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What Are Ocean Floor Maps — Reading Comprehension

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NGSS 4-ESS2-2

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This Grade 4 science reading passage introduces students to ocean floor maps and how scientists create them using sonar and satellites. Aligned with NGSS 4-ESS2-2, the passage explains that the ocean floor is not flat but contains dramatic features like underwater mountains, deep trenches, and flat plains. Students learn why we cannot see the ocean floor directly and how mapping technology helps scientists discover patterns in where these features are located. The passage uses simple, age-appropriate language to build foundational understanding of ocean floor topography and mapping techniques. Audio-integrated components support diverse learners. Activities include comprehension questions, writing prompts, and graphic organizers that help students organize information about ocean floor features and mapping methods. This resource is perfect for introducing earth science concepts related to ocean systems and helps students understand how technology enables scientific discovery.

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"(Manuscript painting of Heezen-Tharp World ocean floor map by Berann)" by Berann, Heinrich C., Heezen, Bruce C., Tharp, Marie. / Wikimedia Commons.

Ocean floor maps are special maps that show what the bottom of the ocean looks like. These maps are important because they help scientists understand the hidden world beneath the water. The ocean covers most of our planet, but we cannot see its bottom from the surface.

Scientists use tools called sonar and satellites to make ocean floor maps. Sonar works by sending sound waves down to the ocean floor. When the sound bounces back, it tells scientists how deep the water is and what shapes are on the bottom. This is similar to how you hear an echo in a canyon. Satellites in space also help by measuring tiny changes in the ocean's surface that show what lies below.

Ocean floor maps reveal amazing features underwater. There are tall underwater mountains called seamounts that rise from the ocean floor. Some are taller than mountains on land! Maps also show deep trenches, which are like giant canyons that drop far below the ocean floor. Between these features are flat plains that stretch for miles.

The ocean floor is not flat at all. It has features just as dramatic as those we see on land. Ocean floor maps help scientists find patterns in where trenches and underwater volcanoes are located. These patterns teach us about how Earth's surface changes over time.

Interesting Fact: The deepest part of the ocean is the Mariana Trench, which is almost 7 miles deep—deep enough to fit Mount Everest inside with room to spare!

What do ocean floor maps show?

What the bottom of the ocean looks likeWhere fish swim in the oceanHow warm the ocean water isWhere boats travel on the ocean

How does sonar help scientists map the ocean?

It takes pictures of the ocean floorIt sends sound waves that bounce backIt measures the temperature of waterIt collects rocks from the bottom

What are underwater mountains called?

Ocean peaksWater hillsSeamountsDeep trenches

Why can't we see the ocean floor directly?

It is covered by waterIt is too small to seeIt is always movingIt is covered by sand

What do patterns on ocean floor maps teach?

Where to catch the most fishHow Earth's surface changes over timeWhen ocean storms will happenHow deep ships can travel

What features are found on the ocean floor?

Mountains, trenches, and flat plainsOnly flat sand everywhereTrees and forests underwaterRoads and buildings