How is a river valley formed
How Do Valleys Form? What Are Valleys?
in geology a valley is an extended
depression typically between hills or
mountains that is longer than it is wide
and normally has a river running through
it valleys are among the most common
features in the world and they're
typically formed through erosion which
is the gradual wearing down of material
by wind water and or other methods the
majority of valleys are either u-shaped
broad Plains or v-shaped and steep sided
or mixture of them however a valleys
form depends on many factors like what's
eroding it the slope of the land the
type of the rock and soil and the amount
of time that is vast there exist many
types of valleys however the most common
are v-shaped valleys u-shaped valleys
and flat floored valleys v-shaped
valleys are narrow with steep sloped
sides most of the time they're formed by
strong flows of water from a river or
stream which have eroded the rock under
them grinding it down to create a valley
through a process called down cutting
these rivers can often slope towards an
outlet which might be another river a
lake or an ocean these valleys often
form in mountainous or high areas with
youthful quick flowing streams that flow
rapidly a good example of this is the
Grand Canyon in the United States which
was formed by the Colorado River eroding
the rock of the Colorado Plateau over
the course of millions of years forming
its iconic shape u-shaped valleys also
known as glacial troughs have steep
sides that curve in at the base of the
valley wall and have wide floors most
are formed by massive glaciers that move
slowly down slopes eroding away the
earth these valleys are typically found
in areas high in elevation and in high
latitudes where glaciers are present
glaciers and high altitudes are called
continental glaciers or ice sheets and
while those in mountain ranges are
called alpine or mountain glaciers the
sheer size and weight of these glaciers
can completely change maps over the
course of thousands of years Yosemite
Valley in California is one of the
world's most famous u-shaped valleys it
was eroded by glaciers during the last
glaciation and now has the Merced River
running through it
flat floored valleys are the most common
in the world these like v-shaped valleys
are often formed by rivers and streams
but these streams are no longer new and
quit flowing but instead become a
meander a meander is one of a regular
series of curves bends loops turns or
windings in water course this slower
moving water tends to erode the banks of
the water channel rather than the valley
walls widening the floor of the valley
over time the shape changes from a V or
u-shape into a broad and flat valley
floor an excellent example of this type
is the Nile River Valley
there are also rift valleys that are
formed by the action of a geological
rift or Fault on the edge of tectonic
plates creating valleys like the East
African Rift at the bottom of many
valleys there's usually a base level
where the water levels smooth out due to
reaching the limits of erosion whether
by reaching sea level or erosion
resistant material this area is usually
called a floodplain
a floodplain is the area of land next to
a stream or river stretching from the
banks of the channel to the base of the
enclosing valley walls and experiences
flooding during periods of high water
discharge flood plains can support
incredibly rich ecosystems both in
quantity and in diversity they can
contain 100 or even a thousand times as
many species as rivers when they
periodically flood it releases a massive
surge in nutrients which causes
microorganisms to thrive and many other
species to take advantage of it
valleys and their associated parts
aren't just cool-looking landmarks
they've also had a great value to human
civilization from the beginning of human
society people have built near valleys
and floodplains for a number of reasons
like close proximity to rivers this is
so common there's an entire category of
River civilizations there are many
advantages to these locations like easy
access to a reliable source of water for
agriculture and human needs easy
transportation thanks to boats on the
river and very importantly the periodic
flooding of the floodplains makes for a
very nutrient-rich soil which is
excellent for farming which made it
possible to grow more crops than
necessary to sustain a population which
freed up people to engage in activities
like construction metalworking trade and
learning allowing civilizations to grow
ancient Mesopotamia was the earliest
verve Valley Civilisation forming around
3500 BC in the Tigris Euphrates River
system they were one of the first Ron's
age societies in the world developing
many technologies like metal and copper
working glass and lamp making water
storage and irrigation and many others
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