Science · 6th Grade · Human Impact and Engineering · Weeks 28-36

Natural Hazards: Earthquakes and Tsunamis

Students investigate the causes and impacts of geological hazards.

• Common Core State Standards
• MS-ESS3-2

About This Topic

Earthquakes and tsunamis are among the most dramatic and destructive natural hazards on Earth, and they are directly linked through the mechanics of plate tectonics. An earthquake occurs when stress accumulated along a fault is suddenly released, sending seismic waves radiating outward from the focus. When a large earthquake occurs on an undersea fault -- particularly a subduction zone where one tectonic plate dives beneath another -- the sudden vertical displacement of the seafloor generates a tsunami: a series of long, fast-moving waves that can travel across entire ocean basins before rising to devastating heights near shore.

Severity is not determined by magnitude alone. A magnitude 7.0 earthquake beneath a densely populated city with unreinforced masonry construction can be far more deadly than a magnitude 8.0 in a remote area with earthquake-resistant buildings. Soil type matters: loose, water-saturated sediments can liquefy during shaking, causing buildings to sink and topple. Proximity to fault lines, depth of the earthquake, and directional focusing of seismic waves all contribute to the pattern of damage.

Active learning approaches -- analyzing seismograph data, mapping fault lines and vulnerable coastlines, evaluating real building codes -- give students the analytical tools to move from passive concern to informed understanding. This topic also connects naturally to how communities prepare for and respond to hazards.

Key Questions

1. Explain how earthquakes generate tsunamis.
2. Analyze the factors that determine the severity of earthquake damage.
3. Predict the areas most vulnerable to tsunamis based on geological features.

Learning Objectives

• Explain the relationship between undersea earthquakes and tsunami generation, citing specific plate tectonic processes.
• Analyze seismic wave data to identify earthquake characteristics (magnitude, depth, location) that increase tsunami risk.
• Evaluate the impact of geological features (e.g., seafloor topography, coastal shape) and soil conditions on tsunami wave height and earthquake damage.
• Predict areas most vulnerable to tsunamis by interpreting geological maps and historical data.
• Compare and contrast the damage caused by earthquakes and tsunamis, considering their distinct mechanisms and impacts.

Before You Start

Plate Tectonics and Earth's Structure

Why: Students need to understand the basic concepts of tectonic plates, their movement, and the layers of the Earth to grasp the mechanisms behind earthquakes and tsunami generation.

Types of Waves and Energy Transfer

Why: Understanding that waves transfer energy is fundamental to comprehending how seismic waves travel and how tsunamis propagate across oceans.

Key Vocabulary

Subduction Zone	An area where one tectonic plate slides beneath another, often causing powerful earthquakes and volcanic activity.
Seismic Waves	Vibrations that travel through Earth's layers, originating from the point of an earthquake's rupture.
Tsunami	A series of large ocean waves caused by sudden displacement of water, typically triggered by undersea earthquakes or volcanic eruptions.
Liquefaction	The process where water-saturated soil temporarily loses strength and acts like a liquid during intense shaking, causing structures to sink or tilt.
Fault Line	A fracture or zone of fractures between two blocks of rock, where the blocks move relative to each other.

Watch Out for These Misconceptions

Common Misconception

The strongest earthquakes cause the most deaths.

What to Teach Instead

Building quality, population density, soil conditions, time of day, and emergency preparedness often matter more than magnitude. The 2010 Haiti earthquake (M7.0) killed over 200,000 people; a similarly sized earthquake in California in the same year would likely have caused far fewer deaths due to stricter building codes and better infrastructure.

Common Misconception

You can outrun or escape a tsunami by swimming or retreating to a boat.

What to Teach Instead

Tsunamis in open ocean travel at jet-aircraft speeds (500-800 mph) and are nearly imperceptible on the open sea. Near shore, the wave slows but rises dramatically in height. Survival depends on moving to high ground immediately after ground shaking stops, not on swimming or boats. No warning system is fast enough to allow outrunning a locally generated tsunami.

Common Misconception

Earthquakes only happen in certain well-known places like California and Japan.

What to Teach Instead

While the most seismically active zones follow tectonic plate boundaries, intraplate earthquakes occur throughout the interior of continents. The New Madrid Seismic Zone in the central US has produced some of the largest historical earthquakes in North America, and Charleston, South Carolina experienced a major earthquake in 1886.

