PHSC 210 WEEK 5 Mastering Geology Assignments 8  Mastering Geology Assignments 8  Item 1  Part A Which of the following is the primary step that allows water to enter the groundwater system? evaporation infiltration runoff precipitation Part B Which of the following statements about the global water supply is true? Decreased precipitation could impact water supply available for humans. Most of the global freshwater supply is easily accessible. A majority of the world’s water is drinkable by humans. Rivers are the most likely source of water for humans. The loss of glaciers and ice sheets due to climate change will not have a large impact of global freshwater supply.   Part C – Ranking water sources   Rank the following sources of water from largest to smallest in terms of percentage of the world’s total supply. Rank from largest to smallest. To rank items as equivalent, overlap them.         Item 2 Stream drainage patterns develop in response to variability in the material over which the streams are flowing and by following the path of least resistance. As they flow downslope due to gravity, a number of factors can influence where streams will establish their channels. Some of these factors present variability in resistance to erosion caused by differences in rock type, degree of fracturing, and/or underlying geologic structures. Stream drainage patterns can often provide clues about the geology underlying the landscape. Drainage patterns: ·         Dendritic drainage patterns resemble a branching tree. Dendritic patterns are the most common type of stream drainage, and typically form where streams flow over materials that are uniform in their resistance to erosion. ·         Radial drainage patterns develop where streams radiate outward from an isolated high area. ·         Rectangular drainage patterns can form where streams flow over rocks that are heavily fractured. Since fractures (joints) often run nearly perpendicular to each other, stream channels in a rectangular drainage pattern join each other at right angles as they follow the fractured, more easily eroded bedrock. ·         Trellis drainage patterns form where streams flow over alternating bands of harder and softer ground (for example, flowing over folded layers of alternating resistant and less resistant rock). This pattern of erodible and less erodible ground leads to channels that run nearly parallel to one another, connected in breaks in ridgelines. These have the appearance of a garden trellis.     Part A – Classifying stream drainage patterns In the diagram below, there are examples of five different landscapes. For each landscape, determine whether you have enough information to tell what type of stream drainage pattern would develop on it. If so, associate the landscape with the correct name of its drainage pattern. Drag the appropriate labels to their respective targets.     Part B – The origin of stream drainage patterns Stream drainage patterns are controlled by the slope and type of material over which the streams are flowing. ·         Streams follow the path of least resistance as they flow downhill due to gravity. ·         The variability of geologic materials will determine the magnitude of slope, meaning that differing geology lead to steep or more gently sloped streams. ·         The material’s resistance to erosion influences where the streams will erode the material the fastest and establish a channel. For each of the landscapes described below, determine whether the location and direction of streamflow is controlled primarily by slope or by geologic variability. Drag the appropriate items into their respective bins.       Item 3   Part A Which of the following rivers is the largest river in North America? the Mississippi River the Colorado River the Missouri River the Rio Grande the Mackenzie River Part B Which of the following choices does not directly affect stream velocity? stream gradient stream discharge channel shape channel size location of the drainage divide   Part C The amount of meandering that occurs in a stream influences the gradient in which of the following ways? With more meanders, the stream gradient increases. Meanders do not cause a change in stream gradient. With more meanders, the stream gradient decreases. With more meanders, the gradient will change, but only where the stream enters the ocean. Having more meanders increases the stream’s potential for flooding. Part D   What type of drainage pattern would you expect to find developing on rocks that have been folded and exposed by differential erosion over time? a trellis drainage pattern a yazoo drainage pattern a rectangular drainage pattern a radial drainage pattern a dendritic drainage pattern   Part E While working on a stream in your field study area, you find that the channel width is 20 meters, the channel depth is 2 meters, and the velocity is 1.2 meters/second. What is the discharge of this stream? 4.8 m3/s 23.2 m3/s 48 m3/s 10.6 m3/s 480 m3/s   Item 4   Streams reshape the landscape through erosion and deposition of continental earth. Erosion removes earth, which creates stream channels and stream valleys. Deposition, on the other hand, allows sediment to accumulate in an area. The force of flowing stream water determines whether erosion or deposition will occur at a particular location along a stream. In order for a stream to move sediment, the force of stream water flow must be greater than the frictional forces holding the sediment grains in place. Recall that force = mass × acceleration Thus, we would expect erosion to occur where stream water has high acceleration and deposition to occur where stream water has low (even negative) acceleration.   Part A – Erosion and deposition along a meandering stream Streams are said to meander when they have a single stream channel and don’t flow along a straight line. The Colorado River, as shown below, is a typical meandering river: Drag the appropriate labels to their respective targets.   Part B – Base level and stream valleys   The term stream gradient is used to describe the ratio of drop in elevation of a stream per unit of horizontal distance. In other words, streams with steeper beds are considered to have higher stream gradients. The force of stream flow increases with stream gradient. Therefore, erosion tends to occur where a stream has a steep gradient and deposition tends to occur where the stream has a gradual gradient. The gradient of a stream is impacted by several factors; one of the most important is base level—the level below which a stream cannot erode. Streams cannot erode below base level (usually sea level), because in order to do so they would have to defy gravity and flow uphill. As a consequence, streams tend to have gradual gradients when they are flowing near base level. Steep stream gradients can only occur where streams are flowing far above their base level. The diagrams below show the evolution of a stream valley into a floodplain. Stream valleys are narrow, V-shaped terrains formed by stream erosion. In contrast, floodplains are broad, flat plains formed by stream deposition. Whether a stream valley or floodplain forms in a particular region depends on the stream’s proximity to base level. Arrange the diagrams based on the proximity of the stream to its base level. Arrange them from highest above stream base level (left) to nearest stream base level (right).       Part C – Stream features   A river system can be divided into three zones: a zone of erosion, a zone of transportation, and a zone of deposition, as shown in the figure below. Determine the zone where each of the depicted features occurs. Drag the appropriate items into their respective bins. Each item may be used only once.   Item 5   Part A Which of the following zones is the location of the most biological activity? the unsaturated zone the zone of soil moisture the zone of saturation the intermediate belt the capillary fringe Part B In terms of freshwater storage, groundwater is second only to which of the following sources? the atmosphere soil moisture freshwater lakes stream channels glaciers Part C The majority of groundwater is stored within which of the following zones? the zone of saturation the zone of soil moisture the water table the capillary fringe the unsaturated zone Part D During a summer with little rainfall, your house on a hill slope experiences an interval during which your well runs dry. You have to borrow water from your neighbor who lives downslope from you. Why does your neighbor have water when you don’t? As the water table drops due to the lack of precipitation, it goes below the base of your well. Your neighbor is drawing the water away from your well. The zone of saturation has risen at your neighbor’s house. As the water table goes below your well, it is going up at your neighbor’s. The zone of soil moisture has risen at your neighbor’s house.