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Rising Sea Levels — Reading Comprehension

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MS-ESS3-5

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This science passage, written for grades 6-8, explores the phenomenon of rising sea levels, a key topic aligned with NGSS standard MS-ESS3-5. Students will learn about the scientific evidence and mechanisms behind rising sea levels, including thermal expansion and melting land ice, and how these factors interact with Earth's systems. The passage presents real-world examples, such as the impact on cities like Miami and river deltas in Bangladesh, and explains consequences like coastal flooding, storm surge, and saltwater intrusion. It emphasizes scientific thinking by describing how scientists measure and study sea level change, and connects the topic to broader environmental and societal issues. Audio integration supports diverse learners. This resource is suitable for use in physical science, earth science, and environmental science units, and includes interactive activities, a glossary, and graphic organizers to deepen understanding.

CONTENT PREVIEW

"NASA-Satellite-sea-level-rise-observations" by NASA / Wikimedia Commons (Public domain).

Sea level is the average height of the ocean's surface, measured around the world. Over the past 140 years, global sea level has risen about 8 to 9 inches (20 to 23 centimeters), and the pace is getting faster. This change is a clear sign of how Earth's systems are affected by climate. Rising sea levels threaten millions of people, especially those living near coasts, on islands, or in low-lying cities. Scientists study this problem to understand its causes, impacts, and what can be done.

Why Are Sea Levels Rising?
There are two main reasons for rising sea levels. The first is thermal expansion. As the planet warms, ocean water absorbs heat and expands, which means the same amount of water takes up more space. This process has contributed to about half of the observed rise. The second cause is the melting of land ice, like glaciers and ice sheets in places such as Greenland and Antarctica. When this ice melts, the water flows into the ocean, increasing its volume. Scientists use satellites and tide gauges to measure these changes, confirming that the rate of sea level rise is now much faster than it was a century ago.

Impacts on Coastal Areas
Rising sea levels do not affect every place equally. Some regions, like the U.S. Gulf Coast and Southeast Asia, see water rise faster because of local factors. For example, land subsidence—where land sinks due to natural or human causes—can make the problem worse. Ocean currents and wind patterns also influence local sea levels. As seas rise, coastal flooding happens more often, especially during storms or king tides. Saltwater can move into freshwater aquifers, threatening drinking water and crops. Coastal erosion increases, and valuable land is lost. Vulnerable places include low-lying islands like the Maldives and Tuvalu, coastal cities such as Miami and New Orleans, and river deltas in Bangladesh and Vietnam. Already, some communities are relocating as their homes become unsafe.

Looking to the Future
Future sea level rise depends on how much greenhouse gas humans release and how fast ice sheets melt. Projections suggest global sea level could rise by 1 to 8 feet (0.3 to 2.5 meters) by 2100. Even small increases can make storm surges worse and cause more frequent flooding. Scientists use computer models to predict these changes and help governments plan. Adapting to sea level rise may involve building sea walls, restoring wetlands, or moving entire neighborhoods. Understanding the connections between climate, the ocean, and human activities is key to making smart choices for the future.

Rising sea levels highlight how Earth's systems interact and why monitoring environmental changes is essential for protecting people and ecosystems.

Interesting Fact:
About two-thirds of the world's largest cities are located near coasts, putting hundreds of millions of people at risk from rising seas.

How much has global sea level risen since 1880?

About 8 to 9 inches (20 to 23 centimeters)About 2 to 3 inches (5 to 8 centimeters)About 15 to 20 inches (38 to 51 centimeters)About 1 foot (30 centimeters)

What are the two main causes of rising sea levels mentioned in the passage?

Thermal expansion and melting land iceEvaporation and rainfallEarthquakes and volcanoesWind and tides

Which tool do scientists use to measure changes in sea level?

SatellitesThermometersBarometersSeismographs

What does 'thermal expansion' mean as used in the passage?

Water takes up more space as it gets warmerWater freezes at low temperaturesIce melts into liquid waterLand expands when it is heated

What is meant by 'land subsidence'?

The sinking of the ground’s surfaceMelting of polar iceMovement of ocean currentsIncrease in rainfall

Why do some areas experience faster sea level rise than others?

Because of local factors like land sinking and ocean currentsBecause of more rainfallBecause of mountain buildingBecause of higher wind speeds

If greenhouse gas emissions continue to rise, what could happen by 2100?

Sea level could rise 1 to 8 feet worldwideGlaciers will stop meltingOcean water will cool downThere will be fewer storms