Describe two characteristics of oceanic crust.

Briefly outline the oceanic circulation in the Pacific Ocean during an El Niño event.

Explain the wind and pressure systems in an El Niño event.

Examine the spatial and temporal consequences of overfishing.

In each case, award [1] for a valid characteristic, and a further [1] for development/exemplification.

For example: Oceanic crust is dense [1], and is mainly basaltic [1].
It is relatively young [1], being nowhere older than 200 million years [1]. It increases with age away from a mid-ocean ridge [1] where new ocean crust is formed [1].

It is thinner than continental crust [1], 6–10 km thick as opposed to 35–70 km [1].

Description of oceanic landforms (for example, ridge, trench) [1]; development including details of oceanic crust [1].

Surface water moves eastwards from west/Australia to east/South America [1] before sinking and returning at depth to the west [1].

Full credit may be awarded for a suitably annotated diagram.

Award [1] for each valid point.

For example: High pressure is located in the western Pacific/Australia and low pressure over the eastern Pacific/South America [1].
This causes surface winds to blow from the western Pacific eastwards [1].
This pushes warm water towards South America, warming the air above and causing low pressure [1].
Winds at high altitude blow from east to west, and the subsiding air in the western Pacific leads to high pressure at ground level, eg Australia and Indonesia [1].

The connection between wind and pressure systems must be made explicit for full marks.

A suitably annotated diagram may be used as part of the explanation.

The consequences of overfishing can include falling fish stocks, extinction of prized species, reduced harvests of fish, economic decline, unemployment, the creation of policies to reduce/combat over-fishing, the movement of trawlers into fisheries more distant from their country of origin, illegal fishing in other territories’ waters.

Examples could include the decline of fishing in the Grand Banks of Canada, North Sea cod, blue-fin tuna in the Mediterranean, and, increasingly, off the coast of West Africa.

Good answers will explicitly address how the consequences are spatial and temporal, for instance they may examine how impacts can be local (eg falling fish yields) or global (increased prices for top species), short term (seasonal) or
long term. They may also examine whether the consequences are negative (falling stocks and yields) or positive (eg a cause for the development of aquaculture or for greater management and conservation policies eg maximum
sustainable yield/quotas) for different places / on different timescales.

At band D expect a descriptive account of at least two consequences of overfishing. (Do not expect both spatial and temporal consequences to be addressed explicitly at this level.)

At band E expect either a greater range/depth of consequences of overfishing or a structured examination of the spatial and temporal dimensions of overfishing.

At band F expect both of these elements.

Marks should be allocated according to the markbands.