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Transcript of ROCKS
By Sania Tajammul
There are three types of rocks:
Igneous rocks conatin interlocking crystals that are held together very strongly and make the rock hard.
The crystals in igneous rocks have a disorderly arrangement.
The size of the crystals depends on how quickly the igneous rock solidifies.
Igneous rocks never contain fossils.
Sedimentary rocks sometimes contain fossils and may react with acid.
Sedimentary rocks may have layers with different appearances and textures.
These rocks come in a wide variety of colours and sizes
Sedimentary rocks usually have pores between pieces and sometimes have mud cracks and raindrop impressions.
The word metamorphic translates, meta means change, while morph means shape.
Metamorphic rocks have been exposed to remarkable heat and pressure which causes them to change into another type of rock.
They are generally unaffected by weathering and erosion.
Metamorphic rocks are very hard-wearing.
Examples of Rocks.
Slate is a metamorphic rock and is very fine-grained. It shows great rock cleavage and is used for many things for its uniform flat plates. It is used extensively for roof and floor tiles. It has also been used for blackboards and is the general material for the beds of pool tables.
The sedimentary rock, Limestone is made from the mineral calcite which came from the beds of evaporated seas, lakes and from animal shells. Limestone rocks are used in concrete and are great for building in humid areas.
The Igneous rock, Basalt, is an extrusive rock and is as of very dark in colour. It is very common in the Earth's crust and makes up most of the ocean floor. It is made of lots of dark coloured minerals. It is also made up of some light crystals. The mineral crystals can't be seen without the help of a microscope.
How Sedimentary rocks are made and why you often find fossils in them?
Sedimentary rocks are made of sediment particles such as sand or clay or the skeletons and shells of sea creatures.
When layers of loosed sediments are pressed down and buried under more layers, slowly and slowly the particles cement together and form rock (lithify). Rocks that are classified as chemical sedimentary rocks, are formed when minerals dissolved by water are deposited again.
How igneous rocks are formed?
Igneous rocks are made when magma cools down and turns solid. Extrusive igneous rocks form when magma reaches the surface and cools quickly. Fine-grained rocks are formed when the cooling is sped up and instrusive rocks are formed when magma cools slowly underground which allows the minerlas to grow into coarse grains.
Igneous rocks consist of erratically arranged interlocking crystals. The size of the crystals depends on how quickly or slowly the molten magma solidifies. The slower magma cools, the bigger the crystals.
Salol, is a white powder with a pleasant taste and smell. It is used to absorb light, in sun tan lotions or as a preservative or an antiseptic. If molten salol cools quickly, you get small crystals.
How are Metamorphic Rocks formed?
Why can you sometimes find broken fossils in them?
Metamorphic rocks are formed when the minerals in rocks are changed underground by heat and pressure. Rocks that are folded or crushed by extreme pressure, deep in the crust are called regional metamorphic rocks.
Metamorphic rocks sometimes contain fossils if they were formed from a sedimentary rock but the fossils are usually compressed and out of shape.
Cliff erosion is when waves crash against a cliff and they wear away the rock to form a wave cut notch. A wave cut notch is an indentation in the rock at sea level, by the processes of hydraulic action and corrasion. This is referred to as undercutting.
In size, the notch increases and the weight of the rock above is unsupported and becomes unstable. Finally the overhanging area of cliff falls into the sea.
Physical weathering can be breaking down rocks by natural processes. If the temperature changes quickly, rocks will crack. After a hot day; eventually the outer layers of the rock will crack and may peel off. If water freezes in the cracks of rocks it will eventually split pieces off the rock. Plants can also do phsyical weathering of rocks. They can wedge the rocks apart.
Chemical weathering is the chemical breakdown of rocks. When water and air react with different minerals in the rock, the new minerals formed are usually softer, which causes the rock to crumble.
Chemical weathering takes place in almost all types of rocks. Smaller rocks are more prone but because they have a greater amount of surface area.
Erosion is the movement of soil and other weathered materials from one place to another. The main agents of erosion are wind, water and ice. The eroded material is deposited somewhere else as a sediment. Erosion is a natural process but human activity often causes it to occur quickly.
Running water erosion
Sediments are matter that settles to the bottom of a liquid. Sediments are deposited at the river mouth, before it finally empties its water into the ocean. Sediments are transported and deposited usually at the time or during a flood.
The rock cycle is a constant process which begins as rocks are pushed up by forces from the tectonic plates and are eroded by wind and rain. The eroded rocks move by wind or running water until they are deposited and then form into layers. Further eroded rocks may cover the layers until heat and pressure change the original layers to metamorphic rocks. Extra rocks may squeeze and press the layers into sedimentary rocks. Buried rocks may also melt and recrystallise into igneous rocks. Igneous, sedimentary and metamorphic rocks may then be pushed up by tectonic forces, starting the rock cycle again.
Wallaman Falls is in North Queensland and to be specific, Tropical Wetlands, Ingham, Queensland, Australia. Wallaman Falls has been through tough conditions and yet remains to be fully well-structured. It was affected by Cyclone Yasi but minorly. The land formation has been weathered and some parts have eroded.
Year 8 Science 2013
By Sania Tajammul