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

The Process of Weathering Rocks

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

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.

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

Ice Wedging Exfoliation

4 Types of Mechanical Weathering Thermal Biotic (force)

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.

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.

4 Types of Chemical Weathering Oxidation Hydrolysis

Carbonation Biotic (Acid) 4 Types of Chemical Weathering