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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 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.
a wave that travels along the boundary between the crust and mantle P: a P wave in the mantle p: a P wave ascending to the surface from the focus R: a Rayleigh wave S: an S wave in the mantle s: an S wave ascending to the surface from the focus w: the wave reflects off the bottom of the ocean No letter is used when the wave reflects off of the ...
The Prairie Bluff Chalk is a geologic formation in Alabama and Mississippi.It preserves fossils dating back to the Cretaceous period. [2] [3]The chalk was formed by marine sediments deposited along the eastern edge of the Mississippi embayment during the Maastrichtian stage of the Late Cretaceous.
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]
This tree is a rare phenomenon due to its unique appearance and the red sap it produces. It can live for hundreds of years, thrives in the island’s harsh, dry climate and is part of the island's ...
Plate tectonics is a scientific theory developed in the 1960s that explains major land form events, such as mountain building, volcanoes, earthquakes, and mid-ocean ridge systems. [26] The idea is that Earth's most outer layer, known as the lithosphere , that is made up of the crust and mantle is divided into extensive plates of rock.
A hole in a 600-mile-long fault line has been discovered at the bottom of the Pacific ocean - and it could be the trigger of a magnitude-9 earthquake on the US coast. Just outside of Oregon ...