Physics, 05.05.2020 17:03 elise47

The oxygen isotopic composition of ocean water is measured by determining the ratio of 18O to 16O, expressed as 18O/16O. The isotope 16O preferentially evaporates into the atmosphere. During periods of global cooling, the 18O/16O ratio will:

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Answer from: CyanideFaux

The ¹⁸O/¹⁶O ratio will decrease.

Explanation:

The ¹⁸O/¹⁶O ratio changes as a result of temperature. When the climate is warm, the ¹⁶O evaporates first for being lighter than ¹⁸O. When the climate is cold, the ¹⁸O precipitates first for being heavier than ¹⁶O. Thus the cold regions are rich in ¹⁶O (have little ¹⁸O) and the tropics regions are rich in ¹⁸O (have little ¹⁶O). Hence, the ratio ¹⁸O/¹⁶O is high in warm areas (for the evaporation of ¹⁶O) and lower in cold areas (for the precipitation of ¹⁸O).

Therefore, during periods of global cooling, the ¹⁸O/¹⁶O ratio will decrease.

I hope it helps you!

Answer from: Quest

sequence is a continuous and distinctive band of stars that appears on plots of stellar color versus brightness. these color-magnitude plots are known as hertzsprung–russell diagramsafter their co-developers, ejnar hertzsprungand henry norris russell. stars on this band are known as main-sequence stars or dwarf stars. these are the most numerous true stars in the universe, and include the earth's sun.after condensation and ignition of a star, it generates thermal energy in its dense core region through nuclear fusion of hydrogen into helium. during this stage of the star's lifetime, it is located on the main sequence at a position determined primarily by its mass, but also based upon its chemical composition and age. the cores of main-sequence stars are in hydrostatic equilibrium, where outward thermal pressure from the hot core is balanced by the inward pressure of gravitational collapse from the overlying layers. the strong dependence of the rate of energy generation on temperature and pressure to sustain this balance. energy generated at the core makes its way to the surface and is radiated away at the photosphere. the energy is carried by either radiation or convection, with the latter occurring in regions with steeper temperature gradients, higher opacity or both.the main sequence is sometimes divided into upper and lower parts, based on the dominant process that a star uses to generate energy. stars below about 1.5 times the mass of the sun (1.5 m☉) primarily fuse hydrogen atoms together in a series of stages to form helium, a sequence called the proton–proton chain. above this mass, in the upper main sequence, the nuclear fusion process mainly uses atoms of carbon, nitrogen and oxygen as intermediaries in the cno cycle that produces helium from hydrogen atoms. main-sequence stars with more than two solar masses undergo convection in their core regions, which acts to stir up the newly created helium and maintain the proportion of fuel needed for fusion to occur. below this mass, stars have cores that are entirely radiative with convective zones near the surface. with decreasing stellar mass, the proportion of the star forming a convective envelope steadily increases. main-sequence stars below 0.4 m☉undergo convection throughout their mass. when core convection does not occur, a helium-rich core develops surrounded by an outer layer of hydrogen.in general, the more massive a star is, the shorter its lifespan on the main sequence. after the hydrogen fuel at the core has been consumed, the star evolves away from the main sequence on the hr diagram, into a supergiant, red giant, or directly to a white dwarf.

Answer from: Quest

To use anything transparent

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The oxygen isotopic composition of ocean water is measured by determining the ratio of 18O to 16O, e...

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