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Selasa, 08 Februari 2011

Jenis gerakan massa
Jenis gerakan massa yang dibedakan berdasarkan bagaimana tanah, regolith atau batu lereng bawah bergerak secara keseluruhan.


1.Creep
Downhill creep adalah proses jangka panjang. Kombinasi gerakan kecil dari tanah at...au batuan dalam arah yang berbeda dari waktu ke waktu secara bertahap diarahkan oleh gravitasi lereng bawah. Lereng yang curam, semakin cepat creep. creep ini membuat pohon dan semak-semak kurva untuk mempertahankan tegak lurus mereka, dan mereka dapat memicu tanah longsor jika mereka kehilangan pijakan akar mereka. Tanah permukaan dapat bermigrasi di bawah pengaruh siklus pembekuan dan pencairan, atau suhu panas dan dingin, beringsut jalan ke bagian bawah lereng membentuk terracettes. Hal ini terjadi pada tingkat yang tidak terlihat dengan mata telanjang.


2,Longsor
Dimana gerakan massa memiliki zona baik pasti atau bidang geser, itu disebut tanah longsor. Ini termasuk slide rock, merosot dan sturzstroms.
Ini juga merupakan salah satu klasifikasi umum wasting massa.


3.Arus
Gerakan tanah dan regolith yang lebih menyerupai perilaku fluida disebut aliran. Includeavalanches ini, lumpur, puing-puing arus, aliran bumi, lahar dan sturzstroms. Air, udara dan es sering terlibat dalam memungkinkan gerak fluidlike material.


4.topples
Topples adalah contoh ketika blok poros batu dan jatuh jauh dari lereng.


5.Slump
Sebuah tergelincir dari bahan batu koheren sepanjang permukaan melengkung penurunan. Merosot melibatkan massa tanah atau bahan lain meluncur sepanjang permukaan melengkung (berbentuk seperti sendok). Ini membentuk tebing, kecil berbentuk sabit, atau lereng curam mendadak di ujung atas lereng. Ada bisa lebih dari satu lereng curam menuruni lereng.
 

6. Falls
Sebuah jatuh, termasuk runtuhan, adalah tempat cascades regolith menuruni lereng, namun tidak volume yang cukup atau viskositas untuk berperilaku sebagai aliran. Falls dipromosikan di batuan yang ditandai dengan adanya keretakan vertikal. Falls adalah hasil dari meremehkan air serta undercutting gelombang. Mereka biasanya terjadi pada lereng yang sangat curam seperti tebing. Bahan batuan dapat dilonggarkan oleh gempa bumi, hujan, wedging akar tanaman, memperluas es, antara lain. Akumulasi material batuan yang telah jatuh berada di dasar struktur dan dikenal sebagai talus.

Minggu, 23 Januari 2011

Mass wasting

Mass wasting, juga dikenal sebagai gerakan lereng atau gerakan massa, adalah proses geomorfik dimana tanah, regolith, dan lereng bawah batuan bergerak di bawah gaya gravitasi.Jenis mass wasting termasuk creep, slide, aliran, topples, dan jatuh, masing-masing dengan ciri khas sendiri, dan berlangsung selama rentang waktu dari detik ke tahun. mass wasting terjadi pada kedua lereng terestrial dan kapal selam, dan telah diamati di Bumi, Mars, Venus, dan Jupiter bulan Io. Ketika gaya gravitasi yang bekerja pada lereng melebihi kekuatannya menolak, kegagalan lereng (membuang massa) terjadi. Kekuatan material lereng dan kohesi dan jumlah gesekan internal antara membantu bahan menjaga stabilitas lereng dan dikenal secara kolektif sebagai kekuatan geser lereng itu. Sudut lereng curam bahwa cohesionless dapat menjaga tanpa kehilangan kestabilan dikenal sebagai sudut atas istirahat.Ketika lereng memiliki sudut ini, kekuatan geser dengan sempurna counterbalances gaya gravitasi yang bekerja atasnya.
Mass wasting dapat terjadi pada tingkat yang sangat lambat, terutama di daerah yang sangat kering atau daerah-daerah yang menerima curah hujan yang memadai seperti vegetasi yang telah stabil permukaan. Hal ini juga bisa terjadi pada kecepatan yang sangat tinggi, seperti di slide batu atau tanah longsor, dengan konsekuensi bencana, baik langsung dan tertunda, misalnya, hasil dari pembentukan bendungan longsor.

