Geology 305
ONL/ ch4
Concept Check
1. The alternate expansion and contraction of surface material caused by freezing and thawing, or wetting and drying lifts particles at right angles to the slope, and thawing or drying allows the particle to fall back to a slightly lower level. Each cycle therefore moves the material a short distance downhill.
2. Solifluction occurs during the summer and winter. Solifluction is common in regions underlain by permafrost, permanently frozen ground that occurs in Earth’s harsh tundra and ice-cap climates. In a zone above the permafrost called the active layer(thaws in summer and refreezes in winter). During summer water is unable to percolate into the impervious permafrost layer below, as a result the active layer becomes saturated and slowly flows.

Give It Some Thought

1.Roots of plants can promote mechanical weathering by pushing into a rock, causing root wedging, widening fractures, and exposing it to elements that could further weather rock. Chemical weathering can be caused by roots, fungi getting into fractures, or encrust a rock produce acids that promote decomposition. Plants, however, prohibit erosion because the roots of the plants hold the soil together and help prevent soil from being moved by water, wind, rain.

2. Chemical weathering is predominant, basalt will weather more rapidly, basalt does not contain quarts like granite, so the fine grained basalt will weather faster.

3. The material does not satisfy the definition we use for soil on earth because earths soil is composed of a combination of mineral and organic matter, disintegrated and decomposed rock, humus, the decayed remains of animal and plant life, water and air.

4. Time, plants, animals, topography, and climate.

5. South Americas Amazon River is classified as Alfisols, moderately weathered soils. Fertile, productive soils, they are neither too wet nor too dry.

The American South West soil is classified as Mollisols, dark, soft soils that have developed under grass vegetation, generally found in prairie areas.

They share in common their execellent fertile soil formed under leafage, both have two strong mineral pillars, Alfisols: iron and aluminum, and, Mollisols; calcium and magnesium.

6. Mass wasting, the step that follows weathering, transfers the debris down slope where a strea acting as a conveyor belt, usually carries it away, eventually to its