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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.
A stack or sea stack is a geological landform consisting of a steep and often vertical column or columns of rock in the sea near a coast, formed by wave erosion. [1] Stacks are formed over time by wind and water, processes of coastal geomorphology. [2] They are formed when part of a headland is eroded by hydraulic action, which is the force of ...
If waves carve notches at a narrow point on both sides of a promontory on the rocky cliffed coast, a natural arch may be formed. [4] When the arch collapses as the coastline recedes further a stack is left behind on the wave-cut platform. The best-known example in Germany is the Lange Anna on Heligoland, while, in England, a prominent example ...
The secondary principle to the creation of seaward sediment fining is known as the hypothesis of asymmetrical thresholds under waves; this describes the interaction between the oscillatory flow of waves and tides flowing over the wave ripple bedforms in an asymmetric pattern. [4] "The relatively strong onshore stroke of the waveforms an eddy or ...
Marine sediment, or ocean sediment, or seafloor sediment, are deposits of insoluble particles that have accumulated on the seafloor.These particles either have their origins in soil and rocks and have been transported from the land to the sea, mainly by rivers but also by dust carried by wind and by the flow of glaciers into the sea, or they are biogenic deposits from marine organisms or from ...
The chalk of Old Harry Rocks used to be part of a long stretch of chalk between Purbeck and the Isle of Wight, but remained as a headland after large parts of this seam were eroded away. As the headland suffered hydraulic action (a process in which air and water are forced into small cracks by the force of the sea, resulting in enlarging cracks ...
The putative galloanseran bird Austinornis lentus has been found in the Austin Chalk. [2] [3] The general absence of dinosaurs is a reflection of the Austin limestone being marine in origin, primarily composed of microscopic shell fragments from floating sea organisms known as "coccolithophores" (the same organisms that contributed to the White Cliffs of Dover, on the south coast of England). [4]
The coccolithophores lived in the upper part of the water column. When they died, the microscopic calcium carbonate plates, which formed their shells settled downward through the ocean water and accumulated on the ocean bottom to form a thick layer of calcareous ooze, which eventually became the Chalk Group.