Nitrogen Cycle

Nitrogen is a gas . It makes up 71%
of the gases in the atmosphere!
It helps us by keeping living things
 alive so we can eat them ! Here
is how nitrogen dose it. It is called
the nitrogen cycle . First the
nitrogen falls with rain or snow.
Then goes into the dirt and mud.
Bacteria that are on plants make
 this nitrogen edible for the plants.
The nitrogen is turned into compounds.
Then the the plants use it. Animals eat it .
When the animals die the nitrogen goes
 back to the earth . Where it turns into
food for the Plants. Some nitrogen compounds
don't get used because another bacteria takes
them and makes them plain nitrogen. This
nitrogen Then goes back into the atmosphere
to fall down in rain or snow again. This cycle
keeps animals and plants alive so we can eat
them . That is the nitrogen cycle.








Source: Brainpop

Wind

Wind
Wind is moving air. Here is how it happens:
Wind is caused by the sun . The Sun heats the earth
and the warm air rises. Colder air fills the gap while
the warm air is cooling down . This makes a lot of
moving air which is wind! There are many types of
winds like Jet streams ( are fast moving streams of air
that move in circles around the earth ) , Constant winds
( Winds that are constant . The warm air moves toward
the poles and cools off ) and trade winds ( these winds
move toward the equator. ) 

Wind Energy
Pepole have been using wind as a power source for
ages. The first windmills were in Persia. they were
used for grinding wheat . These don't look like the
European windmills but they looked like eggbeaters.
The modern ones are not for grinding wheat but are
for making electricity. The wind turns the windmill
and a generator makes the movement into electricity.
In wind farm you can see lots of windmills.


Wind Storms
There are many storms made 
by wind like hurricanes and tornadoes 
  
Hurricanes
Are Storms made over hot water . The Hot water heats
the air . Then cold air fills the gap making a small storm
gather over the hot water. The storm grows in power as
it is moving over the hot water and winds fly over it .
When the winds are faster then 73 miles per hour it is a
Hurricane.

5 Over 157 mph
_|____________
4 130-156 mph
_|___________
3 111-129 mph
_|___________
2 96-110 mph
_|___________
1 74-95 mph


Hurricanes can do a lot of damage . When they hit land
they lat out their water as rain and have high winds.
Tornadoes  
Are fast winds in a whirling column .
They come out of thunderstorms . Th
ey can be very destructive . Tornadoes
are measured by something called the
Fujita scale

F0 | weak
F1 | medium
F2 | stronger
F3 | bad
F4 | destructive
F5 | Greatly destroying


Source: Brainpop