Geoscience reveals secrets Journey through Earth’s hi

If you look carefully at a mountain range, you can often see how layers of rock have been deformed into structures that look like “waves” – these waves are called folds by geologists. The folding is caused by forces operating in the Earth’s crust.

A majority of earthquake and volcanic activity occurs above plate

boundaries.

You can see this folding at a scale of kilometres. What is fascinating, is that if you should pick up a rock from the same terrain, you may see the same fold patterns reflected on a smaller scale, possibly millimetres. And if you look at a very thin section of the rock under a microscope, you may also see fold patterns at a scale of tens of microns (there are a thousand microns in a millimetre).

So, whatever scale you use, the deformations, resulting from the forces in the Earth’s crust are all related. These forces exert pressures that cause certain minerals in the rock to deform, and in some cases some of the minerals become plastic, “flowing” like a liquid would. As the minerals deform, so they cause the rocks to deform, resulting in the fold patterns that you can see in individual rocks and mountainous landscapes.

A solid Earth

Did you know that the Earth is in fact not solid?

The centre of the Earth, which is called the core, begins at a depth of 3 000 km below the surface and extends to 6 000 km. This region is made up of molten nickel and iron, and is therefore not solid.

The upper solid portion of the Earth that we stand on, rests on moving plates, called tectonic plates (seven large plates, and about 20 smaller ones) and these plates, which are between 75 and 120 km thick, “float” on the molten and semimolten

regions of the Earth’s interior.