As you drive along many of the roads in the Stockyard Hill and Stoneleigh areas, you will struck by what is almost a ‘moonscape’ of dozens of stony mounds and ridges in the land.
This landscape was formed between 100,000 and 500,000 years ago by massive lava flows, mainly from the Stockyard Hill volcano.
STOCKYARD HILL is a very low but very wide volcano that is approximately 5km to the south west of this location.
It was initially formed when hot magma (lava that is under the earth’s surface) broke through the earth’s surface and came into contact with water, the resulting reactions forming the wide but shallow MAAR crater of Stockyard Hill.
The volcano then went through a phase of explosive FIERY ERUPTIONS, ejecting ash, basalt rocks and scoria into the air. Today, farmers will have cleared many of these rocks from their paddocks, and you may see them used in stone walls, or simply piled into heaps or lines in the paddocks or along the roadside.
In between these explosive phases, Stockyard Hill produced extensive LAVA FLOWS, dribbling massive amounts of hot lava that flowed for kilometres, mainly to the west and to the south. It is estimated that these lava flows are up to 60 metres deep.
As these lava flows cooled, they formed a hard crust that was, over time, weathered by wind and rain into the mineral rich soils that we see on these farms today.
During the cooling of the lava flows, pockets of hot magma were still present underneath, and would sometimes break through the crust, pushing up more rock and lava through these vents and fissures, causing the mounds and ridges of the stony rises.
In summary:
The shapes, ridges and depressions of lava flows are influenced by several factors, including:
- The underlying topography of pre-existing hills, rivers and valleys.
- Pockets of hot liquid lava breaking through the cooling and hardening crust of a lava flow as it rolls along.
- Other vents, where lava is pushed up to or breaks through the earth’s surface.
- Other lava flows from distant volcanoes.
- Weathering and erosion.
Aerial view of the stony rises of Stockyard Hill and Stoneleigh
Earthcache Logging Requirements:
In order to log this earthcache as a find, you need to answer the following questions and email or message them to the cache owner (chooknchunk).
You may go ahead and log this cache immediately however you need to submit your answers within a week of logging. Logs that are not backed up by submitted answers will be deleted.
At the posted co-ordinates, it is safe to park on either side of the road where there are clearings. This earthcache is viewable from the car or the side of the road.
Questions:
Q1. In your own words, describe the landscape and the stony rise features you can see around you (eg. how many, shape, dimensions, colours etc).
Q2. How do you think they were formed? (Hint: Use the information given above. There are no definitive answers, we are just after your thoughts).
Thank you for visiting the stony rises of Stockyard Hill and Stoneleigh.