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Why Oceans Hold Most Water

Interactive passage with audio narration, comprehension questions, and printable PDF.

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Format: Interactive (Online), Printable (PDF)
Grades: 5678
Subjects: scienceela
Standards: MS-ESS2-4
Languages: English, Spanish

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Reading passage

Reading comprehension

Audio narration

With word word highlighting

Comprehension quiz

Auto-graded

Writing activity

Open-ended response

Glossary & flashcards

Vocabulary practice

Differentiated version

Adapted for varied levels

Spanish translation

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About this reader

This comprehensive middle school science passage examines why oceans hold most of Earth's water, aligned with NGSS standard MS-ESS2-4 and Disciplinary Core Idea MS-ESS2.C. Students explore how oceans cover 71% of Earth's surface and average 12,000 feet deep, making ocean basins the lowest places on our planet. The passage explains the cause-and-effect relationship between gravity, topography, and water distribution, highlighting how the Pacific Ocean alone contains about half of all ocean water. Through audio-integrated content, students learn about salt accumulation over billions of years and understand Earth's hydrosphere. The passage includes differentiated versions for struggling readers and English Language Learners, Spanish translations, interactive vocabulary glossary, multiple-choice comprehension questions, writing activities, and graphic organizers. This resource helps students analyze and construct explanations for how water flows to the lowest elevations and why ocean basins serve as Earth's primary water reservoirs, supporting scientific literacy and NGSS science standards for grades 6-8.

Written by Workybooks TeamPublished by Workybooks

Sample passage and quiz content

CONTENT PREVIEW

A captivating view of ocean waves under a dramatic twilight sky, offering a peaceful seascape. — Oceans hold 97% of Earth's water because they occupy the lowest places on our planet. Image by Ricky Esquivel / Pexels.

Oceans hold 97% of Earth's water because they occupy the lowest places on our planet. Water naturally flows downhill due to gravity. Over billions of years, water has collected in ocean basins, which are huge depressions in Earth's crust. These basins cover 71% of Earth's surface and average about 12,000 feet deep.

The depth and size of ocean basins explain their enormous water capacity. Evidence shows that ocean basins formed through geological processes that created low areas in Earth's crust. When rain falls on land, rivers carry water downhill toward the ocean. This process has continued for billions of years. The Pacific Ocean alone holds about half of all ocean water because it is both wide and deep. Scientists observe that the Pacific basin extends across nearly one-third of Earth's surface.

Salt concentration in oceans developed over geological time through natural processes. Rivers dissolve minerals from rocks as they flow across land. These dissolved minerals, including salt, reach the ocean. Water evaporates from the ocean surface, but salt remains behind. This cycle has repeated for billions of years. The hydrosphere includes all water on Earth, but oceans contain most of it.

Understanding ocean water distribution helps scientists explain Earth's water cycle and climate patterns. Oceans store heat and influence weather systems across the planet. The vast amount of water in ocean basins affects sea level, coastal environments, and marine ecosystems. When scientists study climate change, they examine how ocean water temperatures and volumes may shift. Ocean basins serve as Earth's primary water reservoirs because gravity pulls water to the lowest elevations. The shape and depth of these basins determine how much water they can hold.

Interesting Fact: If you could drain all the water from the Pacific Ocean, the Mariana Trench would be visible as a canyon deeper than Mount Everest is tall—nearly 36,000 feet below sea level!

What percentage of Earth's water do oceans hold?

71%97%50%36%

Why does water collect in ocean basins?

Because ocean basins are the warmest places on EarthBecause gravity pulls water to the lowest places on EarthBecause ocean basins have the most saltBecause rivers push water into ocean basins

What percentage of Earth's surface do ocean basins cover?

50%97%71%36%

What does the term 'hydrosphere' mean in the passage?

Only the water in oceansAll water on EarthWater that evaporatesSalt water only

According to the passage, what is the term for large depressions in Earth's crust that hold ocean water?

River valleysOcean trenchesOcean basinsContinental shelves

Why does ocean water contain salt?

Salt falls from the sky with rainRivers dissolve minerals from rocks and carry them to the ocean, where water evaporates but salt remainsOcean animals produce saltSalt forms naturally in deep ocean water

Which ocean holds about half of all ocean water?

Atlantic OceanIndian OceanArctic OceanPacific Ocean

Based on the passage, what can scientists learn by studying ocean water distribution?

Only how deep ocean basins areEarth's water cycle, climate patterns, and how climate change may affect oceansOnly where rivers flowHow much salt is in the ocean

Ocean basins formed through geological processes over billions of years.

TrueFalse

When water evaporates from the ocean, salt also evaporates with it.

TrueFalse