In the 1930s, fierce dust storms created by drought conditions and farming
techniques that led to soil erosion swept the prairies of the western United
States, causing widespread ecological calamity.
But this so-called Dust Bowl period was just a small example of a huge increase
in dustiness in the US West in the past 150 years due to human activities such
as settlement, farming and livestock grazing, scientists said on Sunday.
The researchers drilled into lake-bed sediments in two small alpine lakes high
in the San Juan Mountains of southwestern Colorado to measure the amount of dust
deposited in the past 5,000 years. Dust blown into these lakes settles to the
bottom and accumulates as sediment.
Starting in the period from about 1860 to 1900, the dust deposit rates surged at
least fivefold over previous levels -- coinciding with a upswing in human
activities that kicked up dust into the atmosphere, scientific dating ...