Active learning ideas
Rock deformation explains how the Earth's crust bends and breaks under tectonic stress. This topic introduces the concepts of stress (the force applied) and strain (the resulting deformation). Students explore the factors that determine whether a rock will behave in a brittle way (fracturing) or a ductile way (folding), including temperature, confining pressure, and the rate of strain. This is a core element of the OCR Geology specification.
Activity 01
Students use different materials (e.g., cold vs. warm plasticine, dry biscuits, silly putty) to model rock behaviour. They apply stress at different speeds to see which materials fracture and which flow, recording the conditions for each.
What is the difference between stress and strain?
Activity 02
Students are shown images of a fold, a normal fault, and a strike-slip fault. They must identify whether the stress was tensional, compressional, or shear, and then explain their reasoning to a partner using hand gestures to show the force.
How do temperature and pressure affect rock deformation?
Activity 03
Groups create a poster showing a cross-section of the crust. they must place different structures (folds vs. faults) at the correct depths and explain how temperature and pressure changes influence this 'brittle-ductile transition'.
Why do some rocks fracture while others fold?
A few notes on teaching this unit
Watch Out for These Misconceptions
Rocks are always hard and can only break.
Under high pressure and temperature, rocks behave like very viscous liquids. Using 'Silly Putty' to show that it snaps when pulled quickly but stretches when pulled slowly helps students understand the role of strain rate.
Stress and strain are the same thing.
Stress is the 'cause' (force per unit area), while strain is the 'effect' (change in shape). A simple 'pushing on a sponge' demonstration can visually separate the force applied from the deformation observed.
Methods used in this brief
Faults and Folds
Classify different types of faults (normal, reverse, strike-slip) and folds (anticlines, synclines). Understand the tectonic regimes that produce these geological structures.
8 methodologies
Interpreting Geological Maps
Develop the spatial skills required to read and interpret geological maps and cross-sections. Students will deduce geological histories and calculate true dip and strike from map data.
8 methodologies