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Earth's inner core is the innermost geologic layer of the planet Earth. It is primarily a solid ball with a radius of about 1,220 km (760 mi), which is about 20% of Earth’s radius or 70% of the Moon 's radius. [1][2] There are no samples of Earth's core accessible for direct measurement, as there are for Earth's mantle. [3]
Earth's inner core is the innermost geologic layer of the planet Earth. It is primarily a solid ball with a radius of about 1,220 km (760 mi), which is about 19% of Earth's radius [0.7% of volume] or 70% of the Moon 's radius. [32][33] The inner core was discovered in 1936 by Inge Lehmann and is generally composed primarily of iron and some nickel.
Earth is the third planet from the Sun and the only astronomical object known to harbor life. This is enabled by Earth being an ocean world, the only one in the Solar System sustaining liquid surface water. Almost all of Earth's water is contained in its global ocean, covering 70.8% of Earth's crust.
Stars are known to get brighter as they age, and the Sun has become 30% brighter since its formation 4.5 billion years ago. [70] Many models indicate that the early Earth should have been covered in ice. [71] [66] A likely solution is that there was enough carbon dioxide and methane to produce a greenhouse effect. The carbon dioxide would have ...
An illustration of ice age Earth at its glacial maximum. A "greenhouse Earth" is a period during which no continental glaciers exist anywhere on the planet. [6] Additionally, the levels of carbon dioxide and other greenhouse gases (such as water vapor and methane) are high, and sea surface temperatures (SSTs) range from 28 °C (82.4 °F) in the tropics to 0 °C (32 °F) in the polar regions. [7]
The entire ocean, containing 97% of Earth's water, spans 70.8% of Earth's surface, [8] making it Earth's global ocean or world ocean. [23] [25] This makes Earth, along with its vibrant hydrosphere a "water world" [43] [44] or "ocean world", [45] [46] particularly in Earth's early history when the ocean is thought to have possibly covered Earth ...
The Pleistocene (/ ˈplaɪstəˌsiːn, - stoʊ -/ PLY-stə-seen, -stoh-; [ 5 ][ 6 ] often referred to colloquially as the Ice Age) is the geological epoch that lasted from c.2.58 million to 11,700 years ago, spanning the Earth's most recent period of repeated glaciations. Before a change was finally confirmed in 2009 by the International ...
The Canadian Shield (French: Bouclier canadien [buklje kanadjɛ̃]), also called the Laurentian Shield or the Laurentian Plateau, is a geologic shield, a large area of exposed Precambrian igneous and high-grade metamorphic rocks. It forms the North American Craton (or Laurentia), the ancient geologic core of the North American continent.