Tectonic Movements: How Earthquakes Happen

Earth-cutaway-schematicAccording to the science of plate tectonics, the earth’s lithosphere (top level areas of the Earth) contains plates that move gradually over the asthenosphere (area directly under the lithosphere).

Major geological formations, such as the creations of volcanoes and mountains occur at the interaction of these plates, called orogeny.

Creation of Mountains

Capital Reef National Park
Capital Reef National Park, Utah

Mountains big and small have been the result of plate teconics.

The formation of the Himalayas was created when the Indian subplate burrowed under the European continent and formed the Appalachian Mountains,

When the North American and African plates collided, a large separation of earth materialized and the Atlantic Ocean opened up.

The volcanic and seismic activity of the West Coast of the US occurs as a result of grinding of the North American and Pacific plates.

The above are just a few examples of the effects of plate tectonics. The geological history of Earth is littered with such phenomena that have made the Earth what it is today.

What Else Occurs When the Teconic Plates Collide?

Earthquakes are caused by these collisions, as one plate moves over the other, the Earth shakes.

Less pronounced movements are witnessed every year as the plates collide under us. The measurement of intensity is rated using a Richter Scale, which records the magnitude of the collisions, with 1 being unnoticeable, up to 10, which can cause massive death and destruction. Fortunately, an earthquake of 10 is very rare.

Tetonic activity map over the Earth's history
Tetonic Activity Map Over the last One Million Years

What Causes the Plates to Move?

The latest theory is called slab pull, where areas of the lithosphere is less dense than the asthenosphere, but becomes denser over the years and subsequently cools and thickens.

This causes these areas above to sink further down into the mantle, pulling slabs of the lithosphere apart, resulting in these regions spreading or rifting.

Other causes of plate movements are thought to occur as heat rises from the Earth’s crust, causing the plates to move in different directions.

Where are the Areas on the Earth of Most Danger?

The most dangerous regions where earthquakes are known to occur are in areas called faults, which are cracks in the lithosphere caused by the previous mentioned stresses of plate collissions.

It is thought that the regions where the plates move in opposite directions is what results in faults. These plates are not stationary, but slowly moving against each other in inches per day. It is when these movements occur at a greater intensity, that we feel the disturbance, otherwise known as earthquakes.

The known fault areas are shown below.

Map of earthquakes from 1900 to present
Map of earthquakes from 1900 to present. Wikipedia

The Latest Findings

But as it turns out, such interactions between continental plates is not the only reason for various geological processes. Research led by a joint team of the University of Toronto and University of Aberdeen researchers have achieved an enormous breakthrough!

According to the research that uses supercomputers to run a model of the Earth’s upper mantle and crust, the prehistoric geological events could have left deep ‘scars’ that may play a significant role in earthquakes, tsunamis, formation of mountains or ocean trenches and many other ongoing geological processes.

The models created by the researchers indicate that the previous plate boundaries could stay buried deep below the surface of the Earth. These structures, which are no less than many millions of years old, are located far from the current plate boundaries and may cause drastic changes in the surface properties and structure of the interior of the continents.

The researchers went a step further to propose a new map highlighting the ancient geology of the Earth. The ‘perennial plate tectonic map’ explains through illustrations how the prehistoric geological events could affect today’s geological processes. The map is based on the common tectonic map, which is taught in elementary school, but it has been modified to include the concealed, ancient plate boundaries that may be involved in plate tectonic activity in the past as well as the present.

Owing to this recent breakthrough, some major revisions are required to the fundamental idea of plate tectonics. The research paper titled, ‘Lasting mantle scars lead to perennial plate tectonics’ appeared in the Nature Communications issue of June 10, 2016.


So we see that plate movements below the Earth’s surface can cause these disturbances to occur, but how they occur is still a forum for debate. At least we know where it happens most and precautions have been and will be taken for earthquakes to minimize damage.

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