Earthquakes
Picture showing a magnitude 6.4 earthquake that shook Taiwan
An earthquake is a vibration in the earth's crust caused by the sudden release of stored energy in the rocks found along fault lines. They occur when there is plate movement along plate boundaries, which cause the slow-build up of stress on the rocks found on either side of the fault.
- When the rocks can no longer withstand the increasing stress, they suddenly slip and release energy in the form of seismic waves which radiate from a focal point (i.e. focus).
- The amount of energy released is measured using the Richter Scale and described as the magnitude of an earthquake.
- The point on the earth's surface directly above the focus is also known as the epicentre.
After an earthquake event, the stress from the ground may cause many smaller earthquakes called aftershocks to occur along the fault lines. These series of aftershocks may occur for several months after the initial earthquake, with some of them being nearly as powerful as the original earthquake.
Recent example of major earthquake events include the 9.0 magnitude in 2011 - Tohoku, Japan, with a death toll of 28,000 people.
The extent of damage caused by an earthquake may vary based on population density of an area, level of preparedness, distance from the epicentre, time of occurrence and type of soil,
Test Your Knowledge: What are some countries that frequently experience earthquake events? Why?
Tsunamis
Some of the hazards commonly associated with an earthquake is a tsunami. Tsunami refers to an unusually large sea wave which may be formed by
- Movement of sea floor during a large earthquake at the subduction zones
- Underwater landslide
- Landslide above sea level due to earthquakes or volcanic eruptions which causes large amount of materials to plunge into water
This causes loss of lives, disruption of services, fires, landslides, destruction of properties and properties (e.g. tsunami in Banda Aceh, Indonesia caused by earthquake in the Indian Ocean).
Watch the video below to get a better understanding on how tsunamis are formed and its threats.
Volcanic Eruptions
Volcanic eruptions can occur on land or on the sea floor. They occur depending on whether a volcano is active, dormant or extinct.
- Active - a volcano that is currently erupting or expected to erupt in the future
- Dormant - a volcano that is currently inactive but may erupt in the near future
- Extinct - a volcano without current seismic activity and has no evidence of eruptions for the past thousand years.
Some of the risks of living near volcanic areas include
- Destruction of properties and infrastructure caused by volcanic materials (i.e. lava, pyroclasts, lahar)
- Disruption of services (i.e. aircrafts and flight services)
- Landslides due to structural collapse of a volcanic cone
- Environmental pollution from ash particles ejected during the volcanic eruption
- Effects on weather due to release of gases such sulphur dioxide reflect sun's energy back into space and temporarily cools the earth ranging from a few months to years.
Why Do People Still Live Near Volcanic Areas Since There Are Risks?
Although there are many risks in living near volcanic areas, many people continue to live there due to its numerous benefits and opportunities. These includes
- Fertile volcanic soil for agriculture due to the breaking down (weathering) of volcanic materials to enrich the soil, making it favourable for agriculture
- Precious stones and minerals which can be used for commercial or building and construction purposes
- Tourism
- Geothermal energy
People may choose to continue living in areas prone to tectonic activity for a variety of reasons, considering the risks and opportunities. They cannot prevent natural hazards but live in harmony with nature through mitigation and preparedness measures which will be discussed in the next post.
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