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Where Does Dirt Come From?

Eyespy

Eyespy

Abominable Snowman
Joined
Oct 6, 2010
Messages
556
This is a question asked of me by my son, aged about 7- I was doing A level Archeology at the time and he was browsing my aeriel photographs, home work.

he asked why all the Archeology stuff was buried underground- who buried it? I explained that soil builds up and deposits on buildings and remains concealing it and protecting it fo future people to find .

This led to the question above (he was 7) he then went on to ask if the Earth was getting bigger because of all this dirt burying things.

I was never able to satisfy his curiosity on this point and it was a recurring topic with him for some time along with the one about Americans having a separate heaven.
 
The continental plates upon which all of our dirt piles up are constantly moving up and over each other, so there are many millions of years worth of piled up dirt that get lost to being re-consumed by tectonic shift. It takes a little while though.
 
Dirt is made from the following:
  • Bird and animal poo
  • Skin cells
  • Rotted down vegetation
  • Rotted down animals and insects
  • Bacteria (lots of bacteria)
  • Mould
  • Sand and small rock fragments
  • Any old toot you can think of
 
Oh oh oh I know this one! :D

In respect of archaeological remains such as building foundations and Roman mosaic floors, the dirt is formed by the efforts of earthworms.
They turn random organic matter into fertile soil.

Here's a reliable quote about it -

They break down organic matter, like leaves and grass into things that plants can use. When they eat, they leave behind castings that are a very valuable type of fertilizer. Earthworms are like free farm help. They help to "turn" the soil—bringing down organic matter from the top and mixing it with the soil below.

They also aerate the soil, making the volume of dirt expand upwards.
 
Yithian said:
Meteorite dust.

I've read figures ranging between 14 and 44 tonnes per day.
Click to expand...
Yes! I forgot that one.
I remember doing an experiment when I was a teenager. I took a magnet to the grass verge and moved it about in the dirt. I couldn't believe how many tiny pebbles stuck to the magnet. Some of it was probably steel debris from vehicles, but I think most of it was meteoric dust.
 
Yithian said:
Meteorite dust.

I've read figures ranging between 14 and 44 tonnes per day.
Click to expand...
Assuming 20 tons (2000 lbs.)/day x 365 days/year x 1B years = 7.3B tons.
7.3B tons/land mass of 1.4904B square kilometers = 0.49 tons per sq km
Over past 4.5B years: 2.2 tons/ sq km

We are stardust.
 
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Endlessly Amazed said:
Assuming 20 tons (2000 lbs.)/day x 365x 1B years = 7.3B tons.
7.3B tons/land mass of 1.4904B square kilometers = 0.49 tons per sq km
Over past 4.5B years: 2.2 tons/ sq km

We are stardust.
Click to expand...
And we've got to get ourselves back to the garden. That lawn is gonna need mowing soon.
 
Mythopoeika said:
Yes! I forgot that one.
I remember doing an experiment when I was a teenager. I took a magnet to the grass verge and moved it about in the dirt. I couldn't believe how many tiny pebbles stuck to the magnet. Some of it was probably steel debris from vehicles, but I think most of it was meteoric dust.
Click to expand...
My Grandad once stuck a huge magnet (from a washing machine I think) to my Nan's iron and couldn't get it back off. How we I laughed until we I cried.
(For the pc members, these were the days when the iron belonged to the woman of the house and if you think that's wrong- tough. That's how it was).
 
CharmerKamelion said:
Can I put you on hold while I work on a joke about 'polishing your newel post' and maybe something about a crevice tool? It's past my bed time.
Click to expand...
I certainly can young man. You young 'un's can't keep the pace like us old 'uns. I'm my usual bottle of red and two beers in (Brew-Dog tonight- a new beer I've discovered that is great), and I reckon I've got another hour or two in me yet.
 
The dust that you breathe in on the London Underground, (then hopefully get rid of when you blow your nose when you get home) is comprised of, amongst other things:

Dead skin cells
Dead mice
Dead rats
Dead pigeons
Particles of metal which are shaved off the rails by train wheels
Particles of rubber from train brakes
General dirt from the street which gets blown into stations
Mouse poo
Rat poo
Pigeon poo
Particles of paper from the newspapers given out to commuters
Particles of decayed kebabs and burgers eaten by late night revellers
 
Victory said:
The dust that you breathe in on the London Underground, (then hopefully get rid of when you blow your nose when you get home) is comprised of, amongst other things:

Dead skin cells
Dead mice
Dead rats
Dead pigeons
Particles of metal which are shaved off the rails by train wheels
Particles of rubber from train brakes
General dirt from the street which gets blown into stations
Mouse poo
Rat poo
Pigeon poo
Particles of paper from the newspapers given out to commuters
Particles of decayed kebabs and burgers eaten by late night revellers
Click to expand...

And my poo, sorry about that.
 
I recall as very young kid interested in history and natural history understanding that the deeper something was, the older it is, I didn't understand the mechanism by which soil accumulated but decided that if the newer stuff ended up on top of the older stuff then the Earth must constantly be getting incrementally bigger. I now appreciate that things sink and rise do to tectonic action but still don't understand how the Earth is slowly expanding.
 
Victory said:
The dust that you breathe in on the London Underground, (then hopefully get rid of when you blow your nose when you get home) is comprised of, amongst other things:

Dead skin cells
Dead mice
Dead rats
Dead pigeons
Particles of metal which are shaved off the rails by train wheels
Particles of rubber from train brakes
General dirt from the street which gets blown into stations
Mouse poo
Rat poo
Pigeon poo
Particles of paper from the newspapers given out to commuters
Particles of decayed kebabs and burgers eaten by late night revellers
Click to expand...
Oh wow. I just thought it was random black stuff. I am never breathing on the Underground again.
 
Trevp666 said:
The continental plates upon which all of our dirt piles up are constantly moving up and over each other, so there are many millions of years worth of piled up dirt that get lost to being re-consumed by tectonic shift. It takes a little while though.
Click to expand...
This is the right answer. Geological processes raise rocks upwards to form hills and mountains, and inorganic weathering processes such as rain, frost, river flows and wind convert the solid rock into fragments such as pebbles, gravel, sand and silt. Then organic weathering processes take over, colonising the gravel and silt, introducing organic detritus and humus into the soil. Gradually you get a nice, rich topsoil overlaying various layers with different organic content.

The reason why archaeological relics get buried is interesting, too; the action of earthworms is important, especially in open countryside, but it is not the only process.
Humans constantly bring organic produce from the surrounding countryside into towns, and some of this remains as waste in rubbish dumps, dungheaps and middens, gradually covering up the older ruins. Also, building work in older towns often involves the importation of sand and gravel for construction purposes, which displaces old soil onto the top of disused buildings. Got a nasty, muddy street? Just bring in a load of sand, gravel and cobbles to raise the surface. Burying the dead in old graveyards often raised the ground level by several metres. Wind-blown soil is also important, especially in droughts, when it blows over the ruins as dust. Plants colonise the ruins and provide refuges for wind-blown dust to accumulate; these plants die, and new plants grow on top, raising the soil level. In farmland ruins can be buried by ploughing, which evens the land surface out and can cover quite large relics.

In due course, our older towns have been raised by as much as ten metres (or more in some places) by a variety of processes, some accidental, some deliberate.
 
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