Folds

Force of the Earth: Volcanoes and Earthquakes

When geological stress applies pressure to rock layers, they can bend instead of breaking, creating folds in Earth's crust. Folds are curved rock layers that form due to compression forces over millions of years. These folded layers create mountains, valleys, and underground structures that shape Earth's landscape. By examining how and where folds form, scientists gain insight into the processes behind earthquakes, the rise of mountains, and the shifting of Earth’s plates.

Science and Engineering Practices (SEP): Developing and Using Models

Scientists use models to study how folds form and affect Earth’s surface. By analyzing rock formations, satellite images, and seismic data, they can track how layers of rock bend under pressure. 3D models and computer simulations help scientists predict how compression forces shape landforms over time and how these movements contribute to earthquakes and land deformation.

Activity Ideas:

• Folding Layers with Paper Strips – Stack colored strips of paper to represent rock layers. Push the ends together gently to model how compression forms fold like anticlines and synclines. Observe how different pressures affect the shapes of the folds.
• Foam Fold Model – Use layers of foam or clay in different colors to simulate folded rock. Apply slow compression to mimic tectonic forces and examine how the layers bend, shift, and form mountain-like shapes.

Crosscutting Concepts (CCC): Cause and Effect

Folding in rocks happens due to compression forces acting over long periods.

• Cause: Compression squeezes rock layers together.
  Effect: The rock bends instead of breaking, forming folds such as the Appalachian Mountains.
• Cause: Slow, continuous movement of tectonic plates applies stress to rocks.
  Effect: Over millions of years, folded rock layers create mountain ranges and valleys, such as the Alps in Europe.
• Cause: Uneven pressure causes rock layers to bend in different ways.
  Effect: Different types of folds form, such as anticlines (upward folds) and synclines (downward folds), seen in regions like the Zagros Mountains in Iran.