Landscapes and weathering
Doug Finlayson
Over the last 350 million years the Yass-Canberra region has been in a non-marine environment and erosion has exposed rocks at the surface that were once deeply buried. More recently, during the cool periods of the last 3 million years, there was extensive erosion of steep hillsides by rain and frost action. The net result is the gently rolling landscapes seen across the area of the proposed Murrumbidgee - Ginninderra Gorges National Park with deep river gorges cut through the softer rocks to form rapids, gorges and waterfalls.
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Other consequences include the layers of sand, gravel and silt being deposited on the gently-sloping areas adjacent to the hillsides. Examples are seen along the Murrumbidgee River and its tributaries. Such near-surface deposits form the regolith the term applied to the blanket of weathered rocks and soils that cover the bedrock, often to depths of many metres. |
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Ginninderra Porphyry gravel quarried near Ginninderra Falls for use in landscape gardening. Similar deposits are found elsewhere in the region. |
