風化作用與風化地形
Weathering
and related
landforms
l
Key
terms
| physical (mechanical) weathering | disintegration | hydrolysis | sheeting |
| chemical weathering | decomposition | dissolution | exfoliation |
| differential weathering | oxidation | ice wedge | regolith |
l
Key
concepts (from Hamblin & Christiansen, 1995)
1. Weathering is the breakdown and alteration of rock at Earth's surface through physical and chemical reactions with the atmosphere.
2. Mechanical weathering fragments rock by various physical stresses. Ice wedging and sheeting are the most important processes.
3. Chemical weathering includes a variety of chemical reactions between elements in the atmosphere and those in rocks. Hydrolysis, dissolution, and oxidation are the most important reactions.
4. Rock disintegration is greatly influenced by patterns of joints, bedding, and other planes of structural weakness in the parent rock materials. Because they permit water and gases in the atmosphere to attack a rock body at considerable depth. They also greatly increase the surface area on which chemical reactions can occur.
5. The major results of weathering are (a) formation of a discontinuous blanket of disaggregated and decomposed rock debris (regolith), and (b) rocks of various sizes modified into spherical forms.
6. Climate is the single most important factor in weathering, the two most important variables being precipitation and temperature.
7. Rates of weathering depend mostly on climate and composition of the rock. Rates of weathering can be measured on volcanic extrusions and built monuments, where the age of original surfaces can be dated.
8. Weathering can be defined as the response of materials which were at equilibrium in the lithosphere, to new conditions at or near the contact with the atmosphere and biosphere.
崩壞作用與相關地形
Mass
wasting and related
landforms
l
Key
terms
| slope system | mass movement | angle of repose | rockfall |
| rockslide | landslide | slump | debris flow |
| mudflow | creep | solifluction |
l
Key
concepts
1. Slopes dynamic systems of moving materials that consist of an input of rock debris near the top of the slope and an output of finer rock fragments into a stream.
2. Slopes are open systems in which the effects of weathering, mass movement, and erosion of minor gully tributaries combine to transport rock material downslope to the main stream.
3. Mass movement is the downslope transfer of material through the direct action of gravity. It is a major geologic process operating on all slopes.
4. Gravity is the driving force for the downslope movement of material, but several factors are important in overcoming inertia and causing movement to occur, however, the force of gravity must exceed the cohesive strength of the surface material.
5. The most important are (1) saturation of material with water, (2) vibrations from earthquakes, (3) oversteepening of slopes by undercutting, and (4) alternating freezing and thawing.
6. Many types of mass movement can be recognized on the basis of the behavior of the material and mechanics of movement. The most important are (1) creep, (2) debris flows, and (3) landslides. Other types of mass movement include solifluctions, rockfalls, lahars, etc.
7. Subsidence differs from other types of mass movement in that it has essentially vertical motion. Voids in the subsurface that create subsidence are created by groundwater, lava tunnels, combustion of peat and coal compaction, and the removal of subsurface material by mining, and by the pumping of water, oil and gas.
常見用語
Mass movement（塊體運動）； Mass wasting（塊體崩壞）； Downslope movement （下坡運動）； Slope failure
廣義的landslide （泛指所有快速的崩壞）> 狹義的landslide（e.g., 地滑）
邊坡研究歷史
~1950年代，著重於如何自邊坡形態瞭解地景演育。最近二十年，開始重視詳細的坡面營力。工程的研究投入甚多。
構成邊坡的物質
| type (種類) | size (大小) |
| rocks | mud（泥）、earth（土） |
| soils | debris（岩屑） |
| rocks & soils | rock（岩石） |
| block（岩塊） |
坡面運動的形式
| 側向的 | 垂直的 |
| flow（流動） | fall（墜落） |
| slide（滑動） | subsidence（下陷）[此項通常不在崩壞的單元討論] |
| heave（舉升） |
被移動物質含水量的多寡
vs. 運動的速率
崩壞的主要類型
l 按運動形式分：參見triangle diagram (Carson and Kirkby 1972)。其他還有fall and subsidence
l 也有根據「被搬運物質特性」和「運動形式」兩者來命名，例如：rockslide, rockfall, debris flow
l 有些類型是由一種主要的作用造成，例如：soil creep (heave)或slump(rotational slide)；有些類型是由一種以上的作用所造成，例如：solifluction（heave + slide）
l 不同作者對同一名詞的界定可能不同。有人將debris flow、avalanches, earthflows、 mudflows視為由流動作用造成的各種類型；也有人以debris flow泛指所有由水、泥、沙、礫混合的黏滯性物質因重力作用向下坡流動的崩壞類型的，其下再分為mudflows, earthflows, lahars (volcanic mudflows)
相關的地形 （石再添等 1990, 106-108）
| 崩塌地形 | 緩滑地形 |
| 落岩塊 | 落石堆 | 土石流堆積體 | 圖案地 |
| 山崩窪 | 塌陷塊 | 岩石流 | |
| 山崩溝 | 山崩湖 |
臺灣地區舉例
八堵道路邊坡
淡水米蘭山莊
汐止林肯大郡
其他參考文獻
|
張瑞津(1997) 土石流、土流及泥流之釋義，地理教育，no.23, pp.19-24. 「地滑事件」∼林肯大郡事件請參閱 大地 期 「地震與相關地形變動」請參閱 大自然66期、大地139期(1999/10)、大地140期(1999/11) 經濟部中央地質調查所 (2000) 臺灣山崩災害專輯(一)，145頁。
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河流作用與相關地形
Fluvial
processes
and related
landforms
l
Key
terms
| drainage basin | suspended load | longitudinal profile | river terrace | tributary |
| divide | bed load | pothole | floodplain | distributary |
| discharge | abrasion | meander | natural levee | permanent stream |
| settling velocity | graded river | point bar | delta | stream piracy |
l
Key
concepts
1. Running water is part of Earth's hydrologic system and is the most important agent of erosion. Stream valleys are the most abundant and widespread landforms on the continents. Studies of river systems show that there is a high degree of order among the tributaries, in relation to the size and gradients of their valleys. These relationships indicate that streams erode the valleys through which they flow.
