6.5 The Impacts of Natural Hazards

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What Is a Natural Hazard?

A natural hazard is a natural event — something that happens in nature — that causes harm to people, animals, or the environment. Examples include earthquakes, volcanic eruptions, tropical storms, floods, and droughts. These events become "hazards" when they affect places where people live.

Natural hazards have two main types of impacts:

• Impacts on people — such as injury, death, loss of homes, and financial hardship.
• Impacts on the environment — such as destruction of habitats, pollution of water, and loss of farmland.

Impacts of Tectonic Events

a) Damage to Buildings and Infrastructure

When the ground shakes violently during an earthquake, or when lava and ash pour out of a volcano, buildings can collapse or be buried. Infrastructure means all the essential systems a society depends on — roads, bridges, railways, electricity lines, water pipes, hospitals, and schools. When these are destroyed, communities cannot function properly. People may have no shelter, no clean water, and no access to medical help.

b) Fire

Earthquakes can snap gas pipes and electricity cables. When gas leaks and sparks from broken wires ignite it, large fires can break out across a city. These fires can spread quickly, destroying homes and businesses that may have survived the initial quake. Volcanic eruptions also cause fires when hot lava flows through forests and settlements.

c) Tsunamis

A tsunami is a series of enormous ocean waves triggered when an underwater earthquake suddenly shifts the seabed, displacing a huge volume of water. These waves travel across the ocean at very high speed and can reach coastal areas as walls of water several metres high. When a tsunami hits land, it floods entire coastal towns, sweeps away buildings, and can kill thousands of people in minutes.

d) Landslides

The violent shaking from earthquakes can loosen soil and rock on slopes and hillsides, causing them to slide downhill rapidly. This is called a landslide. Landslides can bury villages, block roads, and dam rivers, causing further flooding upstream. Volcanic eruptions can also trigger landslides when loose volcanic material collapses.

e) Loss of Farmland and Habitats

Lava flows from volcanoes cover farmland in rock, making it impossible to grow crops for many years. Ash fall can also bury fields. Earthquakes can crack open the ground and permanently change the landscape. Forests and wetlands (natural habitats where animals and plants live) can be buried or burned, causing local species to lose their homes.

f) Water-Related Disease

After a tectonic event, sewage (waste water from toilets and drains) systems often break. Sewage mixes with the water people drink or wash in. This contaminated water can spread diseases like cholera (a serious illness causing severe diarrhoea and dehydration), typhoid, and dysentery. These diseases are called water-related diseases because they spread through dirty water. People in temporary shelters with no proper sanitation (toilets and clean water systems) are especially at risk.

g) Loss of Life

Buildings collapse on top of people. Tsunamis drown thousands. Fires trap and kill people. Landslides bury entire communities. The death toll (number of people killed) from a major tectonic event can reach tens or even hundreds of thousands.

h) Trauma

Trauma means serious emotional and psychological (mental) harm. Survivors who have lost family members, seen destruction, or narrowly escaped death often suffer from severe mental distress. Conditions like post-traumatic stress disorder (PTSD) — a lasting state of fear, nightmares, and anxiety caused by experiencing a terrifying event — are common after disasters. This type of harm is invisible but can affect people for years.

i) Financial Losses

Rebuilding destroyed buildings, repairing infrastructure, replacing lost equipment, and providing emergency aid all cost enormous amounts of money. Businesses are destroyed, meaning people lose their jobs and income. Countries, especially poorer ones, can be set back economically by decades after a single major tectonic event.