easc121tr3 

EASC 121 TEST THREE REVIEW SHEET

THE TEST REVIEW SHEET IS NOT ALL INCLUSIVE.  THIS IS JUST A GUIDELINE TO HELP YOU STUDY FOR THE EXAM.  WHEN I SAY TO KNOW SOMETHING THAT DOES NOT SIMPLY MEAN TO KNOW A DEFINITION OF IT BUT TO KNOW ALL THE APPLICATIONS OF THAT CONCEPT.

Know the difference between erosion & weathering; the differences between chemical & mechanical weathering; and differential weathering  & erosion

Know what William Morris Davis’ role was in geomorphology

Know what karst topography is and the examples of it across the landscape

What is gradation and what are its physical agents?

Know threshold, equilibrium, response time, angle of repose

What is slump and why does it occur?

What is a drainage basin?

What is the difference between permeable and impermeable rock?

Know the different types of stream drainage patterns

Know the process of stream erosion and deposition

Know the various types of stream load

Know the landform features produced by streams

Know groundwater, water table, aquifers, aquicludes, vadose zone, zone of aeration, phreatic zone

Know how glaciers erode and deposit material

Know snowline, ablation, and accumulation

Know the types of glaciers and the anatomy of a glacier

Know stoss and lee topography and its related features

Know the glacial erosional and depositional features for both alpine and continental glaciers

Why did the climate change to form glaciers?

Know the glacial and interglacial periods

Know permafrost and the other periglacial landform features

SAMPLE TEST QUESTIONS

1. Frost wedging caused by the freeze and thaw cycle is an example of:

a. mechanical weathering

b. chemical weathering

c. mechanical erosion

d. chemical erosion

 

2. Alluvial terraces form when:

a. the stream's have periods of decreased energy

b. the stream's have periods of increased energy

c. sea level was lower

d. none of these

 

3. A valley glacier is a type of:

a. alpine glacier

b. continental ice sheet

c. continental ice cap

d. unconfined glacier

 

4. Where would you find the placement of an esker?

a. in the outwash plain

b. along the sides of a glacier

c. in stream tunnels under a stagnant glacier

d. in a melted isolated ice block left by the glacier

 

 

WEATHERING & EROSION


 

Summary

The following statements summarize and describe many of the key terms and concepts presented in the chapter.

     

  • External processes include (1) weathering—the disintegration and decomposition of rock at or near the surface, (2) mass wasting—the transfer of rock material downslope under the influence of gravity, and (3) erosion—the incorporation and transportation of material by a mobile agent, usually water, wind, or ice. They are called external processes because they occur at or near Earth's surface and are powered by energy from the Sun. By contrast, internal processes, such as volcanism and mountain building, derive their energy from Earth's interior.

     

  • Mechanical weathering is the physical breaking up of rock into smaller pieces. Chemical weathering alters a rock's chemistry, changing it into different substances. Rocks can be broken into smaller fragments by frost wedging, unloading, and biological activity. Water is by far the most important agent of chemical weathering. Oxygen in water can oxidize some materials, while carbon dioxide (CO2) dissolved in water forms carbonic acid. The chemical weathering of silicate minerals frequently produces (1) soluble products containing sodium, calcium, potassium, and magnesium, (2) insoluble iron oxides, and (3) clay minerals.

     

  • The rate at which rock weathers depends on such factors as (1) particle size—small pieces generally weather faster than large pieces; (2) mineral makeup—calcite readily dissolves in mildly acidic solutions, and silicate minerals that form first from magma are least resistant to chemical weathering; and (3) climatic factors, particularly temperature and moisture. Frequently, rocks exposed at Earth's surface do not weather at the same rate. This differential weathering of rocks is influenced by such factors as mineral makeup and degree of jointing.

     

  • Soil is a combination of mineral and organic matter, water, and air—that portion of the regolith (the layer of rock and mineral fragments produced by weathering) that supports the growth of plants. Soil texture refers to the proportions of different particle sizes (clay, silt, and sand) found in soil. The most important factors that control soil formation are parent material, time, climate, plants and animals, and topography.

     

  • Soil-forming processes operate from the surface downward and produce zones or layers in the soil called horizons. From the surface downward the horizons are designated as O, A, E, B, and C, respectively.

     

  • In the United States, soils are classified using a system known as the Soil Taxonomy. It is based on physical and chemical properties of the soil profile and includes six hierarchical categories. The system is especially useful for agricultural and related land-use purposes.

     

  • Soil erosion is a natural process; it is part of the constant recycling of Earth materials that we call the rock cycle. Rates of soil erosion vary from one place to another and depend on the soil's characteristics as well as such factors as climate, slope, and type of vegetation. Human activities have greatly accelerated the rate of soil erosion in many areas.

