Oceans

Question 1

Define continental shelf

Answer 1

Nearly flat plains / terraces located beneath the drowned edges of continents
Slope gently seaward at an angle of 0.5 degrees
Shelf break st the end of the feature

Question 2

Define continental slope

Answer 2

Below the shelf break
Steep feature
Average angle is 4 degrees
Thick layers of mud and sand which have eroded from nearby continents

Question 3

Define submarine canyons

Answer 3

Found on continental slope
Steep sided with V-shaped profiles and topographic relief
Serve as chutes for the transfer of sediment from the continental margins to the deep-ocenas basins

Question 4

Define continental rise

Answer 4

Exist where the ocean bottom flattens out to a mere gradient of ~1 degree
Consist of sedimentary deposits (very thick) and topography is only extended by submarine canyons

Question 5

Define abyssal plain

Answer 5

Flattest areas found
Slopes of ~ 0.5 degrees
Braod areas conposed mainly of land derived sediments that have been buried and buried by irregular volcanic topography of the crust
At water depths of 3-5km

Question 6

Define abyssal hills

Answer 6

Domes or elongated hills no higher than 1000m

Composed of igneous rock covered by a thin layer of sediment

Question 7

Define seamounts

Answer 7

Type of abyssal mountain
Many extinct or active volcanoes with conical tops ans steep sides
Do not extend above water surface
Occur in groups or isolated peaks

Question 8

Define guyots

Answer 8

Flat topped seamounts
Once active volcanos but tope were levelled and flattened by marine erosion
Edges colonised by coral reef before islands sank completely underwater

Question 9

Define deep sea trenches

Answer 9

Relatively steep sided long and narrow depressions or basins
Deeper than the surface of the surrounding ocean floor
Deepest regions on earth and are located on the edges of oceans
Associated with destructuve plate margins and seismic activity

Question 10

What drives sea floor spreading?

Answer 10

Tectonic plates split apart from each other
Mantle convection carry heat fromthe lower mantle and core to the lithosphere
Occurs at divergent plate boundaries
Heat from convection currents make the crust more plastic and less dense

Question 11

Explain the formation of mid-ocean ridges

Answer 11

Convection currents in mantle caused by radioactive decay in the core
Heat generated in core heats the bottom of the mantle
Heated magma becomes less dense and rises through the mantle colling at the crust
Friction at tectonic plates as magma reaches crust
Causes plates to move with convection currents
Plates pulled apart creating a gap allowing magma to rise
This cools and creates new rock
Process repeated forming basalt

Question 12

Give examples of mid-ocean ridges

Answer 12

Mid-Atlantic ridge = tall narrow underwater cliffs and mountains from slow spreading ridges
East Pacific ridge = gentle slopes rapidly spreading ridges

Question 13

Name the 5 oceans

Answer 13

Pacific 
Atlantic 
Indian 
Southern 
Arctic

Question 14

Explain how ocean trenches are formed

Answer 14

Oceanic plates collide in oceans by convection currents
The faster moving plate (denser) is subducted below the other in the subduction zone
Forms a Benioff zone and deep ocean trench on destructive plate boundsries
Can form oceanic vs continental as well = oceanic plate subducts into the mantle and point of subduction is where the trench forms

Question 15

Give an example of an ocean trench

Answer 15

South sandwich trench in southern ocean

Tonga trench in Tonga

Question 16

How does precipitation affect salinity?

Answer 16

Parts where there is lots of rain
Freshwater added to surface diluting seawater
Reduces salinity less dense seawater as a result
Equatorial areas

Question 17

How does evaporation of seawater affect salinity?

Answer 17

Hardly any rainfall and warm dry winds cause lots of evaporation
Water vapour removed into atmosphere leaving salt
Salinity increases making seawater more dense
Red and Mediterranean seas

Question 18

How does freezing of seawater affect saliniy?

Answer 18

Salt in water is removed
Does not fit in lattice structure of ice
Less saline water freezes faster than more saline water
Pockets of unfrozen water (dense brine) highly saline
Some bacteria can live in these pockets
Arctic and southern oceans

Question 19

How does melting of glaciers and icebergs affect salinity?

Answer 19

Salt is diluted by freshwater of glaciers and icebergs
Decreases salinity
Seawater less dense
Arctic and southern oceans

Question 20

How does goundwater and river flow affect salinity?

Answer 20

Rain replenishes freshwater rives and streams reducing salinty
Groundwater has freshwater run-off into rivers and streams
Oceans collect all salt and minerals from all rives that flow into them
Baltic sea

Question 21

What is the halocline?

Answer 21

Vertical zone in oceanic water column in which salinity changes rapidly with depth

Question 22

What do maps show about ocean salinity?

Answer 22

Isohaline maps / contors show greater salinity around equatorial regions and less around thr poles

Question 23

What is the pattern of coastal temperatures?

Answer 23

Colder at poles and deep ocean

Warmer at equator and on the surface ocean

Question 24

How do oceans regulate the temperature of the land near them?

Answer 24

Water has a high specific heat capacity due to having hydrogen bonding, meaning lots of kinetic energy is needed to break the strong intermolecular forces between the water molecules

Question 25

Where does the ocean absorb heat?

Answer 25

At the eqautor - solar radiation hits this point on the earth’s surface due to the tilt of the earth’s axis

Question 26

Distribution of warm and cold ocean currents?

Answer 26

Large quantities of heat can be absorbed and stored in the surface layers of the ocena - transported by ocean currents.
Warm water at the surface and decrease in temperature with depth
Ocean currents awat from the equator bsorb as much hear whilst they remain within the tropics
Away from the tropics the currents radiate heat e.g. north atlantic current
Surface ocean current are driven by global winds
Polar regions - oceans curents become cooler in temps. And increase in salinity - increase in density so cooler water sinks to ocean depths
Deep currents flow back to the equatorial regions where. Water rises in the thermohaline circulation

Question 27

What is the effect of El Nino?

Answer 27

Southern oscillation

Warm water is transported westwards in the pacific towards south america

Question 28

What is the photic zone?

Answer 28

Layer of water where there is enough light for photosynthesis to take place

Question 29

What are the 3 zones of the ocean?

Answer 29

Photic zone - photosynthesis
Dysphotic zone - no photosynthesis 200m
Aphotic zone - no sunlight - darkness - 1000m

Question 30

What 5 factors affect ocean currents?

Answer 30

Winds
Rotation of earth (coriolis effect)
Variation of temp
Density of ocean water
Shapes of the coastline

Question 31

What is the coriolis effect?

Answer 31

Earth roates circulating air is deflected
Air deflects towards the right in the northern hemisphere and to the left in the southern hemisphere = curved paths
Deflection is coriolis effect

Question 32

Difference between warm and cold currents?

Answer 32

Warm currents less saline and less dense distributed along the equator
Cold currents more saline and more dense distributed around the poles

Question 33

What are gyres?

Answer 33

Large circulating ocean currents

Question 34

How many ocean currents made up the North Atlantic currents?

Answer 34

9 e.g. Gulf stream and Canary current

Question 35

Where does the water flow from and to in the NAC?

Answer 35

Coast of florida to northwest of gulf stream
N. Atlantic drift flows all the way to the norwegian coastline and onto the arctic
Flows into labrador current southwards

Question 36

Warm water in NAC?

Answer 36

Gulf stream water from coast of florida towards greenland

Question 37

Where is the water cool in NAC?

Answer 37

From north to northwest atlantic by labrador current which flows southwards from the arctic