Caves - IELTS Listening Answers & Explanations
From IELTS Recent Actual Test 6 Academic Listening Test 3 · Part 4 · Questions 31–40
Audio
Questions
Questions 31–33 Multiple Choice (One Answer)
Choose the correct letter, A, B, or C.
Questions 34–40 Table Completion
Complete the table and notes.
Write NO MORE THAN TWO WORDS for each answer.
| Three Main Reasons for Cave Formation | ||
|---|---|---|
| Dissolution | Volcanic Lava Tubes | Action of Waves |
| mainly involves 34 |
|
waves pound in to cliffs then erode into 36 or less rigid rocks. |
| Limestone caves |
|
| e.g. Lechuguilla |
|
Answers & Explanations Summary
| # | Answer | Evidence | Explanation |
|---|---|---|---|
| Q31 | C | Whatever the ease, if the caves are known, as complex and difficult as they usually are, they will be explored | Excerpt/Transcript Explanation: The transcript explains that caves are normally very complicated and hard to travel through. Answer Explanation: The answer means that caves are frequently hard and potentially dangerous to go inside and travel through. Reason For Correctness: The correct answer is chosen because the lecturer describes caves as being 'complex', 'difficult', and 'challenging'. The text mentions that whether caves are found in far-away places, are very long, or are filled with water, they are usually not easy to navigate. Additionally, the speaker notes that people who go underground face 'difficulties and dangers', which confirms that caves are hard to explore. |
| Q32 | C | If the exploration is just for fun, the activity is known as caving, but with the difficulties and dangers involved, the average caver is often involved with one of these speleological sciences | Excerpt/Transcript Explanation: The transcript explains that even people who explore caves just for fun usually participate in the scientific study of caves because of the challenges and risks involved. Answer Explanation: The answer means that people who go inside caves to explore them usually have some knowledge about the science of caves. Reason For Correctness: The correct answer is correct because the lecturer states that most people who explore caves for fun (cavers) also study the science of caves (speleology). This is because exploring caves is hard and dangerous, so an 'average caver' is usually 'involved' with a science related to caves. This matches the idea that they know about cave sciences. |
| Q33 | A | China, for example, has huge areas of limestone bedrock—prime material for cave formation—and logically must contain among the largest number of caves in the world, yet only few are documented due to the lack of interest in caving there | Excerpt/Transcript Explanation: The transcript explains that China has the right kind of ground to have many caves. It says that logic suggests China should have some of the highest numbers of caves globally, but because people don't explore them much there, very few are actually on record. Answer Explanation: The answer means that China likely has a very large number of caves that people have not found or recorded yet. Reason For Correctness: The correct answer is A because the speaker mentions that China has a lot of 'limestone bedrock,' which is the perfect material for making caves. Because of this, it should have one of the highest numbers of caves in the world. However, since people in China are not very interested in the hobby of 'caving,' very few of these caves have been 'documented' (written down or put on a map). If a place has many caves but only a few are written down, it means most of them are still undiscovered. |
| Q34 | limestone | The largest and most common of these involves limestone, although other materials are possible, including gypsum, marble, and even salt | Excerpt/Transcript Explanation: The transcript explains that while caves can form in several types of rock through dissolution, the biggest and most usual examples are found in limestone. Answer Explanation: The answer is a type of hard, grey rock often used for building and where many caves are found. Reason For Correctness: The correct answer is "limestone" because the lecturer explains that the process of dissolution, which is the most common way caves are made, usually happens in this type of rock. The speaker notes that while other materials like salt or marble can form these caves, limestone is the most frequent material involved. |
| Q35 | solidifies | When lava from volcanoes flows downhill, the topmost surface cools and solidifies first, leaving the hotter lava to continue to flow beneath | Excerpt/Transcript Explanation: The transcript explains that when hot lava moves down a mountain, the very top part loses heat and turns into a hard crust. This hard part stays in place while the hot, liquid lava inside continues to flow forward. Answer Explanation: The answer "solidifies" means to become hard or turn from a liquid into a solid material (like a rock). Reason For Correctness: The correct answer is "solidifies" because the lecturer describes how volcanic lava tubes are created. He explains that when hot lava flows, the top part loses heat and becomes hard (solidifies) while the hotter liquid lava stays underneath and keeps moving. This process creates the hollow tube or cave. Key words to look for are "topmost surface," "cools," and "lava." |
