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

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

   • Water vapor
   • Methane
   • Oxygen gas
   • 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)?

   • About the same as today
   • One-tenth of today's
   • No carbon dioxide
   • 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)?

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

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

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

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

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

   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
   • Volcanic water vapor and ice from impacting bodies
   • Oxygen from cyanobacteria

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

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

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

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

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