This is an extended caption of the GIF graphics file called EARTH.GIF.

RELIEF MAP OF THE ENTIRE EARTH WITH VEGETATION

This computer generated illustration of Earth is part of NASA Goddard
Space Flight Center's program of Earth-science research.  This view,
generated from orbiting and ground-based instruments, shows a
computer-generated topographic image of the continents with the
vegetation of Earth superimposed over it.

The vegetation covering the continents was recorded by the Advanced
Very High Resolution Radiometer (AVHRR) aboard the NOAA-7, NOAA-9,
and NOAA-11 satellites.  The yearly average of the AVHRR vegetation
index is shown, although similar images are also acquired daily.  The
amount of vegetation ranges from light brown, representating little
vegetation cover, through yellow and orange to green, which shows
heavy vegetation. 

Note especially the lack of vegetation in the Sahara Desert of North
Africa, mountainous regions, and the polar regions.  Changes in the
Sahel region, south of the Sahara, have been studied extensively
because of the droughts and famine that occur there, expecially in
the Sudan and Ethiopia.  The Amazon basin of South America and Congo
basin of Central Africa have much vegetation because of their
rainforests.  There is international concern about the loss of
tropical forests through their destruction by mankind, the resulting
increase of global carbon dioxide, and tremendous loss of biological
diversity.

The topography of the continents and oceans is shown in shaded relief,
as if the Sun is shining from the east.  The vegetation data from the
AHVRR covers the topographic image of the continents.  The Mid-Atlantic 
Ridge, in the center of the Atlantic Ocean, occupies much of the center 
part of the image.  The crest of this ridge is a spreading center which 
pushes North and South America to the west and Eur-Asia and Africa to 
the east at the rate of about an inch a year.  For the oceans, the 
topographic database is obtained from mapping the ocean floor by ships.  
For the continents, it is obtained from stereo imagery from spacecraft 
and from surface topography surveys.  On land, the Rocky Mountains, the 
Pyranees of Spain, and the Atlas Mountains of North Africa are some of 
the features shown.

This study is part of NASA's multiyear global research program called
Mission to Planet Earth.  It will use ground-based, airborne, and
space-based instruments to study Earth as a complete environmental
system.  Mission to Planet Earth is NASA's contribution to the US
Global Change Research Program, a multi-agency effort to better
understand, analyze, and predict the effect of human activity on 
Earth's environment.  Images such as this one can provide for the 
first time a vegetation survey of the whole Earth on an annual,
seasonal, and even daily basis so scientists can determine where and
how vegetation is changing.


Credits: This image came from vegetation index data supplied by the
Goddard Space Flight Center Biospheric Branch, Greenbelt, MD, and 
topographic data distributed by NOAA's National Geophysical Data 
Center, Boulder, CO.  It was created by J. Frawley of Herring Bay
Geophysics, Dunkirk, MD.