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)?

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

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

   • About the same as today
   • No carbon dioxide
   • Ten to 200 times as much as today
   • One-tenth of today's
3. 3.

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

   • Cyanobacteria, by photosynthesis
   • Lightning
   • Volcanoes
   • Breathing animals
4. 4.

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

   • Carbon dioxide
   • Oxygen
   • Methane
   • Volcanic ash
5. 5.

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

   • About 2.7 to 2.8 billion years ago
   • About 2.7 million years ago
   • At Earth's start, 4.6 billion years ago
   • Within the last 10,000 years
6. 6.

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

   • There was no water anywhere
   • Oxygen blocked the rain
   • The oceans were frozen into the core
   • The surface was too hot until it cooled
7. 7.

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

   • Oxygen from cyanobacteria
   • Melting of the iron core
   • Volcanic water vapor and ice from impacting bodies
   • The Sun's light turning into water
8. 8.

   Drawing of an icy body striking young Earth. NASA says some icy bodies that hit Earth came from beyond Jupiter and Saturn. What did their ice do, by Ren's reading?

   • It formed Earth's iron core
   • It melted and helped make the oceans
   • It made the oxygen in the air as it melted
   • It froze Earth solid

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

    • About 78%
    • About 1%
    • About 100%
    • About 21%
11. 10.

    The young Sun was only about 70% as bright as today. Why didn't Earth freeze over, by Esme's reading (Smithsonian)?

    • Greenhouse gases trapped enough heat
    • It did freeze solid for billions of years
    • The Sun was brighter than today
    • Oxygen in the air kept it warm