雅思阅读 46: The Day the Reign Ended（王朝终结之日）

改编由 ScienceDaily / Smithsonian Magazine / Science（2025）。雅思阅读 Section 3 难度，约 1050 词。 素材来源：https://www.sciencedaily.com/releases/2025/01/250116133822.htm

Reading Passage

A. Sixty-six million years ago, an asteroid roughly ten kilometres across crossed the orbits of the inner planets and struck what is now the northern coast of the Yucatán Peninsula, in Mexico. At the moment of impact, the surrounding landscape was a shallow tropical sea floored with limestone, carbonate rocks and sulphur-bearing minerals — a geological setting that would prove fateful. The kinetic energy of the incoming object, travelling at perhaps twenty kilometres per second, was converted within seconds into heat, seismic shaking and a blast wave that excavated a crater about two hundred kilometres across — the structure now known as Chicxulub. Within hours, tsunamis hundreds of metres high swept across the Gulf of Mexico, dumping layers of gravel and shell onto inland coastlines; within days, soot and sulphate aerosols were circling the globe on stratospheric winds. Roughly seventy-five per cent of all species on Earth, including every non-avian dinosaur, disappeared from the fossil record at exactly this boundary, which geologists call the Cretaceous–Paleogene, or K–Pg, extinction. The layer of iridium-rich clay that marks the boundary was first identified in Italy in 1980, by the father-and-son team Luis and Walter Alvarez, who immediately recognised its extraterrestrial origin.

B. For decades, the standard story held that the impact was an ecological calamity almost too terrible to measure. Numerical climate models suggested that the vapourised target rock released as much as three hundred billion tonnes of sulphur into the stratosphere, where it would have reflected sunlight back into space and plunged the planet into a freezing "impact winter" lasting years. Crops failed, photosynthesis shut down, food chains collapsed, and temperatures may have dropped by double digits for a decade or more. That picture was challenged in January 2025 by a team that analysed drill cores recovered from within the Chicxulub crater itself, together with boundary sediments from around the world. Their empirical measurements, published in Nature Communications, suggested that the total sulphur release was closer to 67 billion tonnes — about five times lower than earlier estimates. The implication was that the impact winter, while severe, was milder and shorter-lived than the models had predicted, and that climate recovery was correspondingly fast enough for at least a quarter of species to hang on through the worst of the cold. The revised figure is still catastrophic — 67 billion tonnes of sulphur is roughly the annual output of all human industry — but it is less apocalyptic than the earlier three-hundred-billion-tonne estimate.

C. Yet the timing of the disaster is nearly as important as its intensity. A long-running debate has asked whether the dinosaurs were already in decline before the asteroid arrived — sapped by volcanic eruptions in India, cooling climates and falling sea levels — or whether they were ecologically thriving until the very afternoon of the impact. Fossil beds in western North America, where the uppermost Cretaceous rocks are best exposed, have yielded conflicting answers, and critics have long argued that the fossil record is too patchy to support either conclusion. In October 2025, a team led by scientists from University College London and the New Mexico Museum of Natural History weighed in with a study in Science based on newly described fossil sites in New Mexico. Their occupancy models — a statistical technique borrowed from conservation biology, used to estimate how common a species actually is from incomplete sighting data — suggested that dinosaur diversity in the latest Cretaceous was actually high, and that populations were not shrinking. The lead researcher was quoted as saying that, had the asteroid not intervened, dinosaurs would probably still be here today, and mammals might still be rat-sized. The study's authors are careful not to claim that dinosaurs were under no pressure at all — climate change was altering ecosystems at the end of the Cretaceous — but they maintain that no irreversible decline was under way.

