Robert W. ChristophersonCharlie Thomsen

Chapter 13Weathering,

Karst Landscapes, and Mass Movement

Geomorphology: science of landforms (origin, evolution, forms and spatial distribution)

Weathering Processes: a group of processes by which surface and subsurface rocks disintegrates into mineral particles or dissolves in water 

Physical weathering process: breaking down rocks without changes in the mineral or chemical composition

Chemical Weathering: breaking down materials via chemical reactions

Regolith, Soil, and Parent Materials

Figure 13.4

Regolith: partially weathered rock overlying bedrockSoil: mixture of organic and inorganic materialParent materials: bed rocksJoints: fractures or separations in rocks that occur without displacement of the sides.

Types of Physical weathering1. Frost Action: Water inside the rocks freezes and ice crystals expand to break the rock into pieces(water expands 9% in volume when freezes).Example: pavement damages in cold climate zones.

Figure 13.5

Shattered Rock Debris,

Rock Slide

Figure 13.7

2. Crystalization (salt-crystal growth): salt crystals grow and enlarge to spread apart individual minerals grains and break apart the rocks (Physical Weathering inSandstone)

Figure 13.8

3. Pressure-release jointing: the uplift of land and/or removal of materials reduces the pressure on the rock and rocks expand and break into pieces layer by layer (Exfoliation in Granite)

Figure 13.9

Exfoliation in Granite

Figure 13.9

Types of Chemical Weathering

Figure 13.10

1. Spheroidal Weathering: sharp edges of rocks and corner of the rocks are weathered in thin plates that created a rounded, spheroidal form.

Figure 13.11

2. Hydration and hydrolysisHydration: combination with water and water

become part of the chemical composition of minerals. A cycle of hydration and dehydration can lead to granular disintegration and further susceptibility to chemical weathering.

Hydrolysis: minerals chemically react with water

3. Oxidation: certain metallic elements combine with oxygen to form oxides

Figure 13.12

4. Carbonation (Carbon acid action): acid water has chemical reaction with minerals in the rocks (Dissolution of Limestone and marbles)

Figure 13.13

Formation of Karst  Lands Covered with Sinkholes  Caves and Caverns  

Karst Topography and Landscapes  

Karst and Limestone Regions

Figure 13.14

Karst landform: Pitted, bumpy, surface topography, poor surface drainage, and well-developed solution channel underground (15% of the land areas).

Sinkhole: nearly circular depression caused by weathering of Karst landscapes with subterranean drainage.

Figure 13.16

Sinkhole

Figure 13.18

Tower Karst

Figure 13.19

Cavern Features

Figure 13.20

Stalagmites: calcium carbonate precipitated out of the evaporating solution and accumulated on the floor and grow upwardsStalacites: the same process but build from ceiling

Mass movement (mass wasting): downward movements of materials propelled and controlled by gravityDriving forces: gravity, slope, water (hydration: swelling due to water)Resisting force: cohesiveness and internal friction that work against gravity and mass wasting  

Mass Movement Processes  

Madison River Landslide

Figure 13.21

Earthquake triggered landslide in 1959.

Mass-Movement Classes

Figure 13.22

Debris Avalanche: falling and tumbling rocks, debris, and soil

Figure 13.25

Rock fall: individual rock falls independently.

Landslide: a sudden rapid movement of a cohesive mass of regolith or bedrock that is not saturated with moisture.

Earth flow, mudflow: high moisture content of moving material

Soil Creep: persistent, gradual mass movement of surface soil

Figure 13.28