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Deserts
Deserts evoke images of uninhabited
arid lands in which the phenomenon of life seems to
be a complicated undertaking. But the truth is that
they are ecosystems with their own flora and fauna
and cover more than a fifth of the Earth's land surface.
"The desert is a land of
extremes," according to the web site Desert
Topics. One example of this is the abrupt change
in temperatures between hot days and frigid nights.
And rainfall is noteworthy for its absence.
Dryness is the main characteristic
of a desert. They are arid places, regardless of whether
they are cold or hot, or if they are dominated by
mountains or plains, rocks or sand. Of course sand
is the image we most closely associate with deserts,
but it covers just 20 percent of the territory worldwide
that is classified as such.
The plant and animal species
that live in deserts are numerous. However, they all
share one trait: the ability to survive with little
water. This means they have a special capacity to
find and store liquid, and possess biological mechanisms
that prevent water loss or evaporation.
On the Internet, deserts are
present throughout the many web sites that attempt
to explain the unique nature of these ecosystems,
or that reflect the influence of these mysterious
lands on human activity, for example, in literature.
Scientific evidence shows that
deserts date back more than 100 million years. The
arid conditions that caused them to appear are closely
linked to climate. Today, the expansion or growth
of deserts is a serious environmental problem, known
as desertification.
Deserts can be found in diverse
places around the world, though their sizes can
vary greatly. The most extensive are the Sahara, Arabian,
Gobi, Kalahari and Australian deserts.
Deserts:
geology and resources
Desert
Topics: What is a desert?
United
Nations Convention on Combating Desertification
Deserts:
A literary adventure
The
world's deserts
Principal
deserts of the world
Digital
desert library
The Alpaca
The alpaca, whose official name
is 'Lama Pacos', entered into the lives of humans
some 5,000 years ago, when Andean civilizations began
to domesticate this member of the camel family. Today,
the alpaca, also related to the llama, is the basis
of a global industry.
A bit of Internet surfing turns
up a great deal of information about this animal that
is identified with South America's Andes Mountains.
The surprise is that many of the web
sites are produced by alpaca
farms in places ranging from Australia to the
United States, Canada to Spain.
This craze was sparked by the
commercial discovery of the high quality of alpaca
wool, a fact that has been known since remote times
by the indigenous peoples of Peru, Bolivia and Chile,
where more than 90 percent of the alpaca population
is concentrated, believed to number more than three
million.
Although by the mid-19th century,
alpaca wool was already known by some European textile
companies, the "boom" that is evident today
dates only to the 1980s, when commercial alpaca farms
began to spring up across the United States.
Internet sites about this business,
such as Alpaca.com,
offer all sorts of information about this South American
species, and about the risks of investing in breeding
this animal for its prized wool. There are on-line
sales of alpaca products and even auctions to buy
these animals, some of which sell for as much as 20,000
dollars.
Alpacas
are small camelids, a word that reveals its similarity
to camels found in other regions of the world. In
South America, this family includes llamas, vicuñas
and guanacos.
In the high altitudes of the
Andes Mountains, many indigenous communities make
their living by raising these animals. The alpaca
is particularly important because it is a species
that can be domesticated and produces great quantities
of wool.
The existence of non-Andean alpacas,
those that are raised outside their region of origin,
creates an uncertain future for the indigenous shepherds.
Some experts predict that by the year 2030 there will
be more alpacas in other places around the world,
and will thus monopolize the global markets for their
special wool.
Alpaca
Facts
Alpaca.com
Origin
of Domestic Camelids
International
Alpaca Association
Alpaca
Nation
Alpaca
links
Yahoo!:
Alpaca Breeders
Tornados
First comes the calm, and then
the fury is unleashed. In the center of it all could
be a tornado, a natural storm formation that spins
at incredible speed and always - like in the movies
- seems unstoppable as it approaches.
Tornados are a natural phenomenon
that can occur in many
parts of the world, and there have been tornado-related
catastrophes in Asia and Europe, as well as the Americas.
A web
site of a British research institute keeps watch
over that region, where records of the phenomenon
date back to the 11th century.
But the United States is the
principal stage for these violent storms. In one year,
there may be 1,000 tornados, claiming 80 lives and
leaving 1,500 injured, according to the web site of
the U.S.
National Oceanic and Atmospheric Administration
(NOAA).
A tornado is a column of air
that spins at violent speed as a result of the meeting
of cold and warm weather fronts. The cone-shaped formation
can move at great speeds across the Earth's surface.
There are a series of standards
in place to protect the population from tornados,
whose intensity is measured on a system known as the
Fujita
Scale. The United States has an emergency system
that activates sirens when a tornado is detected.
But sometimes they can spring up without warning.
The dramatic meteorological phenomenon
has given rise to movies and there are even some adventuresome
tourists who take part in "safaris"
to hunt down tornados.
A safer spot to view tornados
as in a chair in front of a computer, where you can
browse the great
number of Internet sites featuring these storms,
beginning with those that explain how
they come about.
NOAA:
Tornados
British
Tornado and Storm Research Organisation
Discovery:
Tornado
Tornado
Links
Tornado
Project
Tornado
Project: Worldwide Tornadoes
Fujita
Scale
NOAA:
All about tornadoes
Tornado
Safari
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