Weathering in Australia

When we look at the earth, we look at it for what it is now. No one, besides geographers and other scientists, really stop and think what it use to look like. How a tiny rock on the ground could have been part of a huge mountain thousands of years ago, if it could have came from a breakdown of a rock also known as chemical weathering, or if it could have just chipped off from another rock also known as physical weathering. All these little processes are part of a major process called weathering. Weathering is the break down of rock or rock decay; also known as “the beginning to the changing of the earths surface.” When it comes to weathering there are two main types that occur like I just stated, either physical weathering and chemical weathering.

Physical weathering is the break down of rock without using chemical interactions while chemical weathering is the break down of rock with a chemical interaction. The most drastic kind of weathering is the weathering due to wind…….NOT!!!! When it comes to wind and weathering, WIND IS WIMPY, always remember that. The main cause of weathering is the climate at which With Australia being such a hot dry place, there is a lot of weathering that goes on there, especially salt weathering. Salt weathering is a physical weathering process in which there is a lack of water to wash the salt from the rocks. Salt then seeps into the joints of rocks, which are cracks in the rocks that make them weak, expand and cause chunks of the rock to fall off.

Since Australia has a lot of weathering that takes places, it has great rock formations to look at.

Devils-marbles

This formation is called Devils Marbles

Its crazy the things that weathering can do because just by looking that this it looks like these rocks were places on top of each other. The truth is that these rocks originally started out as molten rock that came up to the surface and settle into a solidified layer of granite. Then over millions of years this granite started to receive both horizontal and vertical cracks also known as joints. Which caused them to turn into rectangular blocks of granite.

devils-marbles-rectangles

This image shows both horizontal and vertical joints in the rock which form the rectangular blocks

Through millions of years of weathering this rock eventually starts to decay. Since Australia has desert like climate, I’m pretty sure this weathering process was due to salt weathering. Other processes of physical weathering that can decay rock are frost weathering and pressure release. Frost weathering only happens in cold places, it’s when water seeps into the joint of a rock, freezes and expands, and cause chunks of the rock to crack and break off. Pressure release is when a massive rock forms under great pressure and quick erosion causes slabs shells of the rock to pop off.

frost_wedging

Frost Weathering: Expansion of water in joints by freezing, wedging the rock apart.

exfoliation

Pressure Release:As pressure is decreased due to removal of overlying rock by erosion, igneous/metamorphic rock expands and fractures in large sheet-like layers

Over millions of years these process take place and decay the rock little by little eventually causing the rock to become rounded at the corners. The thing that so great about these features is that each rock has its own look and characteristics; not one rock looks exactly the same.

devils_marbles_0007

as you can see some of the rocks still have a hint of the rectangular shape but are starting to become more and more rounded

Unlike physical weathering where bits and pieces of the rocks are broken down, which chemical weathering the minerals of the rocks are the things that are broken down. Slightly acidified water is usually the case of most chemical weathering. Some of these chemical weathering processes are known as dissolution, Hydrolysis, Hydration and dehydration, and oxidation. Dissolution is when the mineral is completely dissolved by water. Hydrolysis is when H+ or OH replaces an ion in the mineral. Hydration and dehydration is when there is and addition or removal or H2O as a mineral. Finally, oxidation is when the rock kind of rusts and chips off. All of these weathering processes lead to the production of grus, and are so important because they make new minerals that we use in our everyday lives, including aluminum, iron, mobile cations, quartz, and many more.

Research Sources

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