Chapter 2Chapter 2

Earth and the Sun’s EnergyEarth and the Sun’s Energy

The Big IdeaThe Big Idea

• Earth’s movement and the sun’s energy interact to create day and night, temperature changes, and the seasons.

Main IdeasMain Ideas

• Earth’s movement affects the amount of energy we receive from the sun.

• Earth’s seasons are caused by the planet’s tilt.

Earth’s movement affects Earth’s movement affects the amount of energy we the amount of energy we

receive from the sunreceive from the sun..

All life on Earth requires All life on Earth requires solar energysolar energy, or energy from , or energy from the sun, to survive.the sun, to survive.

– Amount of solar energy received changes constantly

– Earth’s rotation, revolution, tilt, and latitude all affect the amount of solar energy Earth receives.

RotationRotationEarth 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.

RevolutionRevolutionEarth follows an Earth follows an orbitorbit, , or path, around the or path, around the sun.sun.

Orbit is not a perfect Orbit is not a perfect circlecircle. .

It takes Earth It takes Earth 365¼365¼ days to complete one days to complete one revolutionrevolution, or , or triptrip around the sun.around the sun.

Our Our calendarcalendar yearyear is is based on the time it based on the time it takes Earth to takes Earth to complete its orbit.complete its orbit.

TiltTiltTiltTiltEarth’s axis is tilted at Earth’s axis is tilted at

an angle of an angle of 23½23½ degrees from vertical.degrees from vertical.

At any give time of At any give time of year, some places on year, some places on Earth tilt Earth tilt towardtoward the the sun, and others tilt sun, and others tilt awayaway..

Places tilting toward Places tilting toward the sun receive the sun receive moremore solar energy and have solar energy and have warmer temperatures warmer temperatures than those that tilt than those that tilt away.away.

LatitudeLatitudeLatitudeLatitude

LatitudeLatitude is the is the distance north or distance north or south of Earth’s south of Earth’s equator.equator.

Low-latitude areas, Low-latitude areas, those nearest the those nearest the equator, receive equator, receive directdirect rays from rays from the sun all year.the sun all year.

High-latitude areas, High-latitude areas, those farther from those farther from the equator, the equator, receive receive indirectindirect rays from the sun rays from the sun and have and have coldercolder temperatures.temperatures.

Questions of the DayQuestions of the Day

1.1. What is solar What is solar energy?energy?

2.2. How does the How does the Sun affect life on Sun affect life on Earth?Earth?

3.3. What four things What four things affect the affect the amount of amount of sunlight we sunlight we receive?receive?

Take the next 5 Take the next 5 minutes in class to minutes in class to answer these answer these questions.questions.

Refer back to your Refer back to your notes for help!notes for help!

Earth’s seasons Earth’s seasons are caused by are caused by

the planet’s the planet’s tilt.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

SummerSummer

Earth tilts Earth tilts towards the sun in towards the sun in summer.summer.

Winter Winter

Earth tilts Earth tilts away from sun in winteraway from sun in winter

SpringSpring and and FallFall

• In spring: tilt In spring: tilt towardtoward sun, solar sun, solar energy energy increasesincreases, temperatures , temperatures riserise, and days grow , and days grow longerlonger..

• In fall: tilts In fall: tilts awayaway from sun, s from sun, solar olar energy decreasesenergy decreases, , temperatures temperatures decreasedecrease, days are shorter, days are shorter

TropicsTropics TropicsTropics: seasons are : seasons are

marked by marked by rainfallrainfall rather than rather than temperaturetemperature..

MonsoonsMonsoons, winds , winds bring either dry or bring either dry or moist air to the moist air to the tropics, creating tropics, creating wetwet and and drydry seasons. seasons.

The SeasonsThe SeasonsWinter 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.

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 EarthWater on EarthWater is a dominant feature on Earth’s surface and is

essential for life.

• Salt water and freshwater make up Earth’s water supply.

• In the water cycle, water circulates from Earth’s surface to the atmosphere and back again.

• Water plays an important role in people’s lives.

Salt water and freshwater make Salt water and freshwater make up Earth’s water supply.up Earth’s water supply.

About About 9797 percent of the Earth’s water percent of the Earth’s water

Unsafe to Unsafe to drinkdrink because of high levels of salt because of high levels of salt

In general, found in Earth’s oceans, which In general, found in Earth’s oceans, which cover some cover some 7171 percent of the planet’s surface percent of the planet’s surface

Also found in some of Earth’s Also found in some of Earth’s lakeslakes

Earth’s Water Water covers some Water covers some two-thirdstwo-thirds of the planet. of the planet.

Salt Water

Water without saltWater without salt

Makes up only Makes up only 33 percent of our water supply percent of our water supplyFreshwater

FreshwaterFreshwater Much of Earth’s freshwater is locked in Much of Earth’s freshwater is locked in glaciersglaciers, large areas of , large areas of

slow moving ice, and in the ice of the Arctic and Antarctic slow moving ice, and in the ice of the Arctic and Antarctic regions.regions.

