Total solar eclipse 2002 December 4

in South Australia

Location Report for the Roxby Road and Andamooka district
part 1 of 2

Roxby Road & Andamooka

Click here to download a high-resolution version of this map (6.6MB zip).

If you have come directly to this page from another website; you can find my other eclipse information here.

NOTE : This page should be read in conjunction with the Stuart Highway Location Report, which contains some more general discussion about terrain and driving conditions.

The photos on this page were taken on cloudy days in mid-winter; so the sunlight is much less intense than what is expected for eclipse day.

General notes

Like the landscape west of Pimba, the region south of Andamooka and Roxby Downs is also the product of hundreds of millions of years of erosion. Apart from the numerous gullies flowing into Lake Torrens, and the 20 - 40 metre high slopes along its western shore, there is not much in the way of topography in this region.

The Lake occupies a geologic trough along the western side of the Flinders Ranges. Sediments washed down from the Flinders have filled Lake Torrens with deep deposits of mud and silt, leaving the lakebed about thirty metres above sealevel. The Flinders creeks have also deposited massive amounts of sand east of the Lake.

Lake Torrens has a lower salt content than the other big lakes in SA; and it is hypothesised that it has overflowed southwards to the Gulf in the past. The lower salt content of the lakebed muds slows the development of a strong crust when the Lake evaporates; but this, in an unexpected way, is beneficial to safety because the majority of the exposed lakebed still presents an obvious "soft and muddy" appearance to the eye.

Some of the vast quantities of sand east of Lake Torrens has found its way to the dunefields south of Roxby Downs. Additional sand has been blown down from the north; eroded from the rocks that formed in a shallow Jurassic - Cretaceous inland sea, and in the lakes that replaced it.

Consequently, the Roxby region contains much more sand than the land along the Stuart Highway; and a lot of this sand is piled into linear dunes between two and five metres in height. These dunes are often colonised by Callitris pines growing up to 8 metres high, as well as many lower shrubs and perennials. A substantial rainfall will invigorate these plants, and germinate countless seeds, resulting in a beautiful display of wildflowers.

A regolith substrate (similar in composition to the Stuart Highway regolith) underlies many of the dune fields; typically exposing itself as small clay-pans and flat silty patches between the sand ridges. These can be driven upon when dry; but the slightest rain will turn them into a zero-traction mud trap. Driving on the sand dunes themselves is not recommended. Their sand is often loose enough to trap most four-wheel-drive vehicles.

South of centreline on the Roxby Road

As with the Stuart Highway Location Report we begin our description at Pimba; turning off the Stuart Highway to travel north. From here it is 6.5 km by road to the Woomera turnoff, but we continue north, past Woomera's massive concrete water storage tanks (fed from a ~500 km long pipeline from the Murray River) to the Roxby Road turnoff. If we choose to drive past this intersection, we would soon be approaching the main entrance into the Woomera Prohibited Area (WPA). Access to the WPA - which is sometimes used for military exercises involving live ammunition and explosives - is restricted for safety reasons. However anyone can visit the town of Woomera.

Former residents like me can find today's Woomera a bit depressing, because we remember what the place used to be like. The population has plummeted from a peak of ~9,000 in the early 1970's, when Woomera was a focus for European spaceflight operations and US/Australian military activities, to less than 500 today. Many of the houses have been removed leaving large swathes of vacant blocks and depopulated streets. But a lot of the town's major infrastructure, such as its swimming pool, shopping centre, sportsgrounds and other public facilities, has survived to the present day. The town is slowly regenerating itself as a venue for commercial space launches, aerospace and military research; and flight tests of just about anything that might need the WPA's 127,000 square km in case of a prang. A consortium of Japanese universities and the University Of Adelaide also operate gamma-ray telescopes in the desert north of the town.

The Woomera Heritage Centre, and the actual aircraft, rockets and missiles mounted in the middle of town, convey to the visitor some idea of what Woomera used to be like, and some of what goes on in the WPA today. The WPA Location Report describes the special arrangements for eclipse visitors. Woomera itself will have a 99.8 percent partial eclipse - this means that the sun will shrink down to the slenderest of crescents, possibly broken into discontinuous arcs of dazzling light by silhouetted lunar mountains....

powerline Returning to the Roxby Road, we drive north through a broad but shallow valley, past Phillip Ponds (the only semi-permanent natural water in the district), before climbing out onto the peneplain once more. This part of the Roxby Road is much like the terrain west of Pimba: flat and covered with countless gibber stones. At about 30 km (road distance) from Pimba, the Road is crossed by two sets of powerlines on these big pylons. And a cattlegrid. On a clear day in this flat terrain, it is possible to see the powerlines all the way to the horizon - and then curving down beyond it as they follow the curvature of the Earth. A telling demonstration that the Earth isn't really flat, even though it seems to be around here! Another cattlegrid, this one 32.4 km from Pimba, is not far south of South Limit.

Roxby Road near south limit The eclipse's South Limit crosses a featureless piece of the Road 35.6 km from Pimba. As shown by this photo, it's barren terrain covered in gibber stones on top of a deeply weathered regolith. But because of the occasional flooding in this region, the Road is elevated on a low embankment (just like the Stuart Highway) which may make it a little difficult to get your car right off the Road. Fortunately the gibber stones in this location have compacted themselves over the millennia to create a surface that can support cars. But drive slowly and be careful not to wheelspin. If eclipse day is unusually cold (eg: 10 C instead of 30 C) then atmospheric refraction could move the South Limit 0.3 km (road distance) closer to Pimba.

carpark 47k N of Pimba The larger of the two off-road public parking areas on the Roxby Road is about halfway between South Limit and centreline, at 47.4 km from Pimba (or 37.9 km from Roxby Downs) on the west side of the Road. This all-weather parking area, shown here in a photo looking southwest, is about half the size of a footy field and will get 24 seconds of totality. The pylons of the Roxby Downs powerlines can be seen in the distance. Don't even think of pitching a tent in this parking area - it's been packed down with hundreds of tons of crushed rock, graded flat, and compacted by heavy vehicles. Put up your tent in the sandy terrain nearby.

51km N of Pimba This view of the Roadside was taken 51km (road distance) north of Pimba; and shows the typical disposition of vegetation for this region. Note that the Road is raised above the natural ground surface to alleviate flood problems.

Click here to show a high-resolution version of this image (142kB jpg).

line of maximum eclipse The final approach to centreline from the south is down a long gentle slope, because the centreline approaches the Road along a wide but shallow east-west depression in the landscape. This slight elevation might provide a chance to see the Moon's shadow hurtling across the landscape; but safe parking may be difficult because the Road here runs on an embankment bordered by loosely-consolidated sands and clays. As if to emphasise the parking hazard here, another north-bound road train rushed by just as I took this photo.... The top of this slope, 53.3 km from Pimba, is where the maximum duration of totality (27.1 seconds) occurs on the Roxby Road.

Click here to show a high-resolution version of this image (156kB jpg).

CONTINUE to part 2 of this report....

Copyright © 2002   Fraser Farrell. All rights reserved.