Interactions Between the Climate and Plate Tectonic Systems Grotzinger • Jordan Understanding Earth Seventh Edition Chapter 16: WEATHERING, EROSION, AND MASS WASTING Interactions Between the Climate and Plate Tectonic Systems © 2014 by W. H. Freeman and Company

Weathering, Erosion, and Mass Wasting: Chapter 16 Weathering, Erosion, and Mass Wasting: Interactions between the Climate and Plate Tectonic Systems

About Weathering, etc. Weathering produces all the soils, clays, sediments, and dissolved substances. Erosion is the removal of sediments by natural processes such as wind and rivers. Mass wasting is the downslope movement of masses of Earth materials.

Lecture Outline Weathering, erosion, mass wasting, and the rock cycle 2. Controls on weathering 3. Chemical weathering 4. Physical weathering 5. Soils: the residue of weathering

Lecture Outline 6. Mass wasting 7. Classification of mass movements 8. Understanding the origins of mass movements

Weathering, Erosion, Mass Wasting, and the Rock Cycle ● Weathering is the process of converting rock into sediment and forming soils, a main process in the rock cycle. ● Erosion and mass wasting are the processes that loosen and transport soil and rock downhill.

● Properties of the parent rock ● various minerals weather at 2. Controls on Weathering ● Properties of the parent rock ● various minerals weather at different rates ● a rock’s structure affects its susceptibility to cracking and fragmentation

● Other important factors ● climate (rainfall and temperature) 2. Controls on Weathering ● Other important factors ● climate (rainfall and temperature) ● soil (presence or absence) ● time (length of exposure)

2. Controls on Weathering

● Occurs when minerals react with air and water 3. Chemical Weathering ● Occurs when minerals react with air and water ● role of water (hydrolysis) ● carbon dioxide (carbonic acid) ● moist soils

The Disintegration of Granite 3. Chemical Weathering: The Disintegration of Granite

The Disintegration of Granite 3. Chemical Weathering: The Disintegration of Granite

The Role of Increasing Surface Area 3. Chemical Weathering: The Role of Increasing Surface Area 2 cm 2 cm

2 cm 1 cm 1 cm 2 cm

2 cm 1 cm 1 cm 2 cm Large rocks have less surface area for chemical weathering …

2 cm 1 cm 1 cm 2 cm Large rocks have less surface area for chemical weathering… … than small rocks do, so smaller rocks weather more quickly.

3. Chemical Weathering: Carbon Dioxide

● Chemical stability: a speed control for weathering ● solubility 3. Chemical Weathering ● Chemical stability: a speed control for weathering ● solubility ● rate of dissolution ● relative stability of common rock-forming minerals

● Role of oxygen in weathering: from iron silicates to iron oxides 3. Chemical Weathering ● Role of oxygen in weathering: from iron silicates to iron oxides ● ferric and ferrous iron ● hematite, a common mineral ● red and brown – the colors of oxidized iron

Chemical Weathering: Iron and Oxygen Pyroxene dissolves, releasing silica and ferrous iron. Pyroxene (FeSiO3) Silica Ferrous iron Ferrous iron is oxidized, forming ferric iron. Ferric iron Ferric iron precipitates a solid, iron oxide. Iron oxide (hematite) Fe2O3

3. Chemical Weathering: Red Means Iron

Thought questions for this chapter Which igneous rock would you expect to weather faster, a granite or a basalt? What factors influenced your answer? Assume that a granite with crystals about 4 mm across and a rectangular system of joints spaced about 0.5 to 1 m apart is weathering at the Earth’s surface. What size would you ordinarily expect the largest weathered particle to be?

Thought questions for this chapter Rank the following rocks in order of the rapidity with which they would weather in a warm, humid climate: a sandstone made of pure quartz, a limestone made of pure calcite, a granite, and an evaporite deposit of halite. What would a planet look like if no weathering occurred at the surface?

● What determines how rock breaks? ● natural zones of weakness 4. Physical Weathering ● What determines how rock breaks? ● natural zones of weakness ● activity of organisms ● frost wedging ● exfoliation

4. Physical Weathering: Joints in Rocks

4. Physical Weathering: Frost Wedging

4. Physical Weathering: Exfoliation

● Physical weathering and erosion ● duration of weathering ● bedrock type ● climate ● topography

4. Physical Weathering

Thought questions for this chapter Why do you think a road built of concrete, an artificial rock, tends to crack and develop a rough, uneven surface in a cold, wet region even when it is not subjected to heavy traffic? Pyrite is a mineral in which ferrous iron is combined with sulfide ions. What major chemical process weathers pyrite?

● Soils as geosystems ● input material ● transformations and 5. Soil: The Residue of Weathering ● Soils as geosystems ● input material ● transformations and translocations ● output material

● The basic soil-forming processes result in losses 5. Soil: The Residue of Weathering ● The basic soil-forming processes result in losses (transformations) and additions (translocations).

Losses Additions Organic material Airborne dust Water erosion Chemicals and minerals from bedrock Wind Leaching BEDROCK

Losses Additions Organic material Airborne dust Water erosion Chemicals and minerals from bedrock Wind Leaching BEDROCK Minerals, grains, and aggregates may move through the soil. TRANSLOCATION

Losses Additions Organic material Airborne dust Water erosion Chemicals and minerals from bedrock Wind Leaching BEDROCK Minerals are transformed into other minerals. Minerals, grains, and aggregates may move through the soil. Other minerals precipitate from fluids. TRANSLOCATION TRANSFORMATION

Losses Additions Organic material Airborne dust Water erosion Chemicals and minerals from bedrock Wind Leaching BEDROCK Minerals are transformed into other minerals. Minerals, grains, and aggregates may move through the soil. Other minerals precipitate from fluids. TRANSLOCATION TRANSFORMATION Transformation and translocation occur throughout the soil profile.

