Excavations: Where does all that soil come from?

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In summary, according to this TED talk, recent agricultural practices have resulted in a gradual improvement in soil depth.
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I'm reading some books that describe site excavations. The archaeologists dig layers of dirt up to get to the ancient settlements many feet below. I'm wondering how they get buried in the first place. There are some photographs that look like a town from the ninth century with a series of rooms that look more than ten feet deep. Did people dig cellars or below-ground rooms? Or was the ground level much lower then than it is today? But even closer to the surface, where is all the soil coming from? How do these places get buried?
 
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Look about you; all sorts of things move earth, from earthworms and earthquakes to volcanoes and wind. If you can think of it, some archaeologist somewhere has dug through it. In Pompeii and Herculaneum it was volcanic tephra. In tropical rainforests it has been jungle bioturbation, in mountainous regions it has been landslides, and in valleys, floods. There even are places where human activity was responsible, such as building over old sites.

Actually it was not a bad question; firstly a lot of people take such stuff for granted, and secondly, the nature of the stuff covering a dig may tell a great deal of what we want to know about the place.

Go well,

Jon
 
  • #4
There's a talk up on TED (on the topic of sustainable food, esp. goose-liver) that happens to assert soil is made of dead roots. That is, the grass grows (essentially condensing solid out of the atmosphere for the most part) and the roots push and grow in proportion, then each time the grass is grazed down the roots die back in proportion, stranding material below the surface (whereas material decaying on top might erode faster than it accumulates). The claim is that particular types of agriculture continually improve the soil depth. I'm not sure how accurate this picture is?
 
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  • #5
Andre said:
In addition, don't forget wind blown (aeolian) dust (facies) and sand.

Interesting link, thanks.
I am relieved to note that I did indeed mention wind though. Sorry about forgetting to mention the term aeolian. I am puzzled however by your wording. Are you suggesting that aeolian dust forms facies and sand doesn't? I assume not!

cheers,

Jon
 
  • #6
cesiumfrog said:
There's a talk up on TED (on the topic of sustainable food, esp. goose-liver) that happens to assert soil is made of dead roots. That is, the grass grows (essentially condensing solid out of the atmosphere for the most part) and the roots push and grow in proportion, then each time the grass is grazed down the roots die back in proportion, stranding material below the surface (whereas material decaying on top might erode faster than it accumulates). The claim is that particular types of agriculture consistently improve the soil depth. I'm not sure how accurate this picture is?

Hm??

If you think that topic is worth looking at, please give me an url. As stated the proposition hardly makes sense. Certainly the main source of plant food (not counting H2O) is atmospheric CO2, but (ignoring topics concerning H and O) that is only the main source of carbon.
Roots are only a dominant source of soil material in organic-rich soils such as peats, and then other plant material figures as well.

Don't misunderstand me; roots and other humus are very important in many aspects of soil formation, including supporting biological action (worms, grazing etc), trapping wind- and water-borne particles, rock decomposition, storing mineral nutrients, and adding bulk and aeration to the soil, but that doesn't make much sense in the terms you mention.

If you are interpreting what they say correctly, they seem to be putting valid concepts together in misleading, effectively meaningless, perspective. Practically everything to do with soil involves many variously interdependent factors, and it takes a lot of knowledge and experience to make any sense of it. That lot don't seem to be cutting it.

Cheers,

Jon
 
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There is a small but steady rain of dust from space. Approximately 10 tons per day. Over the eons this builds up.
 
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Antiphon said:
There is a small but steady rain of dust from space. Approximately 10 tons per day. Over the eons this builds up.

:biggrin:
Quite right of course; I had left that one out. But in fairness it is a bit part only. Let's see... roughly ten million billion nanograms per day, spread over 216e12 square metres of planetary surface. If I haven't miscounted (don't rely on it!) that gives us something like 46 nanograms per square metre per day. In other words, about 17 kg per square metre in the last billion years. Lucky for us the first couple of hundred million years of Earth's history were less stingy than that, or we still would be waiting for a planet larger than say, Phobos! :wink:

Cheers,

Jon
 
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1. What is the primary source of soil in excavations?

The primary source of soil in excavations is the ground itself. When digging, the soil is removed from the ground and piled onto trucks or other containers for removal.

2. Can the soil be reused after excavation?

Yes, in most cases, the excavated soil can be reused. However, this depends on the type and quality of the soil, as well as the regulations and restrictions in the area where the excavation is taking place.

3. How is the soil removed from the excavation site?

The soil is typically removed using heavy machinery such as excavators, bulldozers, or dump trucks. These machines are specifically designed to handle large amounts of soil and transport it to designated areas for disposal or reuse.

4. Is the removal of soil from excavations harmful to the environment?

The removal of soil from excavations can potentially harm the environment if not properly managed. This is why it is important to follow regulations and guidelines for excavation and disposal of soil, as well as using proper techniques for minimizing soil disturbance and erosion.

5. How do excavations affect the surrounding area and structures?

Excavations can potentially affect the surrounding area and structures, especially if they are in close proximity. The removal of soil can cause changes in the ground stability and can potentially damage nearby structures if not properly managed. This is why it is important to carefully plan and execute excavations to minimize any potential impacts.

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