6 Markers

1. Explain the global distribution of warm and cold ocean surface currents.

2. Explain the distinctive features of mid-ocean ridges.

Mid-ocean ridges are 2 parallel chains of submarine mountains formed in the boundary between 2 diverging oceanic plates. 

Mid-ocean ridges are where magma escapes from the Earth’s mantle and as it cools, forms a new crust. As the 2 oceanic plates are diverging, more magma escapes and it pushes the crust away from the mid-ocean ridge.

An example is the Mid-Atlantic ridge, where the Atlantic Ocean is diverging both east and west, reaching around 3km from its base to peak. 

As the crust moves away from the ridge, more sediment accumulates over time, sediment is thicker and older further from the ridge, forming abyssal plains which cover vast areas of the ocean, roughly 40% of the Earth’s sea floor. It is less than 100 metres in width, a distinct contrast to mid-ocean ridges.

3. Explain variations in nutrient supply within oceans.

1. Explain horizontal and vertical variations in temperatures in the world’s oceans

2. Explain factors that influence the biodiversity in inter-tidal ecosystems

3. Explain the distinctive features of guyots

4. Explain how acidification of oceans contributes to depleting fish stocks

5. Explain the pattern of circulation in the North Atlantic Ocean.