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Rocks
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Question | Answer | ||||||
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Some rocks may be different shapes and sizes as they be changed by the conditions in their | environment. | ||||||
The breakdown of rocks into smaller fragments is called | weathering. | ||||||
In alphabetical order, the 3 types of weathering are; | biological weathering, chemical weathering and physical weathering. | ||||||
Freeze-thaw weathering is the repeating of both | freezing and thawing. This is done to both | water and ice in the | gaps inside | rocks. When the water freezes, turns to ice and expands making the gaps | larger and eventually causes pieces of rocks to | break away. | |
Often with freeze-thaw weathering, the water off freezes during | day, while it thaws during | night. This process is | repeated until the fragment of rock | breaks off. | |||
Freeze-thaw weathering is a type of | physical weathering. | ||||||
Exfoliation weathering or | onion skin weathering is the repeating of both | heating and cooling of | rocks, which causes the surface layer to | flake off, possibly leading to that rock | splitting. | ||
With exfoliation weathering, often the heating is done during the | day, while the cooling is done during the | night. | |||||
Exfoliation weathering is a type of | physical weathering, where as that rock keeps expanding and | contracting, pieces of that rock's surface begin to | flake and eventually | fall off. | |||
With exfoliation weathering, during the day, the surface of that rock is heated by the | sun, causing that rock to | expand. During the night, instead of being heated, that rock | cools and then | contracts. | |||
With biological weathering, plant roots and | shoots can get into minute | cracks in | rocks. As the plant grows, roots and shoots can push their way through the | rock, which (in those rocks) forces | cracks. The growth of cracks in this way causing small pieces of rock to | break off. | |
Chemical weathering is the break-down of | rocks when there are | chemical reactions between | acid rain and | certain minerals in | rocks. Some types of rock are easily weathered by chemicals. For example, limestone and chalk are made of a mineral called calcium carbonate; when acidic rainwater falls on limestone or chalk, a chemical reaction happens: new [] substances are formed in t | soluble. These are washed away and the rock is | |
Rainwater is naturally acidic because rainwater reacts with | carbon dioxide in the | air to form | carbonic acid.This type of acid rain is weakly | acidic and reacts | slowly with | ||
The burning of fossil fuels produces both | oxides of Sulphur and Nitrogen which make rainwater more | acidic. This type of acid rain reacts | quickly with | minerals and weathers rock more | |||
3 ways that rock fragments can be transported are(in alphabetical order); | glaciers, rivers and strong winds. Rivers and stream and the like moving pieces of rock is called | transport. [] flowing rivers can transport large rocks, but [] moving rivers can only transport tiny pieces of rock. | fast---slow. As the pieces of rock are carried along by the water, they bash against each | other and the river | bed, thus, they eventually [] [] | wear away. They become s[] and more r[]. | They become smaller and more rounded. |
Deposition occurs when pieces of weathered | rock sink to the | bottom of either the | river bed or sea forming | sediment. Dead creatures can get trapped in | sediment and form | fossils. It is considered that the time it takes for something to become a fossil is | 10,000 years. |
Sediment, such as sand and silt is deposited in | layers. The build up of layers is called | sedimentation. The layers become compacted to form | sedimentary rock. The distinct | layers of | rock are related to the | time intervals at which there is an occurence of | sedimentation. |
The 5 parts of the cycle of which rocks partake are (in consecutive order); | weathering, erosion, transportation, deposition and sedimentation. | ||||||
The process of weather and transportation is known as | erosion. | ||||||
Sometimes, metamorphic rocks are formed when rocks are close to some | molten magma, and so get | heated. Metamorphic rocks may form from rocks heated by | magma.When a metamorphic rock is formed under pressure, its crystals become arranged in | ||||
Wind, rain and waves can all cause physical weathering. The wind can blow tiny grains of sand against a | rock, that wear the rock | away and [] it | weather. [] and [] can also wear away rock over long periods of time | Rain and waves. | |||
[] is the movement of the broken pieces away from the site of weathering. | Erosion | ||||||
With freeze-thaw weathering, water enters the | gaps inside | rocks, then when the temperature reaches 0° or | less, the water in consecutive order | freezes then expands leading to rock fragments | breaking off. | ||
What happens to weathered rock? The fast moving water picks up large pieces of | rock, which are | eroded as they are | carried along, then as the river widens out, large pieces of | rock are deposited by the | slow moving water. Most of that rock fragments are deposited at the | mouth of the river where it is both | wide and slow-moving. |