Geography K–10 · Years 7–8

Angle of repose: how steep a slope of loose material can stand

Landscapes and landforms (ACARA Year 8 sub-strand); NSW Stage 4 focus area Landscapes and Landforms (2015 syllabus) and Landscapes and landforms (2024 syllabus); geomorphological hazards, where AC9HG8K05 is cited for the causes half of its descriptor (how steep loose material can stand, and so when a slope fails) with the paper vegetation mat as the only mitigation element; the entry does not address impacts on people and places

PracticalMedium risk

School laboratory, not for home

In a school laboratory, with a teacher supervising, under the school's risk assessment. Not for home.

The idea

Loose material piles up to a fixed maximum angle that depends on the grains and their wetness, and a slope cut steeper than that angle fails.

Safety card

Medium riskA teacher supervises

Setting: In a school laboratory, with a teacher supervising, under the school's risk assessment. Not for home.

Hazards

respirable crystalline silica dust from dry sand being poured, spread and cleaned up
spilt grains underfoot

Controls

pour inside the tray with the funnel low over it, at or below bench height, so grains fall a short way and the tray catches the cone and the spills
safety glasses for everyone at the bench, as the dune practical requires for the same sand
work outdoors or in a well-ventilated room; keep the dry fine sand in a closed container between trials and pour slowly
clean up damp: mist spills with water and wipe them up with a damp cloth, or damp-sweep; never dry-sweep or brush dry sand, which puts the dust back into the air; hands washed afterwards

Note

No chemical is added and no heat is used, but the fine sand is silica sand and pouring, spreading and sweeping it dry puts dust into the air. Respirable crystalline silica has an eight-hour time-weighted-average workplace exposure standard of 0.05 mg/m³ set by Safe Work Australia and is the dust behind silicosis, which is why the pour is low and contained, eye protection is worn and the clean-up is damp rather than swept. Record the practical in RiskAssess (riskassess.com.au) with the dust hazard named. The NSW Department of Education Chemical Safety in Schools package is not triggered, because no chemical is added.

What you need

1 kg each of dry fine sand, coarse sand, 5 mm gravel and dry rice; the fine sand is silica sand and this method pours and spreads it dry, so read the safety block first
A funnel on a stand 5 cm above a tray; a protractor and a ruler; a card cut to measure the cone's height and base
A 100 mL measuring cylinder, a mixing bowl and a spoon
A 30 cm × 20 cm board hinged at one end with a protractor at the hinge; a 1 cm layer of each material for the tilt test

How to do it

Pour each dry material slowly through the funnel until a cone forms. Measure the cone height h and base diameter D; angle = arctan(2h / D). Repeat three times per material.
Mix 30 mL of water into 1 kg of the fine sand and build a damp cone by spooning it onto one spot (damp sand will not run through the funnel); then mix in more water until a film of water stays on the surface (saturated) and build the cone the same way.
Tilt test: spread 1 cm of dry fine sand on the board and tilt slowly until the layer slides; read the angle. Repeat three times, then with the damp sand, then with a "vegetation mat" of paper strips glued to the board surface.
Tabulate mean angles for each material and condition.

What you should see

Each dry material gives a cone angle whose three trials the learner compares, reporting their spread; the angle does not depend on pile size. The materials are expected to differ, with more angular grains standing steeper than rounded ones. Damp sand is expected to stand steeper than dry (water films bind the grains) and saturated sand to slump to a lower angle. The tilt-board sliding angle is compared with the cone angle, and the paper mat is expected to raise the sliding angle. The learner reports mean angles in degrees.

What changes

What you change: material and moisture
What you measure: angle of repose (degrees)
What you keep the same: pour height and rate
three trials
same funnel and board

Common misconceptions

Each of these ideas is wrong, and the activity is a chance to test it.

A bigger pile of sand can stand steeper.
Wet slopes are always weaker than dry ones.

Curriculum references

The NSW syllabus outcomes and Australian Curriculum v9 codes this activity supports. They are references, not a verified or complete curriculum alignment.

Geography K–10 Syllabus (2015), NESA; current and taught in 2026, replaced from 2027. The outcome codes are not printed on the NESA landing page for this syllabus, which only links the document, so the url given is the syllabus document itself (geography-k-10-syllabus-2015.docx); the code and its outcome text were read in that document on 23 September 2026.GE4-2 GE4-5
Geography 7–10 Syllabus (2024), NESA; implementation from 2027, not yet taught; code read on this page on 22 September 2026GE4-PRI-01 GE4-MAN-01
Australian Curriculum v9AC9HG8K01AC9HG8K05AC9HG8S02

Sources

The pages the author read to write this activity.

All Concept Studio activities