Transcript Chapter 2: Planet Earth

Pages 26-41
Ch. 2 Section 1: Earth and 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.
 Earth’s rotation creates a sense
that the sun moves from east to
west.
Earth’s Rotation
Ch. 2 Section 1: Earth and The
Sun’s Energy
Revolution
 Earth follows an orbit, or
path, around the sun.
 It takes Earth 365¼ days to
complete one revolution, or
trip around the sun.
 February 29, leap year, is
added every four years to
allow for the fraction of a
day of the revolution.
 Revolution effects the
amount of solar energy
that the planet receives.
Earth’s Revolution
Ch. 2 Section 1: Earth and The
Sun’s Energy
Tilt
 Earth’s axis is tilted at an
angle of 23½ degrees from
vertical.
 Places tilting toward the
sun receive more solar
energy and have warmer
temperatures than those
that tilt away.
 Tilt creates Earth’s
change in seasons.
Latitude
 Latitude is the distance north or
south of Earth’s equator.
 Low-latitude areas, those
nearest the equator, receive
direct rays from the sun all year.
 High-latitude areas, those
farther from the equator, receive
indirect rays from the sun and
have colder temperatures.
 Areas near the Arctic and
Antarctic circles can receive
up to 24 hours of sunlight a
day.
Ch. 2 Section 1: Earth and The
Sun’s Energy (The Seasons)
Winter and Summer
Spring and Fall
 Earth tilts away from sun in
 In spring, Earth begins to
winter and towards the sun in
summer.
 Because of the Earth’s tilt,
the Northern and Southern
hemispheres experience
opposite seasons (Ex:
When it is summer in the
Southern Hemisphere, it is
winter in the Northern
Hemisphere)
tilt toward sun, solar
energy increases,
temperatures rise, and days
grow longer.
 In fall, the opposite occurs.
Ch. 2 Section 1: Earth and The
Sun’s Energy (The Seasons)
 In the tropics, regions close to the equator,
seasons are marked by rainfall rather than
temperature.
 At certain times of year, seasonal winds called
monsoons bring either dry or moist air to the
tropics, creating wet and dry seasons.
Ch. 2 Section 1: Earth and The
Sun’s Energy (The Seasons)
Ch.2 Section 2: Water on Earth
Freshwater
Salt Water
 Freshwater makes up only 3
percent of our water supply.
 Much of Earth’s freshwater is locked
in glaciers in the ice of the Arctic
 About 97 percent of the
and Antarctic regions.
 Surface water, less than 1% of the
freshwater supply, is found in
Earth’s streams, rivers, and lakes.
 Precipitation is water that falls to
Earth’s surface as rain, snow, sleet,
or hail.
 Most available freshwater is
groundwater, water
underground.
Earth’s water
 Unsafe to drink because of
high levels of salt
 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
Ch.2 Section 2: Water on Earth
Water Cycle
 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.
 The main processes of the water
cycle are evaporation,
condensation, precipitation, and
runoff.
Water Cycle in Action
Ch.2 Section 2: Water on Earth
Water Problems
Water Benefits
 Shortages of freshwater
 Provides us with food to
can be caused by
drought.
 Contaminated, or polluted,
water can harm humans,
plants, and animals.
 Flooding can damage
property and threaten
lives.
eat
 Important source of energy
 Provides us with
recreation, including
swimming, fishing,
surfing, and sailing
Ch.2 Section 3: The Land
 Landforms, or shapes on the planet’s
surface, make up the landscapes that
surround us.
 Earth’s landforms include
mountains, valleys, and peninsulas.
Ch.2 Section 3: The Land
The Earth’s Layers
 Crust: the solid outer layer
of the Earth.
 Mantle: the Earth’s liquid
layer.
 Core : the solid inner layer
of the Earth.
The Earth’s Layers (crosssection)
Ch.2 Section 3: The Land
Earth’s Plates
Movement of Continents
 The planet’s continents, or
 Continental drift, a theory
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.
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.
Ch.2 Section 3: The Land
Plate’s Collide
Plate’s Separate
 Two ocean plates: one
 As plates move apart,
gaps between plates
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.
allows lava to rise
and forms a midocean ridge.
Ch.2 Section 3: The Land
Weathering
Erosion
 Weathering is the process
 Erosion is the movement of
sediment from one location to
another.
Wind Erosion: Winds lift sediment
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.
into air and carry it across great
distances .
Glacial Erosion: Glaciers crush
rock into sediment and move it
great distances.
Water Erosion: Waves and flowing
water can cut through rock, carry
sediment, and deposit sediment in
new locations.