Earth and Environmental Science 11–12 · Year 12
Sediment layers in a jar: superposition, grading and reading a sequence
Module 5: Earth’s Processes
The idea
Sediment settles with the oldest layer at the base, coarsest grains first in each pulse, which is the rule that lets a rock sequence be read in order.
What you need
- tall clear jar or measuring cylinder 1 L, a mixed sediment of gravel, sand and mud (500 g), water
- three coloured sands for separate pulses, stopwatch, ruler
- a photograph of a local road cutting with visible bedding
How to do it
- Add the mixed sediment to the water-filled jar, shake, stand it and observe for 5 minutes, then again after an hour.
- Measure the thickness of each graded band and note grain size from base to top.
- Add the three coloured sands one pulse at a time, letting each settle, to build a layered sequence; record the order of addition.
- Hand the jar to another group and ask them to state the order of events from the layers alone.
- Apply the same reasoning to the road-cutting photograph: which bed is oldest, and what does each grain size say about the water that laid it down.
What you should see
Each shaken pulse produces a graded bed, gravel at the base fining upward to mud on top, and later pulses lie above earlier ones; the second group reads the order of addition from the layers and checks it against the record. Mud stays cloudy for an hour or more, matching the Stokes settling times, so the finest layer is the last to appear.
What changes
This activity lists no variables to change, measure and keep the same.
Common misconceptions
Each of these ideas is wrong, and the activity is a chance to test it.
- Layers form at the same rate as the years pass (a bed can be one flood).
- The top layer is the oldest because it was there first.
Safety card
Hazards
- heavy wet jar
Controls
- carry with two hands
Note
No hazardous chemicals or heat sources: record the activity in the school's RiskAssess risk assessment, following the NSW Department of Education Science safety and compliance page; the Chemical Safety in Schools package is not triggered.
Curriculum references
The NSW syllabus outcomes and Australian Curriculum v9 codes this activity supports. They are references, not a verified or complete curriculum alignment.
- Earth and Environmental Science Stage 6 Syllabus (2017), NESA; current, replaced by the 11–12 Syllabus (2025) from 2028EES12-12EES11/12-5EES11/12-6EES11/12-7
- Earth and Environmental Science 11–12 Syllabus (2025), NESA; to be implemented from 2028, not yet taughtEES-12-01
- Australian Curriculum v9No Australian Curriculum v9 code is listed.
Sources
The pages the author read to write this activity.