An earthquake is the literal name of the phenomenon of the surface of the earth-shaking due to seismic activity happening beneath the crust! These seismic waves, created by the Earth’s lithosphere (upper crust and mantle), cause the various tectonic plates that make up the uppermost part of the Earth to shudder, which, in turn, makes the ground we stand on begin to shake violently. Of course, there are various levels for earthquakes and other circumstances required. Still, earthquakes are known for being massive destructive forces that have wreaked havoc upon countless countries, islands, cities, and even the moon!
Earthquakes are important phenomena to study to help prevent the disastrous fallout they can create. But how do earthquakes happen in detail? And what more is there to learn about them? So come along with us to learn about these earthquake facts for kids!
What causes earthquakes?
To answer that, we must look at what’s happening beneath the Earth’s surface! The Earth comprises four main layers: crust, mantle, outer core, and inner core. Together, the crust and mantle form the Earth’s lithosphere, which acts as a solid outer shell. This shell isn’t one continuous smooth surface, like an eggshell; it’s more akin to an enormous rocky jigsaw puzzle in which some pieces span entire countries and continents. Below the lithosphere is the outer core, a hot metallic liquid made up of mostly nickel and iron. And at the center of the Earth, nearly 2000 miles below the surface, lies the inner core, a dense, molten ball of compacted iron, the temperature of which is believed to be around 9,000 °Fahrenheit.
So, how do earthquakes occur? Well, it’s all about how those different parts of the lithosphere interact with one another. Known as tectonic plates, these huge pieces of rock are constantly changing positions due to movement in the mantle below and the planet’s steady rotation. The constant motion of tectonic plates can cause cracks, known as faults, in the Earth’s crust. Earthquakes occur when the crust moves suddenly on or near one of these fault lines.
How long do earthquakes last?
Most earthquakes typically last for a few seconds, usually 10-30 seconds. It is assumed that a larger earthquake than we have ever experienced may last minutes at a time, but for the most part, earthquakes typically last about half a minute or less! This may feel like a lifetime if you find yourself caught in the center of one, but know that it will soon end faster than you expect! After the earthquake, the ground may still tremor for a few more hours, days, or years. These shudders are called aftershocks!
What is an aftershock?
Aftershocks or aftershock earthquakes are the after-effects of past earthquakes. These slight tremors can last for years and are, in reality, the earth’s mantle trying to realign itself after the small fault or crack that caused the initial quake. These aftershocks will never be as extreme as the earthquake that caused them, but they can still be devastating if left unexpected.
Types of Earthquakes
Like most scientific worlds, earthquakes are often categorized by specific types and levels. For example, you can experience the strongest earthquake, anything above 8.0 magnitude. At this level, the earth shakes violently, and communities near the center of the earthquake’s origin will most likely be destroyed. Usually, though, people will experience a magnitude of 5.4 and lower.
As for types, there are four in particular that you can usually classify earthquake as volcanic, tectonic, collapse, and explosion.
- Volcanic: Perhaps the most self-explanatory earthquake type, the Volcanic Earthquake usually occurs in tandem with volcanic activity. When a volcano starts erupting, the ground shakes, and there is your volcanic earthquake!
- Tectonic: Tectonic Earthquakes occur thanks to the tectonic plates, which may move and scrape against each other to create the tremors we feel on the crust. These geological forces make them the most common types of earthquakes in places that sit upon many tectonic fault lines, like California!
- Collapse: Unlike volcanic and tectonic earthquakes, Collapse Earthquakes occur underground, in caves and mines. These earthquakes are usually small tremors produced by the explosion or spill of rocks on the surface.
- Explosion: The final earthquake type is the Explosion Earthquake, which occurs when usually human-made bombs. The detonations cause an earthquake effect.
Most Famous Earthquakes
Earthquakes are devastating natural events that can destroy the areas they affect. Here is a list of some of the most powerful and destructive earthquakes throughout history:
- Knossos, Crete, Greece, c. 1500 B.C.E
The first earthquake on this list dates back to Ancient Greece. As this earthquake was so long ago, there is no exact recording of its magnitude or intensity. Still, it is known to be one of several events that completely leveled the capital of the Minoan civilization.
- Pompeii and Herculaneum, Italy, 62 C.E.
Jumping forward a few years to Ancient Italy, these two important Italian cities were struck by the same earthquake in 62 C.E. This earthquake was so devastating that neither Pompeii nor Herculaneum had recovered from its aftermath by the time Mount Vesuvius erupted in 79 C.E.
- Shaanxi province, China, 1556
This devastating earthquake that hit China back in the mid-1500s is widely regarded as the deadliest earthquake of all time. The quake caused 830,000 deaths and destroyed the Shaanxi province.
- Port Royal, Jamaica, 1692
Before the earthquake that struck this very famous British West Indies port in 1692, Port Royal was a popular haven amongst pirates and slave traders. When the quake struck, however, 2,000 people were killed, and the entire port was pretty much submerged beneath the sea.
- Lisbon, Portugal, 1755
The earthquake that struck Lisbon in 1755 was not restricted to this city. This deadly earthquake was felt as far away as Algiers and triggered a tsunami that reached the Caribbean. The total amount of deaths caused by this earthquake was recorded as 62,000.
