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Chalk is so common in Cretaceous marine beds that the Cretaceous Period was named for these deposits. The name Cretaceous was derived from Latin creta, meaning chalk. [10] Some deposits of chalk were formed after the Cretaceous. [11] The Chalk Group is a European stratigraphic unit deposited during the late Cretaceous Period.
The products of chalk weathering are dissolved in rainwater and are transported in stream flow. Chalk streams transport little suspended material (unlike most rivers), but are considered "mineral-rich" due to the dissolved calcium and carbonate ions. The surface water of chalk streams is commonly described as "gin clear".
The Cretaceous is justly famous for its chalk; indeed, more chalk formed in the Cretaceous than in any other period in the Phanerozoic. [26] Mid-ocean ridge activity—or rather, the circulation of seawater through the enlarged ridges—enriched the oceans in calcium ; this made the oceans more saturated, as well as increased the ...
It is formed in marine or freshwater environments, often through the activities of algae. Marl makes up the lower part of the cliffs of Dover, and the Channel Tunnel follows these marl layers between France and the United Kingdom. Marl is also a common sediment in post-glacial lakes, such as the marl ponds of the northeastern United States.
The Chalk Group (often just called the Chalk) is the lithostratigraphic unit (a certain number of rock strata) which contains the Upper Cretaceous limestone succession in southern and eastern England. The same or similar rock sequences occur across the wider northwest European chalk 'province'.
When heating hard water on the stove, these gas bubbles form on the surface of the pan prior to boiling. Gas exsolution can also occur when the confining pressure is released such as when you take the top off a beer bottle or where subsurface water is flowed into an atmospheric pressure tank.
Niobrara Chalk was weathered and opalized in the Valentine phase of the Ogallala Formation. The Niobrara Formation / ˌ n aɪ. ə ˈ b r ær ə /, also called the Niobrara Chalk, is a geologic formation in North America that was deposited between 87 and 82 million years ago during the Coniacian, Santonian, and Campanian stages of the Late ...
Downland develops when chalk rock becomes exposed at the surface. The chalk slowly erodes to form characteristic rolling hills and valleys. As the Cretaceous chalk layer in southern England is typically tilted, chalk downland hills often have a marked scarp slope on one side, which is very steep, and a much gentler dip slope on the