Living dunes
Read Living dunes and check the IELTS Reading answers. Armies of giant sand dunes are advancing across the world's deserts, engulfing anything that crosses their path. They are tens of metres tall and hundreds of metres long. Fortunately, they aren't going very fast. Even the smallest, speediest du…
Passage preview
Armies of giant sand dunes are advancing across the world's deserts, engulfing anything that crosses their path. They are tens of metres tall and hundreds of metres long. Fortunately, they aren't going very fast. Even the smallest, speediest dunes only travel about 100 metres over the course of a year, while the bigger ones, which weigh something in the order of 10,000 tonnes, barely move one metre in that time. However, their insidious creep can have serious consequences if there is an oil installation or a railway line in their path.
Vocabulary from this passage
9 words worth learning before you sit the test, each with the sentence it appears in.
- accumulate verb
To gather together or acquire an increasing number or quantity of
Toxins can accumulate in the food chain, posing risks to top predators.
- arid adjective
Having little or no rain; too dry or barren to support vegetation
The cactus is well-adapted to survive in arid environments where water is scarce.
- engulf verb
To sweep over something so as to surround or cover it completely
The panic threatened to engulf the financial markets after the sudden crash.
- insidious adjective
Proceeding in a gradual, subtle way, but with harmful effects
High blood pressure is often described as an insidious condition because it has few early symptoms.
- pragmatic adjective
Dealing with things sensibly and realistically in a way that is based on practical rather than theoretical considerations
A pragmatic approach to problem-solving often yields better results than idealistic theories.
- prevailing adjective
Existing at a particular time; current; having the most appeal or influence
The prevailing view among economists is that inflation will stabilize next quarter.
- replicate verb
To make an exact copy of; to reproduce or repeat a scientific experiment
Other laboratories failed to replicate the initial findings of the study.
- synchrony noun
Simultaneous action, development, or occurrence
The dancers moved in perfect synchrony, interpreting the rhythm as one entity.
- veneer noun
A thin decorative covering; a superficial appearance that disguises someone's true nature
A thin veneer of politeness hid the deep animosity between the two negotiators.
Answers with explanations
- 27. iv
The paragraph mentions the **serious consequences** for **oil installations** or **railway lines** (industry and communications) in the path of dunes. This matches Heading iv: **A potential threat to industry and communications**.
- 28. viii
The paragraph states that **linear sand dunes** make up **over half** of the sand-covered desert, making them the most common. This matches Heading viii: **The commonest type of dune**.
- 29. vi
The paragraph explains that Barchan dunes require specific conditions: **one-directional winds**, **edge of sandy deserts**, and **near coastal areas**. This matches Heading vi: **Needing a specific combination of conditions**.
- 30. vii
The paragraph describes the movement of sand grains as a repeating process or cycle (**repeat the process**). This matches Heading vii: **A continuous cycle**.
- 31. v
The paragraph describes dunes **colliding** and then returning to their shape (**re-forming**). This matches Heading v: **Dunes coming together and re-forming**.
- 32. ix
The paragraph contrasts **local legends** (spirits) with the **scientific explanation** (pragmatic view). This matches Heading ix: **Old superstitions demystified**.
- 33. ii
The paragraph describes scientists taking samples to a **laboratory** (ENS in France) to **replicate** the sound. This matches Heading ii: **Recreating the process in a laboratory**.
- 34. C
The text describes linear dunes as forming in a **long curving wave**. This matches the option stating they develop in a **recognisable shape**. Other options are incorrect: they are formed by winds from **several quarters** (not one direction), they are **static** (do not move), and they make up half of the 20% sand-covered area (so ~10%, not 20% of deserts). Answer: C.
- 35. B
Bagnold's discovery concerning movement relied on the fact that dunes are **granular** (composed of grains) rather than solid. This refers to the **composition** of the dunes. Answer: B.
- 36. D
The question asks why Douady compares a barchan to a **living organism**. He says the dune can **regulate its own shape** and **maintain it as it moves**, and even after a collision the dunes quickly **take on** their distinctive shapes again. So the outline stays the same despite movement, which is the correct choice. Growing from small to large is never mentioned, and effects on surroundings or desert organisms are not what the comparison explains.
- 37. barchans
The gap follows "known as" and needs **one word**, a plural noun naming the type of dune. The passage says moving dunes are known as **'barchans'**, and the later paragraph states that some **barchans** actually **sing**, linking them to the singing dunes. The summary already says "type of dunes", so repeating dunes would not fit the gap; the single accepted answer is barchans.
- 38. shape
The text states that research (studies) shows the grains have a **uniform shape**. The summary asks what property is similar (uniform) among grains.
- 39. tone
The summary says differences in **dimensions** alter the [39] of the song. The source word for dimensions is **size**: the passage says that **variations in size** affect the **tone**. The gap needs a singular noun meaning the quality of the sound, and the answer is lifted verbatim from the text. Scan the paragraph on sample sounds replicated in France to find it, and note it is one word, within the limit.
- 40. minerals
The gap follows "a mixture of different" and needs a plural noun. The summary's **mixture** paraphrases the passage's **precise combination**, and the grains are covered with a coating, the **desert glaze**. This glaze is made from **minerals** from surrounding rocks, then named: iron, aluminium and others. The answer is one word copied from the text. Metals such as iron are examples, not the general term used in the sentence.