Rocks+and+Weathering

Rock Hounds Sedimentary Rock Formation
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The Rock Cycle - Rocks and Minerals 4U
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Rock Hounds - Sandstone
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Rock Hounds Limestone
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Rock Hounds - Shale
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Rock Hounds Conglomerate Rocks
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Sedimentary Rock Formation - Rocks and Minerals 4U
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Igneous Rocks - Rocks and Minerals 4U
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Groundwater and Rocks - AGSO
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River Nile Delta
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Images of a River Delta






China
China’s Huang He (Yellow River) is the most sediment-filled river on Earth. Flowing northeast to the Bo Hai Sea from the Bayan Har Mountains, the Yellow River crosses a plateau blanketed with up to 300 meters (980 feet) of fine, wind-blown soil. The soil is easily eroded, and millions of tons of it are carried away by the river every year. Some of it reaches the river’s mouth, where it builds and rebuilds the delta. []



Definition of a river delta

 * || [|resource center >] [|background & facts] > [|the detailed story] ||
 * WHAT IS A RIVER DELTA?
 * WHAT IS A RIVER DELTA?

**DELTAS** Deltas are the result of interacting fluvial (river) and, usually, marine systems. However, they can form anywhere a stream flows into shallower open water. ||  || **from Wright, 1978** **Whence the name Delta?** //Delta// was coined by //Herodotus// (the father of history, 484-425 BC) after the Greek letter //delta// because of the deltoid-shape at the mouth of the Nile.

**//Delta// definition**: Coastal accumulations, both subaqueous and subaerial, of river-derived sediments adjacent to, or in close proximity to, the source stream, including the deposits that have been secondarily molded by various marine agents, such as waves, currents, or tides. [L. D. Wright, 1978]

Deltas occur throughout the world, except at the poles (see slides). They all have three characteristics in common: 1. The presence of a large catchment, or drainage, basin (the area where all run-off water drains to the river). The top 30 river deltas all have catchment basins in excess of 1,000,000 sq km.

2. They all are at the mouth of large river systems that carry large quantities of clastic sediments (soils or portions of rocks that have been moved by water from where they formed). 3. They are not near geologically active coastlines. In order to have a large catchment basin, a very complex tributary system is necessary. These long, complex systems take a long time to develop, so they are very rarely situated on tectonically active coasts. **ANATOMY OF A DELTA:**


 * **Subaqueous** (=under the water) delta - That part of the delta that is below the low-tide mark. Seaward, finer and finer soil particles are found. The seaward-most portion has the finest soils (clays) and is called the //prodelta//.

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