Describe the role of external processes in the rock cycle?
Earth's external processes, weathering, mass wasting, and erosion, occur at or near the surface and are powered by energy from the Sun. These processes are a basic part of the rock cycle becasue they are responsible for transforming solid rock into sediment.
If two identical rocks were weathered - one mechanically and the other chemically- how would the products of waethering for the two rocks differ?
Mechanical weathering simply yields smaller pieces of the same rock. Chemical weathering however, yield new substances; that is , the minerals composing the rocks are deomposed.
How does mechanical weathering add to the effectiveness of chemical weathering?
By breaking rocks into increasing small pieces, mechincal weathering increases the surface area available to chemical attack.
Describe the formation of an exfoliation dome. Give an example of such a feature.
Exfoliation domes form when the reduction in pressure that accompanies unloading leads to sheeting. Fractures tpically develop parelle to the surface and gives these exhumed granite masses a domed shape. Continued weathering causes the slabs produced by sheeting to seperate and spall off. Examples include Stone Mountain, Georgia, and Half Dome, and LIberty Cap in Yosemite National Park.
Granite and basalt are exposed at the surface in a hot, wet region.
A. Which type of waethering (mechanical or chemical)
B. Which of the rocks will weather most rapidly? Why?
A. Moisture and warm temp. accelerate rates of chemical reactions, so chemical weathering will predominate. Also, mechanical weathering processes dependent on freezing and thawing will not be operative.
Heat sppeds up a chemical reaction. Why then does chemical whethering proceed slowly in a hot desert?
In general, high temp. do raise chemical weathering reaction rates, but most of these reactiong take place in an aqueous (watery) media or on the moist surfaces of rock and soil particles. Reaction rates decrease drastically under very dry conditions.
How is carbonic acid (H2CO3) formed in nature?What results when this acid reacts with potassium feldspar?
Carbonic acid is a very weak acid formed by the solution of carbon dixide( CO2) in water. Carbon dioxide is a minor component of the atmospher but it often enriched in soil gases by the ixidation of organic matter. The common cation of feldspar (K=+1, Na= +1, and Ca =+2) are fairly soluble in acidic solution, so reactionof carbonic acid with potassium feldspar causes the feldspar to chemically decompose. Potassium, sodium, and calcium are then released to the soil and precipitated as minerals.
Using the siol-texture diagram (Figure 4.13) , name the soil that consists of 60% sand, 30% silt, and 10% clay
A soil concicting of 60% sand, 30% silt, and 10% clay is a sandy loam.
What factors might cause different soils to devlop from the same parent material, or similar soils to form from different parent materials?
Different soil are likely to form from the same parent material if the climates are different. Other factors, which would contribute to diferences, would include the nature of the vegetation, the slopes, and the length of time the soils have been forming. Similar soils from different parent materials would result if the preceding factors were essentially the same in each situation.
Which of the controls of soil formation in most important? Explain
Climate is considered most important, for it determines the type and degree of weathering as well as being important control on the type of plant and animal life present.
How can slope affect the development of soil? What is meant by the term slope orientation?
Slope greatly influnces drainage and the amount of erosion that will occur. Because of accelerated erosion on stepp slopes, soils are thin. Conversely, in flat bottomlands soils are often waterlogged. Optimmum conditions for soil development are flat-to-undulating upland surface. Here erosion is at a minimum and drainage is good. Slope orientation refers to the amount of sunlight recieed. This affects the soil temp. and moisture conditions, which in turn influence tha nature of the vegetation and the character of the soil.
List tha characteristics associated with each of the horizons in a well-developed soil profile. Which of the horizons constitute the solum? Under what circumstances do soils lack horizons?
O-This is dark, surface layer of decaying plant matter (humus)
A- The A horizon (just below the O horizon)
E- This is a light-colored horizon of resistant mineral gainsas in horizon , but depleted inslit and clay-sized particle that have been transported downward(eluviated) to the B horizon; humaus is sparse or absent.