Active Learning Ideas

Data Analysis: Mapping Earthquake and Tsunami Risk

Provide students with world maps showing tectonic plate boundaries and historical earthquake epicenters. Students overlay tsunami runup data from NOAA's database for three to four major events (e.g., 2004 Indian Ocean, 2011 Japan, 1964 Alaska). Groups identify patterns in where tsunamis originate and which coastlines are most vulnerable based on geography.

35 min·Small Groups

Simulation Game: Building for Seismic Resistance

Using spaghetti, marshmallows, and index cards, student teams build structures of a specified height, then test them on a simulated shake table (a tray of jello or a board on wheels that is pushed side to side). Teams record the mode of failure, modify their designs, and test again. Debrief connects design features to real seismic engineering principles like base isolation and moment frames.

50 min·Small Groups

Think-Pair-Share: Earthquake Damage Factors

Present three brief scenarios: a M6.5 earthquake in the Tokyo metropolitan area, a M7.8 in a rural Himalayan village, and a M8.2 offshore of a well-prepared Pacific coast city. Ask: Which would likely cause the most deaths and why? Pairs discuss, then share reasoning with the class, drawing out the role of building quality, population density, preparedness, and soil type.

20 min·Pairs

Real-World Connections

• Seismologists at the Pacific Tsunami Warning Center analyze real-time seismic data from networks of sensors across the Pacific Ocean to issue timely tsunami warnings for coastal communities in Hawaii, California, and beyond.
• Civil engineers in Japan, a country highly susceptible to earthquakes and tsunamis, design earthquake-resistant buildings and coastal defenses like seawalls and breakwaters based on detailed geological surveys and historical hazard data.
• Emergency management agencies in coastal states like Oregon and Washington develop evacuation plans and conduct drills for residents living in tsunami inundation zones, using maps that show predicted wave arrival times and run-up heights.

Assessment Ideas

Exit Ticket

Provide students with a scenario: 'An M8.0 earthquake occurred on an undersea fault near a coastal city with loose soil and steep cliffs.' Ask students to write two sentences explaining how this earthquake could cause a tsunami and one factor that might affect the tsunami's impact on the city.

Quick Check

Display a map showing several coastal areas with different geological features (e.g., wide continental shelf, narrow shelf, volcanic islands). Ask students to label two areas as 'High Tsunami Vulnerability' and 'Low Tsunami Vulnerability,' justifying their choices with one sentence each.

Discussion Prompt

Facilitate a class discussion using the prompt: 'Imagine you are advising a town council on a coast prone to both earthquakes and tsunamis. What are the top three most important factors they should consider when planning for these hazards, and why?'

Frequently Asked Questions

How do earthquakes generate tsunamis?

When a large earthquake occurs on an undersea fault (particularly at a subduction zone), the sudden vertical movement of the seafloor displaces an enormous column of water. This displacement creates a series of long waves that radiate outward in all directions. In the open ocean these waves may be only a meter high but travel at hundreds of miles per hour; as they approach shallow water they slow, compress, and rise to heights of tens of meters.

What factors determine how much damage an earthquake causes?

Earthquake damage depends on magnitude, depth, distance from population centers, local soil conditions, building construction quality, and time of day. Loose, saturated sediments can amplify shaking and liquefy. Unreinforced masonry buildings collapse far more readily than wood-frame or engineered steel structures. A moderate earthquake in a dense city with poor building codes can be far more deadly than a larger earthquake in a well-prepared region.

Which areas are most vulnerable to tsunamis?

Low-lying coastal areas near active subduction zones face the highest tsunami risk: the Pacific Rim (Japan, Alaska, the Pacific Northwest, Chile), the Indian Ocean coastlines, and the Caribbean. Within those regions, shallow-sloping coastlines with wide continental shelves and coastal valleys facing the tsunami source experience the greatest wave heights and inland flooding.

How does active learning help students understand earthquake and tsunami hazards?

Building and shake-testing model structures makes seismic engineering principles tangible -- students see why triangular bracing and flexible materials outperform rigid, heavy designs. Mapping historical tsunami events and damage patterns develops geographic reasoning and pattern recognition. These active approaches move students from passive concern to analytical thinking about what determines risk and how humans reduce it.