What is the earth made of?
School textbooks tell us that we live on a round ball with an outer crust, various layers of the mantle and an inner core of hot liquid stuff, which occasionally squirts out through holes or gaps in the crust as volcanoes.
Geologists may quite rightly wince when they read this explanation, but this is basically what we are taught at school. The film, ‘Journey to the Center of the earth’, also graphically covered these basics, so it must be true right?
How do we know what lies below our feet?
We have traveled millions of miles into space and gazed even further into distant galaxies, but amazingly, we have not traveled very far into our own planet. Actually, we have only just scratched its surface.
Russia’s Kola Superdeep Borehole is the deepest hole on earth, and it only reaches a mere 12.2KM (7.5 miles) below the surface of our planet. Yes, 12.2 KM depth of knowledge of what we are actually living on. It’s rather surprising how little we know about our own backyard, isn’t it?
Why do we know so little?
Basically, digging holes becomes more complex and expensive the deeper we go. Just think about the many mining collapses or the cost of an oil-rig and these don’t even break through the outer layer of the earth’s crust!
Complexity and cost are both an issue as you go deeper into the earth, but it is hard to believe that it is more complex and costly than flying someone to the moon.
I suspect that the real reason for us having more space-rockets than holes in the ground is that space travel is deemed to be far more ‘exciting’ and ‘glamorous’. It is more likely to capture the imagination of a nation than digging a hole ever will. Hence, there are many famous astronauts and many more frustrated geologists.
This may be the sad reality of being a geologist, but I still find this to be rather odd. Especially as the earth is so much closer to home, but at least we have the Kola Superdeep (deep-ish) Borehole, which has turned up some surprising results.
The missing layer.
Geologists have long since talked about the ‘Conrad discontinuity’ which is amply described in the Dictionary of Earth Sciences as:
‘A boundary within the Earth‘s continental crust that can be detected seismically at about 10–12 km depth, although exploratory deep drilling has failed to locate it’.
This boundary has been identified by previous seismic activity and should be a general change from granite to basalt somewhere around 6-12km below the surface of the earth. Oddly, it decided not to show up in the Kola borehole. Its absence basically means that a complete layer of the earth’s crust that we have always assumed to be there, was not there – at least at the site of our one and only deep (-ish) hole in the ground.
Bugs in the system.
In addition, it turns out that far below where we stand today, the earth contains water. This was also not expected at such depth. Then, to cap it all, there were some bugs found in the system. To be more precise, twenty-four different types of plankton were found at depths where they really should not have been.
None of these discoveries are really that surprising given that we have not drilled this far into the earth before – we are bound to find new and unexpected things. But what is really surprising is that this information is not new.
Drilling at the Kola borehole was stopped in the 1990’s due to increasing technical difficulties and the temperatures at the bottom of the hole increasing much quicker than expected (yet another unexpected discovery) and has not been restarted since.
I guess that the main problem was that they did not find diamonds, gold, uranium or at least a blob of oil at the bottom of this hole. This meant that there was nothing for some mega-corporation to make money out of, and as a result, it was abandoned. Once again geologists were left high and dry watching millions being pumped into the Olympics, space flight or anything else more headline grabbing than digging holes in the ground.
So, as a little support for those comparatively cash-strapped Clever geologists, who would love to discover more about what we are actually standing on, but have not had the funding or support they need to do it. Please be sure that, whenever you are shown an image or description of the make-up of the earth, you ask your school teacher, geographer, geologist or researcher.
“How do you know that?”
Perhaps this will help to stimulate enough interest into finding out what actually lies below our feet so that we can start digging holes again!
Author CW “Conrad discontinuity.” A Dictionary of Earth Sciences. Retrieved February 10, 2017, from Encyclopedia.com: http://www.encyclopedia.com/science/dictionaries-thesauruses-pictures-and-press-releases/conrad-discontinuity
Images: Main Original Pixabay Skeeze. School children: Pixabay White77. Inside the earth: Original Pixabay Skeeze.