OxfordAQA A Level Geography: Physical Geography 1 — Practice Questions

These are original questions written for Marlbridge, in the style and at the standard of the examination. They are not reproduced past-paper questions — examination boards hold copyright in their own papers. Use these alongside the official past papers available free from your board.

Related: Physical Geography 1 revision notes

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Section A

1. Define the terms system, input, store, flow and output as applied to physical geography. [3]

2. Explain the difference between dynamic equilibrium and negative feedback. [3]

Section B

3. Explain four major stores in the global carbon cycle and state their relative size. [8]

4. Explain how the following affect the carbon cycle: photosynthesis, decomposition, combustion of fossil fuels, ocean uptake. [8]

5. Explain the concept of a sediment cell and why it matters for coastal management. [5]

6. Evaluate the view that human activity has fundamentally altered the global water and carbon cycles. [12]

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Answers

1. A system is a set of interrelated components working together [1]. Inputs are what enters the system and outputs what leaves it [1]. Stores are where matter or energy is held, and flows (transfers) are the movements between stores [1].

2. Dynamic equilibrium is a state in which inputs and outputs are balanced over time, so the system is stable although its components are constantly changing [1]. Negative feedback is a self-regulating response that counteracts a change and returns the system towards equilibrium [1] — for example increased plant growth absorbing more CO₂ as atmospheric concentrations rise [1].

4 — see below.

3. The lithosphere — by far the largest store, holding carbon in sedimentary rock, particularly limestone, and in fossil fuels; on the order of 100 million gigatonnes, but exchanged over geological timescales [1] [1]. The oceans — around 38 000 GtC, mostly as dissolved bicarbonate in the deep ocean, making it the largest actively exchanging store [1] [1]. The terrestrial biosphere and soils — vegetation holds around 500 GtC and soils around 1500 GtC [1] [1]. The atmosphere — the smallest of the four, around 850 GtC, but the one whose changes most directly affect climate [1] [1].

4. Photosynthesis — plants remove CO₂ from the atmosphere and fix it as organic compounds, transferring carbon to the biosphere store [1] [1]. Decomposition — micro-organisms break down dead organic matter, returning carbon to the atmosphere as CO₂ and to the soil as humus [1] [1]. Combustion of fossil fuels — releases carbon that has been locked in the lithosphere for millions of years back into the atmosphere within decades, a transfer far faster than the natural sinks can absorb [1] [1]. Ocean uptake — CO₂ dissolves at the surface and is transported to depth by the thermohaline circulation and the biological pump, but this also lowers ocean pH — acidification [1] [1].

5. A sediment cell is a largely self-contained stretch of coastline within which the movement of sediment is effectively closed [1], bounded by major headlands or estuaries that prevent significant transfer to adjacent cells [1]. It contains sources, transfers and sinks of sediment [1]. It matters for management because intervention at one point affects the whole cell [1] — building groynes at one resort starves beaches downdrift, so management must be planned at the scale of the whole cell, which is why shoreline management plans are organised on this basis [1].

6. Evidence of fundamental alteration — carbon cycle: atmospheric CO₂ has risen from about 280 ppm pre-industrial to over 420 ppm, a change of a scale not seen in hundreds of thousands of years [1] [1]. Deforestation removes a major sink and releases stored carbon [1]. Fossil fuel combustion transfers carbon from a geological store to the atmosphere thousands of times faster than natural weathering can return it [1]. Ocean acidification demonstrates measurable alteration of the largest active store [1]. Water cycle: dam construction and reservoirs have altered the timing and volume of river discharge worldwide [1]; groundwater abstraction exceeds recharge in many aquifers, so a store is being depleted [1]; urbanisation replaces infiltration with rapid surface runoff, changing flows at basin scale [1]; deforestation reduces evapotranspiration, altering regional rainfall [1]. Counter-arguments: the magnitude of natural fluxes still dwarfs the anthropogenic ones — photosynthesis and respiration exchange around 120 GtC per year against roughly 10 GtC of emissions, so humans alter the balance rather than dominate the flows [1] [1]. The water cycle is closed at global scale and its total volume is unchanged; human impact is on distribution, timing and quality rather than quantity [1]. Many impacts are regional rather than global — an over-abstracted aquifer is a local crisis, not a global one [1]. Negative feedbacks such as increased CO₂ fertilisation and ocean uptake continue to absorb a substantial share of emissions [1]. Judgement: the carbon cycle has been altered more fundamentally than the water cycle, because a geological store has been mobilised and the atmospheric concentration changed measurably worldwide [1] [1]. The water cycle has been redistributed and its local flows transformed, but its global stores and total volume remain governed by natural processes [1]. In both cases the significance lies less in the size of the human flux than in its speed relative to the natural sinks [1].

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Where marks are usually lost

• Confusing stores with flows.
• Giving carbon stores without any sense of relative magnitude.
• Describing the sediment cell without linking it to management.
• Treating the water and carbon cycles as equally altered without distinguishing them.