- Charleston, South Carolina, U.S., 1886
This earthquake was one of the largest quakes ever to hit the eastern United States. The total amount of deaths recorded for this earthquake was 60.
- Gansu province, China, 1920
While the earthquake that hit the Gansu province in the early 1900s was severe, the majority of the deaths surrounding it were caused by the massive landslides that followed. In total, there are 200,000 deaths associated with this earthquake and the following events it triggered.
- Assam, India, 1950
The massive earthquake that hit Assam in 1950 was the largest quake ever recorded in South Asia. However, despite its size, the death toll from the earthquake was relatively small, with only 574 people losing their lives. This is largely because this region along the Indo-Chinese border is sparsely populated.
- Kathmandu, Nepal, 2015
In more recent years, the earthquake that hit Nepal in 2015 measured 7.9 on the Richter Scale and killed 9,000 people. Two similarly devastating aftershocks closely followed this quake, each coming in at 6.6 and 6.7 on the Richter Scale.
How are earthquakes measured?
Earthquakes are measured by scientists using seismographs or seismometers. They measure the earthquake’s size and intensity. These specialist devices measure an earthquake’s strength by picking up vibrations and movement — the seismic waves — in the Earth’s surface. Seismologists (those who study earthquakes) use the Richter Scale to measure the earthquake’s strength. The Richter scoring system runs from one through 10, with one representing a minor tremor and 10 indicating an extremely severe earthquake. The worst earthquake ever recorded was a 9.5 on the Richter scale — earthquakes of this size aren’t as common as the smaller ones (which are often not even felt by people on the ground) but can cause massive amounts of destruction.
Today, scientists measure earthquakes using the Moment Magnitude Scale, which is more accurate than the Richter scale when measuring large earthquakes.
Did you know seismology comes from the Greek “seismos,” meaning earthquake? The awe-inspiring nature of earthquakes implies that you’ll often hear people use the word “seismic” to describe sudden and significant events that have a big impact on our lives, like the outbreak of war or political unrest.
What was the biggest earthquake in history?
The most powerful earthquake ever recorded struck Valdivia, Chile, just after 3 p.m. on May 22, 1960. It left two million people homeless and killed over 1600. In addition, the Valdivia earthquake set off a tsunami that was so strong it reached the coast of New Zealand around 5000 miles away.
Where do earthquakes usually occur?
Earthquakes can happen anywhere in the world, and there are earthquakes every single day; we don’t feel them usually. The places where you will most certainly experience a major quake more than once would be places along fault lines. Fault lines are generally the edge of the tectonic plates and occur when different plates grind against each other. This movement beneath the earth’s surface is what we know as an earthquake, so fault lines, in particular, tend to generate much more obvious quakes than the center of a tectonic plate might.
There are three known types of faults: normal, reverse, and strike-slip. Normal faults occur when one tectonic plate’s wall moves upwards while the other moves downwards, causing tremors on the surface and developing the mark. Reverse faults form when the Earth’s crust receives significant pressure. This compression causes rocks and tectonic walls to slip underneath one another, creating tremors and responsibility! Finally, the strike-slip mark is formed when two sides of plates or the crust slide past one another, causing a fault and an earthquake. Strike-slip defects are most commonly found in California!
Speaking of California, because of its placement on top of various fault lines, it is perhaps one of the most earthquake-stricken states in the United States!
How to Stay Safe During an Earthquake
There are many ways to protect yourself during an earthquake, though many of them are chalked up to one major tip that everyone who lives in a place where earthquakes are frequent has: always have an earthquake plan! An earthquake plan is a plan developed by a family to ensure they will always be safe during a possible earthquake. Most earthquake plans involve a meeting place after the quake settles, numbers to call in case people get separated, a few to-go backpacks filled with nonperishable foods, water, and more, and reminders of earthquake safety basics!
But what are those safety tip basics? Well, most West Coast natives may be well aware of them, but for those who aren’t, here are five safety tips that will save you from unnecessary danger during a quake!
Five Tips for Earthquake Safety
- Drop, Cover, and Hold on! These three words are the basis for any earthquake safety tips. The general conceit is if you find yourself dealing with an earthquake, you should drop to your hands and knees, cover your head and neck (either beneath a sturdy table or with your arms) and hold on to something that won’t move around with the earthquake. This simple action will protect your head and neck from unnecessary damage and keep your body from being thrown around by the tremors!
- Hide under tables. While in the past, many may have suggested hiding beneath a doorway, modern houses do not often account for making stronger doorways like in the past. A sturdy table is much safer to hide beneath and can protect you from falling debris.
- If you are outside, stay outside. If you find yourself out during an earthquake, move slowly and safely towards an open area with trees, utility poles, street lights, or buildings and get close to the ground until the shaking stops. If you find yourself in a city, try and find a secure location away from the dangers of falling glass and rubble.
- If you’re driving, pull over. When you’re in a car and a quake starts, find a safe place to pull over and park until the shaking stops. Your car is probably the safest place to be during a tremor and can protect you from small debris!
- Finally, if you find yourself in an earthquake, DO NOT PANIC. Panicking is the worst thing you can do! Instead, keep a clear mind and move slowly and surely to the secure locations you may have around you. And, if in a crowd, never run. Instead, always walk to a safe place.