One Million Years of Not Sweeping the Floors: The Soils of Beijing

Copyright 2006 G.R. Morton  This can be freely distributed so long as no changes are made and no charges are made.

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My office has only one small view (between two buildings) of the distant Yang Shan mountains outside of Beijing. They are now building a skyscraper to fill the gap and deprive me of my view.  But one good thing is coming out of this. I have now seen how much dust has accumulated in Beijing.
Soil comes from eroded rock.  As one digs down, one finds chemical changes in the soil (called a soil profile) and then one begins to find cobbles of the original rock and even deeper one finds more and more of the original underlying rock.  Often this change takes place over less than 10 feet.  But parts of Beijing are different.
The construction site across the street from my office has now dug down about 35 feet.  The dirt they are pulling out of the site looks identical to the dirt at the surface.  As they have dug, there has been no visible soil profile.  It is one homogeneous mass of dirt apparently made of the same material from top to bottom.  A geologist who works in my group and I have discussed this at length. We both think this stuff is loess--a wind blown dust formed when glaciers grind rock to a find powder. The powder is then blown by the wind.  Beijing is on the very easternmost edge of the Chinese Loess plateau. (see
This loess creates a huge problem for young-earth creationists because it means that the earth must be older than they think.  Every year about this time (March-June) Beijing gets some dust storms. We had one on Friday March 10th.  A tiny dusting of yellowish dust is found on everything--including inside of buildings (mostly the lobby where the doors open).
Well, this dust is identical in color and texture to the soil being dug up across the street. That is what loess is.  Here is a picture of the construction site

The wall at the back is about 20 feet tall. The horizontal line at the base of the wall is 2-3 feet higher than the level the excavating machines are on.  You can see that they have now excavated another 10-12 feet of this material--this dust of Beijing. (as an aside I am surprised that they park the shovel as close to the edge as they do. If the excavated cliff were to collapse, the shovel would  fall with it.)
Below is a better look at the site taken yesterday (3-22-06) on a day with less pollution.

Now, how fast does this stuff accumulate?  Well I have been in Beijing one year (admittedly a short time) but the experts say that it accumulates at a rate of .017 millimeters per year (0.000017 meters per year).  Like plate tectonics that continues to shove the Himalayas slowly skyward, loess accumulates gradually -- averaging only 0.017 millimeters per year. 3-22-06

When I first uploaded this page, I had calculated that there were 10.66 meters of dust and that it would take 588,000 years for the dust to accumulate.   But that was on March 22, 2006.  By April 8, 2006 they had dug much deeper. Here is the newer picture. 


I now estimate that there are 60 feet of loess at this site--at the least. They have found the water table and I now have no way to see how much deeper the loess goes. A Chinese geologist in my office tells me he thinks there is 100 meters of it. But lets use the 60 feet we see exposed which is 18.16 m. That means it would take 18.16/.000017 ~ 1,068,000 years for this to accumulate.
Here you have before your eyes the results of about 1,000,000 years worth of not sweeping floor.   Our mothers were right, we best sweep the floor or we will be buried in dust--in about 1,000,000 years.

1 comment:

  1. That is based on the assumption that it did not come there from a flood event, instead of the present wind blown.
    Alot of Rock is soft and easily powdered by the extreme weight of glaciers and rock on rock rolling.

    We are on 70 meters of glacial silt, in our glacial silt there are shell fossils
    but next door is 70 meters of limestone (Sea shells)
    I don't imagine the shells were wind blown?