop surrounding areas of high topography where elevation drops from central high area to surrounding low ex: volcano rectangular - joints or faults and HARD rocks cause streams to cut down along weak areas in rock, 90 degrees trellis - join main river in right angles by eroding SOFT rock

oceans: how do they exist

differences in lithosphere continental lithosphere floats on mantle ocenic lithosphere floats deeper in mantle ocean basins collect water because they're lower

groundwater: artesian well

does not require pumping penetrates a confined aquifer catfish farms well was the greatest flowing well in the world

iso: Crystals of a silicate mineral called zircon were extracted from a rock and analyzed for uranium and lead isotopes. The analysis showed that 0.0039 units of 235U and 0.0273 units of daughter 207Pb were present. The half-life of 235U is 700 million years. How old is the mineral?

first find the original amount .0039 + .0273 = .0312 fraction of parent remaining today is parent/parent original .0039/.0312 = .125 = 1/8 1/8 is 3 half lives one half life is 700 million years so 3 x 700 = 2100 million years or 2.1 billion years

isotopes: A zircon taken from quartzite in northern Canada was measured for its isotopic composition, and found to have 0.253 picomoles of 235U and 3.795 picomoles of daughter 207Pb. ("pico" means "one trillionth of.") The half-life of 235U is 700 million years. Use these data to perform an age calculation (the first three questions) and interpret that age (the fourth).

first, find out the parent Pb 3.795 + .253 = 4.048 find out fraction of parent Pb by dividing whats left of Pb (parent) by the original amount of parent Pb .253/4.048 = 1/16 find out age 1/16 = 4 half lives 4x700=2800 million years

oceans: coastal landform label

foreshore: region b/t high and low tide beach face: formed by wave swash steap and concave backshore: upper beach above high tide coastal plain - flat, lowlying piece of land next to the ocean estuary - tidal mouth of large river where tide meets the stream

energy: how much do we use

fossil fuels: more than 75% oil:33 coal:30 natural gas: 30 asia has become the largest consumer of energy

isotopes: closure temperature

heating a mineral to a super high temp can result in loss of daughter products box opens clock seizes recording time until the mineral falls to a low temp box closes closure temp: the temp marking the transition between open and closed behavior

streams: alluvial fans

high energy streams carrying course sediments emerging from a canyon to an open plain -steep gradient -mountainous terraine

streams: meandering river

individual curves are called MEANDERS and they evolve over time highest velocity water erodes outside of a bend, which is called the CUT BANK -erosion takes place fastest here inside of bend is the POINT BAR and is the site of sediment deposition -water slows here (low velocity) oxbow lake - when stream erodes through the meander neck an abandoned meander filled with water

streams: stream mouth

is at the base level of the river, lowest point that dips into the ocean fine grained sediments low velocity (not fast moving water) depositional low competence gradient flattens, discharge (volume of water) increases

oceans: tidal bulge

large tidal bulge always faces moon smaller tidal budge always on opposite side of earth

groundwater: edwards aquifer

lead to lowering of sea level, rapid burial of the deep sections of the Gulf of Mexico basin, tectonic uplift along the margins, and erosion and karstification have played important roles in the development of the aquifer. The Edwards aquifer receives approximately 80% of its recharge through losing (influent) streams that flow over its unconfined parts. Water enters the aquifer through faults, fractures, sinkholes, or percolation through the soil. This process is called recharge.

plate tectonics: what are they

lithosphere is broken into plates that move over the asthenosphere comprised of crust and upper mantle thicker under continents, thinner under oceans asthenosphere below is soft and able to flow movement is driven by motion within the mantle due to convection

plate boundaries: convergence

lithosphere is consumed subduction ocean-ocean -forms island arc above the subducting ocean plate volcanism is mafic ocean-continent subduction along edge of continent produces continental volcanic arc sediments on downgoing slab form an accretionary prism volcanism is felsic ocean crust always subducts below continental crust continental collision -earthquakes are relatively shallow -no subducting plate -both plates fold

Streams: Saltation

movement of hard particles over an uneven surface through water clasts bounce along the bed and knock other clasts into the water flow