Surface waterSurface water is water that is found in Earth’s streams, rivers, is water that is found in Earth’s streams, rivers, and lakes.and lakes.

– Less than one percent of Earth’s water supplyLess than one percent of Earth’s water supply

– Streams, rivers, and lakes are common sources.Streams, rivers, and lakes are common sources. PrecipitationPrecipitation is water that falls to Earth’s surface as rain, snow, is water that falls to Earth’s surface as rain, snow,

sleet, or hail.sleet, or hail. Most available freshwater is Most available freshwater is groundwatergroundwater, water found below , water found below

Earth’s surface.Earth’s surface.

– Some naturally bubbles from the ground to the surface as a Some naturally bubbles from the ground to the surface as a spring.spring.

– Most obtained by digging wells Most obtained by digging wells

The Water CycleThe Water Cycle Water is the only substance on Earth that occurs naturally as a Water is the only substance on Earth that occurs naturally as a

solid, a liquid, and a gas, or solid, a liquid, and a gas, or water vaporwater vapor..

The The water cyclewater cycle is the movement of water from Earth’s surface is the movement of water from Earth’s surface to the atmosphere and back ; it is driven by the sun’s to the atmosphere and back ; it is driven by the sun’s energyenergy..

– EvaporationEvaporation—water turns from liquid to gas.—water turns from liquid to gas.

– CondensationCondensation —the rising gas cools and condenses, or —the rising gas cools and condenses, or changes from a vapor into tiny liquid droplets, to form changes from a vapor into tiny liquid droplets, to form clouds.clouds.

– PrecipitationPrecipitation —if the droplets in clouds become heavy —if the droplets in clouds become heavy enough, they fall back to Earth as rain, snow, sleet, or enough, they fall back to Earth as rain, snow, sleet, or hail.hail.

– RunoffRunoff —excess water that isn’t absorbed as —excess water that isn’t absorbed as groundwater flows over land and collects in streams, groundwater flows over land and collects in streams, rivers, and oceans.rivers, and oceans.

Water plays an important role in Water plays an important role in people’s lives.people’s lives.

Water ProblemsWater ProblemsLack of available Lack of available

freshwater, which freshwater, which can be caused by can be caused by droughts or overusedroughts or overuse

Contaminated, or Contaminated, or polluted, water can polluted, water can harm humans, harm humans, plants, and animals.plants, and animals.

Flooding can Flooding can damage property damage property and threaten lives.and threaten lives.

Water BenefitsWater Benefits Provides us with food to Provides us with food to

eateat

Important source of Important source of energyenergy

Provides us with Provides us with recreation, including recreation, including swimming, fishing, swimming, fishing, surfing, and sailingsurfing, and sailing

The LandThe LandProcesses below and on Earth’s surface shape the planet’s

physical features.

• Earth’s surface is covered by many different landforms.

• Forces below Earth’s surface build up our landforms.

• Forces on the planet’s surface shape Earth’s landforms.

• Landforms influence people’s lives and culture.

Earth’s surface is covered by Earth’s surface is covered by many different landforms.many different landforms.

LandformsLandforms, or shapes on the planet’s surface, make up , or shapes on the planet’s surface, make up the landscapes that surround us.the landscapes that surround us.

Earth’s surface is covered with landforms of many Earth’s surface is covered with landforms of many different shapes and sizes.different shapes and sizes.

– MountainsMountains, land that rises higher than 2,000 feet, land that rises higher than 2,000 feet

– ValleysValleys, areas of low land located between mountains , areas of low land located between mountains or hillsor hills

– PlainsPlains, stretches of mostly flat land, stretches of mostly flat land

– IslandsIslands, areas of land completely surrounded by water, areas of land completely surrounded by water

– PeninsulasPeninsulas, land surrounded by water on three sides, land surrounded by water on three sides

Earth’s Plates

Movement of Continents

• 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.

• 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

Forces below Earth’s surface Forces below Earth’s surface build up our landforms.build up our landforms.

Plates Collide, Separate, and SlidePlates Collide, Separate, and SlidePlates 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.

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.

Forces on the planet’s surface Forces on the planet’s surface shape Earth’s landforms.shape Earth’s landforms.

WeatherWeather, , waterwater, and other , and other forcesforces change Earth’s change Earth’s landforms by wearing them away or landforms by wearing them away or reshapingreshaping them. them.

WeatheringWeathering is the process by which rock is broken down is the process by which rock is broken down into smaller pieces called sediment.into smaller pieces called sediment.– Heating and cooling can cause rocks to Heating and cooling can cause rocks to crackcrack..

– ExpansionExpansion of water as it freezes can cause cracks to expand. of water as it freezes can cause cracks to expand.

– Roots of trees can pry rocks Roots of trees can pry rocks apartapart..

ErosionErosion is the is the movementmovement of sediment from one location of sediment from one location to another.to another.– Can wear away or build up landformsCan wear away or build up landforms

Types of ErosionTypes of ErosionWind 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.