Americas economic activity has increased in the last year
Friction and Tectonic
Chemical Weathering
Physical Weathering
Wind and Water Erosion
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http://classroom.synonym.com/natural-activities-work-break-down-rock-16920.html
I know that we aren't suppose to paste websites but I believe that this information is necessary, I hope this helped, sorry!</span>
Earth has a liquid outer core because that's the ocean and the earth is mostly made up by water.The earth has a solid inner by the mantle which is hard rock and made out of gas and rocks and it is very hot out there