Earth's early air and oceans

Grade 9 Science Worksheet - Building Confidence

Circle the best answer.

1. 1.

   Timeline ruler at 4.6 billion years ago with volcanoes giving off gas. Where did most of Earth's earliest atmosphere come from, by Ari's reading (Smithsonian)?

   • Rain from the oceans
   • Air left over from the Sun's surface
   • Gases from volcanoes
   • Oxygen from forests
2. 2.

   Carbon dioxide, water vapor, methane and others. Which gas was almost missing from Earth's early air, by Bo's reading (Smithsonian)?

   • Oxygen gas
   • Water vapor
   • Methane
   • Carbon dioxide
3. 3.

   Carbon dioxide then and now. How much carbon dioxide did the earliest air hold compared with today's, by Kira's reading (Smithsonian)?

   • One-tenth of today's
   • No carbon dioxide
   • About the same as today
   • Ten to 200 times as much as today
4. 4.

   Drawing of cyanobacteria in shallow water. What first made oxygen gas on Earth, by Jun's reading (Smithsonian, NASA)?

   • Lightning
   • Breathing animals
   • Cyanobacteria, by photosynthesis
   • Volcanoes
5. 5.

   Carbon dioxide + water + sunlight → sugar + ? What does photosynthesis give off, by Luz's reading?

   • Methane
   • Carbon dioxide
   • Oxygen
   • Volcanic ash
6. 6.

   About when did cyanobacteria begin making oxygen, by Milo's reading (sources give about 2.7 to 2.8 billion years ago)?

   • At Earth's start, 4.6 billion years ago
   • About 2.7 million years ago
   • Within the last 10,000 years
   • About 2.7 to 2.8 billion years ago
7. 7.

   Why could water not collect on Earth's surface at first, by Noah's reading (Smithsonian)?

   • The oceans were frozen into the core
   • Oxygen blocked the rain
   • The surface was too hot until it cooled
   • There was no water anywhere
8. 8.

   Which list names sources of Earth's water, by Pia's reading (NASA, Smithsonian)?

   • The Sun's light turning into water
   • Melting of the iron core
   • Oxygen from cyanobacteria
   • Volcanic water vapor and ice from impacting bodies

9. Read this first

   Oxygen in the air over time (Smithsonian, NASA)

   Time	Oxygen in the air
   before about 2.7 billion years ago	almost none
   about 2.4 billion years ago	first fills the air (NASA)
   about 600 million years ago	about one-fifth of today's level
   today	21%

10. 9.

    About when did oxygen first fill Earth's air, by Tala's reading (NASA)?

    • About 2.4 billion years ago
    • About 240 years ago
    • About 4.6 billion years ago, from the start
    • About 2.4 million years ago
11. 10.

    About what share of today's air is oxygen, by Zee's reading (Smithsonian, NASA)?

    • About 100%
    • About 78%
    • About 1%
    • About 21%