Science 7–10 · Year 8
How far has Australia moved in your lifetime: plate motion from the national datum
Science understanding: Earth and space sciences (NSW Stage 4 focus areas Change and Data science 1)
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The idea
Plates move a few centimetres a year, a rate a class can set beside its own fingernail growth; Australia's motion is large enough that the country's map coordinates had to be moved by about 1.8 metres between 1994 and 2020.
What you need
- the Geoscience Australia GDA2020 page: Australia moves about 7 cm per year, and GDA94 coordinates were about 1.8 m from ITRF coordinates by 2020
- the USGS This Dynamic Earth rates: Mid-Atlantic Ridge spreading about 2.5 cm/yr, East Pacific Rise more than 15 cm/yr
- a ruler, a calculator, a tape measure and chalk
How to do it
- Check the GDA2020 figure: multiply 7 cm/yr by the 26 years from 1994 to 2020 and compare with the 1.8 m the page states.
- Compute how far Australia has moved since each learner was born and mark that distance on the floor with chalk from a start line.
- Compute how long at 7 cm/yr it takes to move 100 km, and how far the plate moves in 1 million years and in 50 million years.
- Compare with the USGS rates for the Mid-Atlantic Ridge and the East Pacific Rise on a bar chart.
- Measure the class's mean fingernail growth over four weeks (mark the nail base with a fine pen at the cuticle and measure the mark's travel) and compare the annual rate with the plate rate.
What you should see
7 cm/yr x 26 yr = 182 cm, matching the approximately 1.8 m Geoscience Australia states; a 13 year old has moved with the continent about 91 cm and a 15 year old about 105 cm. At 7 cm/yr the plate covers 100 km in about 1.4 million years, 70 km in 1 million years and 3,500 km in 50 million years. The USGS spreading rates bracket Australia's rate (2.5 cm/yr and over 15 cm/yr). The class's four-week nail growth, scaled to a year, is set beside the 7 cm/yr plate rate; the comparison, not a set figure, is the result. The learner knows it worked when the 26 year product reproduces the datum shift.
What changes
- What you change
- elapsed time
- What you measure
- distance moved
- What you keep the same
- constant rate assumed
Common misconceptions
Each of these ideas is wrong, and the activity is a chance to test it.
- Plates move too slowly to matter to people; GPS and map datums must be corrected for it every few decades.
- Continents move but Australia is fixed; Geoscience Australia gives its motion as about 7 cm per year.
Safety card
Hazards
No hazard is listed.
Controls
No control is listed.
Note
No hazardous chemical and no flame or heating apparatus: a generic classroom risk assessment (CSIS 1.7 or RiskAssess) covers trips, spills, warm lamps and sharp edges.
Curriculum references
The NSW syllabus outcomes and Australian Curriculum v9 codes this activity supports. They are references, not a verified or complete curriculum alignment.
- Science 7-10 Syllabus (2023), NSW Education Standards Authority (implemented from 2026; codes read at curriculum.nsw.edu.au on 22 and 23 September 2026)SC4-CHG-01SC4-DA1-01SC4-WS-05SC4-WS-06
- Australian Curriculum v9AC9S8U03AC9S8H01AC9S8I04
Sources
The pages the author read to write this activity.