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To most of us, river networks
appear to be fixed features of
the landscape. In fact, many
rivers define political
boundaries that have been in
place for centuries. But what if
those boundaries are moving?
Scientists have long suspected
that river networks are not as
static as they appear. Some
rivers look distorted and others
contain rocks or aquatic
organisms that could only
have come from other rivers
that aren't currently attached.
This suggests that rivers have
been shifting and moving across
the landscape over millions of
years. But until now, there has
been no way to measure this
change. Researchers at MIT and
the Swiss Federal Institute of
Technology have developed a
mapping technique that measures
how much a river network is
changing and in what direction
it may be moving. The technique
focuses on a river network's
drainage divides. The ridge-
lines that that separate two
neighboring river basins. As
rainwater flows down either side
of the drainage divide and into
opposing rivers it erodes the
underlying rock creating an
imbalance in the river network.
To reach a balance the drainage
divide must shift to assume a
more stable pattern. With this
new measuring technique,
researchers can determine the
direction in which a divide
would have to move to bring its
river networks into balance.
Knowing where river systems are
shifting, may help scientists
understand how these rivers
shifted, diverged and merged
over millions of years.
This knowledge may help solve
some long-standing mysteries
in geology and biology. Such as
why some rocks and fish that
seem to belong in one river basin
are also found in another.