What Causes Land Movement? Understanding Landslide Causes and More

Recently, land movements or landslides have made the headlines in the news media. From the slow-moving land movement in Indonesia to the landslide in Congo’s coltan mine, each hazard has similar triggers. What causes land movement?

Landslides are not geological disasters that are caused by a single cause. Several factors contribute to the land shifting. Moreover, these factors are not purely natural. In many cases, man-made activities make the largest contribution to land movement disasters.

Land Movement Definition

Land movements are geological hazards that occur when the soil is no longer able to withstand the load on it or when the soil loses its bearing capacity. Consequently, the earth materials move down the slope at varying speeds.

Some landslides move at devastating speed, burying everything below the slopes without warning. Consequently, they cause high fatalities, infrastructure damage, and large financial losses.

Meanwhile, other land movement disasters occur gradually and slowly. These slow-moving landslides often show some signs before they develop into devastating hazards. Some of these signs are as follows.

• Cracks on the ground and walls

• Bulging or sinking spots on the ground

• Rumbling sounds

• Sudden appearance of water seeping on the ground or new springs

• Tilting poles and trees

What Causes Land Movement?

The primary cause of land movements is the gravity that overcomes the slope’s stability. On the other hand, the slope’s stability is affected by many factors. These factors are the triggers for landslides.

1. Water Saturation

Prolonged, extreme rainfall is the common trigger for landslides in tropical countries. In other countries, melting snow will also cause land movements.

Excess water will cause various effects on the soil. For example, excess water will saturate the soil. Consequently, the weight of the soil will increase, causing the gravity to easily overcome the soil stability.

Moreover, excess water will increase pore water pressure, weakening the soil’s shear strength. Therefore, the soil will easily flow down the slope.

2. Weathering Processes

Specific weathering processes will also cause hillsides to be more vulnerable to land movements. One of them is a prolonged dry season. This condition will cause the water in the soil to evaporate.

Consequently, cracks will appear on the soil surface. These cracks will allow more rainwater to seep deeper into the soil in the rainy season. Thus, the soil will be saturated with water, causing it to lose its stability and shear strength.

Moreover, cycles of freezing and thawing may increase the risks of landslides. These cycles will cause the soil particles to expand and contract, leading them to move perpendicular to the slope.

3. Slope Angle 

Landslides are a common occurrence in hillsides or sloping areas. However, not all these areas have a similar level of land movement risks. 

Hillsides with a slope angle between 25^o and 45^o have higher landslide risks. Moreover, sloping areas with convex slopes are vulnerable to land movements.

4. Tectonic or Volcanic Activities

What causes land movement? Tectonic and volcanic activities are some causes of landslides. Earthquakes can be powerful enough to cause earth materials to move down the slopes. 

Volcanic explosions may also cause nearby slopes to topple down. Moreover, these explosions can result in volcanic mudflows during the rainy season.

5. Erosion

Continued erosion on the bottom of a slope can cause landslides. This trigger is common for slopes on the riverbanks or near the sea. Erosion on the bottom of the slopes will cause the slope angle to be steeper, causing them to be unstable and more vulnerable to landslides.

6. Deforestation

Deforestation on hillsides frequently occur for various reasons, including opening new plantations, farming, mining, and urban development. On the other hand, the root systems of vegetation can bind the soil on hillsides. 

Therefore, when there are no root systems to bind the soil, hillsides will be unstable. Consequently, prolonged, heavy rain can easily cause the slopes to slide down.

Types of Land Movements

Landslides are categorized by various factors, including their movement and material types. Below are several landslide types based on the movements.

• Falls: They are soil or rocks that detach from the slope and then roll, bounce, or fall freely down the slope.

• Creeping: Creeping landslides are slow-moving land movements. They can last for weeks. During this period, the slopes move inch by inch.

• Slides: In this type of hazard, the Earth material slides downslope rapidly and suddenly. This landslide typically has more fatalities.

• Flows: During this landslide, fluid-like earth materials move downslope. It occurs because the earth material is highly saturated with water. Flows are categorized into mudflows, debris flows, earthflows, and rock avalanches.

What causes land movement? Landslides or land movements are typically triggered by heavy rainfall, snowmelt, erosion, and tectonic/volcanic activities. Mitigating this hazard requires a set of complex strategies. One of them is adopting an effective wireless alert system. Authorities can have this system if they utilize cell broadcast technology from smsbroadcaster.com.