it was formed naturally. Glass forms
when silica was heated to 1200ºC and
cooled suddenly. Egyptian desert glass
was almost made of pure silica and was
able to solidify after heating without
crystallisation, resulting in glass rather
than geological crystal structures.The Egyptian desert glass was found
in a large area covering eastern Libya
and western Egypt, part of the Sahara
Desert. Sahara was once a fertile
land but about 5000 years back it
turned into a desert, one of the most
inhospitable lands on earth now. The
glass was found in a large area and
either it was formed in a large area
or it was formed in a small area but
carried away through natural processes
like the moving sand dunes. From the
composition of the glass, it was believed
to be the result from a meteor impact.
Physical exploration and satellite
imagery studies could not identify any
crater, though the latter method has
been able to identify craters of meteorimpact as old as 200 million years ago
as was found in Chad. The age of the
crater is determined through assessing
the uranium decay.When comet Shoemaker-Levy 9
broke apart into 20 pieces in July
1992 and collided with Jupiter in July
1994, it provided with the first direct
observation of an extra terrestrial
collision of the solar system objects.
This comet was captured by the
planet and was orbiting it, and was
the first comet to orbit a planet. The
fragments of the comet collided with
the planet from July 16 to 22, 1994.
It was observed that the fragments do
not hit the planet but exploded above
the surface of the planet and the scars
were visible and more so than even
the Great Red Spot for some time.
The fragments turn into fireball when
passing through the atmosphere of the
planet and explode it above the surface
of the planet and the temperature of the
fireball which is estimated to be around24000ºK. The heat sears the surface and
a huge plume rises above the surface
into space. The biggest fragment which
is about 2 km in diameter released
energy estimated to be equivalent at
around 6 million megaton of TNT.When the first atomic device was
exploded at Trinity site, while all the
steel items were found melted, the
surrounding area was covered with a
thin layer of green glass which crunches
when one walks. Natural glass forms
as mentioned earlier when there is a
volcanic eruption and the molten lava
cools quickly or on meteorite impact.
However the temperature of the lava
is not very high and the glass formed
are different from the glasses one
commonly sees but in meteor impact
the temperature is very high and the
zircon disintegrate leaving light and
dark patched under the microscope, and
it results in clear glass. The Egyptian
desert glass has all the characteristics of
a meteoric origin.Libyan Desert Glass
Silica, CC BY-SA 3.062 neScholar^0 vol 4^0 issue 4