     

  • Weathering creates mineral deposits by concentrating metals into economically valuable deposits. The process, called secondary enrichment, is accomplished by either (1) removing undesirable materials and leaving the desired elements enriched in the upper zones of the soil or (2) removing and carrying the desirable elements to lower soil zones where they are redeposited and thus become more concentrated. Bauxite, the principal ore of aluminum, is one important ore created by secondary enrichment.

     

  • In the evolution of most landforms, mass wasting is the step that follows weathering. The combined effects of mass wasting and erosion by running water produce stream valleys. Gravity is the controlling force of mass wasting. Other factors that influence or trigger downslope movements are saturation of the material with water, oversteepening of slopes beyond the angle of repose, removal of anchoring vegetation, and ground vibrations from earthquakes.

     

  • The various processes included under the name of mass wasting are classified and described on the basis of (1) the type of material involved (debris, mud, earth, or rock), (2) the kind of motion (fall, slide, or flow), and (3) the rate of movement (fast, slow). The various kinds of mass wasting include the more rapid forms called slump, rockslide, debris flow, and earthflow, as well as the slow movements referred to as creep and solifluction.



       

 

RIVERS

Summary

The following statements summarize and describe many of the key terms and concepts presented in the chapter.

     

  • The hydrologic cycle describes the continuous interchange of water among the oceans, atmosphere, and continents. Powered by energy from the Sun, it is a global system in which the atmosphere provides the link between the oceans and continents. The processes involved in the hydrologic cycle include precipitation, evaporation, infiltration (the movement of water into rocks or soil through cracks and pore spaces), runoff (water that flows over the land rather than infiltrating into the ground), and transpiration (the release of water vapor to the atmosphere by plants). Running water is the single most important agent sculpturing Earth's land surface.

     

  • The land area that contributes water to a stream is its drainage basin. Drainage basins are separated by imaginary lines called divides.

     

  • River systems consist of three main parts: the zones of erosion, transportation, and deposition.

     

  • The factors that determine a stream's velocity are gradient (slope of the stream channel), shape, size, and roughness of the channel, and the stream's discharge (amount of water passing a given point per unit of time, frequently measured in cubic feet per second). Most often, the gradient and roughness of a stream decrease downstream, while width, depth, discharge, and velocity increase.

     

  • Streams transport their load of sediment in solution (dissolved load), in suspension (suspended load), and along the bottom of the channel (bed load). Much of the dissolved load is contributed by groundwater. Most streams carry the greatest part of their load in suspension. The bed load moves only intermittently and is usually the smallest portion of a stream's load.

     

  • A stream's ability to transport solid particles is described using two criteria: capacity (the maximum load of solid particles a stream can carry) and competence (the maximum particle size a stream can transport). Competence increases as the square of stream velocity, so if velocity doubles, water's force increases fourfold.

     

  • Streams deposit sediment when velocity slows and competence is reduced. This results in sorting, the process by which like-sized particles are deposited together. Stream deposits are called alluvium and may occur as channel deposits called bars, as floodplain deposits, which include natural levees, and as deltas or alluvial fans at the mouths of streams.

     

  • Stream channels are of two basic types: bedrock channels and alluvial channels. Bedrock channels are most common in headwaters regions where gradients are steep. Rapids and waterfalls are common features. Two types of alluvial channels are meandering channels and braided channels.

     

  • The two general types of base level (the lowest point to which a stream may erode its channel) are (1) ultimate base level and (2) temporary, or local base level. Any change in base level will cause a stream to adjust and establish a new balance. Lowering base level will cause a stream to downcut, whereas raising base level results in deposition of material in the channel.

     

  • When a stream has cut its channel closer to base level, its energy is directed from side to side, and erosion produces a flat valley floor, or floodplain. Streams that flow upon floodplains often move in sweeping bends called meanders. Widespread meandering may result in shorter channel segments, called cutoffs, and/or abandoned bends, called oxbow lakes.

     

  • Floods are triggered by heavy rains and/or snowmelt. Sometimes human interference can worsen or even cause floods. Flood-control measures include the building of artificial levees and dams, as well as channelization, which could involve creating artificial cutoffs. Many scientists and engineers advocate a nonstructural approach to flood control that involves more appropriate land use.

     

  • Common drainage patterns produced by streams include (1) dendritic, (2) radial, (3) rectangular, and (4) trellis.

     

  • As a resource, groundwater represents the largest reservoir of freshwater that is readily available to humans. Geologically, the dissolving action of groundwater produces caves and sinkholes. Groundwater is also an equalizer of streamflow.

