What makes the Earth shake?

Scientists investigate Earth's interior by studying seismic waves

Scientists investigate Earth's interior by studying seismic wavesBelow Earth's atmosphere lies the crust, which extends to the Mohorovičić discontinuity between five and 20 miles below Earth's surface. Below the crust lies the mantle, the liquid-metal outer core, and the solid inner core, which surpasses 5,200 degrees Celsius (9,392 degrees Fahrenheit).

Visualize the power and frequency of earthquake magnitudes

About 150 medium earthquakes—magnitude 6.0—occur every year, resulting in moderate shaking and some property damage. While millions of earthquakes below category 2.0 occur yearly, fewer than one of category 9.0 or higher occurs on average.

Earthquake early warning systems do not predict earthquakes

Systems like ShakeAlert® use a network of hundreds of ground sensors to detect earthquakes moments after they begin. Since seismic waves travel about 5 km/s, individuals may be notified of earthquakes before they feel the seismic activity has reached them.

Tectonic earthquakes are caused by interactions of tectonic plates at fault zones

At these locations, plates slide past one another, deforming rock through friction as energy builds like a stretched rubber band. Volcanic eruptions, the collapse of subterranean caverns, or underground nuclear explosions can also cause earthquakes.

How NASA measures marsquakes

Most probes sent to other planets and asteroids focus on surface phenomena, but NASA's InSight Lander is interested in looking deeper. Studying marsquakes as well as the red planet's crust and core, InSight provided four years of insight into how the rocky planets of the inner solar system formed.

Geological tremors on the moon provide evidence that it is shrinking

Apollo seismometers have collected moonquake data, which scientists have analyzed to map the moon's interior and reveal that fault slips producing tremors are the result of sublunar cooling and contraction. It also revealed that the moon's inner core is about 500 kilometers (311 miles) across.

Explaining why the Earth wobbles

Astronomers going back to Hipparchus in the 2nd century BCE have noticed our planet has a distinct wobble. More recently, scientists have observed that the Earth is 26 miles wider at the equator than from pole to pole. The wobble results from our...

Variations in rock types contribute to uncertainty in earthquake predictions

Different rock types can withstand different amounts of stress before breaking and melt at different temperatures within Earth’s interior, preventing uniform modeling. The planet’s uneven mass distribution also creates variations in gravitational force, complicating mantle movement.

An 800-ton shake table is the world's largest earthquake simulator

After the 1995 Kobe earthquake killed over 6,000 people, Japan created E-Defense to reproduce the force of earthquakes and test them against structures as tall as 10 stories, leading to changes in Japanese building codes to reduce collapse rates.

The Richter scale was only intended to quantify Southern California earthquakes

The scale, designed to rate the energy of the largest seismic waves released by an earthquake, was calibrated to the region’s crust and mantle properties. Since the 1970s, seismologists have instead used the moment magnitude scale, which considers all waves of released energy.

Why starquakes may explain various phenomena associated with neutron stars

Fast radio bursts—repeated millisecond-long pulses of enormous energy from neutron stars—are emitted with a timing that resembles the earthquakes and aftershocks seen on Earth when geological activity releases energy from within the planet. Although pulsars should gradually spin more slowly as they lose energy from emitting jets of radiation, sudden increases may result from interior matter moving during starquakes.

Learn how the Earth was made

Four and a half billion years ago the Earth formed from dust in space to become a molten ball of rock orbiting the sun. Travel back in time to investigate how the Earth was made.

200 million years of tectonic plate movement

The Earth's internal forces have continuously pushed and reshaped how the planet's land masses are arranged. From one supercontinent hundreds of millions of years ago, to present day, the Earth has looked dramatically different throughout the...

The earliest earthquake detection device involved eight ball-wielding dragons

Invented in China in 132 CE, the seismoscope was an urn with dragons facing different directions. If an earthquake occurred, the dragon facing the direction of the tremor released its ball. Like modern seismographs, its mechanism may have involved a suspended weight.

Discover trends in Earth's climate system: What are indicators of climate change?

A comprehensive deep dive tracking components of the climate system over time, such as temperature, sea level, sea ice amounts, ocean heat, greenhouse gases, and more (w/charts and graphs).

What is gravity made of?

Our world at very small scales is governed by quantum mechanics, in which forces and energy come in discrete packets. At large scales, our world is governed by gravity, which moves the planets and stars and can create waves in spacetime. To merge...

Earth is constantly bombarded by material from space

Most of this matter is composed of small particles, with any smaller than 33 feet in diameter burning up in the atmosphere. Larger asteroids can reach the ground, and those larger than several thousand feet cause global damage, including earthquakes and tsunamis.

Ten impact craters you can visit

See photos of ten wild Earth impact craters across the world, the result of impacts occurring between thousands and millions of years ago.

