Serendipity: A meteoric demise?

LAYERS of rock represent moments in history, with each layer representing a more ancient time than the layer above it. The date of the death of the dinosaurs can be pinpointed because there is a sharp transition between layers of rock that are rich in fossils and higher layers that are devoid of fossils. This transition can be dated to 65 million years ago, but for a long time scientists had no idea of the speed of the transition. Did the dinosaurs die off over the course of a few years or a few thousand years?

In the mid-1970s, the geologist Walter Alvarez was in the Italian city of Gubbio studying two layers of limestone dating from the time of the dinosaur extinction. The lower layer was rich in fossils, but the upper layer had virtually none at all. Between the two layers was a one centi- metre thick deposit of clay. If only Alvarez could work out how long it took to deposit the clay, then he would be able to get a handle on the time taken to kill off the dinosaurs.

It was at this point that Alvarez had a remarkable idea. Every day our planet is struck by millions of meteorites - not giant rocks, but tiny granules. This continual dusting from outer space contaminates everything, and Alvarez realised that he could work out how long it took to create the clay layer by measuring the amount of meteorite dust within it. The more meteorite dust, the longer it took to form the clay, the longer it took to wipe out the dinosaurs.

In fact, measuring ancient meteorite granules is impractical, so instead Alvarez set about measuring the amount of iridium in the clay - meteorites are the only source of iridium on earth. He expected to find iridium at levels of about 0.1 parts per billion, but instead the amount was one hundred times greater. Alvarez had set out to look for a gentle smattering of iridium to measure the duration of the extinction, but instead he discovered a whopping dollop of the stuff, thereby indicating that a massive meteorite was the cause of the extinction.

Although scientists have since discovered the meteorite's impact crater in the Yucatan Peninsula in Mexico, one mystery still remains. The fossil record suggests that the dinosaurs were dying off before the iridium layer was formed, in other words before the meteorite hit the earth. As a result, some geologists have put forward an alternative theory. They argue that a spate of volcanic eruptions in India 65 million years ago was responsible for kick-starting the demise of the dinosaurs. The scale of eruption was far greater than anything experienced in human history.

The beauty of the volcano theory is that the Earth has witnessed more than one mass extinction, and each of them can be linked to a massive contemporaneous volcanic eruption. On the other hand, it has been much harder to link a meteor crater to each extinction.

Arts and Entertainment

Listen to his collaboration with Naughty Boy

music
Arts and Entertainment
Daniel Craig in a scene from ‘Spectre’, released in the UK on 23 October

film
Arts and Entertainment
Cassetteboy's latest video is called Emperor's New Clothes rap

film
Arts and Entertainment

Poldark review
Arts and Entertainment
Jess Glynne is UK number 1

music

Have you tried new the Independent Digital Edition apps?
Arts and Entertainment

ebooksNow available in paperback
Arts and Entertainment

ebooks
Arts and Entertainment
TV
Arts and Entertainment
Katie Brayben is nominated for Best Actress in a Musical for her role as Carole King in Beautiful

film
Arts and Entertainment
Israeli-born actress Gal Gadot has been cast to play Wonder Woman
film
News
Top Gear presenter James May appears to be struggling with his new-found free time
people
Arts and Entertainment
Kendrick Lamar at the Made in America Festival in Los Angeles last summer
music
Arts and Entertainment
'Marley & Me' with Jennifer Aniston and Owen Wilson
film
Arts and Entertainment
Jon Hamm (right) and John Slattery in the final series of Mad Men
tv
Arts and Entertainment
theatre
Arts and Entertainment
Place Blanche, Paris, 1961, shot by Christer Strömholm
photographyHow the famous camera transformed photography for ever
Arts and Entertainment
The ‘Westmacott Athlete’
art
Arts and Entertainment
‘The Royals’ – a ‘twisted, soapy take on England’s first family’
tv Some of the characters appear to have clear real-life counterparts
News
Brooks is among a dozen show-business professionals ever to have achieved Egot status
people
Arts and Entertainment
A cut above: Sean Penn is outclassed by Mark Rylance in The Gunman
film review
Arts and Entertainment
arts + ents
Arts and Entertainment
James Franco and Zachary Quinto in I Am Michael

