Download Document

PLANET EARTH - CHAPTER 2
PRE-AP GEOGRAPHY
AUGUST 22nd – 28th
Holt McDougal,
EARTH & THE SUN’S ENERGY

All life on Earth requires solar energy, or energy from
the sun, to survive.

Earth’s rotation, revolution, tilt, and latitude all affect the
amount of solar energy Earth receives.
Secrets of the Sun
Holt McDougal,
EARTH & THE SUN’S ENERGY
Rotation
 Earth
spins on its axis—
an imaginary line that
runs through the center
of the planet around
which it turns.
 It
takes Earth 24 hours
to make one rotation,
or complete spin on its
axis.
 As
Earth spins, different
parts of the planet face
the sun, thus causing
the changes from day
to night.
Holt McDougal,
Revolution
 Earth
follows an orbit, or
path, around the sun.
 Orbit
is not a perfect circle.
 It
takes Earth 365¼ days to
complete one revolution,
or trip around the sun.
 Our
calendar year is
based on the time it takes
Earth to complete its orbit.
EARTH & THE SUN’S ENERGY
Tilt
axis is tilted at
an angle of 23½
degrees from vertical.
Latitude
 Earth’s
 Latitude
 At
 Low-latitude
 Places
 High-latitude
any give time of
year, some places on
Earth tilt toward the sun,
and others tilt away.
tilting toward the
sun receive more solar
energy and have
warmer temperatures
than those that tilt
away.
Holt McDougal,
is the distance
north or south of Earth’s
equator.
areas, those
nearest the equator,
receive direct rays from
the sun all year.
areas, those
farther from the equator,
receive indirect rays from
the sun and have colder
temperatures.
EARTH & THE SUN’S ENERGY

Seasons are periods during the year that are known for a particular
type of weather.

Many places experience four seasons—winter, spring, summer, and fall.

In some parts of the world, seasons are based on the amount of rainfall
Holt McDougal,
EARTH & THE SUN’S ENERGY
Winter and
Summer
• Earth tilts
away from sun
in winter and
towards the
sun in
summer.
• Because of the
Earth’s tilt,
the Northern
and Southern
hemispheres
experience
opposite
seasons.
Spring and
Fall
• In spring,
Earth begins to
tilt toward
sun, solar
energy
increases,
temperatures
rise, and days
grow longer.
• In fall, the
opposite
occurs.
Holt McDougal,
Rainfall and
Seasons
• In the tropics,
regions close
to the equator,
seasons are
marked by
rainfall rather
than
temperature.
• At certain
times of year,
winds bring
either dry or
moist air to the
tropics,
creating wet
and dry
seasons.
WATER ON EARTH
• Water covers some two-thirds of the planet.
Earth’s Water
• About 97 percent of the Earth’s water
• Unsafe to drink because of high levels of
salt
Salt Water
• In general, found in Earth’s oceans, which
cover some 71 percent of the planet’s
surface
• Also found in some of Earth’s lakes
• Water without salt
Freshwater
• Makes up only 3 percent of our water supply
Holt McDougal,
WATER ON EARTH

Much of Earth’s freshwater is locked in glaciers, large areas of
slow moving ice, and in the ice of the Arctic and Antarctic
regions.

Surface water is water that is found in Earth’s streams, rivers, and
lakes.


Less than one percent of Earth’s water supply

Streams, rivers, and lakes are common sources.
Precipitation is water that falls to Earth’s surface as rain, snow,
sleet, or hail.


Streams form when precipitation collects in a narrow channel
and flows toward the ocean.
Most available freshwater is groundwater, water found below
Earth’s surface.

Some naturally bubbles from the ground to the surface as a
spring.

Most obtained by digging wells
Holt McDougal,
WATER ON EARTH

Water is the only substance on Earth that occurs naturally as
a solid, a liquid, and a gas, or water vapor.

The water cycle is the movement of water from Earth’s
surface to the atmosphere and back ; it is driven by the sun’s
energy.

Evaporation—water turns from liquid to gas.

Condensation—the rising gas cools and condenses, or
changes from a vapor into tiny liquid droplets, to form
clouds.