Tree rings can reveal centuries of environmental change and natural events

The width and shape of tree rings reflect yearly growth conditions like rainfall or snowfall. Scars in the rings can record disruptions such as fires, avalanches, or earthquakes, explaining when and how those events occurred.

The ingredients that make up severe weather

A seven-minute video illustrating how a storm is made. These factors—moisture, instability, lift, and shear—are explained through a series of data sets and creative, descriptive diagrams.

The word 'Earth' comes from the German root word for 'ground'

In English, "Earth" means the planet and the land, but many languages identify each with distinct words. Earth is often given a maternal name or one that identifies it as the land of the living.

How do archaeologists know where to dig?

Archaeologists spend their days slowly uncovering buried artifacts, but how do they know where to look in the first place? New tech and old-fashioned shoe leather. Watch this five-minute video to learn more.

The European Space Agency's Euclid telescope maps dark matter

As light rays travel near massive objects in space, their paths can be distorted on their way to Earth, causing objects to appear displaced, magnified, shrunken, or sheared. By simulating these effects for various mass distributions, astronomers can match the distortion to a simulated mass and compare it with the observed visible matter to infer the presence of dark matter.

Stars appear to twinkle because turbulence in the motion of molecules in Earth's atmosphere causes light to bend and wiggle rapidly on its way to the surface—a phenomenon called scintillation.

The mass of a cell can be measured using hollow, vibrating beams

In 2010, scientists at MIT constructed a U-shaped device that vibrates like a guitar string with an internal fluid channel. As cells and bacteria pass through the device, its rate of vibration shifts, with greater mass creating larger shifts.

What Stonehenge sounded like

Researchers built the first scale model of the world's best-known prehistoric stone circle, Stonehenge, to study its acoustic properties. Built approximately 5,000 years ago, the landmark in southern England has puzzled historians for centuries, but...

Scientists can determine Earth's past climate conditions by analyzing air trapped in microscopic bubbles within ice cores—columns of compressed snow layers that build up over hundreds of thousands of years.

Volcanoes 'die' when their supply of magma runs out, if they are shifted away from their underlying magma reservoir, or if they get clogged by collapsing or their magma cooling back into rock.

Learn how your body is, scientifically, like a firework with its own slow, controlled burn.

After NASA's Voyager 1 captured Earth as a single pixel as it left the solar system in 1990, astronomer Carl Sagan used the image to reflect on humanity's fragility and the responsibility to protect 'the only world we've ever known.'

While the sun's gravity keeps the planets in orbit, their gravity also pulls on the sun, causing it and everything else in the solar system to orbit around a mutual balance point called the barycenter—the true center of the solar system.

Visualize the path of every solar eclipse from 1900 to 2099 and see what each looks like when observed from different locations on Earth.

Explore an interactive map built from more than 100,000 survey responses on where people find joy in their lives

Explore chaos in this simulation of two double pendulums, where small differences in the release angles produce wildly different outcomes.

Waves off the coast of Nazaré, Portugal, can reach over 100 feet and are caused by the area's deep underwater canyon geography

As of 2025, the most cited papers in science include a review of graphene, methods to improve image recognition, streamlining electron density calculations, and optimizing protein studies.

Discover the catastrophic consequences of a failure of the US electrical grid—something that is more likely than many Americans think.

Watch how deep-sea mining equipment collects and processes polymetallic nodules—metal-rich, potato-shaped rocks—from the ocean floor and creates environmentally damaging plumes of sediments.

Corals are themselves not coral reefs—the term refers to the tiny marine invertebrates that build the rigid reef.

Explore the history, structure, and species of Australia's Great Barrier Reef with this interactive journey narrated by Sir David Attenborough.

The name 'Silicon Valley' arose from the founding of Shockley Semiconductor Laboratory in Fairchild Semiconductor in 1956-57, founded near Stanford University in Palo Alto

While atoms are normally made of protons, neutrons, and electrons, exotic ones have been built with antimatter—alternate versions of normal matter that live for fractions of a second and are about a billion times as rare.

Fear or disgust related to clusters of holes and cracks, called trypophobia, may stem from evolutionary processes to help us avoid pathogens.

Massive 3D printers have been used to build homes by stacking layers of 'concrete toothpaste,' a fire-resistant material that effectively insulates against outside noise.

See a 3D reconstruction of Tenochtitlan, the Aztec capital that was home to an estimated population of 200,000 to 400,000.

While El Niño moves warm Pacific Ocean waters east along the equator, La Niña moves them west, shifting where rainfall will become more common for months.

The first steps to rebuilding your credit score include getting to know exactly what's on your credit report and figuring out how far you are from the '700 club,' or 'good score' range.

Learn how to read a prospectus, the juicy document that any company must file with the SEC before going public.

Exploring the Larry Bird punch that almost changed March Madness

Scientists have struggled to pin down Ebola's natural reservoir species for decades, but the available evidence suggests that it's very likely fruit and insect-eating bats found in Africa.