🔥Footprints in the muds of time: Đề thi thật IELTS READING (IELTS Reading Recent Actual Test) - Làm bài online format computer-based, kèm giải thích từ vựng

READING PASSAGE 1
You should spend about 20 minutes on Questions 1-13, which are based on Reading Passage 1 on pages 2 and 3.

Footprints in the muds of time

The dinosaurs may have risen to power in as little as 10,000 years...

Everybody knows that the dinosaurs became extinct as a result of a large asteroid; something big hit the Earth 65 million years ago and, when the dust had fallen, so had the great reptiles. There is thus a nice, if ironic, symmetry in the idea that a similar impact brought about the dinosaurs' rise. That is the thesis proposed by Paul Olsen of Columbia University.

Dinosaurs first appear in the fossil record 230 million years ago, during the Triassic period. But they were mostly small, and they shared the Earth with lots of other sorts of reptile. It was in the subsequent Jurassic period, which began 202 million years ago, that they overran the planet and turned into the monsters realistically depicted in modern books and movies. Dr Olsen and his colleagues are not the first to suggest that the dinosaurs inherited the Earth as the result of an asteroid strike. But they are the first to show that the takeover did, indeed, happen in a geological eye blink.

Dinosaur skeletons are rare. Dinosaur footprints are, however, surprisingly abundant. And the size of the prints is as good an indication of the size of the beasts as are the skeletons themselves. Dr Olsen and his colleagues therefore concentrated on prints, not bones. The prints in question were made in eastern North America, a part of the world then full of rift valleys similar to those in East Africa today. Like the modern African rift valleys, the Triassic/Jurassic American ones contained lakes, and these lakes grew and shrank at regular intervals because of climatic changes. Rocks from this place and period can be dated to within a few thousand years. As a bonus, squishy lake-edge sediments are just the things for recording the tracks of passing animals.

By dividing the labour between them, the research team were able to study such tracks at 80 sites and look at 18 so-called "ichnotaxa." These are recognisable types of footprint that cannot be matched precisely within the species of animal that left them. But they can be matched with a general sort of animal, and thus act as an indicator of the fate of that group, even when there are no bones to tell the story.

Their findings show that five of the ichnotaxa disappear before the end of the Triassic, and four march confidently across the boundary into the Jurassic. Six, however, vanish at the boundary, or only just splutter across it; and three appear from nowhere, almost as soon as the Jurassic begins.

That boundary itself is suggestive. The first geological indication of the impact that killed the dinosaurs was an unusually high level of iridium in rocks at the end of the Cretaceous period, when the beasts disappear from the fossil record. Indium is normally rare at the Earth's surface, but it is more abundant in meteorites. When people began to believe the impact theory, they started looking for other Cretaceous-end anomalies. One that turned up was a surprising abundance of fern spores in rocks just above the boundary layer—a phenomenon known as fern spike.

That matched the theory nicely. Many modern ferns are opportunists. They cannot compete against plants with leaves, but if a piece of land is cleared by, say, a volcanic eruption, they are often the first things to set up shop there. An asteroid strike would have scoured much of the Earth of its vegetable cover, and provided a paradise for ferns. A fern spike in the rocks is thus a good indication that something terrible has happened.

The surprises are how rapidly the new ichnotaxa appeared and how quickly they increased in size. Dr Olsen and his colleagues suggest that the explanation for this may be a phenomenon called ecological release. This is seen today when reptiles (which in modern times tend to be small creatures) reach islands where they face no competitors. The most spectacular example is on the Indonesian island of Komodo, where local lizards have grown so large that they are often referred to as dragons. The dinosaurs, in other words, could flourish only when the competition had been knocked out.>> Form đăng kí giải đề thi thật IELTS 4 kĩ năng kèm bài giải bộ đề 100 đề PART 2 IELTS SPEAKING quý đang thi (update hàng tuần) từ IELTS TUTOR

That leaves the question of where the impact happened. No large hole in the Earth's crust seems to be 202 million years old. It may, of course, have been overlooked. Old craters are eroded and buried, and not always easy to find. Alternatively, it may have vanished. Although continental crust is more or less permanent, the ocean floor is constantly recycled by the tectonic processes that bring about continental drift. There is no ocean floor left that is more than 200 million years old, so a crater that formed in the ocean would have been swallowed up by now.

There is a third possibility, however. This is that the crater is known but has been misdated. The Manicouagan "structure," a crater in Quebec, is thought to be 214 million years old. It is huge—some 100 kilometres across—and seems to be the largest of between three and five craters that formed within a few hours of each other as the lumps of disintegrated comet hit the Earth one by one. Such an impact would surely have had a perceptible effect on the world, but the rocks from 214 million years ago do not record one. It is possible, therefore, that Manicouagan has been misdated. That will be the next thing to check.

Questions 1–6

Do the following statements agree with the claims of the writer in Reading Passage 1?
In boxes 1–6 on your answer sheet, write:

• YES if the statement agrees with the claims of the writer.
• NO if the statement contradicts the claims of the writer.
• NOT GIVEN if it is impossible to say what the writer thinks about this.

1. There is still doubt about the theory that an asteroid strike killed the dinosaurs.
2. Books and the cinema have exaggerated the size of dinosaurs.
3. Other scientists have rejected Olsen's idea of a sudden dinosaur occupation of the Earth.
4. Dinosaur footprints are found more frequently than dinosaur skeletons.
5. Ichnotaxa offer an exact identification of a dinosaur species.
6. There is evidence that some groups of dinosaurs survived from the Triassic period into the Jurassic period.

Questions 7–13

Complete the summary below.
Choose NO MORE THAN THREE WORDS from the passage for each answer.
Write your answers in boxes 7–13 on your answer sheet.

