Roots:

Cata = down catacombsCaust = to burn causticCeed = to yield recedeCeive = to take receiveCeler = fast accelerateCent = hundred centipedeCentr = center egocentricCephalo = head encephalitisCerebro = brain cerebralCert = sure certain

MECHANICAL WEATHERING

Chemical WeatheringCHAPTER 5.1 W

EATHERING

MECHANICAL WEATHERING

Occurs when physical forces break rock into

smaller and smaller pieces

without changing the rock’s mineral

composition.

MECHANICAL WEATHERING

Frost Wedging Unloading Biological

Activity

Three main mechanical weathering forces:

Pg. 127 Figure 2Pg. 127 Figure 3

Breaking of rocks into smaller pieces which provides more surface area for chemical weathering processes.

Talus = large piles of broken rock.

Frost Wedging Unloading Biological

Activity

Three main mechanical weathering forces:

MECHANICAL WEATHERING

When large masses of igneous rock are exposed from uplifting and erosion of overlying rocks.

Exfoliation = when outer layers of rock separate and break loose.

Pg 128 Figure 4

MECHANICAL WEATHERING

Frost Wedging Unloading Biological

Activity

Three main mechanical weathering forces:

Pg. 128 Figure 5

Breaking of rocks into smaller pieces by the actions of plants, burrowing animals and humans.

Chemical Weathering

Transformation of rock into one or

more NEW compounds.

Chemical Weathering

Water Granite Weathering

Silicate Weathering

Spheroidal Weathering

• Most important agent of chemical weathering.• Absorbs gases from air and ground.• Oxygen in water reacts to form oxides (like rust).• Carbon Dioxide in water reacts to form carbonic acid.• Sulfur and Nitrogen oxides in water turn into acids that can erode monuments and structures.

Chemical Weathering

Water Granite Weathering

Silicate Weathering

Spheroidal Weathering

• Granite is mostly feldspar and quartz.• Carbonic acid in water turns the feldspar into clay.• Quartz is released and washed away.

Chemical Weathering

Water Granite Weathering

Silicate Weathering

Spheroidal Weathering

• Silicates make up most of Earth’s crust.• Composed of 8 elements .• Sodium, calcium, potassium, and magnesium are carried away by ground water.• Iron becomes rust.• Aluminum, silicon and oxygen turn to clay.

Chemical Weathering

Water Granite Weathering

Silicate Weathering

Spheroidal Weathering

• When chemical weathering changes both the physical shape and the chemical composition of the rock.• Water rounds corners and edges fastest making them rounded. Pg. 131

Figures A & B

RATE OF WEATHERING

1. Physical characteristics of a specific rock (like cracks) influence waterproofing.

RATE OF WEATHERING

2. Mineral composition determines a rock’s resistance to weathering.

RATE OF WEATHERING

3. Crystal formation determines a rock’s resistance to decomposition. (Olivine crystallizes first and weathers rapidly; Quartz crystallizes last and weathers slowly.)

RATE OF WEATHERING

4. Climate (especially temperature and moisture) determines the frequency of freeze-thaw cycles, etc.

5. Differential weathering refers to different parts of a rock that may weather at different rates.

RATE OF WEATHERING