The listed coordinates are at the first waypoint - a large erratic (boulder) in the Loftus Hills Memorial Reserve, within the Henty Glacial Erratics State Reserve.
Park at the suggested parking area (S 41° 59.557' E 145° 29.561').
Loftus Hills Memorial Reserve
The Loftus Hills Memorial Reserve was created due to its interesting geological features. It was named in honour of Tasmanian geologist, Dr Clive Loftus-Hills, who was an influential geologist in the early part of last century.
In the car park you will find some information about the reserve.
Across the road from the southern end of the car park, a trail leads up a short staircase and along a short walk that highlights some unique glacial features, including a number of interesting glacial erratics. Further information about the geological features, together with a memorial plaque dedicated to Dr Loftus-Hills, can be found along the trail. The two waypoints that must be visited to gather the information required to complete this earthcache are along this trail.
Underlying geology
The oldest bedrock visible in this area shows Cambrian rocks comprising ash-rich volcaniclastic siltstones and sandstones of the Mount Read Volcanics, deposited during a period of volcanism about 500 million years ago. The volcanic rocks were subsequently largely eroded and partly deposited beneath the ocean, prior to being exhumed during a Devonian mountain building episode.
Glacial activity
During the Pleistocene epoch (ie between about 2.5 million and 12,000 years ago), the area that is now Tasmania was affected by multiple periods of glacial activity with large ice sheets covering much of the mountainous central and western parts. The Henty Glacial Erratics State Reserve is located near what was the western limit of ice during the Henty glacial event approximately 34,600 years ago (Figure 1).
Figure 1: The limit of Pleistocene glaciations in Tasmania showing the location of the Henty Glacial Erratics State Reserve.
Glacial erratics
As the ice sheet melted, rock debris and clay that were once entrained in the ice were deposited as glacial till in this area.
The glacial till includes large boulders called glacial erratics. Glacial erratics are rocks that differ from the size and type of rock native to the area in which they rest. These erratics can range in size from pebbles to large boulders, often carried over hundreds of kilometres by glacial ice. Sometimes they can end up being ‘balanced’ or ‘perched’ on other rocks or glacial till. They are often distinctively marked, grooved and shaped by the erosional action of the glacial ice.
Geological modelling suggests that the boulders in this area were sourced from the elevated West Coast Range in the Mt Julia – Mt Tyndall area approximately 10–15 km to the northeast (Figure 2).
Figure 2: Schematic map showing source of the glacial erratics.
The erosional contact between the Mt Read Volcanics and the overlying Pleistocene glacial till is exposed in the cutting on the road opposite the car park (Figure 3).
Figure 3: Erosional contact between the Mt Read Volcanics and the overlying Pleistocene glacial till exposed adjacent to the road.
To log this earthcache...
To log the cache, please send me a message or email with answers to the following questions:
At Waypoint 1 (listed coordinates) you will be standing near a large erratic (boulder).
Q1. Describe the shape and dimensions of the boulder.
Q2. Why do you think it is this shape?
At Waypoint 2 you will be standing near an unusual rock feature.
Q3. Describe the unusual rock feature.
Q4. Explain how you think this unusual feature was formed.
The answers can be determined from your observations at the two waypoints and by reading the information in the above cache description.
Please feel free to log your visit as soon as you have submitted your answers to me. I will respond confirming permission to log, or asking clarifying questions if I feel that you have not answered the questions correctly. Logs with no answers sent at the time of logging will be deleted. Please do not post your answers in your log.