B- The B horizon is often called the zone of accumulation. Small-sized soil particles eluviated downward from higher horizons accumulate in the B horizon, and chemical constituents leached from A horizon are precipitated there was as well. These include the most insoluble minerals formed in soils such as the iron oxide and hydroxides, and clays. This zone is usually red, yellow, or brown, depending on the nature of the finely divided iron oxide in the soil.
C-The C horizon os often called the zone of partly weathered bedrock. Weathered fragments and chips of rock found here are evidence of the unweathered parent rock material at depth.
The solum includes all the horizons above the top of the C horizon. Recently exposed regolith lacks distinctive soil horizon because the soil-forming process is still in its infacy, and horizons have not had enough time to develop. A newly deposited floodplain sediment is a good example of regolith.
Is soil erosion a natural process or primarily the results of inappropriate land use by people? Explain.
Soil erosion is a natural process; it is part of the constant recycling of Earth materials that we call the rock cycle.However, soil erosion is a growing problem as human activities expand and distrub more and more Earth's surface.
List three detrimental effects of soil erosion other than the loss of topsoil from croplands.
Soil erosion contributes excess sediment loads to reservoirs, steams, and rivers, thus degrading water quality and adversely affecting aquatic and riparian habitats. It also diminishes the quality of outdoor recreational activities and raise the cost of maintaining navigational channels and hydroelectric power generation facilities. Blowing duct can seriously degrade air quality, causing health problems and premature failure of machinery and electrics equipment.
Name the primary ore of aluminum and describe its formation?
Bauxie is the primary ore of aluminum. Bauxie results when intense and prolonged chemical weathering leaches most of the soluble elements, leaving the highly insoluble aluminum concentrated in soil.
Describe how mass-wasting processes contribute to the development of steam valleys.
Mass wasting is the downslope movement of soil and weathered rock debris. Streams can deepen valley by downcutting (erosion), but, largely, mass wasting widens or enlarges valleys via erosion of the sides or slopes. Mass wasting delivers the weathered rock material and soil to the streams, which carry it away to it away to a site of deposition.
What is the controling force of mass wasting? What other factors can influence or trigger mass wasting?
Gravity is the controlling force of mass wasting. Other factors that trigger or influence mass wasting include water, over-steepened slopes, human activities, and earthquakes.
List the criteria that are used to classify mass-wasting processes?
The criteria that are used to classify mass-wasting processes include the type of material involved, the kind of motion, and the velocity of the movement.
What factors led to the massive rock slide at Gros Ventre, Wyoming?
The following factors contributed to the Gros Ventre slide: the strata were dipping; the sandstone bed was underlain by clay that become saturated with water from heavily rains and melting snow; and the river had cut through the sandstone layer.
What type of mass-wasting event killed thousands of people in the vicinity of the Colombian volcano Nevado del Ruiz in 1985?
Mudflow of water-saturated volcanic ask, known as lahars, were triggered on the steep slopes of this volcano when large volumes of ice and snow were suddenly melted by the hot debris emitted during a violent eruption.
Describe the mechanisms or factors that contribute to the slow downslope moment called creep
The alternating expansion and contraction of surface material caused by freezing and thawing or wetting and drying is one of the factors that contribute to the creep of Earth materials. Others factors include saturation of the ground with water ( resulting in a loss of internal cohesion) and disturbance of the soil ( by plant roots, burrowing animals, or falling raindrops).
During what season does solifluction occur in permafrost region?
Solifluction is the downhill flow of the water-saturated surface soil layer above permanently frozen ground (premafrost). In the summer, the soil thaws to some depth below the surface, but the water is trapped in the thawed soil because the premafrost zone is impermeable. Thus solifluction occurs only in summer, when the surface soil layer is thawed. In winter the surface soil layer is thawed. In winter the surface soil layer is frozen solid.