A stream is any body of flowing fluid. The most familiar type of
stream
is made of water, although
streams
can also be made of air, lava, electricity, or any other
fluid
.
Jet streams, for instance, are cold, fast-moving winds that circulate high in the atmosphere. Lightning is a
stream
of
electricity
that
circulates
from cloud to
cloud
, from the
cloud
to the ground, or even from the ground to a
cloud
. Hydrothermal vents eject a
stream
of
vent
fluid
into the ocean that surrounds them. Although
vent
fluid
contains water, it is much, much hotter than the water surrounding it, and filled with materials from the Earth's crust, such as sulfur, zinc, and copper.
Vent
fluid
is sometimes visible as white or black
streams
pouring from the
vent
.
Still, the most familiar type of
stream
is made of free-flowing water. These
streams
are fed by rain, melting snow and ice, and groundwater—the water that penetrates deeper into the
Earth
after the surface soil is completely soaked.
Streams
vary in size from tiny rills or
streamlets
, to larger brooks, creeks, and rivers. The term “
stream
” is often used interchangeably with “
river
,” though “
stream
” usually refers to a smaller body of water.
Streams
take on different shapes depending on the landscape through which they flow. Cascades, or waterfalls, are formed when shallow water flows over and around large rocks. Normally,
waterfalls
are found in mountainous areas.
A
stream
containing large amounts of sediment lining its bottom and sides can change its shape and develop large curves called meanders. Sometimes,
meanders
are so wide that they e
ventually
are cut off from the main
stream
. The U-shaped body of water left behind is called an oxbow lake.
Large amounts of
sediment
in a
stream
may cause it to split into many intertwined channels, called braided
channels
. Braided rivers are different from
meandering
streams
. While
meandering
streams
find a single new
channel
, braided
streams
flow over a series of wide, shallow
channels
.
Human engineering efforts can change the flow of a
stream
. For example, a
meander
might be straightened to improve a shipping channel.
Multiple
streams
can flow together so that one
stream
e
ventually
carries water that originated from different parts of a large area. This area is known as the
stream
’s drainage basin, or watershed. The Amazon River in South America is the world’s largest
stream
and also has the world’s largest
d
rainage
basin
. At more than 6.9 million square kilometers (2.3 million square miles), it is nearly as large as the entire country of Australia.
Fast Fact
Nile v. Amazon
The Nile and Amazon rivers have shared a long rivalry to determine which is the world's longest stream. Stretching 6,695 kilometers (4,160 miles) from its source in Burundi to its mouth in the Mediterranean Sea, the Nile is generally considered the longest. However, in 2007, a team of Brazilian scientists claimed to have found a new starting point for the Amazon River, 6,800 kilometers (4,225 miles) from its mouth.
