Killer Blow

A meteor as big as the city of San Francisco 1)…………………… towards the Earth at 20 km per second, 2) ………………….. into the tropical lagoons of the Gulf of Mexico and 3) ……………………… a fathomless hole. As a result, a tidal wave 4) ……………. outwards. Fires 5) …………………. across North and South America and fallout 6) ………………… the sun and 7) ……………………….. the Earth into permanent gloom.

This catastrophic event is the classic answer as to why dinosaurs were 8) ……………… 65 million years ago, but does the theory hold water? Everyone agrees that the Earth suffered a large meteor strike towards the end of the Cretaceous period, yet more than 20 years after the Chicxulub impact was proposed as the cause of mass extinction, scientists are still arguing over what really killed the dinosaurs.

On one side are the 'catastrophists', who say the impact snuffed out the majority of life on Earth in a 9) ………………… of months or a few years. On the other are 'gradualists', who point out that the fossil record shows a steady decline in the number of species, starting several hundred thousand years before the end of the Cretaceous period. The gradualists don't deny the Chicxulub impact happened, but maintain that it wasn't responsible for the mass10) ………………...

The debate between the two sides has been polarised and 11) ………………., but thanks to a feat of engineering, scientists may finally be able to find out exactly what happened to our planet on that fateful day 5 million years ago. By boring through solid rock, drilling contractors have pulled out a core, 1112 metres long and 7.6 cms in diameter, which records the full story of the impact and its 12) …………………….. Geologists (mainly catastrophists, of course) are queuing up to analyse the core. In so doing, they hope to confirm whether the impact was devastating enough to kill the dinosaurs.

For the catastrophists, however, there are two big problems. First, they don't know how intense and widespread the meteor's effects were and would have to provide evidence of an extreme global change that lasted for at least a year. Secondly, it wasn't just meteors that were stirring up unrest. At that time, an area known as the Deccan Traps in what is now Western India was enduring one of the most intense 13) ………………….. of volcanism in Earth's history. A 'hot spot' deep in the mantle was producing plumes of superheated lava that burst through the crust, inundating 2,5 million square km of land.

Greenhouse gases and water vapour emerged with the lava and, in 1981, Dewey McLean proposed that the Deccan Traps 14) ………………….. severe global warming and a mass extinction. In support of this theory, the gradualists point out that this is not the only episode of supervolcanism that has occurred simultaneously with a mass extinction. At the Permian-Triassic boundary 250 million years ago, over 90% of marine 15) ………………….. became extinct just as the region that is now Siberia was being flooded with lava.

3 Find the linking words used in the text. Study the way they organize the structure of the text.

e.g. Everyone agrees that …., yet more than 20 years ….

• Study various ways of expressing cause and result.

Noun phrases	Verb phrases	Linking words
cause (of), effect/effects (of... on), explanation (for), outcome/outcomes (of), reason, result	affect, be caused (by), cause... (to + inf), be responsible (for), contribute (to), lead (to), result (in), suffer (from), trigger	as a result, in so doing

• Use some of these phrases in the sentences below, paying attention to any prepositions following the spaces.

1 One of the immediate ……………………. of the meteor strike was a tidal wave.

2 The extensive fires that …………………….. by the impact..........................to a long period of darkness.

3 Catastrophists believe that the Chicxulub impact......................in the extinction of the dinosaurs.

4 Gradualists refuse to believe that the impact......:........................ for the end of the dinosaurs.

5 Dewey McLean's theory suggests that the Deccan Traps................................... the Earth's temperature to rise and, …………………......, there was a mass extinction.

6 Some researchers are convinced that the volcanic activity which formed

the Deccan traps.................................. in part to the end of the dinosaurs.

7 Up until now, many scientists have seen these eruptions as being too infrequent to................................ extreme environmental change.

8 However, new research suggests that this volcanic activity could provide a watertight a................................................for the dinosaurs' extinction, as it shows the Deccan Traps were formed more quickly than previously thought.

4 Write the summary of the article Killer Blow following the suggested structure. (about 100 words) Use the words different from those in the text, such as

biodiversity coincidence adverse crater debris duration eradication incident proof quantities dispute

The Chicxulub meteor strike ……………………. and …………………... Catastrophists believe…………………………, but gradualists don’t ……………………., pointing to …………………... There has been a long-running ……………….. Catastrophists need ……………………….. Moreover, gradualists ………………………….

! Avoid quoting the text, use the vocabulary different from the language of the text.!