1. How does the earth change?
Weathering
How does the earth change?

4. 1 2 3 4 5 6 7 8 9 10 11 12
Weathering Notes (p )
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Weathering — breaking down of rocks into sediments (smaller pieces) by Mechanical or Chemical methods.
1) Mechanical — rocks are broken apart by a physical force.
Chemical makeup of rock is not changed
Heat dries, expands and cracks rocks
Cold freezes water in cracks (ice wedging)
Plants: roots enlarge cracks (root pry)
Animals/Humans: digging, stomping, running, mining
Abrasion: moving particles grind rock

5. 2) Chemical — chemical reactions break down rock 13 14 15 16 17 18 19 20 21 22 23 24 25
2) Chemical — chemical reactions break down rock
Chemical makeup of rock changes
Examples:
Oxidation (oxygen combines with it) forms rust
Carbonic acid (water + carbon dioxide) dissolving limestone to form caves
Plant acids from some roots and decaying plants weakens rock (lichens)
Acid Rain, which is sulfuric acid in rain
Rate of weathering: depends on type of rock and climate. (explanation)
Write key words in the column on the left page.
Write a summary at the bottom of the left page.
(thank you to M. Ward, College Station ISD, and others for example slides)