Chicxulub was responsible for the extinction of the dinosaurs 66 million years ago. This is not a ‘neoadjuvant chemotherapy’ agent as the name might suggest but a huge crater located just off the coast of Mexico’s Yucatán Peninsula formed by a 10km wide asteroid hitting earth at 72,000 km per hour! 2


Being a radiotherapy ‘dinosaur’ myself in relative terms these days it was alarming to find out while watching TV the other day that ‘Gypsum’ was the final nail in the dinosaur’s coffin when Plaster of Paris was a regular part of my working day as a therapeutic radiographer!

Gypsum is actually calcium sulphate with half a molecule of water per molecule of salt and is more commonly known in its powder-based form as Plaster of Paris. This is prepared by heating gypsum at 120°C in rotary kilns, where it gets partially dehydrated and is sold and used commonly as a powder-based substance.

When I was a working as a student and a radiographer, we not only made impressions of patients heads with Plaster of Paris bandages but also filled these with wet plaster that heated up and set. The addition of water to the powder is enough to rehydrate it and allow it to set hard via an exothermic reaction.

My issue was that in those days health and safety was essentially non-existent and so without any mask or venting system to prevent me inhaling the powder in the air, I would likely have breathed it in on a very regular basis. As it rehydrates over the years in my lungs, I worry that it sets and will cause some serious breathing issues later in life however being an ex-smoker I guess the fall-out from that might get me first although I did stop the cigarettes well over 30 years ago!

If you add this to the regular use of lead and cadmium for shielding patients and proximity to some pretty heavy-duty radioactive sources, being a therapeutic radiographer in the 80’s and 90’s carried some risk!

The asteroid was not that large but impacted on earth in the wrong place.

Pic: The asteroid was only very small relatively speaking but travelling very fast!

When the ‘mass extinction’ asteroid hit earth in the shallow waters of the Gulf of Mexico, it injected a large amount of sulphur, a component of gypsum as above into the atmosphere.

As Ben Garrod, one of the presenters of ‘The Day the Dinosaurs Died’ TV program that I was watching put it, ‘the gypsum is what sealed the dinosaurs’ fate, and if the asteroid had landed deeper in the Pacific or Atlantic ocean, the dinosaurs may have survived the catastrophic event.

‘An impact in the nearby Atlantic or Pacific oceans would have meant much less vaporised rock, including the deadly gypsum’, he said. This would have meant that the killer cloud would have been less dense and sunlight could still have reached the planet’s surface, meaning what happened next might have been avoided.

T-Rex was probably the most iconic of the dinosaurs and in the early 70’ s one of the most iconic ‘glam-rock’ bands too!

According to publications the total population of adult Tyrannosaurus Rex at any given time was circa 20,000 individuals. That doesn’t sound many but remember that by nature they would have had huge territories with limited numbers in each. Over the span of the genus’ existence, it is estimated that there were about 127,000 generations and that this added up to a total of roughly 2.5 billion animals until their extinction. I was amazed by this number and so the fossils are out there if you care to look with the best ones to be found in the North-West USA such as Montana, South-Dakota and in Alberta, Canada. This is a good website if finding out more about T-Rex floats your boat from the Natural History Museum of America.

Read more: https://www.amnh.org/dinosaurs/tyrannosaurus-rex

Chris Packham fronted a very good TV documentary recently called ‘The Real T-Rex’- based on what T-Rex actually looked like and how it behaved, this image below is quite a good likeness, better that those ‘models’ used in Jurassic Park! He re-discovers the animal behind centuries of Hollywood misrepresentation, creating an authentic version using CGI and other international scientific discoveries and fossil records.

You can watch it here: www.bbc.co.uk/programmes/b09ksl99

Pic: Over the course of geological time well over 2.5 billion T-Rex existed on earth!

However, as we now know the asteroid missed the deep oceans and with the cloud from this impact blocking out the sun, plants could no longer perform photosynthesis and the dinosaurs that relied on them, along with the dinosaurs that fed on those herbivorous dinosaurs, began to die out very quickly.

If those plants had had enough sunlight to continue carrying out photosynthesis, it’s possible the dinosaurs could have survived and there would have been no great extinction event.

The other T-Rex that sadly was also ill-fated.

