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Types of Weathering. 12. Be ready to speak about geological processes, using the information from the Unit IV, the library or the internet.
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Types of Weathering
In layman's term, weathering is a term in Geology, which means or indicates the 'natural decaying away of the rocks and minerals. ' This process mainly takes place near the Earth's surface. The rocks are either broken down by physical forces or by chemical processes, and sometimes by both. Their exposure to water, air, or to living organisms, often leads to weathering. Due to this, the minerals usually break down into small pieces, which are easily carried away by water and air. With time, these rocks are converted into sand and clay. The duration of weathering often depends upon the climate or the area, where the rock is present.
Physical weathering does not involve the action of chemicals during the whole process of rock disintegration. Abrasion is the main process, by which physical weathering takes place. It is mainly seen in areas characterized by less vegetation, where the temperature fluctuates around 0° C, and also in those places where the diurnal range of temperature (or the difference in the minimum temperature at night and maximum temperature at day) is high. Physical and chemical weathering goes hand in hand. The former increases the surface area so that the latter can take place. Physical weathering can occur due to the following actions:
Frost Shattering. This usually takes place in areas where the temperature goes above or below the freezing point. Water present in the cracks or joints of the rocks, freezes during the night and thaws during the day. This repeated process of freezing and thawing leads to breaking up of the rock into several smaller fragments.
Crystallization. This process occurs when salt water seeps into the cracks and joints of the rocks, and then evaporates leaving behind the salt crystals. Pressure is exerted on the rocks, which leads to weathering, as these crystals expand due to the increasing heat.
Exfoliation. This process mainly takes place in the desert regions, where the daytime temperature goes up to more than 40° C, and at night, the temperature goes below 10° C. Due to this everyday constant change, the rocks start to expand and contract, causing stress within themselves, which in turn leads to the formation of cracks. Finally, the top layers of the rocks are peeled off.
Release of Pressure. This occurs due to removal of the top layer through erosion. Now, since the pressure that was earlier exerted is released, the rocks gets a chance to expand, and this causes interior stress that creates cracks. With time, the top layer breaks away.
Biological Weathering. Sometimes due to plants and animals, physical weathering may also take place. The plant roots might grow into the cracks of the rocks, or sometimes during cultivation, the rocks are exposed to the other agents of weathering like air and water. Other organisms and earthworms also helps in weathering by making underground tunnels.
When weathering takes place as a result of chemical reactions, it is known as chemical weathering. In this process the rock disintegrates chemically as the chemicals in the atmospheric agents react with the chemicals of the rock and the resultant reaction brings about the weathering of the rock. The rate of weathering differs with variation in the chemical composition and structure.
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(from: http: //www. buzzle. com/articles/types-of-weathering. html)
12. Be ready to speak about geological processes, using the information from the Unit IV, the library or the internet.
UNIT V
GEOLOGIC HAZARDS
Start-up.
1. What natural geologic processes can be dangerous to people?
2. What is the most terrible catastrophe occurring in nature?
1. Read and learn the following words.
| 1. avalanche – лавина 2. soil creep – сползание почвы 3. landslide – оползень 4. rock fall – камнепад 5. subsidence – проседание 6. earthquake – землетрясение 7. tsunami – цунами 8. flood – наводнение 9. volcanic eruption – извержение вулкана 10. geologic hazard – опасное геологическое явление, геологическая катастрофа 11. environment – окружающая среда 12. to result in – приводить к, вызывать 13. to result from – происходить в результате, вызываться 14. disaster – бедствие, катастрофа, трагедия 15. to affect - влиять 16. man-induced hazards – антропогенные, техногенные катастрофы 17. naturally occurring hazards – естественные катастрофы 18. damage – вред, ущерб | 19. to inhabit – жить, населять 20. to conduct investigation – проводить исследование 21. to prevent – предотвращать 22. to define – определять 23. approach – подход 24. to solve the problem – решить проблему 25. to eliminate – устранять 26. to avoid – избегать 27. to increase - увеличивать 28. to reduce – уменьшать 29. to predict – предсказывать 30. terrible – ужасный 31. to destroy – разрушать 32. seismic waves – сейсмические волны 33. violent – сильный 34. to shake – трясти 35. to spread – распространяться 36. to involve – включать, вовлекать 37. to take place – происходить 38. force of gravity – сила тяжести 39. nuclear power plant – атомная станция 40. highway – автомагистраль, шоссе |
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