Dr Olsen's group believes that the sudden increase in the size of dinosaurs may have been due to something known as 7. __________.
A current example of this can be found on Komodo Island in Indonesia, where some of the lizards are commonly called 8. __________ because of their size. Apparently, they have grown this big because they do not have any 9. __________.

The asteroid strike that may have cleared the way for dinosaurs to become the dominant group probably occurred 202 million years ago.

According to the writer, there are three possible reasons why we have not found a large hole in the Earth's crust dating back 202 million years. First, it may have been 10. __________ by scientists, because craters are easily covered up. Or, it could have 11. __________; for example, if the hole had been in the ocean, it would no longer exist because of the 12. __________ that produce continental drift. Thirdly, the hole could still exist but have been 13. __________.

1. Asteroid
   • Meaning: Thiên thạch.
   • IELTS TUTOR xét ví dụ từ bài đọc: "Everybody knows that the dinosaurs became extinct as a result of a large asteroid."
   • Explanation in Vietnamese: Thiên thạch là một vật thể nhỏ quay quanh Mặt Trời, thường bằng đá hoặc kim loại.

1. Symmetry
   • Meaning: Sự cân đối, đối xứng.
   • IELTS TUTOR xét ví dụ từ bài đọc: "There is thus a nice, if ironic, symmetry in the idea that a similar impact brought about the dinosaurs rise."
   • Explanation in Vietnamese: Sự cân đối hoặc sự tương đồng trong cách sắp xếp hoặc hình thức.

1. Fossil record
   • Meaning: Hồ sơ hóa thạch.
   • IELTS TUTOR xét ví dụ từ bài đọc: "Dinosaurs first appear in the fossil record 230 million years ago."
   • Explanation in Vietnamese: Hồ sơ hóa thạch là tài liệu lưu trữ những hóa thạch tìm được qua các thời kỳ địa chất.

1. Geological eye blink
   • Meaning: Khoảnh khắc ngắn ngủi trong lịch sử địa chất.
   • IELTS TUTOR xét ví dụ từ bài đọc: "The takeover did, indeed, happen in a geological eye blink."
   • Explanation in Vietnamese: Một khoảng thời gian rất ngắn so với lịch sử hình thành Trái Đất.

1. Rift valley
   • Meaning: Thung lũng tách giãn.
   • IELTS TUTOR xét ví dụ từ bài đọc: "The prints in question were made in eastern North America, a part of the world then full of rift valleys."
   • Explanation in Vietnamese: Một vùng thung lũng hình thành do các mảng kiến tạo tách rời nhau.

1. Sediments
   • Meaning: Trầm tích.
   • IELTS TUTOR xét ví dụ từ bài đọc: "Squishy lake-edge sediments are just the things for recording the tracks of passing animals."
   • Explanation in Vietnamese: Các hạt nhỏ của đất đá hoặc khoáng chất lắng đọng ở đáy hồ, sông, hoặc biển.

1. Ichnotaxa
   • Meaning: Dạng dấu chân hóa thạch.
   • IELTS TUTOR xét ví dụ từ bài đọc: "The research team were able to study such tracks at 80 sites and look at 18 so-called ichnotaxa."
   • Explanation in Vietnamese: Một loại hình phân loại hóa thạch dựa trên dấu vết để lại (dấu chân, dấu bò).

1. Iridium
   • Meaning: Kim loại iridi.
   • IELTS TUTOR xét ví dụ từ bài đọc: "The first geological indication of the impact that killed the dinosaurs was an unusually high level of iridium in rocks."
   • Explanation in Vietnamese: Một loại kim loại quý hiếm thường xuất hiện trong thiên thạch.

1. Anomaly
   • Meaning: Sự bất thường.
   • IELTS TUTOR xét ví dụ từ bài đọc: "When people began to believe the impact theory, they started looking for other Cretaceous-end anomalies."
   • Explanation in Vietnamese: Điều gì đó không giống với tiêu chuẩn hoặc quy luật thông thường.

1. Fern spike
   • Meaning: Đỉnh cao của dương xỉ.
   • IELTS TUTOR xét ví dụ từ bài đọc: "One that turned up was a surprising abundance of fern spores in rocks just above the boundary layer - a phenomenon known as fern spike."
   • Explanation in Vietnamese: Hiện tượng số lượng lớn bào tử dương xỉ xuất hiện trong các tầng đá, thường sau một thảm họa.

1. Ecological release
   • Meaning: Sự giải phóng sinh thái.
   • IELTS TUTOR xét ví dụ từ bài đọc: "Dr Olsen and his colleagues suggest that the explanation for this may be a phenomenon called ecological release."
   • Explanation in Vietnamese: Khi một loài có cơ hội phát triển mạnh mẽ do không còn cạnh tranh từ các loài khác.

1. Continental drift
   • Meaning: Sự trôi dạt lục địa.
   • IELTS TUTOR xét ví dụ từ bài đọc: "The ocean floor is constantly recycled by the tectonic processes that bring about continental drift."
   • Explanation in Vietnamese: Quá trình di chuyển của các mảng kiến tạo làm thay đổi vị trí của các lục địa.

1. Misdated
   • Meaning: Định sai niên đại.
   • IELTS TUTOR xét ví dụ từ bài đọc: "It is possible, therefore, that Manicouagan has been misdated."
   • Explanation in Vietnamese: Xác định sai mốc thời gian hoặc tuổi đời của vật gì đó.

• No
• no
• ng
• yes
• no
• yes
• ecological release
• dragons
• competitors
• overlooked
• vanished
• tectonic processes
• misdated