While walking or cycling along Merri Creek you may be aware of the indigenous plantings, constructed wetlands and the animal life of the creek corridor. But there is an underlying element to this - the Merri valley contains many millions of years of history and secrets.
Over 400 million years ago the sea covering this area receded. It left behind a layer of yellowish marine siltstone and sandstone rocks. Around 65 million years ago non-marine sediments left a sandy layer behind. Over time the ancestral valley of the Merri Creek developed, eroding through these sediments.
Then, from 0.8 to 4.6 to million years ago volcanoes such as Hayes Hill (about 5km east of Donnybrook) and Mt Fraser (near Beveridge) erupted, sending lava on an epic journey along the ancestral valleys of the Merri and Darebin Creeks and into the valley of the Yarra River as far as the CBD.
Our modern day Merri Creek was formed over many years, by incising through the lava surface. One of the many sites of geological interest along the Merri valley is the rocky cliff face on the eastern side of Merri Creek visible from the shared path in Clifton Hill (shown at left). City of Yarra primary school students will explore the site as part of MCMC’s Northern Nature Creek Connections program funded by the Natural Heritage Trust.
The cliff face is a sculptural revelation. Its tall, cracked (or jointed) basalt columns, formed by cooling lava, are clearly visible and the weathering evident in the rocky riffles mid-stream where columns have collapsed and tumbled into the stream. Some of the vertical fractures at the top of the cliff appear to be leaning, forming an amazing radial pattern.
But you don’t have to be a primary school student to explore the fascinating secrets of the Merri valley! Next time you’re in the area see what you can observe in the rocky escarpment features along the way.