Erosion

Today we did an experiment about erosion.
Here are our WALTs

• The surface of the Earth changes. Some changes are due to slow processes such as erosion and weathering
• Landforms are the result of a combination of constructive and destructive forces. Destructive forms include erosion and weathering
• Soil consists of weathered rocks and decomposed organic material

Our experiment came from Dirtmeister's Science Site.


We found out that soil runs off the soil quickly at first, taking some of the top soil with it. The water that collects in the second tray contained dirty water. We let it settle and found out there was a lot of silt or sediment. After the top soil came off, there were a lot of stony soil below it. We thought that if the soil was wetter it probably would soak in more rather than run straight off. We added two of our National Curriculum Maths books to make the slope steeper. The water ran off quicker and caused more erosion. We discussed ways and we thought that
planting trees and plants would help because the roots hold the soil.

We then talked about local farms in the area especially the ones under Mt Aspiring. We thought that the land would be fertile because the top soil would run off onto the flat areas

We used this picture from the NZ ARBs to look at...

The diagram shows a river flowing through a wide plain. The plain is covered with several layers of soil and sediment.
We had to
1. Write down one reason why this plain is a good place for farming.
2. Write down one reason why this plain is NOT a good place for farming.
We came up with many great ideas. Read some of them...

• the soil is fertile (good), abundant

• there is a river (for irrigation, water for animals)

• there is plenty of space or flat areas for farm land

• there is the possibility of flooding, or that the soil will be too wet

• there is the possibility of wind or water erosion

We then looked at this picture and answer questions about it using the information we had learned.

At the spot marked X, the river is wearing away the riverbank. What are two things that could be done to stop the riverbank being worn away?

Here are some of our answers

• Plant trees
• Change course of river, i.e., straighten.
• Use boulders/concrete to protect bank.
• Change the river channel away from this part of the river bank.

Sometimes this river floods the farmland near by. What could be done to stop the farmland being flooded? This was harder but a few children had these answers.

• Build a stop bank
• Build a dam