Grade Levels: K-3

This page provides information to support educators and families in teaching K-3 students about slow land changes. It is designed to complement the Slow Land Changes topic page on BrainPOP Jr.

Before beginning the Slow Land Changes topic, we recommend reviewing the movies on Rocks and Minerals as well as Landforms.This movie will introduce weathering and erosion and help children understand how these important processes change Earth over time.

Weathering is the process of breaking down rocks and minerals in nature. Weathering can happen in many different ways and usually happens slowly over time. Roots of plants and trees can grow into rocks and eventually split them apart. Some children may notice when plants or tree roots break through sidewalks or concrete. This is one example of weathering. Sand can blow into large rocks and break them apart or cause them to change shape. You may want to present pictures of arches and rock formations, such as those found in the Arches National Park in Utah. Weathering can also happen with water and ice. Water can get inside cracks of rocks and freeze. Explain that when water freezes, it expands, or takes up more space. Over time, the freezing and thawing can slowly cause the cracks to become deeper and bigger. Eventually the rocks can weather and break. Water can also change minerals inside rocks.

Remind your children that rocks are made up of materials called minerals. Water can change or break down minerals inside rocks. For example, a rock with copper can turn green when exposed to water. These chemical changes in rocks can weaken them and cause them to break apart. Weathering can also cause caves to form. Water can dissolve and break down limestone, a type of rock. Over thousands of years, a crack in limestone can get larger to form an opening underground, or even underwater. It is important for your children to understand that weathering takes place over thousands or even millions of years.

Erosion is when rocks and soil are carried away by water, wind, ice, or other natural forces. Weathering and erosion happen simultaneously. Erosion causes land to change shape in different ways. Rocks get weathered and carried away by waves crashing into the coastal land. Some rocks on beaches, rivers, and streams are smooth because water has eroded and worn down the rough edges. Canyons are formed when a river slowly wears down land and the rocks and soil are carried away. Remind your children that it takes thousands of years for canyons to form. A glacier is a large mass or river of ice that moves very slowly and takes bits of land with it. Over millions of years, glaciers can wear away at mountains and leave behind valleys.

It is important for your children to understand that Earth is always changing, even if the changes are imperceptible. Encourage your children to find examples of weathering and erosion around them and think about how their area has changed over time. What happens when land is cleared to build houses? How can erosion affect where they live? How did the land look thousands of years ago? Encourage your children to draw conclusions.