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The aquatic toothed bird Hesperornis is the only known Cretaceous bird whose remains are found with any frequency in North America. [82] Near the end of the Cretaceous, the Western Interior Seaway began to withdraw. This regression would end up resulting in both halves of North America reuniting.
The map of North America with the Western Interior Seaway during the Campanian. The Western Interior Seaway (also called the Cretaceous Seaway, the Niobraran Sea, the North American Inland Sea, or the Western Interior Sea) was a large inland sea that split the continent of North America into two landmasses for 34 million years.
The geology of North America is a subject of regional geology and covers the North American continent, the third-largest in the world. Geologic units and processes are investigated on a large scale to reach a synthesized picture of the geological development of the continent.
[notes 1] The hydrosphere plays an important role in the existence of the atmosphere in its present form. Oceans are important in this regard. When the Earth was formed it had only a very thin atmosphere rich in hydrogen and helium similar to the present atmosphere of Mercury. Later the gases hydrogen and helium were expelled from the atmosphere.
Mammoth bones and “ghost” footprints of ancient people are the latest evidence in a scientific debate about when the first humans reached the Americas.
A map of North America's physical, political, and population characteristics as of 2018. North America is a continent [b] in the Northern and Western Hemispheres. [c] North America is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South America and the Caribbean Sea, and to the west and south by the Pacific Ocean.
Air suitable for use in photosynthesis by terrestrial plants and respiration of terrestrial animals is found within the troposphere. [3] The study of Earth's atmosphere and its processes is called atmospheric science (aerology), and includes multiple subfields, such as climatology and atmospheric physics.
The five components of the climate system all interact. They are the atmosphere, the hydrosphere, the cryosphere, the lithosphere and the biosphere. [1]: 1451 Earth's climate system is a complex system with five interacting components: the atmosphere (air), the hydrosphere (water), the cryosphere (ice and permafrost), the lithosphere (earth's upper rocky layer) and the biosphere (living things).