esci 1101 spring_2011_chapter_3_guided_notes

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Physical GeographyPhysical Geographyby Alan Arbogastby Alan Arbogast

Chapter 3Chapter 3

Earth-Sun Geometry and the Seasons

Lawrence McGlinnDepartment of GeographyState University of New York - New Paltz

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Earth-Sun RelationshipEarth-Sun RelationshipMost Physical Processes on Earth powered by

incoming radiation from Sun

Earth-Sun Relationship is Complex – Depends on:– _____________– _____________– _____________– _____________

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Our Place in SpaceOur Place in Space

Big-Bang Theory

Milky Way Galaxy

Our Solar System

Milky Way GalaxyMilky Way Galaxy

Figure 2.1

Our Solar SystemOur Solar System

Figure 2.1

Dimensions and distancesDimensions and distances

Speed of light– __________________________– Universe is _____________ across– Milky Way Galaxy _____________– Our Solar System _____________ across from

Earth’s perspective– Moon is _____________away

Earth’s OrbitEarth’s OrbitAverage distance from Earth to the Sun is _______________________________________ – closest at _____________–_______________________________________ – farthest at _____________–__________________________

Earth is __________________from the SunPlane of Earth’s orbit is the ______________

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Shape of the EarthShape of the Earth

_____________

_____________ - Earth-shaped object

Variation in Sun Angle by _____________

_____________

Sun Angle & Length of Day

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At high latitudes, incoming solar radiation is spread over a larger area than at low latitudes, so energy per unit area is relatively low.

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The SunThe SunAbout _____________Old

Average Star, Nothing Special

_____________diameter of Earth

Powers most natural processes on Earth

_____________for Sun’s energy to reach

Earth

Strong Magnetic Fields/Sunspots

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Earth’s Orbit Around the SunEarth’s Orbit Around the Sun

_____________

One Revolution = _____________

_____________ Orbit

_____________

_____________

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The Earth follows an elliptical orbit around the Sun with its closest point at Perihelion and its farthest point at aphelion

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The Earth’s Rotation & Axial The Earth’s Rotation & Axial TiltTilt

The Earth’s Rotation around its Axis

_____________ Rotation around North Pole

Circle of Illumination

Earth as Viewed from the Sun

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Viewed from above the North Pole, the Earth’s rotation and revolution are both counterclockwise.

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Global TimeGlobal Time

_____________ Time Zones

Prime Meridian

International Date Line

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Earth’s 24 Time Zones

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The SeasonsThe Seasons

Earth’s tilt 23.5 from perpendicular to Ecliptic

Angle and orientation constant in Orbit

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The Earth’s tilt and orientation hold steady as it orbits the Sun.

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The SeasonsThe Seasons

Tilt and revolution combine to cause seasons– Northern & Southern Hemispheres

alternate direct radiation from the Sun– Subsolar Point migrates between 23.5

degrees N and 23.5 degrees S.

Which of the following latitudes will experience the effects of the sun's subsolar point?

A. 0 degreesB. 20 degrees N and 20 degrees SC. 40 degrees N and 40 degrees SD. Both A and BE. Both B and C

Answer: D

5 Factors That Influence 5 Factors That Influence Seasonal Change  Seasonal Change  

RevolutionRotationTilt of the earth's axisAxial parallelismSphericity

RevolutionRevolution    

Earth revolves around the SunVoyage takes one yearEarth’s speed is 107,280 km/h

RotationRotation

Earth rotates on its axis once every 24 hours

Rotational velocity at equator is 1675 km/h (1041 mph)

Revolution and RotationRevolution and Rotation

Reasons for Seasons Reasons for Seasons Tilt of earth's axis

– Axis is tilted 23.5° from perpendicular to the plane of ecliptic

Axial parallelism– Axis maintains alignment during orbit around

the Sun– North pole points toward the North Star

(Polaris)

Sphericity (geodesy)

Axial Tilt and ParallelismAxial Tilt and Parallelism

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The Earth’s orbit and tilt combine to create the seasons.

Orbital View

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Solstice and EquinoxSolstice and Equinox

Spring Equinox (March 20-21)– Subsolar Point – Equator

Summer Solstice (June 20-21)– Subsolar Point – Tropic of Cancer –

23.5 degrees N

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Solstice and EquinoxSolstice and Equinox

Fall Equinox (September 22-23)– Subsolar Point – Equator

Winter Solstice (December 21-22)– Subsolar Point – Tropic of

Capricorn – 23.5 degrees S

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Earth-Sun Geometry on EarthEarth-Sun Geometry on EarthSun’s Arc across the Sky

Seasonal Changes in Sun Position

The Sun as seen from 45°N in June and in December.

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Earth-Sun Geometry on EarthEarth-Sun Geometry on Earth

Variation in Day Length by Latitude

Variations in Day Length on Equinoxes and Solstices by Latitude.

Where is the subsolar pint as of today?

A. Southern hemisphere, near 23.5 degrees SB. Southern hemisphere, near the equatorC. Northern hemisphere, near 23.5 degrees ND. Northern hemisphere, near the equator

Answer: A