Erosion happens when water, wind, or gravity slowly wear away rocks, soil, and land, and move them to a new place.

Over time, erosion can change the land, wash away good soil for plants, change the path of rivers, make canyons, and sometimes hurt animals and plants that live there.

Detachment

Soil particles are loosened or detached from the ground by the impact of raindrops, wind, or other forces.

Transportation

Once soil pieces are loose, they can be moved by water, wind, or gravity.

For example, rain or rivers can carry soil downhill, and wind can blow sand across a desert.

Deposition

The soil and sand that are moved eventually stop and settle in a new place, like at the bottom of a river, the foot of a hill, or along the beach.

What Causes Erosion?

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There are many different forces in nature that cause erosion. Depending on the type of force, erosion can happen quickly or take thousands of years.

The three main forces that cause erosion are water, wind, and ice.

Erosion by Water

Water is the most powerful main cause of erosion on Earth.

• Rainfall - Rainfall can cause erosion both when the rain hits the surface of the Earth, called splash erosion, and when raindrops accumulate and flow like small streams.
• Rivers - Rivers can create a significant amount of erosion over time. They break up particles along the river bottom and carry them downstream. One example of river erosion is the Grand Canyon which was formed by the Colorado River.

Erosion by Water

1. Waves - Ocean waves can wear away the land along the coast. The force of the waves can break off pieces of rock and soil, slowly changing the shape of the coastline.
2. Floods - Large floods can cause erosion to happen very quickly acting like powerful rivers

Erosion by Wind

Wind is a major type of erosion, especially in dry areas. Wind can erode by picking up and carrying loose particles and dust away (called deflation). It can also erode when these flying particles strike the land and break off more particles (called abrasion).

Erosion by Glaciers

Glaciers are giant rivers of ice that slowly move carving out valleys and shaping mountains.

Other Factors

People can make erosion happen faster. This can happen when we farm, cut down trees, or build roads and cities. Every year, a lot of good soil is washed or blown away because of these activities.

Erosion Control

We can help stop erosion caused by people. We can plant trees to block the wind, move animals so the grass can grow back, and plant new trees to replace the ones that were cut down.

؜Erosion in Taiwan’s Mountains

What is happening?

Taiwan’s mountains experience very strong erosion because of steep slopes, heavy rain, and earthquakes.

Main causes:

1. Typhoons bring intense rainfall in a short time Steep terrain makes soil slide easily
2. Earthquakes loosen rocks and soil
3. Deforestation and roads remove roots that hold soil

What erosion looks like:

1. Landslides Mudflows
2. Rivers filled with sediment
3. Slopes collapsing after storms

Erosion in Taiwan’s Cities (Urban Erosion)

؜In cities, erosion is caused less by nature and more by human-made surfaces.

Main causes:

1. Concrete and asphalt prevent water from soaking into the ground
2. Fast rainwater runoff during typhoons
3. Construction near rivers and hills
4. Poor drainage systems

What erosion looks like:

1. Flooded streets
2. Riverbanks breaking down
3. Sinkholes
4. Soil washing away from building foundations

How Taiwan Responds to Erosion?

In mountains:

1. Replanting trees
2. Building retaining walls
3. Slope stabilization systems

In cities:

1. Green roofs
2. Permeable pavement
3. Urban parks that absorb water
4. Riverbank reinforcement

Interesting Facts about Erosion

1. The word erosion comes from a Latin word that means “wearing away.”
2. The Colorado River has been slowly wearing away the Grand Canyon for millions of years.
3. Wind can blow dirt and sand to make big dust storms.
4. Glaciers can move very fast—one even moved over seven miles in three months!
5. Erosion can sometimes uncover fossils hidden in rocks.