Features Of Oceans Flashcards
(30 cards)
How are mid ocean ridges formed
Convection currents caused by radioactive decay in the core heats the bottom of the mantle becoming less dense it rises and cools and creates a convection current the friction pulls the plates apart magma rises and cools and forms rocks
What is the continental shelf
Flat plains located beneath the drowned edge of continents slope angle of 0.5 degrees
Continental rise
Below shelf break average angle of 4 degrees
sub marine canyon
found on the continental slope these features are steep sided with v shaped profiles and topographic releif up to 2 km
abyssal plain
flattest areas on earth having regional slopes of 0.5 degrees lie at water depths of 3-5 km
abyssal hill
domes or elongated hills that are no higher than 1000 metres high
seamount
any type of abyssal mountain that rises above 1000 metres that does not extend out off the waters surface
guyot
flat topped sea mounts their tops were once active volcanoes bit there tops were levelled by erosion edges colonised by coral reefs
trench
steep sided long and narrow depressions some 3-5km deeper than the ocean floor
continental slopes
nearly flat plains that are located between continents average 6 km in width slopes gently sea ward
what 3 things affect salinity
freezing/evaporation of water
lots of rain
rivers and streams
what overall factors affect ocean currents
coasts
Coriolis affect
planetary winds
variation in temperature
how does wind affect ocean water
wind creates friction that creates waves
pulls water along
what is the Coriolis effect
earth spins quicker at the centre so water is deflected towards the poles clockwise for the N. hemisphere and anticlockwise for the S. hemisphere
what are gyres
large areas of circulating water in the sea caused by Coriolis effect
why are some currents warm
found in warm areas possibly near the equator
i.e. gulf stream
how does freezing/evaporation of water effect water salinity
evaporation - when water evaporates the water leaves but the salt doesn’t so all that is left is the salt increasing salinity freezing- when water freezes water is taken out of the ocean as ice floats
what5 factors cause variation in surface salinity
precipitation = diluton of sea water = less salty
evaporation = water molecules removed = higher salt concentration e.g. red sea
freezing = addition of fresh water = lower salt concentration
ground water and river flow = addition of fresh water e.g Baltic sea 10 ppt because of the 200 rivers flowing into it
why do ocean temperatures vary
angle of the sun means that the sun is directed onto the equator. Water has a high specifi heat capacity so it takes longer to warm up but takes longer to cool
how and why do temperatures vary with depth
Temperature is much warmer at the surface where there is wind driven mixing when the surface water is heated and it is mixed with water lower down. Sunlight only penetrates 200m down(photic zone )Below 1000 metres the temperature is roughly 4 degrees centigrade
where are warm ocean currents found
warm ocean currents are found near the equators and flow towards the poles. For example gulf streams from the gulf of mexico to the North pole towards Europe
where are cool ocean currents found
The labrador current flows from the Artic Ocean into the North Atlantic . Cool ocean currents are found near the poles due to less input of solar radiation
How does the global conveyor belt start?
Ocean water near the Poles has little input of heat from the sun and most of the heat inputted near the Equator has dissipated and so the ocean is cooler. Due to the formation of sea ice the salinity is increased as the salt in the seawater is left behind when the ice forms. The water therefore at the Poles is cooler and saltier both of which make it denser so the water sinks off the coasts of Greenland and Norway.
As it sinks it pulls down more water due to the cohesive nature of water. When it reaches the ocean floor then the water disperses horizontally across the abyssal plain towards the Equator.
List 5 facts about ecosystems at hydrothermal vents and cold seeps (include named species)
Species are adapted to live up to 120 degrees centigrade. hydrothermal vents are found in the midnight zone so most live of chemosynthesis Species can include yeti crabs tubeworms and octopus.
