Answer:
three half-lives
Explanation:
Converting 12.5% to decimal gives 0.125
If one half life is 0.5.
0.5*0.5*0.5 gives 0.125
Thus 3-half lives has been elapsed
The U.S. federal system consits of a national government and what other government level
regional level
In general, physical weathering from temperature changes is most common on the shorelines, because waves are able to take down rocks that have been weathers. They would be least noticeable inland, in desert areas with little forestation.
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Answer:
Human activity - Produces greenhouse gasses.
Greenhouse gasses - Cause atmosphere to trap more heat.
Sun's output - Can vary.
Ice age - Peaked 20,000 years ago.
Explanation:
Human activity includes the usage of fossil fuels on a very large scale, and by using them we release huge amounts of greenhouse gasses into the atmosphere.
The greenhouse gasses have the ability to trap the heat that is reflected from the surface of the planet, thus keeping more of it in the atmosphere and causing global temperature rise.
The sun is technically a star, thus an object that produces energy and light, and like every star, it has variations in its activity in accordance with the processes going on on it.
There have been numerous ice ages through the geological past, and the last one of them ended only around 10,000 years ago, with its peak being just 20,000 years ago.