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Part 2 of 2

● Paleosols – ancient soils ● climate history ● ancient atmosphere 5. Soil: The Residue of Weathering ● Paleosols – ancient soils ● climate history ● ancient atmosphere ● history of erosion

Thought questions for this chapter In northern Illinois, you can find two soils developed on the same kind of bedrock: one is 10,000 years old and the other is 40,000 years old. What differences would you expect to find in their compositions or profiles?

6. Mass Wasting ● Mass wasting includes all processes by which masses of rock and soil move downslope. ● Mass movement occurs when the force of gravity exceeds the strength of the material and it moves downslope.

● Three primary factors ● nature of slope materials (angle of repose) 6. Mass Wasting ● Three primary factors ● nature of slope materials (angle of repose) ● amount of water ● steepness and stability

6. Mass Wasting

● Nature of slope materials ● unconsolidated materials ● sand and silt 6. Mass Wasting ● Nature of slope materials ● unconsolidated materials ● sand and silt ● rock fragments, sand, silt, and clay

The Behavior of Dry and Wet Sand 6. Mass Wasting: The Behavior of Dry and Wet Sand

The Behavior of Wet Sand

● Nature of slope materials ● consolidated materials ● rock 6. Mass Wasting ● Nature of slope materials ● consolidated materials ● rock ● compacted (cohesive) sediments and soils

● Steepness and stability ● angle of slope ● accumulation of rubble 6. Mass Wasting ● Steepness and stability ● angle of slope ● accumulation of rubble ● breakage into large blocks

The Accumulation of Rubble on a Slope 6. Mass Wasting: The Accumulation of Rubble on a Slope

6. Mass Wasting ● Water content ● lubrication ● liquefaction

● Triggers of mass movements ● earthquake vibrations 6. Mass Wasting ● Triggers of mass movements ● earthquake vibrations ● rainfall and water infiltration ● overloading

6. Mass Wasting

Mass Wasting: Triggered by Earthquake

Thought questions for this chapter Would a prolonged drought affect the potential for landslides? How? What factors weaken rock and enable gravity to start a mass movement?

● Three characteristics used ● nature of material 7. Classification of Mass Movements ● Three characteristics used ● nature of material (rock or unconsolidated) ● velocity of movement (slow, moderate, or fast) ● nature of movement (flow, slide, or fall)

Classification of Mass Movements Material

Classification of Mass Movements Material Nature of motion

Classification of Mass Movements Material Nature of motion Velocity

7. Classification of Mass Movements

● Rock mass movements ● rock falls ● rock slides ● rock avalanches 7. Classification of Mass Movements ● Rock mass movements ● rock falls ● rock slides ● rock avalanches

7. Classification of Mass Movements: Rock Falls

7. Classification of Mass Movements: Rock Slides

Classification of Mass Movements: Rock Slides

7. Classification of Mass Movements: Rock Avalanches

Classification of Mass Movements: Rock Avalanche

● Unconsolidated mass movements ● creep ● earthflow ● debris flow 7. Classification of Mass Movements ● Unconsolidated mass movements ● creep ● earthflow ● debris flow ● mud flow ● debris avalanche ● slump ● debris slide

7. Classification of Mass Movements: Creep

Classification of Mass Movements: Creep

7. Classification of Mass Movements: Earthflow

Classification of Mass Movements: Earthflow

7. Classification of Mass Movements: Debris Flow

Classification of Mass Movements: Debris Flow

7. Classification of Mass Movements: Mud Flow

Classification of Mass Movements: Mud Flow

7. Classification of Mass Movements: Debris Avalanche

Classification of Mass Movements: Debris Avalanche

Classification of Mass Movements: Debris Avalanche

7. Classification of Mass Movements: Slump

7. Classification of Mass Movements: Debris Slide

Classification of Mass Movements: Debris Slide

8. Understanding the Origins of Mass Movements ● Examples of landslide disasters ● Gros Ventre valley, Wyoming (1925) ● Vaiont Dam, Italy (1963)

Origin of Mass Movement: The Gros Ventre Disaster, 1925

Origin of Mass Movement: The Gros Ventre Disaster, 1925

Origin of Mass Movement: The Gros Ventre Disaster, 1925

Origin of Mass Movement: The Gros Ventre Landslide area today

8. Understanding the Origins of Mass Movements ● The Vaiont Dam disaster (Italy) ● one of world’s largest man-made lakes was formed by this dam ● steep valley walls were made of weak, broken, and layered rock

8. Understanding the Origins of Mass Movements ● The Vaiont Dam disaster (Italy) ● A small rock slide in 1960 should have been a warning. ● In 1963, 240 million m3 of rock fell into the lake, bursting the dam and killing 3,000 people.

Thought questions for this chapter What geologic conditions might you want to investigate before you purchase a house at the base of a steep hill of bedrock covered by a thick layer of soil? What evidence would you look for to indicate that a mountainous area had undergone a great many prehistoric landslides? What factors would make the potential for mass movements in a mountainous terrain in the humid tropics greater or less than the potential in similar terrain in a desert?

Thought questions for this chapter What kind(s) of mass movements would you expect on a steep hillside with a thick layer of soil overlying unconsolidated sands and muds after a prolonged period of heavy rain?

Key terms and concepts Chemical stability Consolidated material Creep Angle of repose Chemical stability Consolidated material Creep Exfoliation Frost wedging Hematite Humus Kaolinite Liquefaction Mass movement Mass wasting Slump Soil Soil profile

Key terms and concepts Talus Unconsolidated material