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The most abundant silicate minerals on the Earth's surface include quartz, the feldspars, amphibole, mica, pyroxene, and olivine. [25] Common carbonate minerals include calcite (found in limestone), aragonite, and dolomite. [26] Elevation histogram of the surface of the Earth—approximately 71% of the Earth's surface is covered with water.
Study of Earth's magnetosphere began in 1600, when William Gilbert discovered that the magnetic field on the surface of Earth resembled that of a terrella, a small, magnetized sphere. In the 1940s, Walter M. Elsasser proposed the model of dynamo theory , which attributes Earth's magnetic field to the motion of Earth's iron outer core .
The solid surface of Earth is dominated by green vegetation, deserts and white ice sheets. [106] [107] [108] Earth's surface is shaped by plate tectonics that formed the continental masses. [93] Earth's planetary magnetosphere shields the surface from radiation, limiting atmospheric stripping and maintaining life habitability. [109]
A terrestrial planet, tellurian planet, telluric planet, or rocky planet, is a planet that is composed primarily of silicate, rocks or metals. Within the Solar System , the terrestrial planets accepted by the IAU are the inner planets closest to the Sun : Mercury , Venus , Earth and Mars .
Most of Earth's land hosts vegetation, [109] but considerable amounts of land are ice sheets (10%, [110] not including the equally large area of land under permafrost) [111] or deserts (33%). [112] The pedosphere is the outermost layer of Earth's land surface and is composed of soil and subject to soil formation processes. Soil is crucial for ...
[17] [84] The core is relatively small, with a mass of only 0.55 Earth masses and a radius less than 20% of the planet; the mantle comprises its bulk, with around 13.4 Earth masses, and the upper atmosphere is relatively insubstantial, weighing about 0.5 Earth masses and extending for the last 20% of Uranus's radius.
By RYAN GORMAN Scientists may have found Planet X -- the long-rumored object believed to be larger than Earth and further from the sun than Pluto. Planet X and another object dubbed "Planet Y ...
For the Earth, this could have been an external magnetic field. Early in its history the Sun went through a T-Tauri phase in which the solar wind would have had a magnetic field orders of magnitude larger than the present solar wind. [60] However, much of the field may have been screened out by the Earth's mantle.