Mapping the Ocean Floor: Reading Answers & Explanations
IELTS Reading practice test · 14 questionsAcademicmedium
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About this passage
The passage opens: “Until surprisingly recently, the floor of the deep ocean was less well known than the surface of the Moon. For thousands of years the only way to measure the depth of the sea was to lower a weighted rope over the side of a ship and wait for it to touch the bottom, a slow technique called sounding.”
- Passage length: about 787 words
- Questions: 14
- Question types: Matching Information, Note Completion, True / False / Not Given
“Mapping the Ocean Floor” is an original IELTS-style practice passage written by IELTS-Bank. It is not taken from an official IELTS or Cambridge test, so these answers only apply to our version.
Answer key at a glance
Mapping the Ocean Floor answers with explanations
Questions 1–6: Matching Information
The passage has six paragraphs, A-F. Which paragraph contains the following information? Write the correct letter, A-F.
- A. Paragraph A
- B. Paragraph B
- C. Paragraph C
- D. Paragraph D
- E. Paragraph E
- F. Paragraph F
- 1
a description of the slowest and earliest way of measuring depth
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Answer: Paragraph A
Why: Paragraph A describes the slowest and earliest way of measuring depth as "sounding," which involved lowering a weighted rope from a ship to the seabed, taking hours for a single measurement.
Where to find it · Paragraph A “For thousands of years the only way to measure the depth of the sea was to lower a weighted rope over the side of a ship and wait for it to touch the bottom, a slow technique called sounding.”
- 2
the first survey to record depths in every ocean of the world
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Answer: Paragraph B
Why: Paragraph B is correct because it describes the HMS Challenger's voyage as the first global survey, recording depths in every ocean and marking the beginning of modern oceanography.
Where to find it · Paragraph B “The first attempt to survey the deep sea across the whole globe was the voyage of HMS Challenger, which sailed from England in 1872 and did not return until 1876.”
- 3
the invention of a method that produced continuous readings
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Answer: Paragraph C
Why: Paragraph C describes the invention of echo sounding, which allowed ships to trace a continuous line of the ocean floor, producing continuous readings instead of isolated measurements.
Where to find it · Paragraph C “Readings that had once taken hours could be made in a matter of seconds, and a vessel steaming along could trace a continuous line of the bottom beneath it.”
- 4
an interpretation that was at first dismissed on account of the scientist's gender
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Answer: Paragraph E
Why: The interpretation in Paragraph E was initially dismissed as "girl talk" by Heezen, indicating that Tharp's idea was not taken seriously partly due to her gender.
Where to find it · Paragraph E “At first her interpretation was brushed aside; Heezen himself is said to have dismissed it as mere 'girl talk'.”
- 5
a modern technique that relies on measurements taken from space
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Answer: Paragraph F
Why: Paragraph F describes a modern technique that uses satellites to measure the sea surface to infer the ocean floor's shape, indicating it relies on measurements taken from space.
Where to find it · Paragraph F “Satellites cannot see the sea floor directly, but they can measure the height of the sea surface with great precision, and that surface is not perfectly flat: the gravity of an undersea mountain pulls a little extra water into a slight bump above it.”
- 6
the discovery of an undersea mountain range with a valley along its crest
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Answer: Paragraph D
Why: Paragraph D is correct because it describes how Marie Tharp discovered a long undersea mountain range with a deep valley along its crest while plotting echo-sounding data in the Atlantic Ocean.
Where to find it · Paragraph D “Working mostly with data gathered in the Atlantic, Tharp plotted profile after profile by hand and noticed a long undersea mountain range running down the very middle of the ocean.”
Questions 7–11: Note Completion
Complete the notes below.
Complete the notes using ONE WORD ONLY from the passage for each answer. Measuring the ocean floor Oldest method was known as (7) ______ : a weighted line was lowered to the bottom. The (8) ______ expedition (1872-1876) made the first worldwide set of soundings. After the First World War, (9) ______ sounding measured depth by timing a returning pulse of sound. Tharp and Heezen mapped the (10) ______ Ocean and found a central rift valley. Modern (11) ______ measure small bumps in the sea surface caused by gravity.
- 7
Oldest method was known as ______ : a weighted line was lowered to the bottom.(max 1 word)
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Answer: sounding
Why: The answer is found in the first paragraph, where it describes the oldest method of measuring ocean depth as "sounding," which involved lowering a weighted rope to the sea floor.
Where to find it · Paragraph A “For thousands of years the only way to measure the depth of the sea was to lower a weighted rope over the side of a ship and wait for it to touch the bottom, a slow technique called sounding.”
- 8
The ______ expedition (1872-1876) made the first worldwide set of soundings.(max 1 word)
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Answer: Challenger
Why: The answer "Challenger" is found in section B, where it describes the HMS Challenger's voyage from 1872 to 1876 as the first global deep-sea survey, recording ocean depths worldwide.
Where to find it · Paragraph B “The first attempt to survey the deep sea across the whole globe was the voyage of HMS Challenger, which sailed from England in 1872 and did not return until 1876.”
