Natures Beautiful Wallpaper

8/20/12

Glaciers Short History And Amazing Images Collection

Short History Of Glaciers:

A huge mass of ice slowly flowing over a land mass. Glaciers form over many years from packed snow in areas where snow accumulates faster than it melts. A glacier is always moving, but when its forward edge melts faster than the ice behind it advances, the glacier as a whole shrinks backward.

Large mass of perennial ice that forms on land through the recrystallization of snow and that moves forward under its own weight. The term ice sheet is commonly applied to a glacier that occupies an extensive tract of relatively level land and that flows from the centre outward. Glaciers occur where snowfall in winter exceeds melting in summer, conditions that prevail only in high mountain areas and polar regions. Glaciers occupy about 11 of the Earth's land surface but hold roughly threetofourths of its fresh water. 99 of glacier ice lies in Antarctica and Greenland.

Glaciers are of four chief types. Valley, or mountain, glaciers are tongues of moving ice sent out by mountain snowfields following valleys originally formed by streams. In the Alps there are more than 1,200 valley glaciers. Piedmont glaciers which occur only in high latitudes are formed by the spreading of valley glaciers where they emerge from their valleys or by the confluence of several valley glaciers. Small ice sheets known as ice caps are flattened, somewhat dome-shaped glaciers spreading out horizontally in all directions and cover mountains and valleys. Continental glaciers are huge ice sheets whose margins may break off to form icebergs. During glacial periods they were far more widespread. Glaciers may be classified as warm or cold depending on whether their temperatures are above or below −10°C.

The causes of glacial movement are exceedingly complex and doubtless are not all operative on the same glacier at the same time. Important elements in glacial movement are melting under pressure followed by refreezing, which may push the mass in the direction of least resistance; sliding or shearing of layers of ice one on top of the other; and rearrangement of the granules when pressure causes melting. Sudden, rapid movements of glaciers, called glacier surges, have been observed in Alaskan and other glaciers, with evidence for such abnormal movements as the crumpled lines of surface debris found on them. It is thought that the relatively sudden movement and melting of glaciers may be indicative of climate warming.

The world's glaciers are slowly disappearing. Global temperatures have risen by about 1 degree Fahrenheit over the last century with winter temps having risen as much as 7 degrees Fahrenheit in the Arctic region.

Images:

Glaciers Amazing Image

Glacier Beautiful Scenery

Glacier Amazing Image

Glaciers Amazing Image

Glaciers Beautiful Scenery

Beautiful Scenery Of Glacier

Beautiful Scenery Of Glacier

8/14/12

Stream Introduction Parts And Very Very Beautiful Images Collection

Introduction:

A stream is a body of water with a current, confined within a bed and stream banks. Depending on its locale or certain characteristics.A stream may be referred to as a branch, brook, beck, burn, creek, kill, lick, rill, river, syke, bayou, rivulet, streamage, wash, run or runnel.

Streams are important as conduits in the water cycle, instruments in groundwater recharge, and corridors for fish and wildlife migration. The biological habitat in the immediate vicinity of a stream is called a riparian zone. Given the status of the ongoing Holocene extinction.Streams play an important corridor role in connecting fragmented habitats and thus in conserving biodiversity. The study of streams and water ways in general is known assurface hydrology and is a core element of environmental geography.

Parts Of Stream:

1. Bar:

A shoal that develops at the mouth of a river as sediment carried by the river is deposited as the current slows or is impedded by wave action. The Temperance River on Lake Superior's north shore is so named because it is one of the few rivers flowing into the lake that does not have a bar at its mouth.

2. Spring:

The point at which a stream emerges from an underground course through unconsolidated sediments or through caves. A stream can, especially with caves, flow above ground for part of its course, and under ground for part of its course.

3. Source:

The spring from which the stream originates, or other point of origin of a stream.

4. Headwaters:

The part of a stream or river proximate to its source. The word is most commonly used in the plural where there is no single point source.

5. Confluence:

The point at which the two streams merge. If the two tributaries are of approximately equal size, the confluence may be called a fork.

6. Bifurcation:

A fork into two or more streams

7. Run:

A somewhat smoothly flowing segment of the stream.

8. Pool:

A segment where the water is deeper and slower moving.

9. Riffle:

A segment where the flow is shallower and more turbulent.

10. Channel:

A depression created by constant erosion that carries the stream's flow.

11. Floodplain:

Lands adjacent to the stream that are subject to flooding when a stream overflows its banks.

12. Stream bed:

The bottom of a stream.

13. Gauging station:

A point of demarkation along the route of a stream or river, used for reference marking or water monitoring.

14. Thalweg:

The river's longitudinal section, or the line joining the deepest point in the channel at each stage from source to mouth.

15. Wetted perimeter:

The line on which the stream's surface meets the channel walls.

16. Knickpoint:

The point on a stream's profile where a sudden change in stream gradient occurs.

17. Waterfall or cascade:

The fall of water where the stream goes over a sudden drop called a nickpoint; some nickpoints are formed by erosion when water flows over an especially resistant stratum, followed by one less so.

18. Mouth:

The point at which the stream discharges, possibly via an estuary or delta, into a static body of water such as a lake or ocean.

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