oceans and coasts

Question 1

what do oceans do?

Answer 1

essential for marine and terrestrial life
regulate weather and climate
regulate CO2 cycle
largest surface reservoir of water but not largest water reservoir, that is the mantle

Question 2

ocean and lithosphere

Answer 2

exist because of differences in lithosphere
lighter FELSIC continental lithosphere floats higher on mantle
heavier MAFIC oceanic lithosphere is pulled lower on mantle
water pools on oceanic lithosphere

Question 3

what is bathymetry?

Answer 3

depth variations and bottom topography of sea floor
measured using satellites and sonar measurements (used to be done w plumb lines)

Question 4

submarine canyons

Answer 4

cut deeply into continental shelves
associated with large rivers
canyons eroded through shelves during sea-level lows
deeper parts of canyons eroded by turbidity currents

Question 5

salinity

Answer 5

normal marine salinity = 3.5%
salinity varies with location
evaporating all water would result in 60m thick salt layer

Question 6

ocean water temperature

Answer 6

warmer at equators, colder at poles
with depth, average temp is 4 degrees celcius
thermocline: rapid transition from warm surface waters to cold deep water

Question 7

ocean currents

Answer 7

surface: due to wind shear
deep: due to density differences
modified by coriolis deflection (direction of flow opposite in northern and southern hemisphere)

Question 8

how did coriolis effect cause the great pacific garbage patch?

Answer 8

coriolis effect caused a circular current called a gyre which acts like a whirlpool and carries debris into the center of the gyre where current is weaker and garbage accumulates

Question 9

thermohaline

Answer 9

drives vertical currents
thermo: colder water is denser, sinks
salinity: saline water is denser, sinks
polar water: cold and salty
deep ocean waters are replensihed from surface waters at poles

Question 10

describe thermohaline circulation

Answer 10

global conveyor belt
sinking of waters at polar latitudes
warmer surface water flows to poles and transfers heat away from tropics

Question 11

what causes tides?

Answer 11

large bulges are caused by the moon, smaller bulges by the sun. both bulges result in high tide with low tides between the bulges
tides rise and fall twice daily

Question 12

surface waves

Answer 12

develop from frictional drag of winds
depend on wind strength and on fetch (the distance over which the wind blows)

Question 13

wave sizes

Answer 13

water molecules move in vertical ellipse. diameter largest at surface, decreases with depth.

Question 14

wavelength and wave base

Answer 14

wavelength is distance between successive wave crests
wave base is at depth where there is no more movement and is equal to 1/2 wavelength
no effect on deep ocean floor

Question 15

what happens as waves reach the shore?

Answer 15

wave base hits (shallower) sea bottom
drag at sea bottom slows the bottom part of the wave
upper part of wave continues at unchanged speed
backwash (due to gravity) drags eroded materials from shoreline

Question 16

rocky coasts

Answer 16

more powerful wave action from deeper nearshore waters
concentrated wave energy erodes rocks
cliffs feel full force of the waves, water can break apart the rock

Question 17

wave-cut notch

Answer 17

see image
overhang eroded into bluff
undercutting of cliff face
wave-cut benches exposed at low tide

Question 18

estuaries

Answer 18

where rivers meet the sea
mixing of freshwater and seawater
funnel shaped

Question 19

fjords

Answer 19

glacier-carved, deep, u-shaped valleys found at sea level
flooded as sea levels rose and glaciers retreated

Question 20

coastal wetlands

Answer 20

gentle slopes, low wave action, extensive vegetation, cover large areas of coastal regions (swamp, marsh, bog), important for biodiversity and marine organic productivity

Question 21

coral reefs

Answer 21

calcite rich structures with skins of living organisms
shallow, clear, warm, well-lit, normal salinity water
just below tide to 60 m depth
all sorts of forms
protect coastlines

Question 22

atolls

Answer 22

form on subsiding, extinct volcanoes
a ring-shaped island, including a coral rim that encircles a lagoon

Question 23

passive margin vs active margin coastlines

Answer 23

passive: vroad, low-lying coastal plain
active: uplifted, rocky coasts

Question 24

islands at risk of sea-level rise

Answer 24

Fiji, tuvalu, maldives, kiribati
note: also challenges optimal

Question 25

problems due to sea-level rise

Answer 25

shorelines migrate landward
coastal erosion accelerated
mangroves and salt marshes are destroyed
challanges optimal growth conditions for coral

Question 26

hurricanes

Answer 26

cyclonic low pressure tropical disturbances pull air inward
warm air flows over ocean, absorbs moisture
air rises, cools, and condenses, forming clouds
enough moisture -> large thunderstorms
storms die out when they rut out of warm water

Question 27

cyclone names

Answer 27

hurricane: atlantic and eastern pacific
typhoon: western pacific
cyclone: Australia and India
saffir-simpson scale: 1 is weakest, 5 is strongest

Question 28

eye of the hurricane

Answer 28

a rgeion of calm at storm center
cold, dry air is pulled into eye to create this calm
eye walls form vertical cylinder of wind
wind velocity is highest in eye wall

Question 29

hurricane Katrina

Answer 29

one of most destructive hurricanes on record
category 5 in gulf of Mexico
reshaped barrier isalnds
destroyed coastal marsh and croplands
80% of new orleans was under water