Earth's early air and oceans

Grade 9 Science Worksheet - Challenge Me

Circle the best answer.

1. 1.

   Four chain cards, labeled A to D. Which chain best explains the rise of oxygen, by Esme's reading?

   • A dimmer Sun froze the oceans solid, and the ice released oxygen
   • Volcanoes made oxygen, which built up at once
   • Photosynthesis took in oxygen and released carbon dioxide
   • Cyanobacteria made it, it reacted away at first, then built up
2. 2.

   Four evidence cards, labeled A to D. Which evidence suggests liquid water was present very early, by Jun's reading?

   • Volcanoes giving off oxygen
   • Today's oceans being salty
   • Oxygen gas found in the earliest air, as today
   • Ancient zircons show solid crust very early

3. 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%

4. 3.

   Why was the Great Oxidation Event one of the biggest changes to Earth's surface, by Kira's reading (NASA)?

   • It removed the oxygen that had been in the air and oceans
   • Oxygen filled the air and oceans for the first time
   • It made the first volcanoes
   • It happened in a single year
5. 4.

   Luz's friend says early Earth's air was just like today's, with plenty of oxygen. Which response is best (Smithsonian)?

   • Agree: air has stayed at 21% oxygen
   • Disagree: it had almost no oxygen until about 2.4 billion years ago
   • Disagree: it had more oxygen than today
   • Agree: volcanoes gave it oxygen
6. 5.

   a volcano giving off gas; cyanobacteria giving off oxygen. Milo's cousin says volcanoes put the oxygen into the air. Which response is best?

   • Agree: lava releases oxygen
   • Disagree: oxygen came from the Moon
   • Agree: volcanoes are full of oxygen
   • Disagree: volcanoes gave carbon dioxide; photosynthesis made the oxygen
7. 6.

   Noah's friend says a dimmer young Sun means Earth must have been frozen for its first billions of years. Which response is best (Smithsonian)?

   • Agree: Earth had no air to trap heat
   • Agree: a dimmer Sun means a frozen, icy Earth for billions of years
   • Disagree: the young Sun was brighter
   • Disagree: greenhouse gases kept Earth above freezing

8. Oxygen in the air (Smithsonian)

   Time	Oxygen
   about 350 million years ago	20%
   about 300 million years ago	up to 35%
   today	21%

9. 7.

   Smithsonian: oxygen was about 20% of the air 350 million years ago and rose to as much as 35%. About how many times today's 21% was that peak, by Pia's math?

   • About 1.7 times
   • About 14 times
   • About 0.6 times
   • About 35 times
10. 8.

    4.6 billion years = 24 hours, starting at midnight. On a 24-hour clock for Earth's 4.6 billion years, about what time of day would the Great Oxidation Event (2.4 billion years ago) fall, by Ren's math?

    • About 11:59 p.m., near the end
    • About 12:30 a.m., near the start
    • About 2:24 a.m.
    • About 11:30 a.m.
11. 9.

    An oxygen bar rising over time, with living things using oxygen. Why does the rise in oxygen matter for living things today, by Ari's reading (Smithsonian)?

    • Oxygen was here for them from the start
    • Volcanoes still make our oxygen
    • Living things like us make oxygen when we breathe out
    • Oxygen-using life grew out of the oxygen rise
12. 10.

    Four order cards, labeled A to D. Which order of events fits Earth's early history, by Bo's reading?

    • Oxygen air, then volcanoes, then oceans
    • Volcanic air, oceans, cyanobacteria, then the oxygen rise
    • Cyanobacteria, then oceans, then volcanic air
    • Oxygen rise, then cyanobacteria