Precipitation—if the droplets in clouds become heavy
enough, they fall back to Earth as rain, snow, sleet, or hail.

Runoff—excess water that isn’t absorbed as groundwater
flows over land and collects in streams, rivers, and oceans.
Holt McDougal,
WATER ON EARTH
WATER CYCLE
Holt McDougal,
WATER ON EARTH
Water Problems
Lack
of available
freshwater, which
can be caused by
droughts or overuse
Contaminated,
or
polluted, water can
harm humans,
plants, and animals.
Flooding
can
damage property
and threaten lives.
Holt McDougal,
Water Benefits
Provides
to eat
us with food
Important
energy
Provides
source of
us with
recreation, including
swimming, fishing,
surfing, and sailing
THE LAND

Landforms, or shapes on the planet’s surface, make
up the landscapes that surround us.

Earth’s surface is covered with landforms of many
different shapes and sizes.
 Mountains,
land that rises higher than 2,000 feet
 Valleys,
areas of low land located between
mountains or hills
 Plains,
stretches of mostly flat land
 Islands,
water
areas of land completely surrounded by
 Peninsulas,
sides
land surrounded by water on three
Holt McDougal,
THE LAND
Earth’s Plates
• The planet’s continents, or large landmasses, are part
of Earth’s crust—the solid outer layer of the planet.
• Theory of plate tectonics suggests that Earth’s surface
is divided into a dozen or so slow-moving plates, or
pieces of Earth’s crust.
Movement of Continents
• The idea that continents have traveled great distances over
millions of years is known as continental drift.
• Theory, developed by Alfred Wegener, states that the
continents were once united in a single supercontinent and
over time, slowly separated and moved to their present
positions.
• As plates collide, separate, and slide, they shape Earth’s
landforms
Holt McDougal,
THE LAND
Holt McDougal,
THE LAND
Plates Collide
• Two ocean plates:
one pushes under
the other,
creating ocean
trenches, or deep
valleys in ocean
floor
• Ocean and
continental plate:
ocean plate drops
beneath
continental plate,
forcing land
above to crumple
and form
mountain range
• Two continental
plates:
land pushes up to
form mountains
Plates Separate
• As plates move
apart, gaps
between plates
allow magma to
rise to Earth’s
crust.
• Lava, magma that
reaches the Earth’s
surface, emerges
from the gap.
• As lava cools, it
builds a mid-ocean
range, or
underwater
mountain, that can
rise above the
surface of the
ocean to form
islands.
Holt McDougal,
Plates Slide
• As plates pass by
each other, they
sometimes grind
together, producing
earthquakes,
sudden, violent
movements of
Earth’s crust.
• Earthquakes often
take place along
faults, or breaks in
Earth’s crust where
movement occurs.
• The region around
the Pacific plate,
called the Ring of
Fire, is home to
most of the world’s
earthquakes and
volcanoes.
THE LAND
I FEEL THE EARTH MOVE UNDER MY FEET
Holt McDougal,
THE LAND

Weather, water, and other forces change Earth’s
landforms by wearing them away or reshaping them.

Weathering is the process by which rock is broken
down into smaller pieces called sediment.
 Heating
and cooling can cause rocks to crack.
 Expansion
of water as it freezes can cause cracks
to expand.
 Roots

of trees can pry rocks apart.
Erosion is the movement of sediment from one
location to another.
 Can
wear away or build up landforms
Holt McDougal,
THE LAND
Wind Erosion
• Winds lift sediment
into air and carry it
across great
distances
• On beaches and in
deserts, deposits
can form dunes.
• Blowing sand can
wear down rock.
Glacial Erosion
Water Erosion
• Glaciers, or large,
slow-moving sheets
of ice, erode the
land by carving
valleys and
mountain peaks.
• Waves and flowing
water can cut
through rock, carry
sediment, and
deposit sediment in
new locations.
• Crush rock into
sediment and move
it great distances
• Floodplains are
created when rivers
flood their banks
and deposit
sediment.
Holt McDougal,
THE LAND
 Landforms can influence where people settle.
 Landforms often influence what jobs are
available in a region.
 Landforms can affect language.
 People sometimes change landforms to suit
their needs.
Holt McDougal,