21°S 138°E Arcadia – Queensland by Degrees

AT THE POINT

Degree confluence 21°S 138°E, Google Earth

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n

Looking north

e

Looking west

s

Looking south

w

Looking east

Location: Degree Confluence 21°S 138°E is approximately 300 m east of the Qld-NT border on the Barkly Tableland. At this location the border is marked by a vermin-proof fence, although the confluence itself is unmarked. A GPS was used find the exact location of the point (accurate to within a few metres). The closest significant settlement is Urandangi, about 75 km to the south-east. The site was visited by a party of RGSQ members in May 2008, who gained access via dirt roads from Alpurrurulum and local property tracks.

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The remains of the old surveyor's campsite near the confluence point

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The marker in the middle of the old surveyor's campsite

Landscape: Degree Confluence 21°S 138°E is located on the Barkley Tableland, which is predominately flat, with an elevation of approximately 200m. Aside from the border fence, there is also a marker from what was probably an old confluence survey located near the point. This marker has the same initials and design as ones located in other areas of Queensland (including 23°S 138°E, 24°S 141°E, 25°S 142°E). There is some sparse vegetation surrounding the point, and the photos show that stones and some grass are scattered over the largely bare ground surface.

At the confluence drainage appears to take place along areas of slightly lower elevation. The closest watercourse is Muddy Creek to the east, which flows into the Georgina River a few kilometres to the south. The Georgina River is part of the Lake Eyre Basin.

The numerous surface stones are generally light in colour. The surface geology at the confluence is given as mainly Tertiary (Miocene) limestone by Queensland geology maps (which note that Cambrian dolomite occurs in the district). In contrast, the Northern Territory maps refer to the surface geology as mainly Upper Cambrian dolomite (while indicating nearby Tertiary limestone).

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Border track and vermin fence shown running north-south
to the west of degree confluence 21S 138E (Google Earth Image)

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Braiding stream pattern, Georgina River to the south-east of the confluence (Google Earth Image)

Point Photos By: Paul Feeney, Mary Comer

IN THE DEGREE SQUARE

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Climate: The closest representative weather station is at Urandangi, which is approximately 100 km to the south-west of the degree confluence, and has an elevation of 174 m. The station has been recording data since 1891.

 

Jan

Feb

Mar

Apr

May

Jun

Jul

Aug

Sep

Oct

Nov

Dec

Year

Mean max
(ºC)

38.5

37.2

35.7

32.4

27.5

24.3

24.0

26.7

31.3

35.1

37.5

38.8

32.4

Mean min
(ºC)

24.0

23.4

21.1

16.7

12.0

8.4

7.0

8.8

13.0

17.6

20.6

22.8

16.3

Mean rain
(mm)

62.2

63.9

41.9

13.2

12.5

9.5

9.0

4.5

6.2

14.4

21.1

38.9

297.7

The highest temperature recorded was 47.0°C in December 1979, and the lowest was -2.0°C in both June 2002 and July 1984. The greatest rainfall recorded in a year was 925.2 mm in 1950, and the lowest was 29.5 mm in 1928. These and other climate statistics for Urandangi can be found at: Australian Bureau of Meteorology, http://www.bom.gov.au/climate/averages/tables/cw_037043_All.shtml.

Extremes of Nature: Despite the area's inland location, it is still subject to the impact of some cyclones. The database maintained by the Bureau of Meteorology shows that four cyclones have passed within 200 km of the confluence since 1906, although none have passed within 50 km. Even distant cyclones bring with them potentially destructive winds and intense rainfall. Cyclone information for this area and all of Australia can be found at the Australian Bureau of Meteorology website, http://www.bom.gov.au/cgi-bin/silo/cyclones.cgi.

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Cyclone tracks within 200 km of point 1906 to 2006 (Bureau of Meteorology web site)

Like most places in the Australian tropics, extreme heat is also a danger. Records show that the Urandangi Station experiences 152 days annually with temperatures 35°C or warmer, 53 days of which reach over 40°C. Such extreme temperatures can cause heat stroke and death if appropriate measures are not taken such as avoiding strenuous physical effort, keeping as cool as possible and drinking lots of water. Heat waves kill more people in Australia than all other natural hazards combined. With a low average rainfall, and only 31 days a year with any precipitation, the area is also among the driest in Australia.

Today: The resident population of the degree square has remained at zero since the 1996 census.

Information: Ken Granger

Climate information: Jo Grant

Edited by: Hayley Freemantle

REFERENCES

Geoscience Australia, NATMAP Raster

Geoscience Australia, Scanned 250 K Geology Maps