Daily Junction.mobi portalScience · January 15, 2026 · Dr. Nadia Okoro · 4 min
Earthquakes happen when stress built up in the Earth's crust is suddenly released along faults. This guide explains plate tectonics, how magnitude is measured, and the safety steps that genuinely help.
An earthquake is the sudden shaking of the ground caused by the rapid release of energy stored in the Earth's crust. That energy builds up slowly over years or centuries as giant slabs of rock push against one another, and is let go in seconds when the rock finally slips.
An earthquake is a sudden release of energy within the Earth that creates seismic waves — vibrations that travel through the ground and make it shake. Most earthquakes are caused by the movement of rock along a fault, a fracture in the Earth's crust where two blocks of rock can move past each other.
To understand why faults slip, you have to start with the structure of the planet itself.
The Earth's rigid outer shell, called the lithosphere, is not one continuous piece. It is broken into about a dozen large pieces, plus many smaller ones, known as tectonic plates. These plates float on the hotter, slowly flowing rock of the mantle beneath, and they move — only a few centimetres a year, about as fast as your fingernails grow, but relentlessly.
Most earthquakes happen at or near the boundaries where plates meet. There are three main kinds of boundary:
At these boundaries, friction can lock the rock so the plates do not slide smoothly. Stress builds. When the stress exceeds the strength of the rock, it ruptures and slips suddenly — and that is an earthquake. The same slow plate movements that cause quakes also build mountains and drive volcanic activity.
Think of bending a wooden ruler. It resists, stores energy, then snaps all at once. The Earth's crust does something similar, on an enormous scale.
Two terms describe where a quake happens:
After a large earthquake, a sequence of smaller quakes called aftershocks often follows as the crust adjusts. These can continue for days, weeks or longer, and occasionally cause additional damage to already weakened buildings.
People often talk about earthquakes in terms of the "Richter scale", but seismologists today generally use the moment magnitude scale, which better captures the size of large quakes.
The crucial thing to understand is that magnitude is logarithmic. Each whole number up represents roughly:
| Magnitude | Typical effect |
|---|---|
| Below 2.0 | Not felt; recorded by instruments only |
| 2.0 to 3.9 | Often felt, rarely causes damage |
| 4.0 to 5.9 | Felt widely; can cause minor to moderate damage |
| 6.0 to 6.9 | Can be destructive in populated areas |
| 7.0 and above | Major earthquake; serious, widespread damage possible |
Magnitude is one number for the whole quake. Intensity, by contrast, describes how strongly shaking is felt at a specific place, and depends on distance from the epicentre, the depth of the focus, and local ground conditions — soft ground can amplify shaking considerably.
Not in the way people often hope. Scientists cannot reliably forecast the exact time, location and size of a future earthquake. What they can do is map fault zones, study past activity, and estimate the long-term probability of quakes in a region. This is enough to inform building codes, land-use planning and emergency preparedness, which save lives even without precise prediction.
Some areas also have early warning systems that detect the first, faster seismic waves and send alerts seconds before the stronger shaking arrives — a short window that can be enough to take cover or halt trains.
Preparation genuinely reduces harm. The internationally promoted advice for when shaking begins is:
Other sensible steps include securing heavy furniture to walls, knowing how to turn off utilities, keeping an emergency kit, and avoiding windows and exterior walls during a quake. Do not run outside while the ground is moving — most injuries come from falling objects.
Like other natural hazards, earthquakes are part of the larger story of how a dynamic planet behaves, a story that also includes the greenhouse effect and the deep-time processes behind evolution.
Earthquakes are caused by the sudden release of stress that builds up as the Earth's tectonic plates grind against one another, usually along faults near plate boundaries. Magnitude measures the energy released on a logarithmic scale, while intensity describes the shaking felt at a given spot. We cannot predict individual quakes, but plate tectonics explains where they cluster — and simple preparation, summed up as Drop, Cover and Hold On, makes a real difference. The forces involved are the same ones that shape continents and mountains, part of the broader study of how matter and gravity behave across the universe — from the ground beneath our feet to black holes in deep space.
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