Transcript Unit 1 * The Basics of Geography

Unit 1 – The Basics of
Geography
Chapter 3
Climate and Vegetation
Page 49
What causes seasons?
The earth revolves
around the sun with a
23.5 degree tilt in
relation to the sun.
Because of the earth’s
revolution and its tilt,
different parts of the
earth receive the direct
rays of the sun for more
hours of the day at
certain times of the year.
Two lines of latitude mark the points
farthest north and south that the
sun’s rays shine directly overhead at
noon. These two lines are the tropic
of Cancer and the tropic of
Capricorn.
Solstice – either of two times of year
when the sun’s rays shine directly
overhead at noon at the furthest
points north or south, and that mark
the beginning of summer and winter.
In the Northern Hemisphere, the
summer solstice is the longest day
Equinox – each of the two days in a year on which day
and the winter solstice is the
and night are equal in length; marks the beginning of
shortest.
spring and autumn.
The two terms weather and climate
are often confused with one another.
Climate – weather conditions at a
particular location over a long period
of time.
Weather – is the condition of the
atmosphere at a particular location
and time.
What causes the weather?
Water vapor determines if there will be precipitation – falling water droplets in
the form of rain, sleet, snow, or hail.
Cloud cover may hold water vapor.
Landforms and bodies of water. Land heats rapidly but loses heat quickly as well
while water heats slowly but also loses heat slowly.
Elevation- As elevation above sea level increases, the air becomes thinner and
loses its ability to hold moisture.
Air movement – Winds move the air and the solar energy and moisture that it
holds. As a result, weather can change very rapidly.
What does precipitation depend
upon?
Precipitation depends on the
amount of water vapor in the air
and the movement of the air.
Water vapor condenses, forms
droplets, and becomes a cloud.
When the amount of water in a
cloud is too heavy for the air to
hold, precipitation falls.
Convectional
Precipitation
Typical of hot
climates,
convection
occurs after
morning
sunshine heats
warm, moist air.
Clouds form in
the afternoon
and rain falls.
Orographic
Rainfall
Associated with
mountain areas,
orographic storms
drop more rain on
the windward
side of a
mountain and
create a rain
shadow on the
leeward side.
Rain Shadow – land on the leeward side of a mountain
which gets little rain from descending, dry air.
Frontal Rainfall
Mid-latitude frontal storms
feature cold, dense air masses
that push lighter, warm air
masses upward, causing
precipitation to form.
What are examples of weather extremes?
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Hurricanes
Tornadoes
Blizzards
Droughts
floods
Hurricanes – Storms that form over
warm, tropical ocean waters
Other names for hurricanes across
the world
Typhoons-Asia
Willy-willies-Australia
Baguios-Philippines
Chubascos-Mexico
Hurricanes allow heat from the
tropics to be moved out of an area.
Tornado – a powerful funnelshaped column of spiraling air.
It’s also known as a twister.
Tornadoes are usually born from
strong thunderstorms.
The largest outbreak of
tornadoes in the United States
occurred during a 16-hour
period, April 3 and 4, 1074. A
total of 148 tornadoes killed 330
people across Ohio and
Tennessee.
The National Weather Service counts
about 700 tornadoes every year.
Blizzard is a heavy
snowstorm with winds of
more than 35 miles per
hour and highly reduced
visibility.
The greatest snowfall for a
24-hour time period was 76
inches in Silver Lake,
Colorado in 1921.
(six feet, four inches)
Drought – is a long period of time
without rain or with very minimal
rainfall.
Droughts cause crop failures and
reduced levels in water storage
areas.
In the 1930s, drought conditions
were so bad that a 150,000 square
mile area was known as the “Dust
Bowl.”
Flood – when
water spreads
over land not
normally
covered with
water.
Flood Plains –
areas prone to
flooding.
What four major factors
influence the climate of a
region?
1. Wind and ocean
currents
2. Latitude
3. Elevation
4. Topography
Wind Currents
Wind and ocean
currents help
move the sun’s
heat from one
part of the world
to another
through
convection.
Convection – the transfer of heat in the
atmosphere by upward motion of the air
Ocean currents
are like rivers
flowing in the
ocean. Warm
water flows
away from the
equator toward
the poles, and
cold water
flows back
toward the
equator.
Ocean currents affect not only the temperature of
an area, but also the amount of precipitation
received.
Zones of Latitude
Geographers divide the earth into
three general zones of latitude.
What are the three general zones of
latitude?
1. Low or tropical
2. Middle or temperate
3. High or polar
Elevation affects climate. The higher you go, the colder it gets.
Topography
Landforms also affect the climate.
This is very true of mountain areas.
Changes in Climate
Climates can change over time.
Scientists use ice-core samples from
thousands of years past to study a
variety of changes in temperature and
precipitation.
Some of the changes in climate appear
to be natural. Some may be the result
of human activity.
El Niño – The warming of the waters
off the west coast of South America
El Niño is a natural change in the
climate. About every two to seven
years, prevailing easterly winds that
blow over the central Pacific Ocean
slow or reverse direction, changing the
ocean temperature and affecting the
weather worldwide.
La Niña is the reverse.
Global Warming is a
theory that believes the
earth is heating up since
the 1800s.
Greenhouse effect – the
layer of gas released by
the burning of coal and
petroleum traps some
solar energy, causing
higher temperatures in
the same way that a
greenhouse traps solar
energy.