Different types of weathering can shape landforms over time.
Landforms have been observed by humans and our understanding of how they have formed has changed over time.
At the end of this step, students will:
understand the different processes that create landforms
learn why landforms are important to people
explore the different landforms from Australia and around the world.
Weathering
Weathering is the process of wearing down land or a surface caused by different weather conditions. The shape and form of a landscape will be changed by swell, wind, rain, snow, ice, temperature, chemicals etc. There are two main mechanisms of weathering. Physical and Chemical. Examples of weathering are often a combination of both.
Weathering happens over long periods of time, sometimes millions of years! When you look at the earths surface you are looking back in time and the results of different climactic conditions in that particular area. It is a natural process.
Weathering occurs in one area with little or no movement. It should not be confused with erosion which is where sediment and rocks are carried away to another location.
Weathering has formed these unusual patterns in the sandstone of Anvil rock in the Blue Mountains National Park. Photo: Elinor Sheargold/DPE
Coastal weathering can be both physical and chemical. Photo: John Yurasek/DPE
Chemical weathering
Involves the breakdown of rocks and minerals through changes in the chemical composition of the material. Often these changes are simply caused by the effects of air and water (and the chemicals within them) interacting with the landscape.
A good example of chemical weathering is the red colour you see on the surface of a rock face. This has been caused by oxidation of the iron present in some rocks. The weathering occurs by a chemical interaction of the iron with the oxygen in the air and it literally rusts. The remaining red dust can then be blown away by wind or washed away by rain.
Physical weathering
Physical weathering involves the disintegration of rocks and their minerals by mechanical processes that break down the materials into smaller portions without altering the chemical makeup.
A good example is frost wedging on cliff faces in cold climates. Small amounts of water trapped inside cracks of rocks can become frozen. When water freezes it increases in volume and expands causing the crack to become bigger and eventually causing the rock to be forced apart.
This is called cryofracturing. The process can sometimes cause big boulders or rock slabs to fall down into the valley.
Water trapped inside rock can cause physical weathering when it freezes and expands. This process is called cryofracturing. Photo: Simone Cottrell/DPE
Riverbanks can be eroded away if there is a reduction in tree roots holding the bank together. Photo: David Morand/DPE
Erosion
Erosion is where particles such as sand, rocks, and soil are moved from one place in a landscape to another, usually after the effects of weathering. The particles will be moved away from the original site by the force of water, ice or wind and this is called erosion.
Erosion is a natural process that has been occurring for millennia to create landforms such as valleys, rivers, caves and coastal marine platforms. Rates of erosion can be sped up by human interactions with the environment such as deforestation, cropping, grazing animals, and mining.
An example of erosion is soil erosion. Plants and tree roots hold soil in place and stabilise if from the effects of weathering. Without the matrix of roots holding a riverbank together, heavy rain can have enough force to carry the soil particles away and downstream. Soil erosion can be devastating for some environments, changing the landscape completely.
Deposition
Deposition in geographical terms is defined as the laying down of sediment. It is carried by the wind and flowing water such as a river, sea or ice. The process of erosion causes particles to be moved from one place to another. Wherever the particles end up collecting there will be a deposition of those particles. Deposition creates many of the landforms that make up a landscape.
Gravity and mass of rocks can create rockslides on the sides of mountains causing rocks to build up in the valley below
Wind can create patterns in sand dunes as it moves sand particles across the surface. The heavier particles will drop down first making for a variety of patterns
Rivers carry sediment downstream and deposit it in deltas where the flow slows to meet the ocean
Beaches, sand bars and tombolos are created by the forces of the ocean waves depositing sand over time.
Deposition creates landforms such as tombolos. Photo: John Spencer/DPE
Uluru sits within Uluru-Kata Tjuta National Park.
The Three Sisters; Meehni, Wimlah and Gunnedoo. Blue Mountains National Park. Photo: Stephen Alton/DPE
Wollumbin National Park. Photo: Damien Hofmeyer/DPE
Uluru, previously referred to as Ayers Rock, is arguably one of the most famous rock formations in the world.The name Uluru was given to the formation by the local Aboriginal community – The Anangu people.
