VOLCANO MADNESS: Re: [Geology2] The Haboobs of Arizona -the How's and Why's

Thursday, October 13, 2011

Re: [Geology2] The Haboobs of Arizona -the How's and Why's

OMG, I love them too and miss having them here in the good old mid-west.

When I was a kid living in Phoenix we had dust storms fairly often during the summer. Sometimes they would be so heavy that a person couldn't see across the street. Then it would rain after the dust storm and it would rain mud for a minute or two, until the rain cleared the sky. When a dust storm appeared on the horizon, we would say "here comes Casa Grande." Accidents occur during a dust storm that occurs between Phoenix and Tucson occur because people who haven't lived there for very long don't know the rules of a dust storm -- at the first sign of a dust storm, pull off to the side of the road as far as you can get, turn off engine, turn off lights and above all keep your feet off the brakes.

Bre

In a message dated 10/13/2011 10:24:51 A.M. Central Daylight Time, kimnoyes@gmail.com writes:

I love haboobs. ;-p

On Thu, Oct 13, 2011 at 6:07 AM, Lin Kerns <linkerns@gmail.com> wrote:

Dust Storms Roll Across Arizona

USGS Science Explains the Phenomenon
Posted on October 6, 2011 By Seth M. Munson, Jayne Belnap, and Richard L. Reynolds

A car approaches a dust storm near Winslow, Arizona, in April 2011. In drought years, low vegetation cover and disturbance to soil surfaces leads to more dust storms.

A dust storm that rolled across the Arizona desert on Tuesday, October 4, 2011, effectively blinded motorists, leading to a large string of motor vehicle crashes, multiple injuries, and at least one death.

Both this storm and another storm that passed through Phoenix on July 5, 2011, carried large quantities of airborne particulates and caused considerable property damage and potential harm to human health.

But what is causing these storms?

USGS and partner science show that there are many causes of dust storms. Two contributing factors are low vegetation cover and disturbance to soil surfaces.

Vegetation contributes to ecological integrity. The presence of plants reduces soil erosion and dust storms, because it keeps the soil intact, reduces wind momentum, and traps moving soil particles (See Figure 1). In spaces between the plants, many undisturbed desert soils are naturally armored by hardened physical and biological crusts.

Low vegetation cover can especially be a problem in drought years in abandoned agricultural fields, which are generally dominated by annual plants. This means that the consequences of dust storms, including motor vehicle crashes, are high in a drought year and low in years with more precipitation (See Figure 2).

Similarly, in places where land-use activities destroy or reduce soil crusts and weaken soil stability, experts know to assume higher dust storm activity than in places where soils are left undisturbed.

Future climate scenarios predict that drought conditions will worsen, and therefore more dust storms are likely.

Nevertheless, site restoration and reduced disturbance can mitigate some of the factors that promote dust emission.The USGS and land managers are working together to better understand the causes and sources of dust storm activity in the southwestern United States.

Figure 1: The presence of plants reduces soil erosion and dust storms because it keeps the soil intact, reduces wind momentum, and traps moving soil particles. Intact soil surfaces, which may include soil crusts, can also reduce the risk of dust storms.

Figure 2: The number of motor vehicle crashes caused by dust storms in Arizona has generally been lower when the annual precipitation has been higher. In a changing climate, climate scenarios predict more drought, which will likely mean more dust storms. But site restoration and reduced disturbance can mitigate some factors that promote dust emission

source

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