21°S 150°E Penrith Island – Queensland by Degrees

AT THE POINT

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Confluence point location 21°S 150°E, Google Earth

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Location: This confluence point is located at sea within the Great Barrier Reef, 10 km east of Penrith Island. It has not been visited.

The Landscape: The waters of the Cumberland Channel.

Point information and photos: Ken Granger and Google Earth, 2009

IN THE DEGREE SQUARE

The Country: The square contains a dozen or so small continental islands that lie inside the Great Barrier Reef. These islands are made up of granite and rhyolite of Cretaceous age (141 to 65 million years). The largest island is Scawfell Island which has a maximum elevation of 397 m ASL, Prudhoe Island in the south is 331 m high and most of the other islands have elevations of at least 100 m ASL. They are very steep sided and are covered with numerous granite tors.

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The Climate: The climate is classified as being sub tropical with a dry winter. The maritime location may modify the extremes of temperature experienced on the mainland. The Bureau of Meteorology climate station in Mackay provides representative statistics.

Mackay Met Office (033119) 1959 to 2009 (elevation 30 m ASL)

 

Jan

Feb

Mar

Apr

May

Jun

Jul

Aug

Sep

Oct

Nov

Dec

Year

Mean max
(ºC)

30.1

29.6

28.6

26.7

24.2

21.9

21.2

22.5

25.2

27.5

29.2

30.1

26.4

Mean min
(ºC)

23.5

23.4

22.2

20.1

17.1

14.0

12.8

14.0

16.6

19.7

21.

22.9

19.0

Mean rain
(mm)

278.1

325.5

251.4

147.4

108.2

64.7

40.2

30.9

16.4

36.8

88.7

179.9

1 578.2

The highest temperature ever recorded in Mackay was 39.4°C in December 1964 while the lowest temperature was 3.8°C in July 1965. Rainfalls also vary greatly. The highest total of 2744.7 mm was recorded in 1963 and the lowest total of 794.6 mm in 1987.

Extremes of Nature: The point lies within one of the more active cyclone areas on the Queensland coast. The database maintained by the Bureau of Meteorology shows 60 cyclones have passed within 200 km of the point in the 101 years from 1906-7 to 2006-7. Of these four passed within 50 km of the point. They were: an unnamed cyclone in February 1915, an unnamed cyclone in January 1946, TC Pierre in February 1985 and TC Ivor in March 1990. These cyclones would have produced very high seas that would have caused damage to the reefs within the square.

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Cyclone tracks that passed within 200 km of the confluence point 1906-2006 (BoM web site)

The earthquake database maintained by Geoscience Australia contains details of two events on the boundaries of the square. The largest was the ML 4.7 quake of 19 October 1960 located on the western boundary of the square south-west of the point. The other event was a ML3.2 quake on 6 April 1991 located on the northern border of the square. No damage was reported from either event.

The Indigenous Story: The land and waters within the degree square is the traditional country of the Yuwi people.

MORE INFORMATION WELCOME

European Exploration and Settlement: The first European navigator to pass through the area was james Cook on HMS Endeavour in 1770. He was followed in 1819 by Philip Parker King in HMS Mermaid. King named several of the islands in the square.

Today:

There is no population within this degree square.

The waters of the Cumberland Channel form part of the main shipping channel inside the Great Barrier Reef.

The islands from Penrith Island north are all part of the Cumberland Islands National Park while those to the south are all part of the Northumberland Islands National Park. The northern section falls within the Mackay regional Council area and the southern part is within the Isaac Regional Council area.

MORE TO COME.

Compiler: Ken Granger, 2009

Edited by:  Hayley Freemantle