     

  • Groundwater is water that occupies the pore spaces in sediment and rock in a zone beneath the surface called the zone of saturation. The upper limit of this zone is the water table. The zone of aeration is above the water table where the soil, sediment, and rock are not saturated.

     

  • The quantity of water that can be stored depends on the porosity (the volume of open spaces) of the material. The permeability (the ability to transmit a fluid through interconnected pore spaces) of a material is a very important factor controlling the movement of groundwater.

     

  • Materials with very small pore spaces (such as clay) hinder or prevent groundwater movement and are called aquitards. Aquifers consist of materials with larger pore spaces (such as sand) that are permeable and transmit groundwater freely.

     

  • Springs occur whenever the water table intersects the land surface and a natural flow of groundwater results. Wells, openings drilled into the zone of saturation, withdraw groundwater and create roughly conical depressions in the water table known as cones of depression. Artesian wells occur when water rises above the level at which it was initially encountered.

     

  • When groundwater circulates at great depths, it becomes heated. If it rises, the water may emerge as a hot spring. Geysers occur when groundwater is heated in underground chambers, expands, and some water quickly changes to steam, causing the geyser to erupt. The source of heat for most hot springs and geysers is hot igneous rock.

     

  • Some of the current environmental problems involving groundwater include (1) overuse by intense irrigation, (2) land subsidence caused by groundwater withdrawal, and (3) contamination by pollutants.

     

  • Most caverns form in limestone at or below the water table when acidic groundwater dissolves rock along lines of weakness, such as joints and bedding planes. Karst topography exhibits an irregular terrain punctuated with many depressions, called sinkholes.


 


 

GLACIERS

Summary

The following statements summarize and describe many of the key terms and concepts presented in the chapter.

     

  • A glacier is a thick mass of ice originating on land from the compaction and recrystallization of snow, and it shows evidence of past or present flow. Today, valley or alpine glaciers are found in mountain areas where they usually follow valleys that were originally occupied by streams. Ice sheets exist on a much larger scale, covering most of Greenland and Antarctica.

     

  • Near the surface of a glacier, in the zone of fracture, ice is brittle. However, below about 50 meters, pressure is great, causing ice to flow like a plastic material. A second important mechanism of glacial movement consists of the whole ice mass slipping along the ground.

     

  • Glaciers form in areas where more snow falls in winter than melts during summer. Snow accumulation and ice formation occur in the zone of accumulation. Beyond this area is the zone of wastage, where there is a net loss to the glacier. The glacial budget is the balance, or lack of balance, between accumulation at the upper end of the glacier, and loss at the lower end.

     

  • Glaciers erode land by plucking (lifting pieces of bedrock out of place) and abrasion (grinding and scraping of a rock surface). Erosional features produced by valley glaciers include glacial troughs, hanging valleys, cirques, arętes, horns, and fiords.

     

  • Any sediment of glacial origin is called drift. The two distinct types of glacial drift are (1) till, which is unsorted sediment deposited directly by the ice; and (2) stratified drift, which is relatively well-sorted sediment laid down by glacial meltwater.

     

  • The most widespread features created by glacial deposition are layers or ridges of till, called moraines. Associated with valley glaciers are lateral moraines, formed along the sides of the valley, and medial moraines, formed between two valley glaciers that have joined. End moraines, which mark the former position of the front of a glacier, and ground moraine, an undulating layer of till deposited as the ice front retreats, are common to both valley glaciers and ice sheets.

     

  • Perhaps the most convincing evidence for the occurrence of several glacial advances during the Ice Age is the widespread existence of multiple layers of drift and an uninterrupted record of climate cycles preserved in seafloor sediments. In addition to massive erosional and depositional work, other effects of Ice Age glaciers included the migration of organisms, changes in stream courses, adjustment of the crust by rebounding after the removal of the immense load of ice, and climate changes caused by the existence of the glaciers themselves. In the sea, the most far-reaching effect of the Ice Age was the worldwide change in sea level that accompanied each advance and retreat of the ice sheets.

     

  • Any theory that attempts to explain the causes of glacial ages must answer the two basic questions: (1) What causes the onset of glacial conditions? and (2) What caused the alternating glacial and interglacial stages that have been documented for the Pleistocene epoch? Two of the many hypotheses for the cause of glacial ages involve (1) plate tectonics and (2) variations in Earth's orbit. Other factors that are related to climate change during glacial ages include changes in atmospheric composition, variations in the amount of sunlight reflected by Earth's surface, and changes in ocean circulation.

     




 

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