(i) State one natural cause and one human cause of sand dune degradation.

(ii) Identify two ways in which people are attempting to restore the sand dunes shown in the photograph.

Briefly explain the characteristics and formation of two ocean floor landforms found at a constructive plate boundary.

Examine the possible impacts of changes in the ocean carbon store.

(i) Natural cause – strong winds / blow outs / storms [1]
    Human cause – trampling/foot path erosion / fire/barbeques / introduction of exotic species (eg rabbits) / dune boarding [1].

[3 marks]

(ii) Award [1] for each valid statement.

Possibilities include:

• fencing off/closing off areas to prevent further erosion of the dunes/destruction of the vegetation
• signage to keep people out
• replanting of sand dune species, eg sea couch and marram grass.

[3 marks]

For each landform explained, award up to [2] for a description of the landform’s characteristics and up to [2] for an explanation of its formation, up to a maximum of [3].

For example: A mid-ocean ridge is a submarine linear mountain range [1] formed by two plates moving apart due to convection currents [1] and magma rising to produce a volcanic ridge [1].

Other possibilities include:

• rift valleys at constructive plate boundaries
• seamounts (guyots) are formed at constructive boundaries but have since moved away
• transform faults
• shield volcanoes
• pillow lava
• black smokers.

[6 marks]

Oceans play a key role in the carbon cycle. The major reservoirs of carbon dioxide are fossil fuels (10 000 × 10¹² kilograms of carbon), the atmosphere (750 × 10¹² kilograms of carbon) and the oceans (38000 × 10¹² kilograms of carbon). Photosynthesis by plankton generates organic compounds of carbon dioxide. Some of this material passes through the food chain and sinks to the ocean floor, where it is decomposed into sediments.

Oceanic uptake of CO₂ has halved since the 1990s. This may be due to the oceans being saturated with respect to CO₂. As the oceans absorb more carbon, they become more acidic. The implications of this are that climate change may accelerate if the oceans can no longer absorb carbon; coral reefs may die back due to acidification; species such as crabs and lobsters may decline due to the decrease in calcium building.

Good answers may be carefully structured around different kinds of possible impact, eg positive and negative, environmental and economic, short-term and long-term. These will be grounded in an understanding of the role of the oceans as a store of CO₂.

At band D, expect a description of the role of the oceans in the carbon cycle.

At band E, expect either a more detailed explanation of the role of the ocean carbon store or an examination of possible impacts of changes.

At band F, expect both.

[10 marks]