Active learning ideas
Sedimentary environments provide a window into Earth's past climates and landscapes. In this topic, students follow the 'sedimentary cycle', from the physical and chemical weathering of source rocks to the eventual lithification of sediment into rock. This is a core part of the OCR A-level, focusing on how grain size, sorting, and roundness act as proxies for transport energy and distance.
Activity 01
Using a simple trough and water, students observe how different flow velocities transport and deposit various grain sizes. They record the formation of ripples and deltas, linking flow energy to the resulting sedimentary structure.
How do weathering and erosion produce sediment?
Activity 02
Stations feature rock samples and photos of structures (e.g., desiccation cracks, cross-beds). Students must identify the structure and use it to argue whether the environment was terrestrial, coastal, or marine.
What can grain size and sorting tell us about transport energy?
Activity 03
Students define the two terms individually, then pair up to categorize a list of processes (e.g., freeze-thaw, river transport). They must explain to the class why weathering is 'in situ' while erosion involves movement.
How do sedimentary structures indicate past environments?
A few notes on teaching this unit
Watch Out for These Misconceptions
All sedimentary rocks are formed in the ocean.
Many sedimentary rocks form in deserts (aeolian), rivers (fluvial), or lakes (lacustrine). Comparing the red sandstones of a desert to the grey shales of a deep sea in a sorting task helps students broaden their environmental scope.
Rounding and sorting happen at the same rate.
Rounding depends on the hardness of the mineral and the transport medium, while sorting depends on the consistency of energy. A peer-led investigation into 'textural maturity' helps students see that a rock can be well-sorted but poorly rounded.
Methods used in this brief
Mineral Identification and Properties
Develop practical skills in identifying common rock-forming minerals using diagnostic physical properties. Students will investigate hardness, cleavage, lustre, and specific gravity.
8 methodologies
Igneous Processes and Rocks
Examine the formation of igneous rocks from magma and lava, focusing on cooling rates and crystal size. Classify igneous rocks based on their mineral composition and texture.
8 methodologies
Metamorphism and Metamorphic Rocks
Investigate the changes in rocks subjected to high heat and pressure without melting. Differentiate between contact and regional metamorphism and their resulting rock types.
8 methodologies