W, S & MM

This week on NS we had a report about Weathering, Soil and Mass Movement, and the other group reported about the Earth Resources. We told our classmates some important things to know about weathering and we showed them a short video for the class to not get bored.

WEATHERING

The action of the weather conditions in altering the color, texture, composition, or form of exposed objects

The physical disintegration and chemical decomposition of earth materials at or near the earth’s surface

MECHANICAL WEATHERING

        -It occurs when physical forces break rock into smaller and smaller pieces without changing the rock’s mineral composition.

3 PHYSICAL PROCESS

ž  Frost Wedging

ž  Unloading

ž  Biological Activity

1. Frost wedging

   The mechanical breakup of rock caused by the expansion of freezing water in cracks and crevices

2. Unloading

                  Reduced pressure on igneous rock causes it to expand and allows slabs of outer rock to break off in layers in a process called exfoliation.

3. Biological activity

                  The activity of organisms, including plants, burrowing animals, and humans, can also
cause mechanical weathering.

ž  CHEMICAL WEATHERING

Ø                    is the transformation of rock into one or more new compounds.

Ø  Chemical weathering changes the composition of rocks, often transforming them when water interacts with minerals to create various chemical reactions.

The reactions as follows:

CO₂ + H₂O => H₂CO₃

carbon dioxide + water => carbonic acid

Rate of Weathering

1. Rock characteristics

2. Climate

3. Differential Weathering

SOIL

Characteristics of Soil

v      Soil is part of the regolith that supports the growth of plants.

        Regolith is the layer of rock and mineral fragments that covers most of Earth’s land surface.

v  Soil Formation

The most important factors in soil formation are parent material, time, climate, organisms, and slope.

1. Parent material

ž        Residual soil —parent material is the bedrock

 Transported soil —parent material has been carried from elsewhere and deposited

2. Time - Important in all geologic processes

         The longer a soil has been forming, the thicker
         it becomes.

3. Climate - Greatest effect on soil formation

4. Organisms - Organisms influence the soil's physical and 
                  chemical properties.

5. Slope

ANGLE

 Steep slopes often have poorly developed soils.

Optimum slope is a flat-to-undulating upland surface.

ž  

Soil Types

1. Pedalfer

  Accumulation of iron oxides and aluminum-rich clays in the B horizon

  Best developed under forest vegetation

2. Pedocal

  Accumulates calcium carbonate

  Associated with drier grasslands

3. Laterite

  Hot, wet, tropical climates

  Intense chemical weathering

ž  MASS MOVEMENTS

Triggers of Mass Movements

                   Among the factors that commonly trigger mass movements are saturation of surface materials with water, oversteepening of slopes, removal of vegetation, and earthquakes.

                  The transfer of rock and soil downslope due to gravity is called mass movement.

Types of Mass Movement

1.     Rockfall

2.     Slides

3.     Slumps

4.     Flow

5.     Creep

The reporters are exempted for the quiz

Thanks to Prof Cresencio Paner some of the information and pictures in our powerpoint got from him and Wikipedia and Google J