Dinosaurs and the Himalayas

About 30 years ago I heard of the new controversial theory that an asteroid impact caused the extinction of most dinosaurs.  I immediately embraced this as an interesting and plausible possibility.  However, evidence soon appeared that seemed to contradict the theory.  It appears that many dinosaur species existed for some time after the event.  For example, dinosaur fossils were found in sedimentary layers laid down hundreds of thousands or even millions of years after the boundary that marked the event.  (There is a clear line in sedimentary layers all over the world that has much more Iridium precisely marking the impact of the asteroid about 65 million years ago.)

Recently a new possibility occurred to me.  The idea was triggered by a recent question/challenge on QI (one of my favourite TV shows).  The challenge was to put 4 things in chronological order.  Two of the things were a picture of a dinosaur and a picture of Mt Everest.  (I can't remember the other two.)  This got me thinking that maybe the event that wiped out the dinosaurs also created the Himalayas, as I explain below.

But first I go back to the 1980's....

A Bad Idea

After the abovementioned theory was proposed it was quickly disputed but it still seemed likely to me that the events were linked.  The dinosaurs had been around for hundreds of millions of years.  To suddenly disappear within even a few million years of such a huge event seemed to be more than coincidence.

Now when I began this blog (see Intro) I promised to document some ideas that I had when I was younger.  Some were good.  Here is a bad one.

One idea that occurred to me at the time (1980?) was that the asteroid had hit with such force that it had increased the tilt of the Earth.  With greater yearly fluctuations in temperature this advantaged mammals (and birds) which had hair (and feathers) which could be shed during the warmer months.  So, over the next few million years, dinosaurs lost out to species more suited to the new climatic conditions.   Of course, I now know that the asteroid was too small to affect the tilt of the Earth.  (The tilt was caused by a planetoid almost the size of Mars that hit the Earth more than 4,000 million years ago).

Root Cause

The initial event that, I believe, lead to the demise of the dinosaurs, occurred in the asteroid belt over 70 million years ago.  Apparently there was a major collision event that caused a large rock to be placed in an orbit that intersected the Earth's.  It was just a matter of time before it hit the Earth.  Unfortunately (for them) the dinosaurs were oblivious.

Volcanoes

Another proposal for the extinction of the dinosaurs was the massive volcanoes in India at about the same time.  These resulted in huge amounts of basalt being spewed onto the surface of the Earth, resulting in the feature that is now called the Deccan Traps.

What if all these events are related?

Another Idea

My latest idea is that the asteroid that hit the Earth 65 million years ago was not the only one, and not the largest one, to do so at around that time.  Perhaps the earlier collision event in the asteroid belt placed not one but several rocks in an orbit that intersected the Earth's.  Perhaps the largest such asteroid was 50 km across and hit the ocean just south-west of India.  (At the time India was a true sub-continent languishing in the middle of the Indian Ocean.)  There is actually some evidence of an impact crater of the right size in the ocean bed there.  The asteroid was so large as to puncture a large hole in the Earth's crust which caused the massive volcanic activity that created the Deccan Traps.  This in turn propelled India towards Asia with enough momentum to cause the Himalayas to be formed.

So why didn't this 2nd impact cause another sedimentary layer of Iridium?  Probably the asteroid was so large that most of it went through the thin ocean crust and ended up in the mantle.  Also the fact it landed in the ocean meant that there would be less dust thrown up.

So perhaps the dinosaurs were wiped out not by a single event but by two asteroid impacts which occurred hundreds of thousands (or even millions) of years apart.  The repeated blows to the ecosystem, occurring on different sides of the planet, and perhaps also the subsequent volcanic activity, eventually took its toll.  Perhaps there were even more impacts - I believe the first Hawaiian Islands were also formed about 65 million years ago.

This would explain several things:

• Why the Himalayas could be formed by such a small continent hitting Asia.  Nothing remotely similar happened when even larger continents collided, such as Africa and Europe.
  
• Why there are massive volcanoes at Hawaii, which is far from any plate boundaries.
  
• How the asteroid that killed the dinosaurs happened to hit land rather than the much more likely event that it landed in the ocean.
  
• Why fossils of many dinosaurs are found in layers above the Iridium layer (which marks the time of the impact of the asteroid that hit land).
  
• Why so many big Earth events happened around 65 million years ago.

The Earth Is Safer Now

The good news is that if I am right then the Earth is probably safer than we thought!

To cause something as large as the extinction of the dinosaurs might require a 50 km asteroid to hit the Earth.  The largest object that could possibly hit the Earth in the next few hundred years is not much more than 1 km in diameter.  It's possible that something could come from afar (such as from the asteroid belt), but even then we would probably have a long time to spot something that big and do something about it.