10 Ways An Earthquake Can Alter The Geography Of A Place

By Victoria Simpson on June 25 2020 in Geography

: Houses destroyed by the earthquake of August 24, 2016, in Amatrice, Italy. Image credit:  Jose Carlos Alexandre/Shutterstock.com
: Houses destroyed by the earthquake of August 24, 2016, in Amatrice, Italy. Image credit: Jose Carlos Alexandre/Shutterstock.com
  • Earthquakes can cause fires in urban areas when gas and electrical lines are ruptured, as happened during the San Francisco earthquake of 1906.
  • Mountains are formed when two tectonic plates meet at a convergent boundary, and earthquakes occur there repeatedly over millions of years.
  • The Atlantic Ocean was formed when three tectonic plates met in a triangle, and two sides eventually split off in seismic activity, open to form the ocean.

Some earthquakes can be so small you do not even notice they just took place. At other times, an earthquake can be a huge event. Seismic records indicate there are about 16 major earthquakes that take place each year around the world. These measure 7.0 and higher in magnitude on the Richter scale. Like all Earthquakes, these devastating quakes are caused when two tectonic plates on Earth slide past each other on a fault line. This releases stored energy in the form of seismic waves. When this happens, different types of waves impact the ground. P waves travel the fastest, and these are the first to shake the Earth. These waves compress and stretch the Earth’s crust horizontally. In contrast, S waves travel more slowly and come later. These waves cause the crustal material on Earth to move in an up-and-down direction, basically moving perpendicularly to the direction in which the S waves are traveling. When these waves hit the ground with tremendous force, they can truly disrupt the surrounding geography and change the local landscape. 

Exactly what impact can a major earthquake have? Here are ten phenomena in a region’s geography that can result from the occurrence of an earthquake.

10. Fire

San Francisco burning after April 18, 1906, earthquake. Image credit: Everett Collection/Shutterstock.com
San Francisco burning after April 18, 1906, earthquake. Image credit: Everett Collection/Shutterstock.com

When an earthquake happens in an urban area one of the largest risks is fire. A fire can start when the quake damages and ruptures underground fuel pipelines as well as electrical lines. In 1906, a major earthquake struck San Francisco, causing many gas pipes to break. An astounding 25,000 buildings caught fire, and chaos reigned as water mains also burst, making it difficult to get water to the fires as needed.

9. Landslide

Landslide caused by a major earthquake in Japan. Image credit: house0402/Shutterstock.com
Landslide caused by a major earthquake in Japan. Image credit: house0402/Shutterstock.com

Some slopes of land already have spots in them that are weak. If an earthquake happens, a landslide can take place. This happens when gravity causes soil, rock and artificial fill (if present) to move down the slope suddenly. Landslides can be deadly, and have been known to wipe out large groups of people. In 2001 in El Salvador, a landslide occurred in Las Colinas, in the city of Santa Tecla, killing more than 500 people.

8. Ground Rupture

Massive Cracks have appeared in The Hunderlee Hills on Highway One, North Canterbury after the 7.5 Kaikoura Earthquake. Image credit: NigelSpiers/Shutterstock.com
Massive Cracks have appeared in The Hunderlee Hills on Highway One, North Canterbury after the 7.5 Kaikoura Earthquake. Image credit: NigelSpiers/Shutterstock.com

A ground rupture, or “surface rupture” takes place when an earthquake pushes the ground apart and upward. A quake can literally tear the surface of the Earth apart, and this happens most often along preexisting fault lines. Some ground ruptures occur under buildings, which can cause damage. In 1992, an earthquake in San Bernardino County, California extended for about 50 miles. 

7. Tsunami

Great East Japan Earthquake and tsunami.
Great East Japan Earthquake and tsunami.

