Download The Water Cycle

The Water Cycle
Where does all the Earth’s water come
from?
• Primordial Earth was a globe made of magma.
• Water set free by magma began to cool the
Earth’s atmosphere until water could stay on
the surface as a liquid.
• Volcanic activity kept and
still keeps introducing
water in the atmosphere.
Water is everywhere
• Earth has a limited supply of water. The supply
is constantly being recycled between the
oceans, atmosphere and land.
– Balance in the water cycle means the average
annual precipitation over Earth equals the amount
of water that evaporates.
water input = water output
Water is everywhere
• The water cycle is a gigantic worldwide system
powered by energy from the sun.
• The atmosphere provides the most important
link between the oceans and land.
• This unending circulation of Earth’s water
supply is the water cycle.
What is one way water enters the atmosphere?
Evaporation
The sun, which drives the water cycle, heats
water in the oceans. Some of the water
evaporates as vapor into the air.
Evapotranspiration
Rising air currents take the vapor up into the
atmosphere, along with water from
evapotranspiration, which is water transpired
from plants and evaporated from the soil.
Condensation
The vapor rises into the air where cooler
temperatures cause it to condense into
clouds.
Precipitation
Air currents move clouds around the globe,
cloud particles collide, grow and fall out of the
sky as precipitation.
What happens to precipitation that falls on
land?
Surface runoff
Most precipitation falls back into the oceans or
land, where, due to gravity, the precipitation
flows over the ground as surface runoff.
Streamflow
A portion of runoff enters rivers in valleys in the
landscape, with streamflow moving water
towards the ocean.
Describe the path of water through
the water cycle.
• Water Cycle Diagram
What is an air mass, and what happens
as it moves over an area?
Air Masses
An air mass is an immense body of air that is
characterized by similar temperatures and
amounts of moisture at any given altitude.
Movement of Air Masses
As the air mass
moves, the
characteristics of an
air mass change and
so does the
weather in the area
over which the air
mass moves.
Formation of Fronts
When two air masses meet, they form a front,
which is a boundary that separates two air
masses.
Types of Fronts
A warm front forms when warm air moves into
an area formerly covered by cooler air.
Types of Fronts
A cold front forms when cold, dense air moves
into a region occupied by warmer air.
What is the relationship between dew
point and condensation?
Dew Point
Dew point is the
temperature to
which a parcel
of air would
need to be
cooled to reach
saturation.
Temperature
Relative Humidity
• Relative humidity is a ratio of the air’s actual water
vapor content compared with the amount of water
vapor air can hold at that temp. and pressure.
• Relative humidity indicates how near the air is to
saturation, rather than the actual quantity of water
vapor in the air.
Describe how relative
humidity is affected by
temperature and levels of
water vapor.
Can you locate an area on the weather
map with 100% relative humidity?
Can you make it rain.. and clear it out?
• Interactive weather maker
Have you ever seen the rain?
Weather map introduction