| Q36 | fault lines | Finally, there are sea caves, formed from waves pounding into coastal cliffs, and eroding into fault lines, or softer rock | Excerpt/Transcript Explanation: The transcript explains that waves hit cliffs by the sea and slowly break apart or wear down parts of the land. This process happens specifically at cracks called fault lines or in rock that is not very strong. Answer Explanation: The answer 'fault lines' refers to cracks or breaks in the rock where the earth has moved. Reason For Correctness: The correct answer is 'fault lines' because the text explains how sea caves are made. It describes waves hitting cliffs and wearing away, or eroding, specific parts of the cliff. The speaker identifies these parts as 'fault lines' or 'softer rock'. In the table, 'less rigid rocks' is used as a synonym for 'softer rock', so 'fault lines' is the correct term to complete the information. |
| Q37 | calcium | As the groundwater seeps downward through the ceiling of the caves, it encounters a different pressure and temperature, causing it to deposit a small amount of its dissolved calcium carbonate | Excerpt/Transcript Explanation: The transcript explains that when water drips through the roof of a cave, the change in environment makes it leave behind a small bit of its dissolved calcium carbonate. Over time, this building material forms the beautiful structures in the cave. Answer Explanation: The answer 'calcium' is a part of the name for a hard material (calcium carbonate) found in caves. It is the mineral that builds up over many years to create the rock shapes inside limestone caves. Reason For Correctness: The correct answer is 'calcium' because the lecturer explains that when water enters a cave, it drops tiny amounts of 'calcium carbonate.' This specific substance is what forms the common shapes we see in limestone caves, such as stalactites (which hang from the top) and stalagmites (which grow from the ground). |
| Q38 | flowstone | this deposition process results in ever-growing masses, known as stalactites of hanging from the ceiling), or stalagmites (if growing from the floor). Alternatively, the water may flow over a large surface of rock, forming flowstone | Excerpt/Transcript Explanation: The transcript explains that mineral deposits create shapes in caves. It explicitly lists 'stalactites', 'stalagmites', and 'flowstone' as the results of this process. Answer Explanation: The answer 'flowstone' is a name for a specific shape that rocks take inside a limestone cave. Reason For Correctness: The correct answer is found in the section about limestone cave formations. The speaker lists different types of shapes created when minerals (calcium carbonate) build up over time. After mentioning 'stalactites' and 'stalagmites', the speaker provides 'flowstone' as another common example of these formations. |
| Q39 | 1986 | It look until 1984 for a group of cavers to gain permission to start digging, and two years later, in 1986 they broke through into a walkable passageway —unlocking, one of the longest cave systems in the world | Excerpt/Transcript Explanation: The transcript explains that cavers started digging in 1984, and after two years of work, they reached the hidden cave area in 1986. Answer Explanation: The answer 1986 is the specific year when explorers finally entered the main part of the Lechuguilla Cave. Reason For Correctness: The correct answer is 1986 because the lecturer mentions that although explorers got permission to dig in 1984, they only managed to break through into the walkable passageway two years later, which was 1986. This was the moment the cave system was finally revealed or unlocked for exploration. |
| Q40 | bottom up | This was forced through fracture lines, combining with existing groundwater to form sulfuric acid, dissolving the limestone from the bottom up, instead of the normal top-down seepage which characterises most limestone cave formation | Excerpt/Transcript Explanation: The transcript explains that the acid in the ground melted the rock starting from the lower part and moving upwards, which is unusual for these types of caves. Answer Explanation: The answer 'bottom up' describes the direction in which the rock dissolved to create the Lechuguilla Cave. Reason For Correctness: The correct answer is 'bottom up' because the lecturer explains that the Lechuguilla Cave formed differently than most limestone caves. While most caves form from 'top-down' seepage (water coming from above), this specific cave was created by acid dissolving the rock from the lower parts toward the higher parts. |
Transcript
SECTION 4
You will hear a lecturer talking about caves.