Faktor-faktor yang mengubah potensi pemborosan massa meliputi: 
    perubahan sudut kemiringan lereng dan melemahnya bahan dengan pelapukan; kadar air meningkat, perubahan tutupan vegetasi, dan overloading. 
Pentingnya air dalam mass wasting
Air dapat menambah atau mengurangi stabilitas lereng tergantung pada adanya jumlah. Sejumlah kecil air dapat memperkuat tanah karena tegangan permukaan air tanah memberikan banyak kohesi. Hal ini memungkinkan tanah untuk menahan erosi lebih baik daripada jika kering.Jika terlalu banyak air hadir air dapat bertindak sebagai pelumas, mempercepat proses erosi dan menghasilkan berbagai jenis wasting massa (yaitu lumpur, tanah longsor, dll). Sebuah contoh yang baik dari ini adalah untuk memikirkan sebuah istana pasir. Air harus dicampur dengan pasir supaya benteng untuk mempertahankan bentuknya. Jika terlalu banyak air ditambahkan pasir menyapu, jika tidak cukup air ditambahkan pasir jatuh dan tidak dapat mempertahankan bentuknya.Jenis gerakan massa
Jenis gerakan massa yang dibedakan berdasarkan bagaimana tanah, regolith atau batu lereng bawah bergerak secara keseluruhan. Creep Downhill creep adalah proses jangka panjang.Kombinasi gerakan kecil dari tanah atau batuan dalam arah yang berbeda dari waktu ke waktu secara bertahap diarahkan oleh gravitasi lereng bawah. Lereng yang curam, semakin cepat creep.creep ini membuat pohon dan semak-semak kurva untuk mempertahankan tegak lurus mereka, dan mereka dapat memicu tanah longsor jika mereka kehilangan pijakan akar mereka. Tanah permukaan dapat bermigrasi di bawah pengaruh siklus pembekuan dan pencairan, atau suhu panas dan dingin, beringsut jalan ke bagian bawah lereng membentuk terracettes. Hal ini terjadi pada tingkat yang tidak terlihat dengan mata telanjang.Longsor Dimana gerakan massa memiliki zona baik pasti atau bidang geser, itu disebut tanah longsor. Ini termasuk slide rock, merosot dan sturzstroms. Ini juga merupakan salah satu klasifikasi umum wasting massa. Arus Gerakan tanah dan regolith yang lebih menyerupai perilaku fluida disebut aliran. Ini termasuk longsoran, lumpur, puing mengalir, aliran bumi, lahar dan sturzstroms. Air, udara dan es sering terlibat dalam memungkinkan gerak fluidlike material. topples Topples adalah contoh ketika blok poros batu dan jatuh jauh dari lereng.Slump Sebuah tergelincir dari bahan batu koheren sepanjang permukaan melengkung penurunan.Merosot melibatkan massa tanah atau bahan lain meluncur sepanjang permukaan melengkung (berbentuk seperti sendok). Ini membentuk tebing, kecil berbentuk sabit, atau lereng curam mendadak di ujung atas lereng. Ada bisa lebih dari satu lereng curam menuruni lereng. Falls Sebuah jatuh, termasuk runtuhan, adalah tempat cascades regolith menuruni lereng, namun tidak volume yang cukup atau viskositas untuk berperilaku sebagai aliran. Falls dipromosikan di batuan yang ditandai dengan adanya keretakan vertikal. Falls adalah hasil dari meremehkan air serta undercutting gelombang. Mereka biasanya terjadi pada lereng yang sangat curam seperti tebing. Bahan batuan dapat dilonggarkan oleh gempa bumi, hujan, wedging akar tanaman, memperluas es, antara lain. Akumulasi material batuan yang telah jatuh berada di dasar struktur dan dikenal sebagai talus. [Sunting] Pemicu membuang-buang massa
Tanah dan regolith tetap berada di lereng hanya sementara gaya gravitasi tidak dapat mengatasi gaya gesek menjaga material di tempat (lihat stabilitas lereng). Faktor-faktor yang mengurangi tahanan gesek relatif terhadap kekuatan lereng bawah, dan dengan demikian memulai gerakan lereng, dapat mencakup: seismik gemetar overburden meningkat dari struktur meningkatkan kelembaban tanah pengurangan akar memegang tanah untuk batuan dasar undercutting lereng dengan penggalian atau erosi pelapukan oleh heave embun beku bioturbation 


Gambar-gambar Mass Wasting




  Referensi
Monroe, Wicander (2005). Bumi Mengubah: Menjelajahi Geologi dan Evolution. Thomson Brooks / Cole. ISBN 0-495-01020-0. Selby, M.J. (1993). Lereng Bahan dan Proses, 2e.Oxford University Press. ISBN 0-19-874183-9. Pudasaini, Shiva P., Hutter, Kolumban (2007).Avalanche Dinamika: Dinamika Arus Cepat Longsoran Granular padat. Springer, Berlin, New York. ISBN 3-540-32686-3.

