AY Honors/Geology/Answer Key

1. Give the geological meaning of the following words:

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  Satellite image of the Nile River Delta

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  The three narrow strips of land shown here are spits in the Baltic Sea

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  Sinkholes near the Dead Sea

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  Map of an oxbow lake

a. Delta

A delta is a landform where the mouth of a river flows into an ocean, sea, desert, estuary or lake.

b. Sand spit

A spit a deposition landform found off coasts. A spit is a type of bar or beach that develops where a re-entrant occurs, such as at a cove, bay, ria, or river mouth. Spits are formed by the movement of sediment (typically sand) along a shore

c. Sinkhole

A sinkhole is a natural depression or hole in the surface topography caused by the removal of soil or bedrock, often both, by water. Sinkholes may vary in size from less than a meter to several hundred meters in diameter and depth, and vary in form from soil-lined bowls to bedrock-edged chasms. They may be formed gradually or suddenly, and are found worldwide.

d. Oxbow lake

n oxbow lake is a type of lake which is formed when a wide meander from a stream or a river is cut off to form a lake. They are called oxbow lakes due to the distinctive curved shape that results from this process. In Australia, an oxbow lake is called a billabong.

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  Moraine, glacier and lake of Arsine, Écrins National Parc, French Alps

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  Iceberg Cirque, Glacier National Park, USA

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  Mesa at Ray Mine (Arizona, USA)

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  A small alluvial fan.

e. Moraine

Moraine is a French word that refers to any glacially formed accumulation of unconsolidated debris. This debris may be plucked off the valley floor as a glacier advances or fallen off the valley walls as a result of frost wedging. Moraine may be comprised of silt like glacial flour to large boulders. The debris is typically angular. Moraine may be on the glacier’s surface or deposited as piles or sheets of debris where the glacier has melted. Moraine may also occur when rocks fall in the sea.

f. Cirque

A cirque is an amphitheatre-like valley (or valley head) of glacial origin, formed by glacial erosion at the head of the glacier. Cirques are typically partially surrounded by steep cliffs. The highest cliff is often called a headwall. They are also known as a cwm in Wales, a coomb or coombe in England, and a corrie in Scotland and Ireland.

g. Mesa

A mesa (Spanish and Portuguese for "table") is an elevated area of land with a flat top and sides that are usually steep cliffs. It takes its name from its characteristic table-top shape. It is a characteristic landform of arid environments, particularly the southwestern United States. Many examples are also found in Spain, North and South Africa, Arabia, India, Australia, and the Badlands and Colorado regions of North America.

h. Alluvial fan

An alluvial fan is a fan-shaped deposit formed where a fast flowing stream flattens, slows, and spreads typically at the exit of a canyon onto a flatter plain.

i. Anticline

j. Syncline