If there is one natural feature which has long fascinated man, it is caves -- those natural underground spaces into which people can enter. No known cave in the world can exist without it being extensively explored, whether it be in remote areas, such as the Clearwater Cave in Borneo, or immensely long and difficult, such as Mammoth Cave in America, or perhaps the most challenging: those caves below the water table, full with water -- in which ease the exploration is known as cave diving. Whatever the ease, if the caves are known, as complex and difficult as they usually are, they will be explored.
The formal name for the study of caves is speleology — and involves many disciplines, such as chemistry, geology, biology, and cartography, or the science of making accurate maps, since the largest caves can be hundreds of kilometers long and highly complicated. If the exploration is just for fun, the activity is known as caving, but with the difficulties and dangers involved, the average caver is often involved with one of these speleological sciences.
As for the number of caves in the world, research suggests that only a fraction have been found and documented, mostly in the areas in which caving has long been a popular activity, such as in America, France, or Australia. China, for example, has huge areas of limestone bedrock—prime material for cave formation—and logically must contain among the largest number of caves in the world, yet only few are documented due to the lack of interest in caving there. Thus, as exploration continues, new caves will be discovered, and it is likely that the numbers could radically change in the future.
With caves being such mysterious and intriguing places, the obvious question concerns how they form. The most common cause is the effect of slightly acidic water in a process called 'dissolution'. Here, water seeps into the ground, and down through rock masses. If this rock is soluble, the water dissolves some of it, and over time, the passage expands to become a cave, or cave system. The largest and most common of these involves limestone, although other materials are possible, including gypsum, marble, and even salt.
Now, if the cave is formed at the same lime as the rock, it is called a primary cave, and the most common of these are lava tubes. When lava from volcanoes flows downhill, the topmost surface cools and solidifies first, leaving the hotter lava to continue to flow beneath. If most of this eventually flows out, a hollow tube is left. The country Iceland, has some excellent caves of this type, and even far-flung Australia has a few. Finally, there are sea caves, formed from waves pounding into coastal cliffs, and eroding into fault lines, or softer rock. These caves are usually the shortest, about 50 meters at most, since the erosive action of the waves can only reach a certain distance.
However, it is limestone eaves which will always be the most interesting. This is due to the presence of limestone formations. As the groundwater seeps downward through the ceiling of the caves, it encounters a different pressure and temperature, causing it to deposit a small amount of its dissolved calcium carbonate. Over time, through the action of millions of drops, this deposition process results in ever-growing masses, known as stalactites of hanging from the ceiling), or stalagmites (if growing from the floor). Alternatively, the water may flow over a large surface of rock, forming flowstone, and with other sorts of processes, can result in beautiful milky-white formations of astonishing complexity.
One of the best examples of this, as well as of what surprising discoveries may yet await, is the Lechuguilla Cave in New Mexico. In the 1950s, some cavers heard the sound of wind underneath some large boulders on the cave floor, a clear sign of a deeper passageway. It look until 1984 for a group of cavers to gain permission to start digging, and two years later, in 1986 they broke through into a walkable passageway —unlocking, one of the longest cave systems in the world, the deepest in America, and some of the most beautiful formations ever found, Unusually, many of these were yellow with sulphur, suggesting that the caves were a result of hydrogen-sulfide from nearby oil deposits. This was forced through fracture lines, combining with existing groundwater to form sulfuric acid, dissolving the limestone from the bottom up, instead of the normal top-down seepage which characterises most limestone cave formation.