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Earth's outer core is a fluid layer about 2,260 km (1,400 mi) in height (i.e. distance from the highest point to the lowest point at the edge of the inner core) [36% of the Earth's radius, 15.6% of the volume] and composed of mostly iron and nickel that lies above Earth's solid inner core and below its mantle. [31]
Earth is rounded into an ellipsoid with a circumference of about 40,000 km. It is the densest planet in the Solar System. Of the four rocky planets, it is the largest and most massive. Earth is about eight light-minutes away from the Sun and orbits it, taking a year (about 365.25 days) to complete one revolution.
Earth formed about 4.54 billion years ago by accretion from the solar nebula, a disk-shaped mass of dust and gas left over from the formation of the Sun, which also created the rest of the Solar System. Initially, Earth was molten due to extreme volcanism and frequent collisions with other bodies.
Minnesota contains some of the oldest rocks on Earth, granitic gneisses that formed some 3,600 mya (million years ago) — roughly 80% the age of the planet. [1] About 2,700 mya, the first volcanic rocks that would later underlie Minnesota began to rise up out of an ancient ocean, forming the Superior craton. [2]
Earth's atmosphere at this stage was somewhat comparable to today's atmosphere of Titan. [ 19 ] The Archean atmosphere is thought to have almost completely lacked free oxygen ; oxygen levels were less than 0.001% of their present atmospheric level, [ 20 ] [ 21 ] with some analyses suggesting they were as low as 0.00001% of modern levels. [ 22 ]
Earth's mantle is a layer of silicate rock between the crust and the outer core. It has a mass of 4.01 × 10 24 kg (8.84 × 10 24 lb) and makes up 67% of the mass of Earth. [ 1 ] It has a thickness of 2,900 kilometers (1,800 mi) [ 1 ] making up about 46% of Earth's radius and 84% of Earth's volume.
The process of super-continent formation and destruction via repeated cycles of creation and destruction of oceanic crust is known as the Wilson Cycle. The oldest large-scale oceanic crust is in the west Pacific and north-west Atlantic — both are about up to 180-200 million years old.
The Earth's mantle is a layer of silicate rock between the crust and the outer core. Its mass of 4.01 × 10 24 kg is 67% the mass of the Earth. [1] It has a thickness of 2,900 kilometres (1,800 mi) [1] making up about 84% of Earth's volume. It is predominantly solid, but in geological time it behaves as a viscous fluid