SHONA BLEWETT:
Hi, I'm Shona. I'm the Education and Outreach Manager at Geoscience Australia. Geoscience Australia brings together experts in Australia's geology and geography. In this series, we're going to explore some of Australia's landscapes and landforms. We're going to learn about some of their features and the processes that shape them. We're also going to think about how landscapes and landforms are valued and the ways humans impact and protect them. In this video, we're going to take a closer look at one of Australia's most iconic coastal Landforms, the Twelve Apostles.
SHONA BLEWETT:
How do you think these incredible landforms have been shaped? Why do we value them and how are they managed? Millions of years ago, the Twelve Apostles would simply have been part of the mainland of Australia. They were created by the constant erosion of the limestone cliffs. The water and the winds of the ocean have shaped them. First, waves cut into the base of the cliffs forming caves. The caves get larger and larger and become arches, and eventually an arch will collapse, leaving a stack of rocks standing on its own up to 50 metres high. Although their name suggests there were once 12 stacks, there were only nine stacks at the beginning of this century. Two have since collapsed. One collapsed in 2005 and the other in 2009, leaving seven stacks. With the ongoing erosion from the waves and wind, these will one day disappear too. But parts of the cliff nearby are expected to become new rock stacks in the future. So the Earth is constantly being shaped.
SHONA BLEWETT:
There is evidence of the presence of Eastern Maar peoples near the Twelve Apostles dating back thousands of years. Shell middens and stone artifacts can still be seen in the area. These landforms are protected by the Twelve Apostles Marine National Park, which runs along 17 kilometres of the coastline. Everything above and below the water is protected. This means things like fishing and mining are banned. Even the weedy seadragons are protected and free to explore the dense kelp forests beneath the water.
SHONA BLEWETT:
Marine National Parks also provide opportunities for visitors to enjoy special natural and cultural environments. Around 2 million tourists visit the Twelve Apostles each year, making it one of Victoria's most popular tourist attractions. Lots of things have been built to accommodate the tourists. There is a carpark, kiosk, toilets, boardwalks, viewing platforms, and walking tracks. What sort of impact have these facilities had on the environment? Boardwalks can help protect sensitive areas by keeping tourists on paths, but they also alter the natural environment. This kind of development helps to create employment and generate income for the small towns along this part of the southern Victorian coastline. Have a think about some other positive and negative impacts of tourism at the Twelve Apostles and investigate how these impacts are being managed.
SHONA BLEWETT:
Okay, experiment time. We're going to take a closer look now at how coastal erosion happens.
STUDENT 1:
Here. We have a plastic tub and we've compacted sand to one side to make a sandy cliff.
STUDENT 2:
And here we also have some water. It represents the ocean.
STUDENT 1:
Let's trace the coastline.
STUDENT 2:
And now to make some waves with our chopping board. We'll do this for about one minute.
STUDENT 1:
Okay, let's see what happened to our trace coastline.
STUDENT 2:
As you can see, the steep cliff has been eroded by the sea water and has made a shallow bank that extends a lot further than it had prior.
STUDENT 1:
Well, from looking at the lines, we can see that as the water has come in, it's created a pocket underneath that has then allowed the top of the cliff to collapse down on top of it.
STUDENT 2:
Coastal erosion like this can also impact buildings that are built close to the shoreline, making them less stable.
STUDENT 1:
And that's why we sometimes see sea walls being built and extra sand being trucked in and placed on beaches.
SHONA BLEWETT:
What a great demonstration. And yes, erosion along our coastlines can cause problems for the way we live.
SHONA BLEWETT:
Here's a fast fact before we go. A few years ago, scientists discovered that there's actually five more Apostles. They're deep in the ocean. About six kilometers out from the Twelve Apostles. These five limestone stacks are around 10 meters tall and stand in front of an ancient underwater coastal cliff. Scientists say that it's highly unusual to find stacks like this in the ocean. They say that around 20,000 years ago, the underwater cliff would've been above the water, and the view from it of the five Apostles would've been very similar to today's clifftop view of the Twelve Apostles. But how have these five Apostles survived in place without being eroded away? Well, it's thought that about 20,000 years ago when the last ice age ended, the melting ice caused the sea levels to rise so quickly that the stacks didn't get fully eroded before they became submerged. It's amazing, isn't it?