What is a Natural Hazard?

Understanding natural hazards is essential for recognising the risks they pose to people and the environment, and how we can prepare for and reduce their impacts.

Definition of Natural Hazard

A natural hazard is a natural event that has the potential to cause harm to people, property, or the environment. These events can threaten lives, damage buildings, and disrupt communities. However, not all natural hazards lead to disasters; a disaster occurs only when a hazard causes significant damage or loss.

Examples of natural hazards include:

• Earthquakes
• Volcanic eruptions
• Storms (such as hurricanes or tropical storms)
• Floods
• Disease outbreaks

The frequency and type of natural hazards vary by location. For example, tropical storms mainly occur in warm ocean regions, while earthquakes are common near tectonic plate boundaries.

Hazard vs Disaster: A hazard is the natural event itself, while a disaster is the damaging impact that happens when people and property are affected. For example, an earthquake in a remote area with no people is a hazard but not a disaster.

Types of Natural Hazards

Natural hazards are grouped into three main types based on their causes:

Tectonic Hazards

These hazards result from movements of the Earth's tectonic plates. The main tectonic hazards are:

• Earthquakes: Sudden shaking of the ground caused by the movement of plates along faults.
• Volcanic eruptions: When magma, gas, and ash escape from a volcano, often at plate boundaries.

Weather Hazards

These hazards are caused by atmospheric conditions and include:

• Storms: Such as tropical storms (hurricanes/typhoons) with strong winds and heavy rain.
• Floods: When water overflows onto normally dry land, often due to heavy rainfall or storm surges.

Biological Hazards

These hazards arise from living organisms and include:

• Disease outbreaks: Epidemics or pandemics caused by bacteria, viruses, or other pathogens.
• Infestations: Such as locust swarms damaging crops.

Causes of Natural Hazards

Understanding what causes natural hazards helps explain why they happen and where they are most likely to occur.

Tectonic Plate Movements

The Earth's crust is divided into large plates that float on the semi-molten mantle below. These plates move slowly due to convection currents. When plates interact, they cause tectonic hazards:

• Convergent boundaries: Plates collide, causing earthquakes and volcanoes.
• Divergent boundaries: Plates move apart, creating new crust and volcanic activity.
• Transform boundaries: Plates slide past each other, causing earthquakes.

Atmospheric Conditions

Weather hazards are caused by changes in the atmosphere, such as:

• Warm ocean temperatures that fuel tropical storms
• Low pressure systems causing storms and heavy rainfall
• Seasonal weather patterns like monsoons or jet streams

Biological Factors

Biological hazards are caused by living organisms, including:

• Pathogens spreading diseases in human or animal populations
• Insect infestations that damage crops or spread illnesses

Risk and Vulnerability

Risk is the chance or probability that a natural hazard will actually cause harm to people or property. It depends on how often hazards occur and how severe they are.

Vulnerability refers to how exposed or susceptible a population is to harm from a hazard. Factors that increase vulnerability include:

• Living in high-risk areas (e.g., near volcanoes or floodplains)
• Poor quality housing or infrastructure
• Lack of resources or knowledge to prepare for hazards

The capacity to cope and adapt means how well people and communities can manage, survive, and recover from hazards. This includes emergency services, planning, education, and economic resources.

For example, two communities may face the same hazard, but the one with better warning systems and stronger buildings will have a lower risk of disaster.

Example: If a coastal town is in the path of frequent storms but has good flood defences and emergency plans, its risk is lower than a similar town without these measures.

For instance, the probability of a volcanic eruption occurring in any given year can be calculated if the average frequency is known.