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What Causes Earthquakes? — Reading Comprehension

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MS-ESS2-2
MS-ESS3-2

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This middle school science passage explains what causes earthquakes, focusing on the interactions between tectonic plates and the elastic rebound theory. Students will learn how stress builds in rocks, how energy is released, and why earthquakes often occur at plate boundaries. The passage covers key vocabulary such as fault, epicenter, and seismic waves, and includes real-world examples and data. Activities and graphic organizers help deepen understanding. The content aligns with NGSS standards MS-ESS2-2 and MS-ESS3-2, supporting learning about Earth's systems and natural hazards. Audio integration makes the material accessible to all learners. This resource is ideal for grades 6-8 science classes, especially for teaching about earth science, plate tectonics, and natural disasters.

CONTENT PREVIEW

earthquakes-2 — What Causes Earthquakes?

Earthquakes are powerful natural events that shake the ground, damage buildings, and change landscapes. Understanding what causes earthquakes is important for predicting their effects and protecting people. Earthquakes are not random; they are the result of complex processes deep within the Earth. Scientists study earthquakes to learn more about the planet’s inner workings and to develop safer building methods.

Earthquake Mechanics and the Elastic Rebound Theory

Most earthquakes happen because of the movement of tectonic plates, which are massive slabs of rock that make up the Earth’s outer shell. These plates are always moving, though usually at rates of just a few centimeters per year. As plates move, they sometimes get stuck along cracks in the Earth called faults. Over time, stress builds up because the plates cannot slide past each other smoothly. When the stress exceeds the strength of the rocks, the rocks suddenly snap back to their original shape. This sudden release of energy is described by the elastic rebound theory. The energy is released as seismic waves that travel through the ground and cause the shaking we feel during an earthquake.

Focus, Epicenter, and Plate Boundaries

The point inside the Earth where the rock first breaks is called the focus (or hypocenter). The spot on the surface directly above the focus is known as the epicenter. Most earthquakes occur at plate boundaries—places where two plates meet. There are three main types of plate boundaries: divergent (plates move apart), convergent (plates move toward each other), and transform (plates slide past each other). Each type of boundary produces different kinds of earthquakes. For example, the San Andreas Fault in California is a well-known transform boundary where many earthquakes occur.

Earthquake Sequences and Exceptions

Earthquakes often occur in a sequence: small foreshocks may come before the main event, called the main shock, followed by aftershocks that can continue for days or weeks. While most earthquakes happen at plate boundaries, some can occur within plates if there are old faults in the crust. For example, the 1811–1812 New Madrid earthquakes in the central United States happened far from any plate boundary.

Studying patterns of earthquakes helps scientists identify high-risk areas and improve building codes. This knowledge also aids in designing early warning systems that give people a few seconds to take cover. Earthquakes demonstrate how the Earth is a dynamic system, always changing due to forces beneath the surface.

Interesting Fact: The strongest earthquake ever recorded was a magnitude 9.5 event in Chile in 1960, releasing energy equivalent to about 20,000 atomic bombs.

What is the main cause of most earthquakes?

Movement of tectonic platesVolcano eruptionsHeavy rainfallWind erosion

What is a fault?

A crack in Earth's crust where rocks moveA type of seismic waveA type of tectonic plateAn earthquake warning system

Which term describes the point underground where an earthquake starts?

EpicenterFocusPlate boundaryAftershock

What is the elastic rebound theory?

The idea that rocks bend and then suddenly snap back, causing earthquakesA way to measure the size of a fault lineA method for building earthquake-resistant buildingsThe process of plates moving apart at divergent boundaries

What are seismic waves?

Waves of energy that travel through the ground during an earthquakeCurrents in the ocean caused by windHigh winds during stormsClouds forming after an earthquake

What usually happens after the main shock of an earthquake?

Aftershocks can occurTectonic plates meltA volcano erupts immediatelyAll faults close up

Where do most earthquakes occur?

At plate boundariesAt the center of tectonic plates onlyOn mountain tops onlyIn the middle of the ocean only

Which of the following is TRUE based on the passage?

Earthquakes can happen inside plates if there are old faults.All earthquakes are caused by volcanic eruptions.

The epicenter of an earthquake is always underground. (True/False)

TrueFalse

Foreshocks are small earthquakes that come before the main shock. (True/False)

TrueFalse