Mass wasting(ENGLISH LANGUAGE)


Mass wasting, also known as slope movement or mass movement, is thegeomorphic process by which soil,regolith, and rock move downslope under the force of gravity. Types of mass wasting include creep, slides, flows, topples, and falls, each with its own characteristic features, and taking place over timescales from seconds to years. Mass wasting occurs on both terrestrial and submarine slopes, and has been observed on EarthMarsVenus, and Jupiter's moon Io.
When the gravitational force acting on a slope exceeds its resisting force, slope failure (mass wasting) occurs. The slope material's strength and cohesion and the amount of internal friction between material help maintain the slope's stability and are known collectively as the slope's shear strength. The steepest angle that a cohesionless slope can maintain without losing its stability is known as its angle of repose. When a slope possesses this angle, its shear strength perfectly counterbalances the force of gravity acting upon it.
Mass wasting may occur at a very slow rate, particularly in areas that are very dry or those areas that receive sufficient rainfall such that vegetation has stabilized the surface. It may also occur at very high speed, such as in rock slides or landslides, with disastrous consequences, both immediate and delayed, e.g., resulting from the formation of landslide dams.
Factors that change the potential of mass wasting include: change in slope angle; weakening of material by weathering; increased water content; changes in vegetation cover; and overloading.

Contents

 [hide]

[edit]The importance of water in mass wasting

Water can increase or decrease the stability of a slope depending on the amount present. Small amounts of water can strengthen soils because the surface tension of water gives the soil a lot of cohesion. This allows the soil to resist erosion better than if it were dry. If too much water is present the water may act as a lubricant, accelerating the erosion process and resulting in different types of mass wasting (i.e. mudflows, landslides, etc.). A good example of this is to think of a sand castle. Water must be mixed with sand in order for the castle to keep its shape. If too much water is added the sand washes away, if not enough water is added the sand falls and can not keep its shape.

[edit]Types of mass movement

Types of mass movement are distinguished based on how the soil, regolith or rock moves downslope as a whole.

[edit]Creeps

Downhill creep is a long term process. The combination of small movements of soil or rock in different directions over time are directed by gravity gradually downslope. The steeper the slope, the faster the creep. The creep makes trees and shrubs curve to maintain their perpendicularity, and they can trigger landslides if they lose their root footing. The surface soil can migrate under the influence of cycles of freezing and thawing, or hot and cold temperatures, inching its way towards the bottom of the slope forming terracettes. This happens at a rate that is not noticeable to the naked eye.

[edit]Landslides

Where the mass movement has a well-defined zone or plane of sliding, it is called a landslide. This includes rock slidesslumps and sturzstroms.
It is also one of the common classification of mass wasting.

[edit]Flows

Movement of soil and regolith that more resembles fluid behavior is called a flow. These includeavalanchesmudflowsdebris flowsearth flowlahars and sturzstroms. Water, air and ice are often involved in enabling fluidlike motion of the material.

[edit]Topples

Topples are instances when blocks of rock pivot and fall away from a slope.

[edit]Slump

A slipping of coherent rock material along the curved surface of a decline. Slumps involve a mass of soil or other material sliding along a curved surface (shaped like a spoon). It forms a small, crescent-shaped cliff, or abrupt scarp at the top end of the slope. There can be more than one scarp down the slope.

[edit]Falls

A fall, including rockfall, is where regolith cascades down a slope, but is not of sufficient volume or viscosity to behave as a flow. Falls are promoted in rocks which are characterised by presence of vertical cracks. Falls are a result of undercutting of water as well as undercutting of waves. They usually occur at very steep slopes such as a cliff face. The rock material may be loosened by earthquakes, rain, plant-root wedging, expanding ice, among other things. The accumulation of rock material that has fallen resides at the base of the structure and is known as talus.

[edit]Triggers of mass wasting

Soil and regolith remain on a hillslope only while the gravitational forces are unable to overcome the frictional forces keeping the material in place (see Slope stability). Factors that reduce the frictional resistance relative to the downslope forces, and thus initiate slope movement, can include:
  • seismic shaking
  • increased overburden from structures
  • increased soil moisture
  • reduction of roots holding the soil to bedrock
  • undercutting of the slope by excavation or erosion
  • weathering by frost heave
  • bioturbation

[edit]References

  • Monroe, Wicander (2005). The Changing Earth: Exploring Geology and Evolution. Thomson Brooks/Cole. ISBN 0-495-01020-0.
  • Selby, M.J. (1993). Hillslope Materials and Processes, 2e. Oxford University Press. ISBN 0-19-874183-9.
  • Pudasaini, Shiva P., Hutter, Kolumban (2007). Avalanche Dynamics: Dynamics of Rapid Flows of Dense Granular Avalanches. Springer, Berlin, New York. ISBN 3-540-32686-3.