2. A river system consists of a main channel and all of the tributaries that flow into it. It can be divided into three subsystems: (1) a collecting system (tributaries, which collect and transport water and sediment into the main stream), (2) transporting system (a main trunk stream, which is largely a transporting system), and (3) a dispersing system (at the river mouth).
3. The most important variables in stream flow are (2) discharge, (2) velocity, (3) gradient, (4) sediment load, and (5) base level. The capacity of running water to erode and transport sediment largely depends on the stream's velocity.
4. A river system is best thought of as a system of moving water and sediment because an enormous volume of sediment is constantly being transported to the ocean by running water. The sediment is moved in suspension, by traction, and in solution.
5. A river system functions as a unified whole, adjusting its profile to establish equilibrium among the factors that influence flow. If one factor changes, the river system adjusts to reestablish equilibrium.
6. Rivers erode the landscape by (1) removal of the regolith, (2) downcutting of stream channels, (3) slope retreat, and (4) headward erosion. Most sediment carried by rivers is derived from the regolith. Weathering therefore plays an important role in preparing solid rock for erosion.
7. As a river develops a low gradient, it deposits part of its load on point bars, on natural levees, and across the surface of its floodplain. Most of a river's sediment is deposited where the river empties into a lake or ocean. The deposition commonly builds a delta at the river's mouth. In arid regions, many stream deposit their loads as alluvial fans at the base of steep slopes.
l
流域系統 (drainage
system) （王鑫1988,
147-154）
水循環
與外部系統的關係
集水區（流域）(catchment; river basin)：河道次系統 + 邊坡次系統；輸入、傳輸、輸出
河系、水系、谷系
河流等級
幾何特性
l
邊坡上的流水侵蝕與溶解質的搬運 (Summerfield 1991, pp. 175-8)
坡面水文 Hillslope hydrology
Wash processes: rainsplash erosion ＋ slope wash ＋ solute transport
雨水濺蝕Rainsplash erosion
6 mm raindrop in diameter à 9 m/sec impact à dislodging 10 mm or coarser particles in diameter
Slope wash
Soil erosion
l
河道類型
沖積河道 (alluvial channel) ：多出現在低地區
底岩河道 (bedrock channel)：多出現在山地區
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地形、地質、工程學者長久以來就體認到山地河道和低地河道有根本上的差異。與氾濫平原的河道相較，山地河道的坡降和形態極為多樣，而且容易受到外部影響的支配。(In contrast to self-formed flood-plain channels, the gradient and morphology of mountain channels are tremendously variable and prone to forcing by external influences.) 雖然山地河道提供了重要的水體棲地，供給沈積物到河口與海洋，並將河源區土地利用的干擾透過水系傳送到下游，但是它們所受到的關注遠比低地的沖積河道為少（Montgomery and Buffington, 1997）。 |
| Montgomery, D.R. and Buffington, J.M. (1997) Channel-reach morphology in mountain drainage basins, Geological Society American Bulletin, 109(5), 596-611. |
l
河流作用（石再添等 1990,
113-114；王鑫1988,
155-164）
河水流動特性
侵蝕
搬運 + 河川負荷(stream loads) 的分類
堆積
河道沈積物「向下游變細的法則」最早是Sternberg (1875)根據阿爾卑斯山萊因河底質的觀察，所提出的簡要定義。[cited from Reid, Bathurst, Carling, Walling & Webb 1997, p.95]
Reid, I., Bathurst, J.C., Carling, P.A., Walling, Des,E. and Webb, B.W. (1997) Sediment, erosion, transport and deposition, Applied Fluvial Geomorphology for River Engineering and Management, edited by C.R. Thorne, R.D. Hey and M.D. Newson, John Wiley and Sons, 95-135.