D. The marine record tells a more nuanced story. The same impact that killed the dinosaurs also collapsed planktonic ecosystems, acidified the oceans and wiped out reefs; in many sections of the geological record, the layers immediately above the boundary are almost barren of fossils. But a separate 2025 study found that the crater itself acted as a refuge: the disturbed waters around Chicxulub became enriched with osmium and other nutrients delivered by the asteroid, stimulating phytoplankton blooms and accelerating the recovery of marine life within a few years rather than centuries. The contrast between terrestrial collapse and marine recovery is one of the most surprising findings to emerge from the last decade of K–Pg research. It suggests that the severity of an extinction event is not uniform across the planet — that some environments bounce back rapidly, fertilised by the catastrophe itself, while neighbouring ones remain desolate for millennia. It also implies that modern attempts to model extinction risk from a single set of parameters may be misleading. The crater's rapid recovery has encouraged some researchers to propose that impact events could, paradoxically, act as evolutionary accelerants, clearing ecological niches that surviving species then fill with surprising speed.

E. What does this mean for the present? The Chicxulub event is the closest analogue in the geological record to the rapid, human-driven climate change now underway. Both involve sudden disruptions to the carbon cycle, both produce rapid shifts in temperature and ocean chemistry, and both selectively wipe out species that cannot adapt or migrate. The 2025 revision of the sulphur budget is a reminder that even the best numerical models can overshoot the real signal — and that direct, empirical evidence from the rocks themselves remains essential before policy decisions are built on extrapolations. For the dinosaurs, the asteroid was a one-off stroke of bad luck; no amount of behavioural flexibility would have changed the outcome. For the living world now, the disturbance is self-inflicted and ongoing, and recovery, as in the crater's waters, may be possible — but only if the warming stops before the long dark winter settles in. The geological record, in other words, does not console; it diagnoses. It warns that the worst extinctions in Earth's history were triggered by sudden shocks, not by slow decline — and that once the shock passes, recovery is possible but takes far longer than a human lifetime.

Questions 1-4

Choose the correct heading for paragraphs B, C, D and E from the list of headings below.

List of Headings i. A revised estimate of sulphur release ii. The debate over whether dinosaurs were already declining iii. Why marine recovery was faster than expected iv. The present-day lesson of the extinction v. How the Yucatán limestone was formed vi. A history of dinosaur breeding programmes vii. The cost of drilling the Chicxulub crater

1. Paragraph B: ____
2. Paragraph C: ____
3. Paragraph D: ____
4. Paragraph E: ____

Questions 5-8

Choose the correct letter, A, B, C or D.

5. How large was the Chicxulub crater? A. About 20 kilometres across. B. About 200 kilometres across. C. About 2,000 kilometres across. D. About 2 kilometres across.

6. What did the January 2025 study find about sulphur release? A. It was five times higher than previously estimated. B. It was about 67 billion tonnes, five times lower than prior estimates. C. It was zero. D. It was entirely in the form of soot.

7. What did the October 2025 Science study conclude about dinosaurs? A. They were already in steep decline before the impact. B. Their diversity was high and populations were not shrinking. C. They had already gone extinct millions of years earlier. D. They were wiped out by volcanic eruptions only.

8. Why did marine life around Chicxulub recover relatively quickly? A. The asteroid delivered nutrients such as osmium that stimulated plankton. B. The oceans froze solid. C. Humans restocked the reefs. D. The crater was emptied of all water.

Questions 9-13

Do the following statements agree with the claims of the writer?

Write:

• TRUE if the statement agrees with the information
• FALSE if the statement contradicts the information
• NOT GIVEN if there is no information on this

9. The asteroid struck approximately 66 million years ago.
10. Approximately 75% of all species disappeared at the K–Pg boundary.
11. The January 2025 study concluded that the impact winter was more severe than previously thought.
12. The 2025 marine study suggested the crater itself acted as a refuge.
13. The asteroid that struck Chicxulub is now believed to have originated in the Oort Cloud.

Questions 14-15

Complete the summary below using NO MORE THAN TWO WORDS from the passage.

The 2025 drill-core analysis revised the total (14) __________ release down to about 67 billion tonnes, implying a milder impact (15) __________ and faster climate recovery.

答案与解析

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