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[探索发现] 【整理】2010-03-03 地球的起源 EarthMade—14

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history

the investigation into how quick the sahara returns to desert has uncovered two
strking clues, ostrich eggshell beans show people and animals inhabited the
green sahara just 7,000 years ago, ocean sediments show that the sahara returned
to desert at break-neck pace in just two hundred years. the next wobble in the
earth axis is set to 15,000 years from now, only then would the sahara turn lush
and green again, but now modern technology is finding ways to speed up that
process,

the investigation into the sahara desert's eventful past now moves to the last
one hundred years, in 1956 French prospectors discovered vast reserves of oil
in the sahara, this triggered an oil rush that led to drilling across the
desert, then they struck something un-expected under the sand, huge quantities
of fresh water, it seemed the sahara had another secret to reveal.

"so this is a classical pumped well drilled for irrigating the fields, and water
is actually pretty hot, which means it's coming up an considerable depth, "

the deeper the well, the hoter the water, water from wells in sahara can reach
up to 150 degrees Fahrenheit. such high temperature means the pump is drawing
water from far enough under-ground to be warmed by the earth internal heat.

"so pump like this can bring up water from three quarters of a mile under-ground
or even deeper."

with no rain for years at the time, this water must be coming from somewhere.
Smith spots another clue,

"actually when i look at the surroundings of the well, i can see some origish
red iron staining"

this is hematite, a mineral that is typically found in water that has been
under-ground for a long time, combined with temperature, this point to some
kind of deep resere water, scientists say that astonishingly great quantities
of water lies under sahara, the key is in the sand-stone, sandstone is made
from the layers of sand compacted into rock over millions of years.

"so what's really incredible about sandstone like this is just how good it is
that holding water, that's because there is a lot of pore space between the
sand grains, that's actually very big, if i pour some water on these rocks,
just like what would've happened when it rain over the sahara, it soaks
right in"

scientists now know that every 20,000 years, a wobble in the earth orbit shifts
the monsoon north, so rain pours down onto the desert,

"much of that rain fell over the sahara is now stored under ground"

it's called the nubian sandstone Aquifer, and like a giant subterranean sponge,
it site below Egypt, Libya and sudan,
history

the investigation into how quick the sahara returns to desert has uncovered two
strking clues, ostrich eggshell beans show people and animals inhabited the
green sahara just 7,000 years ago, ocean sediments show that the sahara returned
to desert at break-neck pace in just two hundred years. the next wobble in the
earth axis is set to 15,000 years from now, only then would the sahara turn lush
and green again, but now modern technology is finding ways to speed up that
process,

the investigation into the sahara desert's eventful past now moves to the last
one hundred years, in 1956 French prospectors discovered vast reserves of oil
in the sahara, this triggered an oil rush that led to drilling across the
desert, then they struck something un-expected under the sand, huge quantities
of fresh water, it seemed the sahara had another secret to reveal.

"so this is a classical pumped well drilled for irrigating the fields, and water
is actually pretty hot, which means it's coming up an considerable depth, "

the deeper the well, the hoter the water, water from wells in sahara can reach
up to 150 degrees Fahrenheit. such high temperature means the pump is drawing
water from far enough under-ground to be warmed by the earth internal heat.

"so pump like this can bring up water from three quarters of a mile under-ground
or even deeper."

with no rain for years at the time, this water must be coming from somewhere.
Smith spots another clue,

"actually when i look at the surroundings of the well, i can see some origish
red iron staining"

this is hematite, a mineral that is typically found in water that has been
under-ground for a long time, combined with temperature, this point to some
kind of deep resere water, scientists say that astonishingly great quantities
of water lies under sahara, the key is in the sand-stone, sandstone is made
from the layers of sand compacted into rock over millions of years.

"so what's really incredible about sandstone like this is just how good it is
that holding water, that's because there is a lot of pore space between the
sand grains, that's actually very big, if i pour some water on these rocks,
just like what would've happened when it rain over the sahara, it soaks
right in"

scientists now know that every 20,000 years, a wobble in the earth orbit shifts
the monsoon north, so rain pours down onto the desert,

"much of that rain fell over the sahara is now stored under ground"

it's called the nubian sandstone Aquifer, and like a giant subterranean sponge,
it site below Egypt, Libya and sudan,
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