Science: 6.10B Science: 6.10B Rocks and How They Form.

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1 Science: 6.10B Science: 6.10B Rocks and How They Form

2 The Process of Weathering Rocks

3 Weathering The breaking down of rock into smaller pieces that remain next to each other. Weathering forms sediments. There are two types of weathering.

4 Two Types of Weathering 1.Mechanical weathering is the breaking down of rock without any change in the chemical composition of the rock. – Sometimes called “physical” weathering – Rock is torn apart by physical force, rather than by chemical breakdown – Smaller pieces do not move to a new location, but remain next to one another until erosion carries them away.

5 Ice Wedging - Water enters the cracks in rocks and then freezes and expands. As the cycle repeats, rocks grow weaker over time. Exfoliation - curved plates of rock are stripped from rock below. Thermal - extreme changes in temperature that causes the expansion or contraction of rock. Biotic (force) - weathering is caused by living organisms. Plants and animals 4 Types of Mechanical Weathering

6 Ice Wedging Exfoliation

7 4 Types of Mechanical Weathering Thermal Biotic (force)

8 Two Types of Weathering 2. Chemical weathering is the breaking down of rock into smaller pieces because of chemical changes within the rock. – Rock reacts with water, gases, and solutions (may be acidic); these reactions will add or remove elements from minerals. – Rocks fall apart because the bonds holding them together are broken down by chemical reactions.

9 4 Types of Chemical Weathering Oxidation: chemical reaction that results in the forming of a new type of rock when oxygen is combined with other elements in rocks. Hydrolysis: when water and chemical compounds in a rock meet and results in the decomposition of the rock surface by forming new compounds. Carbonation: a weak carbonic acid that causes softer substances to form with rocks Biotic (Acid): plant roots give off a chemical that dissolves rocks and minerals.

10 4 Types of Chemical Weathering Oxidation Hydrolysis

11 Carbonation Biotic (Acid) 4 Types of Chemical Weathering