What is Upper Cretaceous?
[[File:Dover-banner.jpg|thumb|center|700px|The white cliffs of Dover]] [[File:The Needles.jpg|thumb|center|300px|The Needles: here the lines of [[flint]] in the chalk can be clearly seen.]] [[File:MERS (1).JPG|thumb|center|300px|Chalk cliff of Mers-les-Bains, at high tide. These photos show that the whole area was part of a high-temperature tropical sea full of chalk-producing microorganisms.]] The '''Upper Cretaceous''' is the last [[geology|geological]] [[Epoch (geology)|epoch]] in the [[Cretaceous]]. It began 100.5 [[million]] years ago, and ended 66 million years ago. The [[Cretaceous]] is traditionally divided into [[Lower Cretaceous]] (early), and Upper Cretaceous (late), because of the different [[Rock (geology)|rocks]]. The rocks reflect the conditions in which they were formed. From lowest to highest, it is subdivided into the Cenomanian, Turonian, Coniacian, Santonian, Campanian, and [[Maastrichtian]] ages. The Upper Cretaceous is the time of [[chalk]]. Chalk is composed of countless millions of [[Calcium carbonate|calcareous]] (CaCO<sub>3</sub>) plates called [[coccolith]]s. They are so small they can only just be seen with a light [[microscope]]; details require an [[electron microscope]]. The plates are formed by single-celled [[plankton]]ic [[algae]] called [[coccolithophore]]s, and were laid down in the off-shore seas. The only other rock found in chalk is the [[flint]], which is [[Silicon dioxide|siliceous]] ([[silica]], SiO<sub>2</sub>). This derives from those algae and animals which have skeletons of silica. Undoubtedly, this marks periods when the climate was somewhat different. The [[Cretaceous]] was the last period when [[dinosaur]]s were the dominant land animals. ''[[Triceratops]]'', ''[[Tyrannosaurus]]'' and ''[[Velociraptor]]'' lived at this time. The huge ''[[Mosasaurus]]'' was the dominant [[Ocean|marine]] [[predator]]. In the Cretaceous period, [[bird]]s became more [[wikt:diverse|diverse]]. [[Flowering plants]] developed more, and became the dominant plants on land. The Upper