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Prep to Year 4: Beneath our feet

Subject Guides

Structure of the Earth

Click on the picture for an Interactive diagram of Earth's structure

Find out more about the structure of the Earth (including a video to watch) here

How Ancient Rock Layers Form

Rocks

Learn about the three types of rocks by clicking on the tabs. Then create your own virtual rock collection here

Igneous means made from fire or heat. When volcanoes erupt and the liquid rock comes up to the earth’s surface, then new igneous rock is made. When the rock is liquid and inside the earth, it is called magma. When the magma gets hard inside the crust, it turns into granite. Most mountains are made of granite. It cools very slowly and is very hard.

When the magma gets up to the surface and flows out, like what happens when a volcano erupts, then the liquid is called lava. Lava flows down the sides of the volcano. When it cools and turns hard it is called obsidian, lava rock or pumice – depending on what it looks like.

 
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granite
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obsidian
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lava rock
 
 
When mountains are first formed, they are tall and jagged. Over time (millions of years) mountains become old. When mountains are old, they are rounded and much lower. This happens because lots of rock gets worn away due to erosion and weathering. Eventually most of the broken bits of the rock end up in the streams and rivers that flow down from the mountains. These little bits of rock and sand are called sediments. When the water slows down enough, these sediments settle to the bottom of the lake or oceans they run into.
Over many years, layers of different rock bits settle at the bottom of lakes and oceans. Think of each layer as a page in a book. One piece of paper is not heavy. But a stack of telephone books is very heavy and would squish anything that was underneath. Over time the layers of sand and mud at the bottom of lakes and oceans turned into rocks. These are called sedimentary rocks. Some examples of sedimentary rocks are sandstone and shale.
        
        Sandstone                               Shale
Metamorphic rocks are rocks that have changed. The word comes from the Greek “meta” and “morph” which means to change form. Metamorphic rocks were originally igneous or sedimentary, but due to movement of the earth’s crust, were changed.

If you squeeze your hands together very hard, you will feel heat and pressure. When the earth’s crust moves, it causes rocks to get squeezed so hard that the heat causes the rock to change. Marble is an example of a sedimentary rock that has been changed into a metamorphic rock.
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marble
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A True Rock Song!

Australian Landforms

Australia has some of the oldest geological features in the world with the oldest known rocks dating from more than 3000 million years ago. 

How Uluru and Kata Tjuta were formed

Click on the image of the Twelve Apostles to find out more about many of Australia's most significant landforms

 

Respecting two cultures

The Devil's Marbles in the Northern territory are smooth, round boulders that look like giant marbles left behind by some huge monster that had played with them. 

The Devil's Marbles are about 1640 million years old. These boulders were originally part of a solid mass of coarse-grained granite which was formed deep within the Earth's surface by cooled-down magma. As the hot magma hardened, granite started to form. This granite mass cracked, splitting into a series of tight-fitting blocks. The forces of erosion have destroyed the overlying rocks, exposing the granite blocks to weathering. Winds and rain have shaped them into the smooth-shaped rocks that exist today. The type of weathering that smoothes rocks is called spheroidal weathering. Spheroidal weathering is mostly a chemical-type of weathering caused by rainwater.

The Aboriginal name for the Devil's Marbles is Karlwe KarlweAccording to Aboriginal legend, the Devil's Marbles are the eggs of the Rainbow Serpent laid during the Dreamtime and Aboriginal people believe that the stones of the Devil's Marbles are sacred and have extraordinary powers.

One of the marbles was removed from the site in 1953 and taken to Alice Springs to form a permanent memorial to John Flynn, the founder of the Royal Flying Doctor Service. Later, this action created great controversy because the rock was removed from a sacred site without the permission of the tribal elders. In the late 1990s, a boulder swap was arranged and the missing marble was removed from the grave, cleaned and returned to its original place. The grave is now marked with a similar boulder donated by the local Arrernte people.

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How Landscapes change

How Mountains turn to dust from Splash ABC

One reason for changes in landscape if the activity of the Earth's tectonic plates. This video makes the tension of the plates easy to understand.

Tectonic plates explained

Weathering and Erosion

Click image below to find out more about how erosion and weathering change landscapes:

Chemical factors like acid rain can also affect landscapes. Click on the image below to learn more.

The Future

Quick Links

TWLH Chart

We use a TWLH chart to show our thoughts and ideas about a topic.A TWLH chart includes four sections with the headings: What we Think we know, What we Want to learn, What we Learned, and How we know.

Save this blank TWLH chart to your computer.

Annotated Diagrams

are drawings which are labelled to explain a scientific process. 

  • give your diagram a heading
  • make a simple outline drawing
  • use arrows, labels and a colour key
  • draw an imaginary magnifying glass as above to show tiny or invisible particles

Understanding Variables

I am a geologist

Click on image to find out moreRanger Rock