Transcript solstice - WeberTube

The Basics of
Geography
Part 6
Climate and Vegetation
Seasons
 As the earth revolves around the
sun, its 23 ½ degree angle
causes much of the world to
have different seasons.
 This tilt causes different parts of
earth to receive more direct rays
at different times of the year.
The Solstices
 Twice a year, we have what is
known as a SOLSTICE.
 These days mark the furthest north
or south from the equator that the
sun’s rays shine directly overhead.
 The solstices mark the first days of
summer and winter.
 The line of longitude at 23½° N
where this happens is called the
TROPIC OF CANCER.
 The line of longitude at 23½° S
where this happens is called the
TROPIC OF CAPRICORN.
The sun’s rays are directly over the Tropic of
Cancer. This would mark the beginning of
summer in the Northern Hemisphere.
The sun’s rays are directly over the Tropic of
Capricorn. This would mark the beginning of
summer in the Southern Hemisphere.
The Equinoxes
 Twice a year we go through an
EQUINOX.
 On these two days, the sun shines
directly over the equator, and the
days and nights are equal all over
the world.
 The equinoxes mark the
beginnings of spring and fall.
The sun’s rays are directly over the
equator twice a year.
• It is interesting to note that the seasons in the
southern hemisphere are exactly opposite of
what we experience here in the northern
hemisphere.
The Difference Between
Weather and Climate
 WEATHER:
The condition of
the atmosphere
at a particular
location and
time.
 CLIMATE:
Weather
conditions at a
particular
location over a
long period of
time.
Weather Extremes
As air masses warm and cool and move
across earth’s surface, sometimes they
clash and cause storms. Sometimes,
these storms can be severe and cause
major property damage and loss of life.
Hurricanes, tornadoes, blizzards,
droughts, and floods are all examples of
weather extremes.
 Storms that form over warm, tropical ocean
waters are called HURRICANES, or
typhoons in Asia. They are also
sometimes called cyclones.
 Air flowing over warm water picks up
moisture and heat energy.
 The center or EYE of the storm is calm,
while elsewhere, winds may blow up to 200
m.p.h.
 The clouds and wind may stretch out over
an area covering hundreds of miles.
 When they hit land, tremendous
damage may occur.
 Howling winds may uproot trees and
tear roofs off of buildings.
 Storm surges may wash away
shorelines and cause flooding.
 Heavy rains may also cause flooding.
 People living in low-lying coastal areas
are at great risk.
Gulfport, Mississippi after
Hurricane Katrina 2005
New Orleans—August 2005
 Hurricanes may take days to develop,
while TORNADOES, or funnel-shaped
columns of spiraling air form quickly.
 Tornadoes are born in thunderstorms
when counter-clockwise winds swirl
around a low-pressure center.
 These winds may reach 300 m.p.h. and
cause horrendous damage.
 On average, they are only about 300 feet
wide and travel a mile or so for a few
minutes. Some may be larger.
Look at the
swath of
damage that
was cut
through this
area.
A Whole Town Devastated
Greensburg,
Kansas was
leveled by a
tornado on
May 4,
2007.
The town of
about 1,500
suffered 11
deaths.
Approximately 3 out of 4 Tornadoes
Occur in the U. S.
Tornado Alley
The largest
outbreak of
tornadoes in U. S.
history occurred on
April 3-4, 1974 in
the Ohio and
Tennessee River
Valleys. During a
16-hour period, a
total of 148
tornadoes killed
330 people.
THE SALT LAKE CITY
TORNADO – AUGUST 11, 1999
A BLIZZARD is a heavy snowstorm
with winds of more than 35 miles per
hour and reduced visibility. The
greatest snowfall for a 24-hour period
was 76 inches in Silver Lake, Colorado
in 1921. A snowstorm that lasted from
February 13-19, 1959 once dumped
189 inches, almost 16 feet of snow, on
Mt. Shasta, California.
Blizzards are dangerous for various
reasons. They endanger people and
livestock who become trapped in
them. They also snarl traffic, and
make travel conditions dangerous.
In the Sierra Nevada and Rocky
Mountains, as well as the Great Lakes
areas, hundreds of inches fall in a
season.
A DROUGHT is a long period of time
without rain or with very minimal
rainfall. This lack of rainfall results in
crop failures and reduced levels in
water storage facilities such as
reservoirs. In extreme cases, this
may cause people to move to new
areas in search of food, or to starve.
DROUGHT
When water spreads over land not
normally covered with water it is
called a FLOOD. Melting snow or
rainwater fills streams or rivers until
they reach flood stage—the point at
which the banks can no longer
contain the water. The water then
flows into the surrounding area
called a floodplain.
Cedar Rapids, Iowa 2008
Teton Dam Disaster –
June 5, 1976
Four major factors influence the
climate of a region:
Wind/Ocean Currents
Latitude
Elevation
Topography
Global
Wind
Patterns
Global Ocean Currents
Zones of Latitude
Low/Tropical
Middle/Temperate
High/Polar
Tropical Zones
 The tropical zones are found on both
sides of the equator, and go from the
TROPIC OF CANCER to the TROPIC
OF CAPRICORN.
 Lands in the tropical zone are hot all
year long.
 Wind patterns may affect the amount
of rainfall in areas.
Temperate Zones
 The temperate zones lie between
the tropical and polar zones.
 Climates range from relatively hot to
relatively cold.
 Variations occur because solar
heating is greater in the summer
than in the winter.
Polar Zones
 In the northern hemisphere, it extends
from the ARCTIC CIRCLE to the
NORTH POLE.
 In the southern hemisphere, it extends
from the ANTARCTIC CIRCLE to the
SOUTH POLE.
 It is cold all of the year, and summer
temperatures may only reach 50°F.
Elevation –
Height Above Sea Level
As ELEVATION increases, the air
temperature drops about 3.5°F every
1000 feet. Places over 12,000 feet in
elevation share similar characteristics
with polar zones. Some mountains
near the equator have snow yearround.
Topography
Landforms also affect climate.
When moisture-filled winds move up the
sides of mountains, they cool and
release moisture. So on the
WINDWARD side of a mountain, it is
greener. On the other side, it does not
receive as much moisture, and is known
as the LEEWARD side.
Windward/Leeward
Vegetation Regions
Vegetation regions are natural
environments that provide the stage for
activities such as farming, raising livestock,
and producing timber. They include:
1. Forests
2. Grasslands
3. Deserts
4. Tundra
DECIDUOUS
Lose their leaves
yearly.
CONIFEROUS
Have cones and
may also be
called
evergreens.
GRASSLANDS are mostly flat regions, dotted
with a few trees, and known by different names.
In tropical areas they are called Savannas, and
in temperate regions are called Steppes.
The World’s Major Grasslands
Plants that can conserve water and
withstand heat dot the DESERT landscape.
Examples include cacti, shrubs, or sagebrush.
The World’s Major Deserts
Plants that hug the ground are best adapted
to survive the cold, dry TUNDRA climate.
Examples include mosses and lichen.
Earth’s Tundra Regions