Ocean Flashcards
Why is Earth called the blue planet?
71% water (oceans and seas)
Are oceans and continents divided evenly btw northern and southern hemisphere
which is the water hemisphere and which is the land hemisphere
no
water: southern; land: northern
List the major ocean basins in order from biggest to smallest
Pacific, Atlantic, Indian, Arctic
What is the largest ocean?
Pacific
What is the deepest ocean?
Pacific
What ocean makes up most of the sourthern hemisphere?
Indian
What is the fifth “ocean” but it really isn’t an ocean?
Antarctica/southern ocean
definition of salinity
total amount of solid material dissolved in water
what is the difference btw % and %o?
%: parts per hundred
%o: parts per thousand
what is the salinity of seawater?
% and %o
3.5%
35%O
If 35%o of seawater are salts, what is the rest?
water
Of the 35%o (salts), most of the salt in seawater is…
sodium chloride (NaCl)
Of the 35%o, what are the other salts other than table salt?
what percent of the 35%o do these salts combined with table salt equal
SO
Mg
Ca
K
99%
TF: does saltwater contain all of Earth’s naturally occurring elements
yes
What are the two most abundant elements that contribute to the ocean’s salinity?
Na: sodium
Cl: chlorine
What are the two sources of sea salts?
- chemical weathering of continental rocks delivered to the ocean via streams
- Earth’s interior via volcanic eruptions through outgassing (source of water in oceans and atmosphere)
Why has the composition of sewater been stable for so many years?
material is removed just as rapidly as material is added
What is the cause behind variations in salinity
change in water content
if you decrease salinity, what is being added
freshwater
what things decrease salinity
precipitation
runoff
melting of icebergs/glaciers/sea ice
What things increase salinity?
formation of sea ice
evaporation
Where is evaporation the highest?
subtropics (25N-35N;25S-35S)
Where is precipitation the highest?
the equator and mid latitudes
What occurs at polar regions?
melting and formation of sea ice varies seasonally
what ocean is the saltiest?
Atlantic
Where do you find a three-layered structure?
what are the three layers
open ocean
mixed/shallow surface layer, thermocline/transition zone, deep zone
What changes with depth in the ocean?
temp and salinity
Describe the surface temperatures of equatorial regions vs polar regions
surface temps higher at equator than at poles
Temp variations and depth: low latitudes
thermocline presence
high surface temp (equator) but decreases with depth
yes
thermocline definition and range in meters
rapid change of temp with depth
300 to 1000m
temperature and depth: high latitude
- what does the line look like
- seasonal changes
thermocline presence
low surface temp (polar) has similar temp as you go deeper
- vertical line
- surface temp might be warm in summer, so might have weak thermoclines seasonally
no, it’s isothermal
What does density determine
water’s vertical position in ocean
if water has low density what is its position in ocean vs high density water
freshwater vs seawater
low: at top
high: sinks
freshwater: low; seawater: high
Whaat are the two factors that affect density
salinity and temp
density:
increase salinity vs decrease salinity
increase: more dissolved subst.=more dense
decrease: less dissolved substances=less dense
density:
increase temp
decrease temp
what kind of relationship is this
increase: expanding atoms, less dense
decrease: compacting atoms, more dense
inverse
what is the most influential influencing factor of density and 3 reasons why
temp
1. polar regions: surface and deep ocean layers are similar, only salinity is a significant factor
2. high salinity (more dense) water on top of low salinity (less dense) if its warmer
3. more variations
Density and depth:
low latitude
what kind of -cline does it have or not have
equator: low density (high surface temps) but density increases with depth bc temp decreases
has pycnocline
pycnocline definition
rapid change of density with depth from 300 m to 1000m
Density and Depth:
high latitude
- what kind of line does this make
what kind of -cline does it have or not have
polar: high density (low surface temp) so density stays similar to surface layer
- vertical
no pycnocline, isopyncocline
What is the surface mixed zone?
describe the temperature and why it is the way it is
layer with uniform temperature
distribution of heat/mixing by tides and currents
what percent of ocean water does the surface mixed zone make up
2
what percent of ocean water does transition zone make up
deep zone
18
80
Why doesn’t 3 layers occur at high latitudes? what does occur?
isothermal and isopycnal
mixing with surface and deep waters=deep ocean currents
wha tkind of -cline does the halocline correspond with
thermocline mirrors halocline
if the temp is high, what’s the salinity
if temp is low, what’s the salinity
low
high
halocline
rapid salinity change btw 200m and 800m
sonar
aka
echosounders
how does sonar work
sends outgoing signal and comes back as a reflected signal, measures depth by seeing how long it takes to reflect
sidescan sonar
used to see shape of ocean floor by sending fans of sound
multibeam
send fans of sound (shape) and record reflected signals (depth)
do satellites measure depth of ocean
no, shape
what are passive cont.margins
eq/volcanic activity
inactive regions far from plate boundaries
weak
how do passive cont. margins develop
rifitng of continents and separated by sea floor spreading
what are the features of passive continental margins
cont. shelf, slope, rise
continental margins
outer margins of continents where continental crust transitions to oceanic crust
continental shelf
flooded extension of continent, gently sloping
continental slope
barrier btw c.c and o.c
how doe seasonal chnages in the amount of sea ice at the poles influence the salinity of the water? is water density greater before or after the ise ice forms?
ice forms: increases salinity
ice melts: decreases salinity
more dense after it forms
cont. rise
thick accumulation of sediment from slope to ocean floor
how is cont. rise created
sediments from turbitity currents ggo down submarine canyons to make fans which accumulate to form rise
why is there larger abyssal plains in the atlantic
trenches are absent
what are the three provinces of the seafloor and what are their features
continental margin: shelf, slope, rise
deep-ocean basin: abyssal plain, seamount, trench, guyots, plateaus
mid ocean ridge: rift valley
deep ocean basin
continental margin
What are active continental margins
processes happening
trenches
along convergent plate boundaries (o.c vs c.c)
accretionary wedge+subduction erosion (sediment scraped off –> mantle
deep with erosion, shallow w accretion
where are passive continental margins
atlantic
where are active continental margins
pacific
trenches how do they form
long narrow troughs
- convergent plate boundaries (subduction)
abyssal plains
what are they interrupted by>
deep flat structures that are accumulations of ssediment that cover otherwise ruddeg seafloor
seamounts
are abyssal plains found in all oceans?
yes
seamounts
where are they most common
submarine volcanoes
pacific
volcanic island
volcano that grows large enough before carried away from magma source
guyots
submerged flat topped sseamounts
how do guyots form
inactive volcanic islands are lowered to sea level by weathering and erosion and are moved away from ridge or hot spot where they formed and sink
oceanic plateaus
vast outpourings of basaltic lava
earth
what is the longest topographic feature on
oceanic ridge system
what is the mid ocean ridge system offset by
transform fault
rift valleys
deeo down faulted structures on axis of ridge system
how does oceanic crust change as it moces away from mid ocean ridge
cools, denser, older as it gets farther from mid ocean ridge and upwelling zone as it enters basin
( seawater circulation in pores and fractures)
increasse in lithosphere thickness away from ridge bc asthenosphere cools to become ltihosphere
where is the thickest sediments found
away from oceanic ridge, near continental margins, most trenches