Mass wasting(ENGLISH LANGUAGE)


Mass wasting, also known as slope movement or mass movement, is thegeomorphic process by which soil,regolith, and rock move downslope under the force of gravity. Types of mass wasting include creep, slides, flows, topples, and falls, each with its own characteristic features, and taking place over timescales from seconds to years. Mass wasting occurs on both terrestrial and submarine slopes, and has been observed on EarthMarsVenus, and Jupiter's moon Io.
When the gravitational force acting on a slope exceeds its resisting force, slope failure (mass wasting) occurs. The slope material's strength and cohesion and the amount of internal friction between material help maintain the slope's stability and are known collectively as the slope's shear strength. The steepest angle that a cohesionless slope can maintain without losing its stability is known as its angle of repose. When a slope possesses this angle, its shear strength perfectly counterbalances the force of gravity acting upon it.
Mass wasting may occur at a very slow rate, particularly in areas that are very dry or those areas that receive sufficient rainfall such that vegetation has stabilized the surface. It may also occur at very high speed, such as in rock slides or landslides, with disastrous consequences, both immediate and delayed, e.g., resulting from the formation of landslide dams.
Factors that change the potential of mass wasting include: change in slope angle; weakening of material by weathering; increased water content; changes in vegetation cover; and overloading.

Contents

 [hide]

[edit]The importance of water in mass wasting

Water can increase or decrease the stability of a slope depending on the amount present. Small amounts of water can strengthen soils because the surface tension of water gives the soil a lot of cohesion. This allows the soil to resist erosion better than if it were dry. If too much water is present the water may act as a lubricant, accelerating the erosion process and resulting in different types of mass wasting (i.e. mudflows, landslides, etc.). A good example of this is to think of a sand castle. Water must be mixed with sand in order for the castle to keep its shape. If too much water is added the sand washes away, if not enough water is added the sand falls and can not keep its shape.

[edit]Types of mass movement

Types of mass movement are distinguished based on how the soil, regolith or rock moves downslope as a whole.

[edit]Creeps

Downhill creep is a long term process. The combination of small movements of soil or rock in different directions over time are directed by gravity gradually downslope. The steeper the slope, the faster the creep. The creep makes trees and shrubs curve to maintain their perpendicularity, and they can trigger landslides if they lose their root footing. The surface soil can migrate under the influence of cycles of freezing and thawing, or hot and cold temperatures, inching its way towards the bottom of the slope forming terracettes. This happens at a rate that is not noticeable to the naked eye.

[edit]Landslides

Where the mass movement has a well-defined zone or plane of sliding, it is called a landslide. This includes rock slidesslumps and sturzstroms.
It is also one of the common classification of mass wasting.

[edit]Flows

Movement of soil and regolith that more resembles fluid behavior is called a flow. These includeavalanchesmudflowsdebris flowsearth flowlahars and sturzstroms. Water, air and ice are often involved in enabling fluidlike motion of the material.

[edit]Topples

Topples are instances when blocks of rock pivot and fall away from a slope.

[edit]Slump

A slipping of coherent rock material along the curved surface of a decline. Slumps involve a mass of soil or other material sliding along a curved surface (shaped like a spoon). It forms a small, crescent-shaped cliff, or abrupt scarp at the top end of the slope. There can be more than one scarp down the slope.

[edit]Falls

A fall, including rockfall, is where regolith cascades down a slope, but is not of sufficient volume or viscosity to behave as a flow. Falls are promoted in rocks which are characterised by presence of vertical cracks. Falls are a result of undercutting of water as well as undercutting of waves. They usually occur at very steep slopes such as a cliff face. The rock material may be loosened by earthquakes, rain, plant-root wedging, expanding ice, among other things. The accumulation of rock material that has fallen resides at the base of the structure and is known as talus.

[edit]Triggers of mass wasting

Soil and regolith remain on a hillslope only while the gravitational forces are unable to overcome the frictional forces keeping the material in place (see Slope stability). Factors that reduce the frictional resistance relative to the downslope forces, and thus initiate slope movement, can include:
  • seismic shaking
  • increased overburden from structures
  • increased soil moisture
  • reduction of roots holding the soil to bedrock
  • undercutting of the slope by excavation or erosion
  • weathering by frost heave
  • bioturbation

[edit]References

  • Monroe, Wicander (2005). The Changing Earth: Exploring Geology and Evolution. Thomson Brooks/Cole. ISBN 0-495-01020-0.
  • Selby, M.J. (1993). Hillslope Materials and Processes, 2e. Oxford University Press. ISBN 0-19-874183-9.
  • Pudasaini, Shiva P., Hutter, Kolumban (2007). Avalanche Dynamics: Dynamics of Rapid Flows of Dense Granular Avalanches. Springer, Berlin, New York. ISBN 3-540-32686-3.