We often think of earthquakes as taking place on land but they also happen out in the ocean. When the Earth’s plates collide on the ocean floor, this can cause a giant wave to form, called a tsunami. (“Tsunami” is a Japanese word that means “harbor wave”). Tsunamis are not dangerous out in the ocean, but they can travel up to 600 miles per hour, racing towards the coasts, putting people in peril. When a tsunami wave comes close to shore, the friction caused by teh wave meeting the rising ocean floor causes the enormous wave to slow down, but increase in height. This means that when the wave hits the land, it can be up to 100 feet tall. Unfortuatenly, this wave is so big it will not crest and break. It moves as a wall of water over everything in its path, destroying everything it meets. When it finally recedes, this wave then takes everything it destroyed back out with it to the ocean. 

Tsunami waves come in multiples and can continue hitting the shore for hours on end.

6. Floods

Image credit: Kingbob86 (Timothy)/Wikimedia.org
Image credit: Kingbob86 (Timothy)/Wikimedia.org

Tsunamis caused by earthquakes cause floods, but in-land earthquakes can also result in substantial floods. Earthquakes can cause dams and levees to break, which can flood surrounding lowland areas.

5. Liquefaction

Broken asphalt road by Chuetsu Earthquake, 2004. Ojiya, Niigata, Japan. Soil liquefaction took place on this road.
Broken asphalt road by Chuetsu Earthquake, 2004. Ojiya, Niigata, Japan. Soil liquefaction took place on this road.

This is one of the most peculiar and interesting results of an earthquake. Liquefaction happens when land that is otherwise solid suddenly becomes liquid that can flow. It seems like divine magic, but there is a scientific reason behind why this happens. When an earthquake strikes, the sediments in the ground are shaken, and if they are saturated with water, the grains can rearrange themselves so that they no longer support one another. The water present pushes the grains apart, allowing the substance to flow like a liquid.

In Japan in 1964, an earthquake caused liquefaction in Niigata, causing entire apartment buildings to fall over intact, like Lego pieces on a table.  

4. Mud Slides

Cars partially submerged after a mudslide. Image credit: Lucky Team Studio/Shutterstock.com
Cars partially submerged after a mudslide. Image credit: Lucky Team Studio/Shutterstock.com

Just like landslides, mudslides can occur during an earthquake. Mudslides happen when water accumulates rapidly in a piece of ground on a steep slope. The rock, debris and soil can let loose a fast-moving surge of mud that can be quite destructive.

3. Mountains

The valley of ten thousand smokes. Katmai National Park and Preserve, Alaska. Image credit: NPS/www.nps.gov
The valley of ten thousand smokes. Katmai National Park and Preserve, Alaska. Image credit: NPS/www.nps.gov

Even mountains can be a result of a quake. In fact, earthquakes are said to be essential to their formation. Of course, one quake does not make a mountain. Mountains are typically formed over millions of years when tectonic plates shift at convergent boundaries. This is where two tectonic plates crash together, causing the land to lift upwards. If one plate contains an ocean and the other a mass of land, a volcano can form.

2. Valleys

A view of the Great Rift Valley in Kenya. Image credit: Shankar S./Flickr.com
A view of the Great Rift Valley in Kenya. Image credit: Shankar S./Flickr.com

The opposite of mountains can also form from multiple earthquakes over time. Valleys are often formed by erosion, but they can form when two tectonic plates meet at a divergent boundary.  This is called a rift valley. Many rift valleys are formed when not just two but three tectonic plates meet at around 120° angles in a triangle. According to National Geographic, two arms of this connection can split to create an entire ocean, leaving the third to form a rift valley. This is how the Atlantic Ocean was formed. A triple junction in what is today the Gulf of Guinea on the west coast of Africa opened to create the vast expanse of the Atlantic. The third side formed the Benue Trough rift valley in what is now southern Nigeria.

1. Glaciers

Technically, glaciers are formed by the accumulation of snow in certain areas over time. Glaciers occur where snow remains in one location all year round, and accumulates to form a bunch of ice. Glaciers grow in size over hundreds of years as more snow adds to last year’s pile, compressing on the ice and snow underneath, causing it to crystalize. Earthquakes play no role in this process. It is true, however,  that some glaciers form on mountain sides, and as such, if it were not for the forces of earthquakes pushing plates together to form mountains, these alpine glaciers would not exist either.

More in Geography

worldatlas.com

WorldAtlas