Dust         Worksheet

Dr Karl Dr Karl here.G'day:

Back in 1846, Charles Darwin while travelling on the British ship, the Beagle, recorded that "the quantity of dust which falls on ships in the open Atlantic is considerable and that the atmosphere is often rendered quite hazy."

Dust is everywhere - even way out at sea - and it hangs around for a long time.

And no matter how much we try to clean it away, it keeps on stacking up!

But there's always been some mystery about where all that dust actually comes from.
God, apparently, has his own explanation for why we might want it everywhere - Genesis 2:7 reads "The Lord God formed the man from the dust of the ground".

of dust gets lifted into the atmosphere - mostly after being stirred up by storms. This dust comes mostly from the world's arid regions - such as deserts in Australia, Asia, North and South America, and of course the big one, the Sahara, in North Africa. These deserts, and other drylands, cover about one third of all the land area on Earth.tonnesEach year, about 2 billion

It turns out that once it's lifted into the sky from places like this, dust travels around the world in intercontinental airborne rivers. But, besides dust, these rivers also carry microorganisms and chemicals - sometimes toxic chemicals.

when this nutritious dust finally lands in the ocean, it can help marine plants grow.SoThe dust from the Sahara Desert in North Africa carries both iron and phosphorous.

But dust storms can also carry microorganisms that cause coral reef damage. Saharan dust storms have also been linked to outbreaks of respiratory disease, such as asthma, in places as far away as North America.

, compared to snow, absorbs more heat.colouringAnd if the dust lands on snow, it can accelerate melting and reduce the duration of snow cover in that area by a month each year - because its darker

In the late 1990s, photographs from satellites were able to show the amazing extent to which wind could turn desert soil into enormous dust storms.

high.kilometresDust storms are strongly linked to droughts and deserts. And they are impressive, monstrous events. They look like vast mountains, moving rapidly across the landscape, blotting out the sun, and towering up to 4

of dust can be whipped up. They can travel vast distances, and sometimes they've reached New Zealand from Australia, producing "red snow" on their highlands.tonnes across parched inland areas. If there are squally winds as well, thousands of cold front racesDust storms will often form when a

The dust particles are usually so powder fine, that they sneak into the most carefully sealed house. Sometimes if rain falls above the dust, it can even rain mud!

The dust storm capital of the world is the mighty Sahara Desert of Africa - an area of wilderness greater than the entire Australian mainland. Huge dust storms are common here and they can travel vast distances out over the surrounding ocean areas.

One major storm in particular shows the global reach of dust. In April 2001, this storm started in the Gobi Desert in China and Mongolia, and after crossing Korea, Japan and the Pacific Ocean in just five days, continued across North America and after crossing the Atlantic it arrived in Europe. Along the way across the USA, the dust was so thick that it dropped the air quality ratings down to "poor".

It's not uncommon that the red dust found in Western Europe on automobiles and snow, came all the way from Africa - after crossing the Atlantic.

But dust can come from more local sources as well.

In the USA, dust levels have increased by 500% over the last two centuries thanks to the massive expansion of livestock grazing, and also agriculture.

Ice cores from the Antarctic, and from places around the world show that dust loads in the atmosphere have increased since the Industrial Revolution.

And what about the dust inside your house? Where does that come from?

To keep it simple, dust is just solid stuff that has been ground very finely.

we thought it was almost entirely generated by a mix of geology, meteorology, and time. In other words, the wind pushed rocks into each other and after several million years of grinding, bingo! - dust. timeFor a long

It turns out only about 60% of the dust in the typical house comes from outside - either carried in by the air, or tracked in by footwear. So, what about the rest?
But one surprising source of dust is bacteria. Some bacteria are after the electrons associated with the element, iron, in some rocks - and so the bacteria grind the rock into dust for energy.

(from paper, clothing, carpets and upholstered furniture). Distressingly, some of it is also sloughed off dead skin cells from people, or pets.fibresThe rest of house dust is organic matter generated within the home, such as organic

So next time you're cursing the world for filling up your home with filthy dust... remember at least a bit of it was once part of your body.

Feeling dusty?