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    • Aidynbek Mussa

      Результаты олимпиады   06/05/2019

      Внимание участники!  Уже известны результаты первой онлайн-олимпиады от нашего сообщества. Прикрепляю файл с результатами внизу Результаты олимпиады по географии - Лист1.pdf 

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Chalk - variety of limestone which is composed mainly of calcite skeletons of plankton (coccoliths)

  1. It forms under reasonably deep marine environment 
  2. Chalk has greater resistance to weathering than clays, therefore when clay layers are washed off, white chalk cliffs are formed, where chalk ridges meet the sea. Due to the similar reason when layers (bands) of chalk reach the surface at an angle escarpments are formed.
  3. Chalk absorbs a lot of water, therefore chalk landscapes look so dry
  4. Cretacious period is called so, because thick layers of chalk formed during that time. When Alps formed these layers got exposed to the surface in England, Germany and France.
  5. Flint (sedimentary rock formed from sponge spicules) and  brachiopodsbivalvescrinoids, and sponges be can found in the chalk deposits, as can sharks' teeth.

When you see thick chalk deposits you can definitely say that for some time in the past there were very stable conditions for over tens of millions of years. (Like during Cretacious period in Europe)

Definitely check out:

https://www.geolsoc.org.uk/ks3/gsl/education/resources/rockcycle/page3824.html

Other useful links:

https://www.nationalgeographic.org/encyclopedia/escarpment/

https://en.m.wikipedia.org/wiki/White_Cliffs_of_Dover

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