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9th grade Earth's early air and oceans worksheet

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Earth's early air and oceans

Grade 9 Science Worksheet

NameDate

Circle the best answer.

  1. Read this first

    Oxygen in the air over time (Smithsonian, NASA)

    TimeOxygen in the air
    before about 2.7 billion years agoalmost none
    about 2.4 billion years agofirst fills the air (NASA)
    about 600 million years agoabout one-fifth of today's level
    today21%

  2. Using the table, about how long after cyanobacteria began (about 2.7 billion years ago) did oxygen first fill the air (about 2.4), by Bo's math?

    • No time; it was instant
    • About 5.1 billion years
    • About 3 years
    • About 300 million years

  3. Why did oxygen take hundreds of millions of years to build up in the air, by Jun's reading (Smithsonian)?

    • The air already held plenty
    • Photosynthesis used up oxygen
    • It first reacted with methane and with iron in rocks
    • Volcanoes kept taking oxygen in

  4. Drawing of reddish rock layers. Smithsonian: after about 300 million years of oxygen-making, reddish redbeds formed. What do they show, by Kira's reading?

    • There was still no oxygen
    • Oxygen had built up enough to rust iron in rocks
    • Volcanoes were giving off oxygen
    • The rocks were heated by the Sun

  5. About when did the methane haze clear and the sky turn blue, by Luz's reading (Smithsonian)?

    • About two million years ago
    • About two billion years ago
    • It was blue from the start
    • At Earth's start

  6. Carbon dioxide + water + sunlight → sugar + oxygen. Cyanobacteria take in carbon dioxide and give off oxygen. How did they change the early air, by Milo's reading?

    • Less carbon dioxide, more oxygen
    • More carbon dioxide, less oxygen
    • No change
    • More methane from their breathing

  7. Today's air and a lifeless model. If volcanoes had kept adding gas but no life had made oxygen, what would Earth's air be like today, by Noah's reading?

    • Pure oxygen
    • Just like today's, 21% oxygen
    • No gases
    • Rich in carbon dioxide, with almost no oxygen

  8. Earth formed about 4.6 billion years ago, and its surface cooled enough for water about half a billion years later (Smithsonian). About when could oceans begin to collect, by Pia's math?

    • Right at 4.6 billion years ago
    • About 0.5 billion years ago
    • About 5.1 billion years ago
    • About 4.1 billion years ago

  9. 1% of today's level, then one-fifth (20%) of today's level. Oxygen rose from about 1% of today's level to about one-fifth of it. How many times larger is that, by Tala's math?

    • About 5 times
    • About 2 times
    • About 20 times
    • About 100 times

  10. NASA describes oxygen oases: patches where cyanobacteria made oxygen before it spread worldwide. What does this suggest, by Zee's reading?

    • Volcanoes made the patches
    • The patches took in oxygen
    • The whole air filled with oxygen at once, with no patches
    • Oxygen built up in patches first, then spread

  11. Oxygen in the air over time (Smithsonian, NASA)

    TimeOxygen in the air
    before about 2.7 billion years agoalmost none
    about 2.4 billion years agofirst fills the air (NASA)
    about 600 million years agoabout one-fifth of today's level
    today21%

  12. Earth is about 4.6 billion years old. For about what fraction of that time has its air held oxygen (since about 2.4 billion years ago), by Ari's math?

    • The whole time
    • About 2.4%
    • About one-tenth
    • About half
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9th grade Earth's early air and oceans worksheet – printable
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About this worksheet

Earth's early air and oceans. Every version has 10 questions, and the answer key prints on the second page.

What your child will learn

  • I can describe Earth's first air (volcanic gases, rich in carbon dioxide, no oxygen gas) and where the ocean water came from.
  • I can explain how cyanobacteria's photosynthesis raised oxygen, why it took hundreds of millions of years, and what redbeds show.
  • I can read the oxygen timeline and explain how greenhouse gases kept the young Earth warm under a dimmer Sun.

Standard: HS-ESS2-7

Words to know

outgassing: Gases released from inside Earth by volcanoes

cyanobacteria: Tiny photosynthesizing microbes that made the first oxygen gas

Great Oxidation Event: When oxygen first filled the air, about 2.4 billion years ago

redbeds: Rock layers reddened by iron oxide, a sign of oxygen

greenhouse gas: A gas that traps heat, such as carbon dioxide or methane

Common mistakes

Your child pictured early Earth's air with oxygen like today's. Smithsonian: the earliest air came mainly from volcanic gases, and there was no oxygen gas for a long time.

Your child named volcanoes as the oxygen source. Volcanoes gave water vapor and carbon dioxide; free oxygen came from photosynthesis by cyanobacteria (Smithsonian, NASA).

Your child reversed photosynthesis. It takes in carbon dioxide and water with sunlight and gives off oxygen.

Questions parents ask

What is the most common mistake with earth's early air and oceans?

Your child pictured early Earth's air with oxygen like today's. Smithsonian: the earliest air came mainly from volcanic gases, and there was no oxygen gas for a long time.

Are these 9th grade science worksheets free to print?

Yes. All 6 printable versions at each level are free to print, with the answer key, and no account is needed.

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