Film review Michael Glatze biopic isn't about a self-hating gay man gone straight

Arts and Entertainment
A scene from the movie 'Get Hard'
tvWill Ferrell’s new film Get Hard receives its first reviews
Arts and Entertainment
Left to right: David Cameron (Mark Dexter), Nick Clegg (Bertie Carvel) and Gordon Brown (Ian Grieve)
tvReview: Ian Grieve gets another chance to play Gordon Brown... this is the kinder version
Arts and Entertainment
Benedict Cumberbatch and Martin Freeman in the first look picture from next year's Sherlock special

TV
Arts and Entertainment
Because it wouldn’t be Glastonbury without people kicking off about the headline acts, a petition has already been launched to stop Kanye West performing on the Saturday night

music
Arts and Entertainment
Molly Risker, Helen Monks, Caden-Ellis Wall, Rebekah Staton, Erin Freeman, Philip Jackson and Alexa Davies in ‘Raised by Wolves’

TV review
  • Get to the point
Latest stories from i100
Have you tried new the Independent Digital Edition apps?

ES Rentals

    Independent Dating
    and  

    By clicking 'Search' you
    are agreeing to our
    Terms of Use.

    No postcode? No vote

    Floating voters

    How living on a houseboat meant I didn't officially 'exist'
    Louis Theroux's affable Englishman routine begins to wear thin

    By Reason of Insanity

    Louis Theroux's affable Englishman routine begins to wear thin
    Power dressing is back – but no shoulderpads!

    Power dressing is back

    But banish all thoughts of Eighties shoulderpads
    Spanish stone-age cave paintings 'under threat' after being re-opened to the public

    Spanish stone-age cave paintings in Altamira 'under threat'

    Caves were re-opened to the public
    'I was the bookies’ favourite to be first to leave the Cabinet'

    Vince Cable interview

    'I was the bookies’ favourite to be first to leave the Cabinet'
    Election 2015: How many of the Government's coalition agreement promises have been kept?

    Promises, promises

    But how many coalition agreement pledges have been kept?
    The Gaza fisherman who built his own reef - and was shot dead there by an Israeli gunboat

    The death of a Gaza fisherman

    He built his own reef, and was fatally shot there by an Israeli gunboat
    Saudi Arabia's airstrikes in Yemen are fuelling the Gulf's fire

    Saudi airstrikes are fuelling the Gulf's fire

    Arab intervention in Yemen risks entrenching Sunni-Shia divide and handing a victory to Isis, says Patrick Cockburn
    Zayn Malik's departure from One Direction shows the perils of fame in the age of social media

    The only direction Zayn could go

    We wince at the anguish of One Direction's fans, but Malik's departure shows the perils of fame in the age of social media
    Young Magician of the Year 2015: Meet the schoolgirl from Newcastle who has her heart set on being the competition's first female winner

    Spells like teen spirit

    A 16-year-old from Newcastle has set her heart on being the first female to win Young Magician of the Year. Jonathan Owen meets her
    Jonathan Anderson: If fashion is a cycle, this young man knows just how to ride it

    If fashion is a cycle, this young man knows just how to ride it

    British designer Jonathan Anderson is putting his stamp on venerable house Loewe
    Number plates scheme could provide a licence to offend in the land of the free

    Licence to offend in the land of the free

    Cash-strapped states have hit on a way of making money out of drivers that may be in collision with the First Amendment, says Rupert Cornwell
    From farm to fork: Meet the Cornish fishermen, vegetable-growers and butchers causing a stir in London's top restaurants

    From farm to fork in Cornwall

    One man is bringing together Cornwall's most accomplished growers, fishermen and butchers with London's best chefs to put the finest, freshest produce on the plates of some of the country’s best restaurants
    Robert Parker interview: The world's top wine critic on tasting 10,000 bottles a year, absurd drinking notes and New World wannabes

    Robert Parker interview

    The world's top wine critic on tasting 10,000 bottles a year, absurd drinking notes and New World wannabes
    Don't believe the stereotype - or should you?

    Don't believe the stereotype - or should you?

    We exaggerate regional traits and turn them into jokes - and those on the receiving end are in on it too, says DJ Taylor