Sternberg, H. (1875) Untersuchungen über Langen und Querprofil deschiebeführende Flüsse, Z. Bauwesen, 25, 483-506.
l 河谷與河道形態
河谷單元
谷坡（有時有河階）、谷底（分為河道和河洲）
河道剖面形態（王鑫1988, 164-170）
橫剖面
縱剖面
均夷剖面（石再添等 1990, p.114）
河道流路形態
直流
曲流
網流
河谷分類（王鑫1988,
172-174）
l
水系形態（石再添等 1990,
118-119；王鑫1988,
174-176）
l
河流地形（石再添等 1990,
120-123；王鑫1988,
155-164）
侵蝕地形
峽谷
河階*
瀑布
河成壺穴
堆積地形
氾濫平原、自然堤、牛軛湖
沖積扇
三角洲
l
流域的長期演育
l
河流地形與人生
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Are tropical rivers different? (Gupta 1993) When streams are affected by large floods from tropical storms occurring at intervals of several years and combined with suitable physiography resulting in the supply of plentiful coarse sediments to the flooded channels, the streams are characterised by channel forms and sedimentation pattern, including - widening of channel - erosion of bars and formation of chutes - scouring of floodplain - increase in competence - channel deposition of coarse gravel - building of transverse gravel waves and bars - deposition on floodplain - formation of a terrace-like feature in the valley - formation of coarse material levees and - destruction of vegetation (Gupta 1988). It is a departure from the traditional approach and recognition that the final processes and landforms are products of a diversity of causes within a tropical climatic belt. Even the climatic influence is not uniform across the tropics. In some areas tropical cyclones which bring episodic but catastrophic changes are likely to be the dominant climatic control on regional processes and landforms. As Frank Ahnert (1990) once asked, which climatic changes are significant geomorphologically and which are not? What is needed in the field at the moment is a combination of modern techniques, a grasp of the basic concepts and an open mind.
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其他參考
河流地形簡介 http://140.115.123.30/earth/river/history.htm
近岸營力與海岸地形
Nearshore
processes and coastal
landforms
l
Key
terms
| wave | wave refraction | barrier island | estuary |
| tide | sedimentary coast | spit | fjord |
| longshore current/drift | rocky coast | berm (of beach) | headland |
l
Key
concepts (from Hamblin & Christiansen, 1995)
1. Shorelines are dynamic systems involving the forces of waves and currents. Wind-generated waves provide most of the energy of erosion, transportation, and deposition of sediment, but tides and tsunamis can be locally important.
2. Waves approaching a shore are bent, or refracted, so that energy is concentrated on headlands and dispersed in bays.
3. Longshore drift is generated as waves strike the shore at an angle.
4. Erosion along coasts results from the abrasive action of sand and gravel moved by the waves and currents. The undercutting action of waves and currents typically produces sea cliffs. As a sea cliff recedes, a shore platform develops.
5. Sediment transported by waves and longshore drift is deposited in areas of low energy. It produces a variety of landforms, including beaches, spits, tombolos, and barrier islands.
6. Erosion and deposition processes tend to develop a straight or gently curving coastline where neither large-scale erosion nor large-scale deposition occurs.
7. Reefs are a special type of coastal feature because the active process is organic. The commonly evolve through a series of types, from fringing reefs, to barrier reefs, to atolls.
8. The worldwide rise in sea level, associated with the melting of the Pleistocene glaciers, drowned many coasts.
9. Tides are caused by gravitational attractions of the Moon and have a significant effect on shorelines.
10. A tsunami is a wave generated by an earthquake or submarine mass movement. It grows higher as it approaches the shore and can be extremely destructive.
其他參考資料
海水面升降與海岸地帶的命運 http://gis.geo.ncu.edu.tw/gis/globalc/CHAP0901.htm
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# 冰河作用與冰河地形 |
http://140.115.123.30/earth/glacier/glacier.htm
王鑫、楊建夫、郭彥超 (2000) 太魯閣國家公園南湖大山圈谷群古冰河遺跡研究初步調查，太魯閣國家公園管理處。 http://www.cpami.gov.tw/taroko/taroko.htm 合作計畫案一欄，可下載全文。
王鑫、楊建夫、郭彥超 (2000) 雪山圈谷群第四紀冰河遺跡研究 (III)，雪霸國家公園管理處。
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# 岩溶作用與石灰岩地形 |
|
長期地形演育 |
Hamblin & Christiansen (1995): ch 13
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# 臺灣地形概論 |
臺灣地質概論 http://www.moeacgs.gov.tw/Area/geology/index.htm
臺灣地質 http://www.moeacgs.gov.tw/live/fossil/taiwangeo.htm
臺灣主要岩石與礦物 http://140.115.123.30/mineral/mineral.htm
岩石入門 http://www.ylib.com.tw/taiwan/watch/stone/common.htm
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# 星球地形學 |