Chapter 2 Earth and the Sun

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Chapter 2Earth and the Suns Energy

• The Big Idea
• Earths movement and the suns energy interact to
  create day and night, temperature changes, and
  the seasons.
• Main Ideas
• Earths movement affects the amount of energy we
  receive from the sun.
• Earths seasons are caused by the planets tilt.

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Earths movement affects the amount of energy we
receive from the sun.

• All life on Earth requires solar energy, or
  energy from the sun, to survive.
• Amount of solar energy received changes
  constantly
• Earths rotation, revolution, tilt, and latitude
  all affect the amount of solar energy Earth
  receives.

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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.

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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.

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Tilt

• Tilt
• Earths axis is tilted at an angle of 23½ degrees
  from vertical.
• At any give time of year, some places on Earth
  tilt toward the sun, and others tilt away.
• Places tilting toward the sun receive more solar
  energy and have warmer temperatures than those
  that tilt away.

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Latitude

• Latitude
• Latitude is the distance north or south of
  Earths 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.

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Questions of the Day

• What is solar energy?
• How does the Sun affect life on Earth?
• What four things affect the amount of sunlight we
  receive?

• Take the next 5 minutes in class to answer these
  questions.
• Refer back to your notes for help!

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Earths seasons are caused by the planets
tilt.

• 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

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Summer

• Earth tilts towards the sun in summer.

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Winter

• Earth tilts away from sun in winter

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Spring and Fall

• In spring tilt toward sun, solar energy
  increases, temperatures rise, and days grow
  longer.
• In fall tilts away from sun, solar energy
  decreases, temperatures decrease, days are
  shorter

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Tropics

• Tropics seasons are marked by rainfall rather
  than temperature.
• Monsoons, winds bring either dry or moist air to
  the tropics, creating wet and dry seasons.

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The Seasons

• Winter and Summer
• Earth tilts away from sun in winter and towards
  the sun in summer.
• Because of the Earths 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.

• 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.

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Water on Earth

• Water is a dominant feature on Earths surface
  and is essential for life.
• Salt water and freshwater make up Earths water
  supply.
• In the water cycle, water circulates from Earths
  surface to the atmosphere and back again.
• Water plays an important role in peoples lives.

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Salt water and freshwater make up Earths water
supply.

• Water covers some two-thirds of the planet.

Earths Water

• About 97 percent of the Earths water
• Unsafe to drink because of high levels of salt
• In general, found in Earths oceans, which cover
  some 71 percent of the planets surface
• Also found in some of Earths lakes

Salt Water

• Water without salt
• Makes up only 3 percent of our water supply

Freshwater
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Freshwater

• Much of Earths 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 Earths
  streams, rivers, and lakes.
• Less than one percent of Earths water supply
• Streams, rivers, and lakes are common sources.
• Precipitation is water that falls to Earths
  surface as rain, snow, sleet, or hail.
• Most available freshwater is groundwater, water
  found below Earths surface.
• Some naturally bubbles from the ground to the
  surface as a spring.
• Most obtained by digging wells

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The 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
  Earths surface to the atmosphere and back it
  is driven by the suns energy.
• Evaporationwater 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 isnt absorbed as
  groundwater flows over land and collects in
  streams, rivers, and oceans.

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Water plays an important role in peoples lives.

• 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.

• Water Benefits
• Provides us with food to eat
• Important source of energy
• Provides us with recreation, including swimming,
  fishing, surfing, and sailing

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The Land

• Processes below and on Earths surface shape the
  planets physical features.
• Earths surface is covered by many different
  landforms.
• Forces below Earths surface build up our
  landforms.
• Forces on the planets surface shape Earths
  landforms.
• Landforms influence peoples lives and culture.

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Earths surface is covered by many different
landforms.

• Landforms, or shapes on the planets surface,
  make up the landscapes that surround us.
• Earths 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, areas of land completely surrounded by
  water
• Peninsulas, land surrounded by water on three
  sides

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Forces below Earths surface build up our
landforms.
Earths Plates

• The planets continents, or large landmasses, are
  part of Earths crustthe solid outer layer of
  the planet.
• Theory of plate tectonics suggests that Earths
  surface is divided into a dozen or so slow-moving
  plates, or pieces of Earths 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 Earths landforms

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Plates Collide, Separate, and Slide

• 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 platesland pushes up to form
  mountains

• Plates Separate
• As plates move apart, gaps between plates allow
  magma to rise to Earths crust.
• Lava, magma that reaches the Earths 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.

• Plates Slide
• As plates pass by each other, they sometimes
  grind together, producing earthquakes, sudden,
  violent movements of Earths crust.
• Earthquakes often take place along faults, or
  breaks in Earths crust where movement occurs.
• The region around the Pacific plate, called the
  Ring of Fire, is home to most of the worlds
  earthquakes and volcanoes.

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Forces on the planets surface shape Earths
landforms.

• Weather, water, and other forces change Earths
  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

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Types of Erosion

• 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
• Glaciers, or large, slow-moving sheets of ice,
  erode the land by carving valleys and mountain
  peaks.
• 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.
• Floodplains are created when rivers flood their
  banks and deposit sediment.
• Sediment carried by a river all the way to the
  sea creates a delta.

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