Misconceptions

Misconceptions about Weathering and Erosion

Students may hold many misconceptions about erosion, including:

• Rocks do not change.
• Weathering and erosion are essentially the same thing. The two words can be used interchangeably.
• Erosion happens quickly.
• Erosion is always bad.

Students tend to view the earth as static, stable, and unchanging. They often have difficulty believing that rocks can change or be worn down through the process of weathering. Students also tend to confuse weathering (the physical or chemical breakdown of rock) with erosion (the process of transporting sediments).

Even once students understand the concepts of weathering and erosion, they tend to have difficulty conceptualizing the long time frames needed for these processes to occur. Many science lessons focus on the negative aspects of erosion (soil loss, ecosystem destruction, sediment buildup in water sources) and lead students to believe that erosion is always bad. However, teachers should stress that erosion does have positive aspects as well. Delta areas, like the Mississippi and the Nile, were created by the deposition of eroded sediments carried downriver. Without erosion, these rich, fertile farming areas would not exist.

Misconceptions about Volcanoes

• Volcanoes are randomly located across the earth’s surface.
• Volcanoes are found only on land.
• Volcanoes are found only in hot climates.
• All volcanoes erupt violently.
• Volcanoes only erupt straight up through the top vent.
• If a volcano doesn’t erupt for a hundred years, it’s extinct.
• If a volcano does not produce lava, it is not dangerous.

Elementary students may believe that volcanoes are randomly scattered across the earth, when the majority are located along tectonic plate boundaries. “Ring of Fire” is the name given to an area along the border of the Pacific Plate with a high concentration of volcanoes. The Pacific Northwest, Alaska’s Aleutian Islands, and Japan are all located in the Ring of Fire. Volcanoes are found on land and under the ocean’s surface, as well as in areas with cold climates (like Antarctica).

Students may also believe that all volcanic eruptions are violent, but many are not. The levels of silica and dissolved gases in the magma determine whether a volcano erupts explosively or effusively. Magma and gas may escape through cracks and weak areas on the sides of the volcano in addition to the top vent. Baking soda and vinegar models, a staple of elementary school science, do not accurately model an eruption and could lead to the formation of misconceptions.

Students may also not understand that volcanoes can be inactive for long periods without being considered extinct. When volcanoes no longer have a lava supply, they are extinct, but it can be quite difficult for scientists to know if and when this is the case. For example, scientists are fairly certain that volcanoes of the Hawaiian Islands chain are extinct. Mount Vesuvius in Italy was believed to be extinct before erupting violently.

The lifespan of a volcano can be measured in millions of years, so a volcano that has not erupted in thousands of years would most likely be classified as dormant, rather than extinct. Yellowstone Caldera in Yellowstone National Park hasn’t erupted violently for approximately 640,000 years, but has had minor activity much more recently. Scientists thus do not consider Yellowstone Caldera to be extinct, but dormant.

Finally, students may believe that volcanoes are only dangerous due to lava flows. In reality, pyroclastic flows, ash clouds, and mudflows can be extremely hazardous. Deadly mudflows (lahars) have occurred recently in Colombia and the Philippines, and the eruption of Mount St. Helens produced an ash cloud and landslides of ice, mud, and rock.

Misconceptions about Earthquakes

• Earthquakes happen randomly across the earth’s surface.
• The ground opens up during an earthquake.

As with volcanoes, students may believe that earthquakes happen in random locations across the earth. Most of the world’s seismic activity is associated with tectonic plate boundaries and fault lines.

While shallow crevasses may form during an earthquake due to landslides or ground failures, the ground does not “open up” along a fault line. If a fault opened up, there would be no friction and no earthquake!

PROBING FOR STUDENT UNDERSTANDING

Erosion

Volumes 1, 2, and 3 of Uncovering Student Ideas in Science each contain 25 formative assessment probes to help teachers identify misconceptions. The first two volumes of this series contain several probes that relate to geologic concepts such as weathering and erosion.

Related formative assessment probes in Volume 1 of Uncovering Student Ideas in Science:

“Beach Sand” asks students to consider the origin of sand on a beach. It elicits ideas about weathering, erosion, deposition, and landforms.

“Mountain Age” asks students to determine the relative age of two mountains. It elicits ideas about the processes that affect the shape of mountains (weathering and erosion).

Related formative assessment probes in Volume 2 of Uncovering Student Ideas in Science:

“Is it a Rock? (version 1)” asks students to decide whether a number of objects are rocks or not. It elicits student ideas about whether rocks come in many sizes and shapes, as well as their understanding of words such as boulder, gravel, and sand.

“Mountain Top Fossil” asks students to explain how a marine fossil could end up on the top of a mountain. It elicits ideas about mountain formation, including weathering and erosion.

Volcanoes and Earthquakes

We have followed the model used by Page Keeley and coauthors in the three volumes of Uncovering Student Ideas in Science (© 2005-2008 by NSTA Press) and created a similar probe to elicit students’ ideas about the location of volcanoes across the world.

Where Are the Volcanoes?
This probe, modeled (with permission from NSTA Press) after those found in Uncovering Student Ideas in Science, Volumes 1, 2, and 3, is designed to elicit student ideas about the locations of volcanoes across the world. The probe could easily be modified to be used with a study of earthquakes instead of volcanoes.

TEACHING THE SCIENCE

Weathering and Erosion

When modeling erosion in the classroom, be sure to discuss the differences between the model and the actual processes at work. Stress that while students are able to see these changes happen relatively quickly, the real processes of weathering and erosion take much longer.

Many science lessons about erosion deal with the negative aspects and ask students to design solutions to prevent erosion. While these are often excellent activities, make sure to include positive aspects such as delta formation. Many elementary students study the Mississippi and Nile River deltas and learn about the fertile farmland. Why not connect the students’ social studies curriculum to their scientific study of weathering and erosion?

Volcanoes and Earthquakes

Mapping and geography activities will help target student misconceptions about the location of volcanoes and earthquakes. Creating accurate models of volcanoes and conducting experiments to determine how lava chemistry affects eruptions will help students understand that volcanoes erupt in many different ways. Finally, researching volcanoes around the world will give students a better understanding of the hazards of mudflows and ash clouds.

LESSONS AND ACTIVITIES

See “Hands-On Science and Literacy Activities about Erosion, Volcanoes, and Earthquakes” and “Developing Map Skills through Earth Science Activities” for lessons and activities that can help target these misconceptions.

National Science Education Standards

Assessing and targeting student misconceptions about weathering and erosion, volcanoes, and earthquakes meets the Earth and Space Science Content Standard and Science in Personal and Social Perspectives Content Standard for grades K-4 and 5-8 of the National Science Education Standards. The entire National Science Education Standards document can be read online or downloaded for free from from the National Academies Press web site. Science Content Standards can be found in Chapter 6.