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The Sun is composed primarily of the chemical elements hydrogen and helium; they account for 74.9% and 23.8%, respectively, of the mass of the Sun in the photosphere.All heavier elements, colloquially called metals in stellar astronomy, account for less than 2% of the mass, with oxygen (roughly 1% of the Sun's mass), carbon (0.3%), neon (0.2%), and iron (0.2%) being the most abundant.
The stratosphere is the second-lowest layer of Earth's atmosphere. It lies above the troposphere and is separated from it by the tropopause. This layer extends from the top of the troposphere at roughly 12 km (7.5 mi; 39,000 ft) above Earth's surface to the stratopause at an altitude of about 50 to 55 km (31 to 34 mi; 164,000 to 180,000 ft).
A stellar atmosphere is the outer region of a star, which includes the layers above the opaque photosphere; stars of low temperature might have outer atmospheres containing compound molecules. The atmosphere of Earth is composed of nitrogen (78%), oxygen (21%), argon (0.9%), carbon dioxide (0.04%) and trace gases. [2]
Rippling beneath the photosphere layer is hot plasma that shifts around in the sun’s convection zone, similar to how hot magma moves within Earth’s mantle.
The height of the PBL is largely driven by convection associated with the changing surface temperature of the Earth (for example, rising during the day and sinking at night). The colored arrows represent the strength and direction of winds at different altitudes. Depiction of where the planetary boundary layer lies on a sunny day.
In observations of the solar disk, cardinal directions are typically defined so that the Sun's northern and southern hemispheres point toward Earth's northern and southern celestial poles, respectively, and the Sun's eastern and western hemispheres point toward Earth's eastern and western horizons, respectively.
Most of Earth's land hosts vegetation, [110] but considerable amounts of land are ice sheets (10%, [111] not including the equally large area of land under permafrost) [112] or deserts (33%). [113] 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 ...
Today, the African plate is moving over Earth's surface at a speed of 32.51 km per million years relative to the Earth's "average" crust velocities (see NNR-MORVEL56) Map of East Africa showing some of the historically active volcanoes (red triangles) and the Afar Triangle (shaded, center) – a triple junction where three plates are pulling ...