Orbital cycles and ice ages

Grade 9 Science Worksheet

Circle the best answer.

1. Read this first

   EPICA Dome C temperature record (NOAA NCEI)

   Years ago	Temperature vs last 1,000 years
   20,000	−9.4 °C
   128,000	+3.4 °C
   140,000	−9.1 °C
   410,000	+1.6 °C
   800,000	−8.9 °C

2. 1.

   About how many 100,000-year ice-age cycles fit in 800,000 years, by Bo's math?

   • About 8
   • About 20
   • About 0.8
   • About 80
3. 2.

   A timeline divided into equal cycles. NASA: between 1 and 3 million years ago, ice ages came about every 41,000 years. About how many fit in that 2-million-year span, by Esme's math?

   • About 4.9
   • About 82
   • About 20
   • About 49
4. 3.

   Earth tilted more and less beside the Sun. NASA: the tilt was at its maximum about 10,000 years ago and reaches its minimum about 10,000 years from now. How does that span compare with the cycle, by Jun's math?

   • About 41,000 years, a full cycle
   • About 20,000 years, about half the 41,000-year cycle
   • About 20 years
   • About 10,000 years, a full cycle

5. Use this

   Earth's orbit with January and July marked.

6. 4.

   NASA: Earth is about 3.4% closer to the Sun in January than in July, and about 6.8% more sunlight arrives. Why is the sunlight change about double, by Kira's reading?

   • Sunlight weakens with the square of distance
   • January days are longer everywhere
   • The Sun itself is brighter in January
   • The Northern Hemisphere tilts toward the Sun in January
7. 5.

   NASA: at its most elliptical orbit, about 23% more sunlight arrives at closest approach; today it is about 6.8%. About how many times larger is 23%, by Luz's math?

   • About 0.3 times
   • About 16 times
   • About 29.8 times
   • About 3.4 times
8. 6.

   Orbit shape, tilt and wobble, each with its cycle. NASA: northern summers are about 4.5 days longer than winters today. Which cycle causes unequal season lengths, by Milo's reading?

   • Earth's daily spin
   • Eccentricity, the orbit's shape
   • Obliquity, the tilt of Earth's axis
   • Growing ice sheets

9. EPICA Dome C temperature record (NOAA NCEI)

   Years ago	Temperature vs last 1,000 years
   20,000	−9.4 °C
   128,000	+3.4 °C
   140,000	−9.1 °C
   410,000	+1.6 °C
   800,000	−8.9 °C

10. 7.

    Using the EPICA table, how much warmer was 128,000 years ago than 140,000 years ago, by Noah's math?

    • About 3.4 °C
    • About 5.7 °C
    • About 125 °C
    • About 12.5 °C
11. 8.

    The table's 140,000- and 128,000-year values lie about 12,000 years apart. What does the change show, by Ren's reading?

    • A glacial period giving way to a warm interglacial
    • A change within a single century
    • An interglacial warm period giving way to a new ice age
    • No change in climate
12. 9.

    In 1976, Hays and colleagues tested Milankovitch's idea with deep-sea sediment cores (NASA). What did they find, by Tala's reading?

    • Orbital cycles matched major climate changes over 450,000 years
    • Tilt by itself explained each ice age, with no help from the other cycles
    • Ice ages came each year
    • Orbital cycles had no link to climate
13. 10.

    Why can orbital changes that alter sunlight modestly still pace large ice ages, by Ari's reading (NASA)?

    • Ice absorbs more sunlight as it grows
    • Orbital changes raise the Sun's output
    • Each ice age lasts a few years
    • Growing ice reflects more sunlight, adding more cooling