Relationship between Earthquakes and Volcanoes

Earthquakes refer to shaking or trembling of the Earth's crust as a result of abrupt release of energy. They are basically seismic waves, generated by the natural phenomena or at times, man-made events. Volcanoes, on the other hand, are openings in the Earth's crust from which hot gases and molten rock materials are ejected on the surface of the Earth.

Earthquakes and volcanoes are related to each other. In fact, earthquakes usually accompany a volcanic eruption. Similarly, unusual earthquakes can lead to volcanic eruptions. Before discussing about the relationship between earthquakes and volcanoes, let's take a brief look at each of them.

Earthquakes

Earthquakes, as mentioned earlier, are caused due to sudden release of pressures that has been accumulated over a period of time. The generated seismic is measured with the help of seismometer in order to indicate the intensity or size of the earthquake.

The earthquake size is represented by moment magnitude scale (MMS); a magnitude of 3 or lower is undetectable, whereas a magnitude equal to or greater than 7 causes maximum damage to life and property. The underground point where the earthquake originates is called the hypocenter or focus. Epicenter refers to the point on the Earth's surface, which is exactly above the hypocenter.

Volcanoes

Volcanic eruptions that involve extrusion of magma usually form mountains or mountain-like landscapes after the ejected materials cool down. They can occur in any part of the earth's surface, either in land or seas and oceans. Volcanoes are classified into active (eruptive), dormant (presently not active) and extinct (not eruptive) types, based on the activeness of a particular volcano. They are further classified into six different types - shield, cinder, submarine, subglacial, stratovolcano and supervolcano, depending upon the mode of ejection and other features.

Relationship between Earthquakes and Volcanoes

The close relationship between earthquakes and volcanoes is evident from the maps depicting the locations prone to both phenomena. If you compare the maps that illustrate earthquake zones and volcanic zones, you will find them matching to each other. The main theory behind both these natural calamities lie in the plate tectonics.

The planet Earth comprises irregular shaped and varying sized plates, which constantly move at different speeds. To be precise, the plates drift over the mantle layer of the Earth. Consequently, magma is generated along the plate boundaries. Earthquakes and volcanoes are generally present at the plate boundaries.

When the plates collide, move apart or slide each other, it leads to generation and accumulation of pressure (strain), which when released causes earthquakes. The strongest earthquakes are manifested during the plate collision, while the slowest earthquakes are observed when plates move apart from each other.

Similar to earthquakes, volcanism or volcanic activity is observed when the plates are divergent (move apart) or convergent (move towards each other). In such plate movements, the magma present in the plate boundaries may rise to the Earth's surface, leading to volcanic eruptions. Divergent plates may cause long volcanic rifts, whereas convergent plates result in individual volcanic eruptions.

In addition, earthquakes and volcanoes occur within a plate, which are referred to as intraplate earthquakes and intraplate volcanoes respectively. It is estimated that about 10 percent earthquakes are of intraplate type.