Landslides

What is a Landslide?

A landslide is the rapid mass movement of soil, mud and/or rocks downhill due to the pull of gravity. Landslides are very common and occur in a variety of forms. Land may topple off in a big chunk, or slip down in bits. Landslide may be composed of mud or may contain rocks and other debris. Most landslides occur gradually, but some may be sudden.

Natural causes of landslides include:

1) Heavy and/or prolonged rain

Gravity is an invisible force that pulls all objects towards Earth. The effect of gravity is more prominent on a steep slope or on a hilly area. When rain falls, water enters or infiltrates into the top soil which makes the soil become heavier and therefore more vulnerable to the pull of gravity. When soil absorbs all the water that it is capable of holding, it is said to be saturated. Soil is therefore heaviest and most susceptible to the effects of gravity, when saturated. When large areas of soil become saturated on steep slopes, the pull of gravity causes the top layers of the soil to slide downhill, therefore resulting in a landslide.

2) Tremors And Shakes

An Earthquake is a tremor or movement in the Earth’s crust. They are a deadly and unpredictable type of natural disaster and are the leading reason for landslides or Rock falls occurring worldwide. Loose soil, rocks and boulders can easily be dislodged from hilly areas and allowed to move downhill when the violent shaking of the ground transpires. Landslides are more likely to take place when the earthquake is of a high magnitude.
Human Induced Activities that produce landslides:

1. Deforestation
2. Quarrying/ Rock Mining
3. Bad agricultural practices such as slash and burn agriculture

Deforestation is the removal or cutting down of trees and other types of vegetation from the land. The firm roots of the trees also help to keep the soil in place, even when it absorbs water, thus diminishing the effects that gravity has on the soil. It is when these trees are removed that the bare and exposed soil is left defenseless against the pulling force of gravity when saturated since trees help to keep soil firmly in place. Soil movement takes place more easily and rapidly resulting in deadly landslides.

Quarrying or rock mining refers to the cutting away or excavation of hilly or mountainous areas so that rocks and minerals can be extracted from the land. Quarrying is rampant in the Northern Range and results in the land being left devoid of trees and vegetation. Without trees to hold the soil in place, soil movement occurs easily and rapidly.