Physical Geography

Class 5: Earth Movements and Seasons

What are the changes that happen seasonally?

• Think about local changes• Changes elsewhere

• List, with your group, as many seasonal differences as you can think of

What do you notice about the Sun’s angle throughout the year?

• Is the sun at the same height each morning when you wake up?

• Is the sun in the same direction every morning when you drive to school?

• Does the sun reach the same height in the sky at its highest throughout the year?

• Think about changes – in your home, along your commute, at school, etc.

Why is it warmer in Summer?

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1. We’re closer to the Sun in our annual orbit

2. We receive more direct sunlight

3. Our hemisphere is tilted toward the sun, making us closer to the sun than the other hemisphere

What causes Earth’s seasons?

• Is it the distance to the Sun?

How does distance to Sun change throughout year?

• Perihelion – orbital point closest to sun• Aphelion – orbital point furthest from sun

So what does cause seasons?

• Angle of sun’s rays changes• This changes the “subsolar point” = point on

Earth that receives Sun’s direct (90 degree) rays

Why is it hotter in summer?

What caused the angle of the Sun’s rays to change?

• From day to night…..

• From season to season……

• And from place to place?

1. Rotation

2. Axial Parallellism

• North Pole stays pointed toward Polaris

• All day long….• All year long

3. Revolution

4. Tilt of Earth

This shows axial parallelism, revolution and tilt

5. Sphericity

• Also shows rotation and tilt

Changing Day Lengths

Where are seasonal changes the most pronounced?

1. Sub Polar2. Mid Latitudes3. Sub Tropical4. Equatorial

Where do daylight hours change the most?

• Sub Polar• Mid Latitudes• Sub Tropical• Equatorial

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What if Earth were NOT tilted?

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1. No change 2. Day lengths would stay same all

year long for every latitude3. All latitudes would experience

the same temp; earth would have one consistent climate

4. There would be no seasonal change in weather conditions anywhere

5. There would be no diurnal (day to night) changes in temp

6. Both 2 and 4 would be correct7. Both 2 and 5 would be correct

What if Earth were more tilted?

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1. Conditions would stay the same2. Summers would be warmer and

winter would be colder, but average temps would be same

3. More direct rays at higher latitudes in summer would lead to warmer overall annual temps

4. Less direct rays at higher latitudes in winter would lead to colder temps, more snowfall, more reflection and less absorption of sun, leading to overall cooling

Special Latitudes

Time lapse “Sunset” at Barrow