Cachoeira no Horto(Rio de Janeiro) : 無料・フリー素材/写真
Cachoeira no Horto(Rio de Janeiro) / Rodrigo_Soldon
| ライセンス | クリエイティブ・コモンズ 表示-改変禁止 2.1 |
|---|---|
| 説明 | As quedas de água (ou quedas-d'água), cachoeiras, cascatas, ou cataratas são formações geomorfológicas nas quais os cursos de água correm por cima de uma rocha de composição resistente à erosão, formando uma súbita quebra na vertical.00000000000000000000000000000000A waterfall is a place where flowing water rapidly drops in elevation as it flows over a steep region or a cliff.Waterfalls are commonly formed when a river is young.[1] At these times the channel is often narrow and deep. When the river courses over resistant bedrock, erosion happens slowly, while downstream the erosion occurs more rapidly.[1][2] As the watercourse increases its velocity at the edge of the waterfall, it plucks material from the riverbed. Whirlpools created in the turbulence as well as sand and stones carried by the watercourse increase the erosion capacity.[1] This causes the waterfall to carve deeper into the bed and to recede upstream. Often over time, the waterfall will recede back to form a canyon or gorge downstream as it recedes upstream, and it will carve deeper into the ridge above it.[3] The rate of retreat for a waterfall can be as high as one and half meters per year.[1] Often, the rock stratum just below the more resistant shelf will be of a softer type, meaning that undercutting due to splashback will occur here to form a shallow cave-like formation known as a rock shelter under and behind the waterfall. Eventually, the outcropping, more resistant cap rock will collapse under pressure to add blocks of rock to the base of the waterfall. These blocks of rock are then broken down into smaller boulders by attrition as they collide with each other, and they also erode the base of the waterfall by abrasion, creating a deep plunge pool or gorge.Streams become wider and shallower just above waterfalls due to flowing over the rock shelf, and there is usually a deep area just below the waterfall because of the kinetic energy of the water hitting the bottom. Waterfalls normally form in a rocky area due to erosion. After a long period of being fully formed, the water falling off the ledge will retreat, causing a horizontal pit parallel to the waterfall wall. Eventually, as the pit grows deeper, the waterfall collapses to be replaced by a steeply sloping stretch of river bed.[1] In addition to gradual processes such as erosion, earth movement caused by earthquakes or landslides or volcanoes can cause a differential in land heights which interfere with the natural course of a water flow, and result in waterfalls. A river sometimes flows over a large step in the rocks that may have been formed by a fault line. Waterfalls can occur along the edge of a glacial trough, whereby a stream or river flowing into a glacier continues to flow into a valley after the glacier has receded or melted. The large waterfalls in Yosemite Valley are examples of this phenomenon, which is referred to as a hanging valley. Another reason hanging valleys may form is where two rivers join and one is flowing faster than the other.[1] Waterfalls can be grouped into ten broad classes based on the average volume of water present on the fall (which depends on both the waterfall's average flow and its height) using a logarithmic scale. Class 10 waterfalls include Niagara Falls, Paulo Afonso Falls and Khone Falls. Classes of other well-known waterfalls include Victoria Falls and Kaieteur Falls (Class 9); Rhine Falls and Gullfoss (Class 8); Angel Falls and Dettifoss (Class 7); Yosemite Falls, Lower Yellowstone Falls and Umphang Thee Lor Sue Waterfall (Class 6); Sutherland Falls (Class 5).------------------------------------------------------------------滝、瀧（たき）とは河川や湖の一部が段差になり水が落下している場所をいう。瀑布（ばくふ）、飛瀑（ひばく）ともいう。水の落下地点で水深が深くなっている場所を滝壷（たきつぼ）という。一部の滝は、侵食が速く、また川の流れが地殻変動で変わりやすい山岳地帯において生じる。このような場所にある滝は、同じ場所を長年に渡って水が流れたことによってではなく、衝上断層（逆断層）や火山活動などの突然の地質の変化によって形成される。 それに対して、多くの滝は、長年に渡って流れる水によって形成される。典型的には、岩石の地層を横切って流れる水流があると、侵食に強い岩脈部分が棚として残るのに対し、その先の侵食に弱い地層部分が削られて落ちる。結果、残った棚は落ちた部分に対して隆起した状態になる。 さらに月日が経過すると、棚の端が徐々に削られ滝は絶えず上流に移動していく。同時に多くの場合、侵食に強い棚に対し、その下の地層は弱い地層からなるため、棚の下の層が侵食され、滝の下では水のカーテンの後ろに洞窟状の窪みが形成される。 滝の上の水流は、堅い棚の上を流れるために流れは広く浅くなり、滝の直下は、落下によって勢いがついた水が地面を叩くために水溜まりができる。 冬季に氷結し、巨大な氷柱となった滝を氷瀑（ひょうばく）という。pt.wikipedia.org/wiki/Queda_de_%C3%A1gua |
| 撮影日 | 2012-01-14 09:55:29 |
| 撮影者 | Rodrigo_Soldon , Rio de Janeiro, Brazil |
| タグ | |
| 撮影地 | Rio de Janeiro, Rio de Janeiro, Brasil 地図 |
| カメラ | NIKON D7000 , NIKON CORPORATION |
| 露出 | 0.25 sec (1/4) |
| 開放F値 | f/16.0 |
| 焦点距離 | 26 mm |