Earth's early air and oceans

Grade 9 Science Worksheet - Building Confidence

Circle the best answer.

1. 1.

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

   • Water vapor
   • Carbon dioxide
   • Oxygen gas
   • Methane
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
   • Ten to 200 times as much as today
   • No carbon dioxide
   • 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
   • Breathing animals
   • Volcanoes
4. 4.

   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
   • Within the last 10,000 years
   • At Earth's start, 4.6 billion years ago
   • About 2.7 million years ago
5. 5.

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

   • The oceans were frozen into the core
   • There was no water anywhere
   • Oxygen blocked the rain
   • The surface was too hot until it cooled
6. 6.

   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
7. 7.

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

8. 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%

9. 8.

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

   • About 4.6 billion years ago, from the start
   • About 2.4 billion years ago
   • About 2.4 million years ago
   • About 240 years ago
10. 9.

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

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

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

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