Earth Events

In the last unit, students explored the properties of different kinds of matter, connecting a material’s properties with the functions for which it is used. In this unit, students focus on Earth materials and the science phenomena of processes that change them (specifically weathering and erosion).

This page is a high-level extract of the first lesson of the unit in which students conduct an experiment to examine how the strength of blowing wind and flowing water affects the shape of a sandy hillside. Students then classify various Earth event diagrams and photos according to their relative timescales (fast vs. slow).

Science Background for Teachers:

This background provides teachers with additional in-depth information about the science phenomena students will investigate in this unit. In this case, the phenomena are Earth events such as erosion and weathering.

At its tallest, Niagara Falls drops 50 meters (165 feet). As the water flows over the rocks, it causes significant weathering and erosion of the land underneath. Weathering is the breakdown of Earth materials (such as rocks, sand, and soil) into smaller pieces, and it can be caused by wind, water, or living things. For example, as water travels, it constantly rubs against soil and rocks. The friction eventually weathers these surfaces, breaking them down into smaller pieces. Erosion is the movement of small pieces of rock, soil, and sand from one place to another. Erosion is different from weathering, which refers only to the physical and chemical breakdown of rocks into smaller pieces. During erosion, these pieces are carried to a new location by wind, water, or gravity.

Over thousands of years, the Niagara River weathered and eroded rocks as it moved over the land and plunged 50 meters below, carrying weathered pieces of matter to new locations. As the land fell away, the falls moved slowly backwards.

And the falls are continuing to move today, even though the change is so slow we cannot see it. Scientists predict that if the falls continue to erode the land at the same rate as today, Niagara Falls will no longer exist in around 50,000 years.

Water is the primary source of weathering and erosion on Earth. Sources of moving water, such as the Niagara River, weather and erode the land as they flow downhill over it. As rain falls onto the ground, the drops cause weathering and erosion of the surface. Ocean waves also weather and erode the land as they pound into the shoreline.

Supports Grade 2

Science Lesson: Investigating Earth Events

Wind and water are two forces that constantly change and re-shape Earth’s surface over time. In this lesson, students are introduced to weathering and erosion with an experiment that compares the amount of erosion that takes place when the intensity of wind blowing and water flowing changes. Students then examine different events that change Earth’s surface, classifying the changes as fast or slow.  

Science Big Ideas

  • Earth’s surface is made up of different materials.  
  • The materials that make up Earth’s surface change over time. To change means to make something different from what it is now.
  • Weathering happens when the Earth materials that make up the land are broken down into smaller pieces, and it can be caused by different things, including wind and water.
  • Weathered Earth materials are often eroded. Erosion happens when weathered pieces of Earth materials are moved to new places.  
  • The amount of weathering and erosion that takes place changes depending on various factors, including how much wind or water is moving and how fast it is moving.
  • We can compare the changes to Earth’s surface based on how long it takes the change to happen.

Sample Unit CTA-2
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Science Essential Questions

  • What materials make up Earth’s surface? Where have you seen some of these different materials?
  • How can you describe the properties of Earth materials?
  • What causes rocks and other Earth materials to become weathered?
  • How is erosion different from weathering? Why do weathering and erosion often happen at the same time?
  • What causes small pieces of rock, soil, or sand to move to new places through erosion?
  • What will happen to Earth materials when a large river flows over them compared to a small river?  
  • Do all changes to Earth’s surface take place quickly?
  • How are slow changes different from quick changes?  

Common Science Misconceptions

Misconception: Erosion always happens quickly.
Fact: Erosion can occur quickly, but it often happens very slowly, over hundreds, thousands, or millions of years.
Misconception: Erosion is always “bad.”
Fact: Erosion isn’t “bad” or “good.” Many landforms are created by the deposition of eroded Earth materials.
Misconception: Earth’s surface, including its rocks, doesn’t change.
Fact: Earth’s surface is constantly changing. Some of these changes happen quickly, and other changes happen very slowly.

Science Vocabulary

Change: to make something different from what it is know

Engineer: anyone who uses scientific knowledge and mathematics to solve a problem by creating new technologies

Erosion: the movement of small pieces of rock, soil, and sand from one place to another by wind or water

Prototype:  a smaller version of what will be engineered

Weathering:   the breakdown of Earth materials (such as rocks, sand, and soil) into smaller pieces; can be caused by wind, water, or living things

Lexile(R) Certified Non-Fiction Science Reading (Excerpt)

A Changing Waterfall

A long time ago, Niagara Falls looked very different. It used to be made up of one waterfall. It also was in a different place. It has moved backwards over time. These changes happened because water changes Earth’s surface as it moves over it. To change means to make something different from what it is now.

Water Changes the Land

Earth’s surface is made up of different materials. For example, the land is made up of soil, rocks, and sand. As water moves over the land, it changes these Earth materials.

Weathering happens when Earth materials are broken down into smaller pieces. Water weathers the land as it moves over it. Wind, plants, and animals also weather Earth materials.

Erosion happens when these weathered pieces of Earth materials are moved to new places. For example, moving water carries with it weathered Earth materials. This is erosion. Wind can also erode Earth materials. As the wind blows, it carries with it small pieces of weathered Earth materials.


Hands-on Science Activity

This lesson has one experiment and one investigation. In the first part, students collaboratively conduct an experiment to answer the question: “How does the amount of water that flows and wind that blows on a hillside affect the shape of the hillside?” In the investigation, students ask questions about the relative timescales of different events that change Earth’s surface. In the experiment, students create a visual model (scientific diagram) of their experiment-in-progress. Students use the model to visualize how the materials will be used in their wind and water experiment and to communicate their experiment to others. They then create a physical model to compare how sand on a hillside moves when different amounts of wind and water move across it.

Science Assessments

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  • Vocabulary Check
  • Lab Checkpoints
  • Concept Check Assessment 
  • Concept Map Assessment 
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Science Standards

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Download the Alignment to NGSS

Standards citation: NGSS Lead States. 2013. Next Generation Science Standards: For States, By States. Washington, DC: The National Academies Press. Neither WestEd nor the lead states and partners that developed the Next Generation Science Standards were involved in the production of this product, and do not endorse it.