Pic: Mark Bolan and T-Rex in 1970

One T-Rex did however regenerate and in the early 1970s ‘Hot Love’, ‘Get It On’, ‘Telegram Sam’ and ‘Metal Guru’ were all No 1 hits, competing with the Beatles for mass-popularity at the time. Sadly, the ill-fated Bolan died far too young in a car crash in his Mini in Barnes in 1977 aged just 29 but the songs echo in eternity and remind me of my secondary school days and the school ‘Disco’, quite fondly sometimes!

Bolan was born as Mark Feld and became close friends with David Bowie when just 17. They were however very competitive but found time to play on each-others songs and live on stage together. Out of interest T-Rex were the headline act at the first ever Glastonbury festival in 1970 and Bowie’s ‘Lady Stardust’ song was written about Bolan.

Maybe it’s ultimately good that the dinosaurs died off during this extinction event. After all, with dinosaurs gone, mammals were able to fill the gaps left behind, and it wasn’t long before they became one of the dominant groups on the planet. Without the dinosaurs dying off when they did, it’s possible that we humans wouldn’t be around today while their nearest relatives are the birds we commonly see now in our gardens and out at sea. That would also mean no blog about my 40-year career in Radiotherapy, probably not missed by many if so.

Masking over the cracks.

Ironically, I should really have been wearing one of these new fine particle dust masks when making my immobilisation masks and would have to if working with plaster now but of course there would be no need as our patients these days have single use, perforated thermoplastic masks made instead and so modern health and safety regulations have fully turned the tables, but should I be worried?

This twin cartridge half-mask from Screw-Fix provides ‘superior low breathing resistance and features a fully adjustable, 4-point cradle suspension harness with quick-release buckles, ensuring an effective fit with durable thermoplastic rubber for a superior fit to most face-shapes’.

‘Press-To-Check’ filters instantly verify the correct seal all for less than £30! Probably overkill in our Covid19 social distanced and mask wearing era but good for air-borne dust and may have protected me in those days but sadly they simply didn’t exist.

Pic: JSP Force 8 Mask Respirator with Press-to-Check Filters available from ScrewFix for less than £30!

Pic: Modern perforated thermoplastic mask, just warm it up and pull over the patient’s head

Making a head mould with plaster bandages and alginate.

For those of you who have trained to be a therapeutic radiographer after let’s say 1990 you will not fully understand the process of making a mould of a patient’s head to create a clear plastic immobilisation mask or shell as we called them back then.

This amazing ‘hobby’ based website I found on the internet goes through the 7 steps and is well worth a look so that you can see what we put our patients through, needless to say it omits using Plaster of Paris for health reasons nowadays as discussed above and employs a far safer product!

A clear plastic mask was then vacuum formed on to the solid plaster-based mould and fitted to the patient and the couch for their course of radiotherapy as per the image below.

You can read more and see the steps here, it’s well worth a look:

Read more: https://www.instructables.com/Making-a-Head-Mold/

To end this blog, I hope that gypsum doesn’t finish me off as it did the dinosaurs, we’ll see!

Duncan Hynd DCR(t) – A Radiographer’s life, a 40-year career in Radiotherapy

June 2021


2 thoughts on “Chicxulub was responsible for the extinction of the dinosaurs 66 million years ago. This is not a ‘neoadjuvant chemotherapy’ agent as the name might suggest but a huge crater located just off the coast of Mexico’s Yucatán Peninsula formed by a 10km wide asteroid hitting earth at 72,000 km per hour!

  • Phil Tapper

    Very interesting Duncan… but you didn’t say why the dinosaurs were killed by gypsum… did it solidify in their lungs, burn them with the exothermic reaction or just block out the sun with dust leaving no vegetation?

    Incidentally, I once read about an artist who wanted to cast her hand in plaster of Paris… she filled a bucket and plunged her hand in the liquid. By the time the temperature had become too hot to ‘handle’ (no pun intended!!) she couldn’t extract her hand from the solidifying mass… she lost her hand in the incident. Oops!

    • Anonymous

      It was the Sun Phil, I did mention that as the shade killed plants but I’m glad you keep reading my blathering! Hope all ok and might catch up one day soon? D

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