- 9
After the First World War, ______ sounding measured depth by timing a returning pulse of sound.(max 1 word)
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Answer: echo
Why: The answer "echo" is found in paragraph C, which describes how echo sounding replaced the older method by sending a sound pulse to the seabed and measuring the time it takes for the echo to return.
Where to find it · Paragraph C “Instead of a rope, a ship now sent a pulse of sound down towards the seabed and measured the time the echo took to return; because the speed of sound in water is known, that time could be turned directly into a depth.”
- 10
Tharp and Heezen mapped the ______ Ocean and found a central rift valley.(max 1 word)
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Answer: Atlantic
Why: The answer "Atlantic" is found in paragraph D, where it mentions that Marie Tharp and Bruce Heezen primarily worked with data collected from the Atlantic Ocean while creating their ocean floor maps.
Where to find it · Paragraph D “Working mostly with data gathered in the Atlantic, Tharp plotted profile after profile by hand and noticed a long undersea mountain range running down the very middle of the ocean.”
- 11
Modern ______ measure small bumps in the sea surface caused by gravity.(max 1 word)
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Answer: satellites
Why: The answer "satellites" is not found in the passage, as it focuses on historical methods like sounding, the HMS Challenger expedition, echo sounding, and Tharp and Heezen's mapping, without mentioning satellites.
Where to find it · Paragraph F “Satellites cannot see the sea floor directly, but they can measure the height of the sea surface with great precision, and that surface is not perfectly flat: the gravity of an undersea mountain pulls a little extra water into a slight bump above it.”
Questions 12–14: True / False / Not Given
Do the following statements agree with the information given in the passage? Write TRUE, FALSE or NOT GIVEN.
- 12
Echo sounding could measure depth more quickly than the older method of lowering a line.
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Answer: TRUE
Why: Echo sounding was faster because it used sound pulses to measure depth in seconds, unlike the older method of lowering a line, which took hours.
Where to find it · Paragraph A “For thousands of years the only way to measure the depth of the sea was to lower a weighted rope over the side of a ship and wait for it to touch the bottom, a slow technique called sounding.”
- 13
Marie Tharp's interpretation of the rift valley was immediately accepted by other scientists.
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Answer: FALSE
Why: Marie Tharp's interpretation of the rift valley was initially dismissed, even by her colleague Bruce Heezen, who reportedly called it "girl talk," indicating it was not immediately accepted by other scientists.
Where to find it · Paragraph D “In the middle of the twentieth century two American scientists, Marie Tharp and Bruce Heezen, set about turning columns of echo-sounding figures into a picture.”
- 14
More women than men now work on ocean-floor mapping projects.
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Answer: NOT GIVEN
Why: The statement claims that more women than men work on ocean-floor mapping projects, but the passage never confirms or denies this, as it only mentions Marie Tharp's contributions without discussing current workforce demographics.
Closest related text · Paragraph A “Sailors built up their charts one laborious sounding at a time, and vast stretches of the ocean floor remained entirely blank, imagined rather than mapped.”
Estimated band score for this test
Your raw score out of 14 scaled to the 40-question IELTS Reading (Academic) conversion table. This is the same estimate the practice page shows after you submit. A single passage is a small sample, so treat it as a guide.
| Correct answers | Estimated band |
|---|---|
| 14 / 14 | 9.0 |
| 13 / 14 | 8.5 |
| 12 / 14 | 7.5 |
| 11 / 14 | 7.0 |
| 10 / 14 | 6.5 |
| 8–9 / 14 | 6.0 |
| 7 / 14 | 5.5 |
| 6 / 14 | 5.0 |
| 5 / 14 | 4.5 |
| 4 / 14 | 4.0 |
| 3 / 14 | 3.5 |
| 2 / 14 | 3.0 |
| 1 / 14 | 2.0 |
| 0 / 14 | 0.0 |
Full-test score? Use the IELTS band calculator.
Tips for the question types in this test
Matching Information
- Read each statement and identify exactly what kind of information you are looking for — a reason, a result, an example, a definition, a contrast.
- Note that the statements do NOT follow paragraph order, so treat each one as an independent search.
Common trap: Assuming the questions run in order — they do not, which makes linear reading inefficient.
Full Matching Information strategyNote Completion
- Use headings and indentation to identify the topic of each blank.
- Predict the answer type and mark the word limit.
Common trap: Treating bullets as unrelated when they belong to one passage section.
Full Note Completion strategyTrue / False / Not Given
- Read the statement first and underline the key idea, especially any qualifiers like "all", "only", "never", "always", "more than" or dates and numbers.
- Because the questions follow the order of the passage, scan for the paragraph that deals with the same topic rather than re-reading everything.
Common trap: Confusing "False" with "Not Given": choose False only when the passage actively contradicts the statement; if the passage is silent, it is Not Given.
Full True / False / Not Given strategyPractise “Mapping the Ocean Floor” under exam conditions
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