this is Cielo it's a crowded place with
bustling markets and around 33,000
people here you can find farms which
grow things like dates and olives and
trees grow as far as the eye can see see
WA has been permanently inhabited since
the 10th millennium BCE or for roughly
12,000 years the city contains several
archaeological sites and is even the
site of an Oracle temple for the
Egyptian deity a moon what's odd about
Siva is that it's located here
completely isolated in the Egyptian
portion of the Sahara Desert the nearest
big city is 460 kilometers away in
Alexandria and the ocean at its closest
is 260 kilometers away this deep in the
desert sea were receives only 9 inches
of rainfall a year and temperatures in
the summer have reached a blistering 118
point 8 degrees Fahrenheit just outside
the limits of sea WA tremendous and
imposing sand dunes linger constantly
threatening to advance so how can a
place so deep in the desert be so rich
with people vegetation and history well
as it turns out see what isn't just a
city but rather an oasis a fertile patch
in an otherwise endlessly barren land
but what exactly is an oasis and how do
they form in the past to desert oases
have served a crucial role in trade and
travel as hospitable stopping points
wedged between vast expanses of sand and
stone in places like sea well merchants
and traders could rest resupply and most
importantly refill their water skins
most releases will have fresh water
Springs or ponds above the surface open
to the air and this is what allows both
people and plants to inhabit the area
but a look from above reveals no River
or even stream feeding into these ponds
and as I mentioned earlier areas like
this receive little to no rainfall
annually so where does this life-giving
water come from then let's keep using C
WA as an example while this land may
receive just a few inches of rainfall a
year over a big enough area a couple
inches can add up to a huge amount of
water and you'll typically find an oasis
at a low point in the desert a look at
an elevation map shows the sea wahoo
ASIS to be right in the middle of a
depression beside the larger Qatar
depression in fact most of the Coss lies
at roughly 19 metres below sea level so
the sea WA and other oases are
essentially funnels for all water from
surrounding areas to flow into
there aren't any rivers or streams on
the surface to bring water to these
places so how does it get there well
beneath the surface of all land is an
area where rainwater collects we called
this in aquifer if it rains a lot the
upper reaches of the aquifer called the
water table will rise if it rains very
little that water table will drop it's
by taking advantage of underground
aquifers that things like wells and
irrigation systems work naturally where
the elevation of the earth is higher so
too will the water table be so if you
have areas of high elevation like
towering sand dunes or hills I rectally
next to areas of low elevation like a
depression you can get spots like this
where the water table nears or even
exceeds the surface at these places
water will seep from the ground and pool
into bodies of water where there's water
and there's life and while most desert
plants are short and dense under the
right conditions they too can grow to be
tall and lush and there you have it an
oasis is formed it helps to know also
that the water table can be further
altered by impermeable layers in the
soil such as rocks or dense layers of
clay called hard pans because water
cannot pass through these substances
it's only choice is to move the water
table upwards and this can be another
factor in bringing water to the surface
even if there's no depression and that's
all an oasis is light rains from a large
enough area can flow through an
underground aquifer hold by gravity
forming basically an underground river
eventually plants and animals will find
these upwellings for water and grow to
create a miniature ecosystem a microcosm
of rich life and an otherwise to void
desert and if conditions remain
quote/unquote favorable no aces can
exist for thousands of years virtually
unchanged in fact in 2007 in the Coss an
early hominid footprint was discovered
fossilized in the rocks with estimates
for its age ranging as far back as 3
million years illustrating just how long
an oasis can remain intact while
completely isolated from the outside
world thanks for watching I hope your
curiosity is satisfied but if not I've
got some more videos you can watch as
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