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)?

   • Gases from volcanoes
   • Rain from the oceans
   • Air left over from the Sun's surface
   • 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)?

   • Carbon dioxide
   • Water vapor
   • Methane
   • Oxygen gas
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)?

   • No carbon dioxide
   • One-tenth of today's
   • Ten to 200 times as much as today
   • About the same as today
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 million 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
5. 5.

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

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

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

   • Oxygen from cyanobacteria
   • Melting of the iron core
   • The Sun's light turning into water
   • Volcanic water vapor and ice from impacting bodies
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 made the oxygen in the air as it melted
   • It formed Earth's iron core
   • It melted and helped make the oceans
   • It froze Earth solid

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 billion years ago
   • About 4.6 billion years ago, from the start
   • 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 1%
    • About 21%
    • About 100%
    • About 78%
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
    • Oxygen in the air kept it warm
    • The Sun was brighter than today