
Landslides change the surface of the Earth. They happen when rocks, soil, and anything else on the ground falls down a slope after becoming too weak or unstable to resist gravity. A slope includes mountains, hills, and cliffs. They happen on every continent on Earth, but they are most common in mountainous regions, such as the Andes Mountains of South America.
3 Causes of Landslides
There are three causes of landslides. First, the morphology of the land. Morphology is the structural combination of rock, soil, and vegetation of the ground. Vegetation is vital for preventing them because it anchors the soil in place. Erosion by water also changes the morphology of a slope and can lead to landslides.
The second cause is the characteristics of the rock under the soil. If the rock is weak or cracked, it will be more likely to fall down the slope.
Finally, human activity can cause a landslide. When humans change a slope through agriculture, construction, deforestation, and excavation, they make a landslide more likely because all of these activities change the land’s morphology. Fires, natural or caused by humans, can also cause them because they strip away the vegetation anchoring soil in place.
Types of Landslides
There are different types of landslides. Some are slow, while others happen in an instant. They are defined by how the material moves down the slope. Falls and topples involve boulders falling down a slope. Slides happen when a less stable surface slides off the layer below it. There are different types of slides, including translational slides, block slides, and rotational slides, depending on how the layer moves. When the soil on a slope becomes saturated with water, it moves down the slope as a flow. Earthflows happen slowly, and debris flows or mud-flows happen quickly.
Lahars are landslides that happen when a volcano erupts. The heat from the eruption melts the volcano’s snow, creating a massive mudslide that rushes down the volcano’s steep slopes. Avalanches are landslides that happen in the snow. Creep is the slowest type of landslide. The top layer of soil moves downhill at just a few millimeters per year.
The Costs of Landslides
Landslides are both costly and dangerous. In the United States, people spend about $3.5 billion per year recovering from landslides. Between 25 and 30 people are killed by landslides in the United States every year. Worldwide, thousands die from them. Knowing the causes of landslides can help us predict when and where they will happen to save lives.
Landslides Reading Passage
You can teach your middle school science students about landslides with a reading passage. Comprehension questions are included to help students integrate what they learn about landslides. Click the picture below to check it out at Teachers Pay Teachers.
The Geosphere
Middle School Science