STREAMS: headwater erosion

near the headwater, gradient is steep, discharge is low, sediments are coarse erosion at the ORIGIN of the stream channel occurs where sheet flow enters uppermost part of a channel

plate tectonics: divergent

new lithosphere created NEW OCEANIC CRUST shallow earthquakes and volcanic activity oceanic divergence -seafloor spreading at mid ocean ridge, produces new sea floor and oceanic crust -asthenosphere rises beneath the ridge and brings up magma -magma cools under the mid ocean ridge axis -oceanic crust moves away from the ridge axis -formation of faults and earthquake scarps continental divergence rifting magma erupts as lava, creating volcanoes along and near the center of the rift the lithospheric mantle begins to stretch horizontally and thin vertically large fault blocks of crust slide down into the widening rift the crust fractures and faults develop As seafloor spreading progresses, the ocean basin widens and continents move apart. When continental lithosphere stretches and thins, the upper crust breaks by faulting. The upwelling asthenosphere initiates volcanism. Rifting may split a continent in two.

groundwater: spring

occurs when the aquifer intersects the surface

streams: define deposition

occurs when the water velocity slows decreasing its capacity to hold material (lower competence)

oceans: thermohaline circulation

oceans have warm salty water near surface cold less salty water in ocean depths ocean currents are driven by wind polar oceans have colder surface water that gets saltier due to evaporation -sinks into the ocean depths because it becomes so dense -the pumping of surface water into deep ocean forces deep water to move horizontally until it can rise back to the surface -usually occurs in the equatorial ocean, pacific and indian oceans surface ocean brings new water to north atlantic ocean around greenland and iceland from the south atlantic and the water returns to the south atlantic via the north atlantic deep water current

groundwater: aquifers of texas

ogalla, -The Ogallala supplies water for eastern New Mexico, much of west Texas, as well as parts of Colorado, Oklahoma, Kansas, Nebraska, Wyoming and South Dakota Largest groundwater aquifer on Earth carrizo-wilco, edwards gulf coast

isotopes: radioactive decay

parent isotopes decay into daughter isotopes # of protons in the atom changes and one element transforms into another

energy: transportation

pipelines transport most of the worlds oil oil tankers distribute

groundwater: porosity vs permeability

porosity: total volume of open space low porosity rocks are relatively dense vesicular basalt: high porosity 20% granite: less than 1% permeability: the ease of water flow due to pore interconnectedness. permeability depends on size of voids and whether the voids are interconnected

oceans: groins

prevents beach erosion by trapping and accumulating sand Groins cause a beach to build up on the upstream side of the longshore current, but they cause sand to erode on the downstream side. Sediment deposition is enhanced in one place. Sediment erosion is accelerated in another.

energy: migration

primary: moving out of source rock to a more porous rock secondary: movement from carrier rock to a trap

oceans: seawalls

protects sites near the coast can hasten erosion in extreme storms can enhance erosion at base of wall and the wall can fail shorten distance over which waves can expend energy waves are reflected from the wall, increases rate of beach erosion

groundwater: edwards aquifer

provide water to two million people including san antonio provides fresh water to the texas gulf coast bays

STREAMS: Stream velocity

rate of flow (not amount of water) meters/second controls how large material a stream can carry discharge and velocity not equivalent can have high discharge with slower velocity in large rivers more friction in wider, shallower streams floods have high discharge and high velocities

ocean: tides

regular up and down motion of ocean in response to gravitational pull of sun and moon neap tide: third or first quarter of moon, least difference between high and low water 6am-6pm spring tide: new or full moon greatest difference between high and low water tidal reach: vertical distance between high and low tide intertidal zone: region between high and low tide

Streams: natural levees

sand ridges that parallel the channel

STREAMS: forming streams

sheet of water from rain erodes the substrate (underlying substance or layer) creates tiny rill channels that deepen eventually concentrating flow into a single channel

history miller and urey experiment

simulated Earth's early atmosphere with H2O, CH4, NH3, H2 (like Jupiter), added a source of energy in the form of an electric spark, and produced an array of organic molecules, including amino acids (not life!) problem: mostly CO2 in atmosphere millions of years ago, the experiment doesnt work under these condititions homochirality constraint:Although most amino acids and proteins can exist in both left and right handed forms, life on Earth is made almost exclusively of left handed amino acids and right handed sugars!