Uluru is a sacred place for Aboriginal people across the Nation and is inseparable from Anangu Tjukurpa (traditional law) practices and stories. The actions of the creation ancestors which make up this law are still visible around the rock and within the landscape today.
Uluru is protected by a UNESCO World Heritage listing, both for natural and cultural significance. It is a huge sandstone monolith that stands proud in the heart of what is sometimes called “The Red Centre '' in the Northern Territory.
The surrounding landscape is relatively flat and the sandstone has a high iron content which gives it a strong red hue. It dominates the landscape and is striking, especially as the light changes during sunrise and sunset.
Fun fact: It is higher than the Eiffel Tower in Paris standing at 348m above sea level and it is believed that it was formed over 550 million years ago.
That predates even the dinosaurs!
The Three Sisters is a famous landform of three distinct sandstone pillars that stand overlooking the Jamison Valley in the World Heritage listed Blue Mountains National Park. The Three Sisters derives its name from the ancient Aboriginal story of three sisters named Meehni, Wimlah and Gunnedoo who are believed to reside within the pillars.
The Three Sisters and the surrounding area are highly valued by the Aboriginal peoples of the Gundungurra, Wiradjuri, Tharawal and Darug nations and has resulted in it being declared an Aboriginal Place in 2014. This means it is legally protected due to its cultural significance to Aboriginal people.
The whole of the Blue Mountains is a dissected plateau. The sandstone that it is mostly composed of, was laid down when the land was underwater about 300 million years ago. Underground forces caused an uplift on the east coast of Australia and since then it has been eroded by rivers and streams to create an impressive mountain range.
The Three Sisters have eroded to stand separately from the rest of the escarpment and are now an icon of the Blue Mountains National Park. There are different traditional stories told by the Aboriginal peoples to explain how they were formed.
Wollumbin, also referred to as Mount Warning is a regional icon; it rises dramatically from green forests of the World Heritage-listed Wollumbin National Park.(link to Gondwanna info on NPws website?)
Wollumbin (The Warrior Chief) was named by the local Aboriginal peoples which include the Nganduwal, Galibal, Gidhabul and Widjabal people of Bundjalung Nation.
The summit of Wollumbin was declared an Aboriginal Place in 2015.
Wollumbin is a remnant central plug of the Tweed shield volcano situated in North East NSW. It is also known as a shield caldera. It has eroded for over 23 million years and has a diameter of over 40 kilometres making it the biggest erosion caldera in the southern hemisphere and one of the largest calderas in the world.
Rising dramatically to a height of 1157 metres above sea level, Wollumbin was seen by James Cook as he sailed up the east coast of Australia in 1770 and he named it Mt Warning.
Fun fact: Due to its height and proximity to Cape Byron, the easternmost part of Australia, Wollumbin is the first place in mainland Australia to feel the sun's rays each day.
Volcanic eruptions have been the cause of many landforms around the world. Learn how they are formed and why they happen in this video.
First nations people from all the different continents have viewed and connected to landforms since the dawn of humankind. Historically, people of all nations have attached special cultural value to landscapes and landforms and this is recorded in creative ways such as poetry, art, song, dance and storytelling.
In Australia, Aboriginal people have a strong cultural and spiritual connection with the land, sky and water. Dreamtime and Everywhen stories explain how the landscape was formed, the waterways were created and the animals came to be.
These stories have been passed down through the generations and are intrinsic to the concept of “Country”. The spiritual connection Aboriginal communities have with the land links to the past, present and future and it binds the people to family and Country.
The spiritual connection Aboriginal communities have with the land links to the past, present and future. Photo: Peter Sherratt/DPE
Landforms are formed in a number of ways. Learn about the different types of erosion, deposition and volcanism.
This video uses specific examples from New Zealand.
Travel around the world with this list of weird and wonderful landforms. Everything from crystal caves to wave shaped rocks and volcanic craters are included on the list. Some are well-known tourist attractions and maybe you’ve seen them before.
Cultural connections
Choose a landform or place that is special to you and write about your connection to it. Use worksheet 2.1 to write your story and draw a picture of your chosen landform.
Investigating erosion and weathering
Create a landscape in the classroom. Observe the effects of water on various different land types and discuss the comparison to natural landscapes. Teachers use activity instructions 2.2.