Earthquakes

More than a million earthquakes rumble the Earth every year, but thankfully most of them are too small to feel below our feet. Some of the most earthquake-prone zones on the planet are Japan, Nepal, and India.

Earthquakes happen all over the world; this has been going on for as long as Earth existed and will continue to occur for billions of years.

Earthquakes are most prevalent along the Earth’s fault lines. These are areas where the plate tectonic movements are most likely to cause earthquakes. Some of the biggest fault lines can be found in Southeast Asia, Central Africa, Gulf of Alaska/Kamchatka, and Peru/Chile. 

The thin crust of rock covering the Earth is not 1 solid piece but more like 12 puzzle pieces called tectonic plates. Even though the ground feels like it isn’t moving, the Earth’s crust creeps along on a slow-moving liquid layer underneath, the mantle. 

While it moves, the edges of the tectonic plates move towards each other, away from each other, or slide against each other. When this happens, pressure builds up far below the Earth’s surface, causing the ground to rumble and shake, an earthquake. 

The crust is relatively thin, around 25 miles deep under the continents. Beneath the crust is the mantle, a semi-liquid layer of melted rocks.

The Ring of Fire is where 81% of the world’s largest earthquakes occur. It is also called the circum-Pacific rim as it extends from the Western side of the Americas to the Eastern side of Asia and Oceania. 

The hypocenter is where the earthquake begins deep below the crust and the location directly above it on the surface of the earth is called the epicenter. The effect of the earthquake then spreads out in a seismic wave. 

The direction in which the tectonic plates are moving determines what kind of earthquake happens. 

Scientists use an instrument called the seismograph to record and measure earthquakes. While scientists can measure the magnitude of an earthquake, there is no way to predict when an earthquake will happen. 

All we know is that if there is a fault line, the likelihood is that an earthquake will happen in that area at some point, although we don’t know when or where exactly.

This heavy instrument stays fixed to the ground and has a weight that hangs from it. During an earthquake, as the ground shakes, so does the heavy base in relation to it. The motion of the earthquake is then recorded onto paper.

The Richter scale measures how powerful an earthquake is, using a range of 1 to 10. Because it is a logarithmic scale, each increase is 10 times more powerful. Earthquakes of Richter scale 1 and 2 happen daily, but a Richter scale 9 earthquake luckily happens only every few hundred years.

Earthquakes themselves generally don’t harm people, but they may cause damage to structures used by people. Furthermore, earthquakes that happen under the sea can cause tremendous tsunamis, gigantic waves that form and can destroy coastal towns and cities.

One of the most devastating earthquakes in recent history was the Indian Ocean earthquake in 2004. It measured 9.1 on the Richter scale and triggered many subsequent earthquakes all over the world. It even went as far as Alaska, which is 6400 miles away.

The tsunamis that resulted from this underwater earthquake killed at least 230,000 people in 12 different countries in Southeast Asia.

The tremors from this earthquake were so strong that the Earth wobbled in its rotation on its axis by almost an inch.

As earthquakes are named specifically for the earth, no other planet can have earthquakes. However Mars has marsquakes. On the first moonwalk Buzz Aldrin placed a seismometer in the Sea of Tranquility. We discovered that the moon has a lot of seismic activity. 

Unlike the earth where quakes will last for about half a minute, the moon does not have a molten core and is solid, so quakes can just keep on going, like a resonating tuning fork.

Quakes on Mars are called Marsquakes.

The Moon also has seismic activities. Even though they are weaker than the average earthquakes, due to the lack of water to dampen the vibrations, moonquakes could go on for up to an hour.

Different cultures had different explanations for earthquakes. As you can imagine, most ancient beliefs about earthquakes involved a very angry god rumbling the earth in all his wrath. 

The Maimas of Peru believed that when an earthquake happened, it was their God walking around the Earth, counting his true believers. During an earthquake, people would run outside and shout “Here I am, here I am,” so that they would be included in the headcount.

An old Hindu belief held that Earth was resting on 4 elephants atop a turtle that was balanced on a cobra. The earth quaked when any of these animals made a tiny movement.