groundwater: karst landscape

sinkholes, caves created by the drainage of water into the ground and the resulting chemical erosion of bedrock - limited to areas of soluble rocks formation: caves form below water table old caves empty water table sinks, new caves form caves collapse, karst landscape develops

oceans: submarine canyons

site of submarine slumps and turbidity currents move sediment from coastline to deeper ocean, forming submarine fans at canyon opening turbidites: deposits that show graded bedding formed when turbulent water and sediments (turbidity currents) exit the mouths of canyons and deposit sediments submarine fans: fan shaped wedges of sediments abyssal plains: remains of volcanic islands that have been eroded at the top to form sea mounts

oceans: types of mass wasting

submarine slumps - blocks break and slip submarine debris flows - moving material breaks apart turbidity currents - sediments move as a turbulent cloud

strat: syncline vs anticline

syncline: fold of rock layers that slope upward anticline: fold of rock layers that slope downward

groundwater: hydraulic gradient

the difference in head at two different locations divided by the length of the flow path h1-h2/J indicated by the SLOPE of the water table

streams: base level

the lowest point to which a stream will erode its channel raising base level results in increase in deposition (the stream is flatter) lowering base level accelerates erosion (stream is steeper) sea level is the ultimate base level

History: Archean Eon

the time between 4.0 and 2.5 Ga, birth of continents and of LIFE on Earth. By ~3.85 Ga, Earth had cooled to form lithosphere, The volume of continental crust increased dramatically This indicates that plate tectonics was in action. first chemical evidence of life is 3.5 Ga life potential existence 3.8 Ga oldest bacterial cell fossils are 3.2 Ga -stromatolites - blue-green algea, cyanobacteria cyanobacteria converted CO2 and H2O into hydrocarbon food and free oxygen Home of modern hypothermophiles - adapted to making a living in extreme environments

streams: delta classification

three main factors controlling sedimentation sediment delivery (rivers) sediment redistribution (waves) sediment removal/erosion (tides)

STREAMS: substrate

underlying substance or layer

strat: physical principles

uniformitarianism: the processes observed today were the same in the past original horizontality: sediments tend to accumulate horizontally principle of superposition: states that in an undeformed sequence of layered rocks, each bed is OLDER than the one above, and YOUNGER than the one below. principle of lateral continuity: strata often form in laterally extensive horizontal sheets. Subsequent erosion dissects once-continuous layers. until they: cut by erosion pinch out cut by a fault abut against older rock cross cutting: if one rock unit cuts across the other, it must be younger than what it cuts baked contacts: baked rock must have been there first, igneous intrusion is younger inclusions: inclusions are always older than enclosing material

oceans: upwelling and downwelling

upwelling - deep, cold water rises to the surface wind moving NORTH to SOUTH(downward) and water moving offshore from results in upwelling -colder, saltier and containts more nutrients so it fertilizes the ocean downwelling - when surface water sinks towards the bottom -wind moving from south to north (upward)and water moving onshore results in downwelling

energy: the source of oil

very little oxygen on the sea floor. -because the ocean is deep and oxygen has not been mixed down from the surface waters. No animal life can survive where the sea bed is completely lacking oxygen. -Without animals to eat the dead plankton, the organic mush builds up on the sea bed. Where ocean sediment contains more than 5% organic mush it eventually forms a rock known as a Black Shale. The black colour comes -from the dark organic matter that it contains. As we will see, Black Shale is what makes oil and gas. the source of oil is plankton organic preservation in marine sediments under anoxic conditions -black shale was abundant during mid mesozoic times

STREAMS: stream discharge

volume of water that passes through an imaginary cross section across a stream volume per time meters3(cubed)/second controls amount of material a river can carry

groundwater: what is it

water in the earth's subsurface filling the porous spaces in soils, sediments and rocks rate of groundwater is very slow compared to currents in surface water

groundwater: groundwater table

water table where all the pores are filled flows from higher to lower elevation humid regions: water table lies close to the surface dry regions: water table sinks deep below the surface

oceans: labeling a wave

wave height and amplitude describe vertical movement of waves crest is the top of the wave trough is the lowest point of the wave wave motion goes to zero beneath the wave base wavelength is length from crest to crest or trough to trough

oceans: headland erosion

wave refraction results in headland erosion by the slamming of waves on land that sticks into the ocean -accelerating erosion

groundwater: cone of depression

when people pump the well too fast, surface of water table drops size of cone is primarily a function of pumping rate

streams: delta

when rivers enter open water, they deposit sediment as they lose energy a delta is a form of a braided river-where water flow is slow and theres a buildup of sediment in the river wave dominated delta - high wave energy, sand is well sorted river dominated delta - river sediment supply exceeds removal, subjec to avulsions(new river channel)

oceans: wave cut bench

when the cliff collapses and retreats erosional remnant of former cliffs often exposed at low tide

oceans: how waves move

wind begins to blow frictional drag on surface water ripples form waves form water follows a circular path circle radius decreases with depth at a depth of 1/2 the wavelength, the circular motion ceases: this is wave base