? ?Even ancient Egypt’s mighty pyramid (金字塔)
builders were powerless in the face of the famine (饥荒)that helped bring down
their civilization around 2180 B．C.. Now evidence collected from mud deposited
by the River Nile suggests that a shift in climate thousands of kilometers to
the south was ultimately to blame and the same or worse could happen
today. ? ?The ancient Egyptians depended on the Nile’s annual
floods to irrigate their crops. But any change in climate that pushed the
African monsoons (季风) southwards out of Ethiopia would have reduced these
floods. ? ?Declining rains in the Ethiopian highlands would have
meant fewer plants to stabilize the soil. When rain did fall it would have
washed large amounts of soil into the Blue Nile and into Egypt, along with
sediment (沉积) from the White Nile. ? ?Blue Nile mud has a different
isotope (同位素) signature from that of the white Nile, so by analyzing isotope
differences in mud deposited in the Nile Delta Michael Krom of Leeds University
worked out what proportion of sediment came from each branch of the
river. ? ?Krom reasons that during periods of drought, the amount
of Blue Nile mud in the river would be relatively high. He found that one of
these periods, from 4500 to 4200 years ago, immediately came before the fall of
the Egypt’s old Kingdom. ? ?The weakened waters would have been
disaster for the Egyptians. ?" Changes that affect food supply don’t have
to be very large to have a ripple (波浪) effect in societies. " says Bill Ryan of
the Lamont Doherty Earth Observatory in New York. ? ?"Similar
events today could be even more devastating," says team member Daniel Stanley, a
scientist from the Smithsonian Institution in Washington D.C.. "Anything humans
do to shift the climate belts would have an even worse effect along the Nile
system today because the populations have increased dramatically.
"
? ?Even ancient Egypt’s mighty pyramid (金字塔)
builders were powerless in the face of the famine (饥荒)that helped bring down
their civilization around 2180 B．C.. Now evidence collected from mud deposited
by the River Nile suggests that a shift in climate thousands of kilometers to
the south was ultimately to blame and the same or worse could happen
today. ? ?The ancient Egyptians depended on the Nile’s annual
floods to irrigate their crops. But any change in climate that pushed the
African monsoons (季风) southwards out of Ethiopia would have reduced these
floods. ? ?Declining rains in the Ethiopian highlands would have
meant fewer plants to stabilize the soil. When rain did fall it would have
washed large amounts of soil into the Blue Nile and into Egypt, along with
sediment (沉积) from the White Nile. ? ?Blue Nile mud has a different
isotope (同位素) signature from that of the white Nile, so by analyzing isotope
differences in mud deposited in the Nile Delta Michael Krom of Leeds University
worked out what proportion of sediment came from each branch of the
river. ? ?Krom reasons that during periods of drought, the amount
of Blue Nile mud in the river would be relatively high. He found that one of
these periods, from 4500 to 4200 years ago, immediately came before the fall of
the Egypt’s old Kingdom. ? ?The weakened waters would have been
disaster for the Egyptians. ?" Changes that affect food supply don’t have
to be very large to have a ripple (波浪) effect in societies. " says Bill Ryan of
the Lamont Doherty Earth Observatory in New York. ? ?"Similar
events today could be even more devastating," says team member Daniel Stanley, a
scientist from the Smithsonian Institution in Washington D.C.. "Anything humans
do to shift the climate belts would have an even worse effect along the Nile
system today because the populations have increased dramatically.
"
Which of the following statements is true?
A.The White Nile is the trunk of the River Nile. B.The White Nile is the trunk of the Blue Nile. C.The White Nile is a branch of the Blue Nile. D.The White Nile is a branch of the River Nile.
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