Regents Earth Science Weathering & Erosion Name: Rivers Use your notes, the handout Weathering and Erosion and your review book to answer the following questions on Rivers. Be sure to read the information for all illustrations. 1. Which of the following statements is true concerning a Youthful River: a. Area erosion is primarily caused by lateral, side-to-side, water movement. b. Area erosion is primarily caused by the river downcutting into the bedrock below. c. Erosional forces cause meander curves to develop in surrounding bedrock. d. Deposition is greater than erosion in Young Rivers. 2. Youthful Rivers carry their sediment load in the following manner: a. In solution only. b. As a suspended load. c. By rolling, bouncing, and saltation. d. All of the above. The following diagram pertains to Questions 3 and 4. It shows a cross section of a portion of Earth's crust. Elevations are shown in meters. Arrows are pointing to 2 elevations of a river flowing through this region. If the distance the river flows from the higher to the lower elevations is 1,200 km, what is the gradient of the river? Use the following equation to compute your answer: Rivers Worksheet 1
3. The approximate gradient of the river is: a. 3.42 m/km b. 3.75 m/km c. 2.58 m/km d. 3,100 m/km 4. Over time, as the river continues to erode the landscape, how will the general appearance of the area change? a. Mountains will continue to rise and the river valley will become more elevated. b. The valley will continue to deepen then river will begin to erode laterally and widen the river valley. c. The ocean will move further back towards the mountains, eventually joining the river. d. No changes to the landscape will occur. 5. Youthful Rivers are generally found: a. Where the river empties into a lake or ocean. b. On flat plains, with hilly landscapes located at great distances from the actual river. c. At higher elevations, often in mountainous areas, where slopes are steeper. d. Within broad, flat floodplains that are saturated with swamps and oxbow lakes. 6. The following illustration shows 4 different river profiles. Which river profile best represents the cross-section of a Youthful River? Rivers Worksheet 2
The illustration to the left pertains to questions 7 and 8. It shows a river flowing over a steep escarpment (cliff). 7. The best indication that the river in the illustration above is a Young River is: a. The rock fragments that are visible to the right in the illustration. b. The bedrock is composed of several horizontal sedimentary rock layers. c. The river is depositing its sediments in the ocean. d. A waterfall is visible in the diagram. 8. The steep escarpment shown in the illustration above may have been formed by: a. River erosion, only. b. A fault in the rock layers. c. Differential weathering and many years of erosion due to down-cutting by the river. d. An igneous intrusion with associated volcanic eruptions. 9. Which of the following would increase the discharge of a Youthful River? a. Precipitation and the evaporation of seawater in large quantities. b. Precipitation and spring snowmelt at high elevations. c. The capillary action of groundwater in loose unconsolidated sediments below the river's floodplain. d. The increase of snow pack on high mountain peaks. Rivers Worksheet 3
10. Which of the following would explain why, in many instances, people cannot sit down next to the bank of a young river, remove their shoes and soak their feet in the river water? a. Young rivers are often situated in steep-sided canyons with no floodplain. b. A young river's floodplain is too swampy to allow people to sit and relax next to the river. c. The extensive lateral erosion in the area makes it too dangerous to visit young rivers. d. There is too much silt in the slow-moving river water, with a resulting muddy appearance, and so the water is not suitable for bathing. The following diagram pertains to Questions 1-5. The pictures show 2 views of the same river flowing from a lake to an ocean bay. The top image is a cross-sectional view and the bottom one is an aerial view. 11. The deposition in Dolphin Bay near location D is caused mainly by: a. Increased wave action in Dolphin Bay. b. Meanders in the river. c. The difference in the salt content between Clear Lake and Dolphin Bay. d. A decrease in the water velocity as it enters Dolphin Bay. Rivers Worksheet 4
12. How do the size and the density of particles deposited in Dolphin Bay generally change as the distance from the shoreline increases? a. Both size and density decrease. b. Both size and density increase. c. Size increases and density decreases. d. Size decreases and density increases. 13. Which diagram best represents the profile of the river bottom between points C and B? 14. Which change will occur if the volume of Turtle River increases? a. Down-cutting will decrease and the river bank erosion will increase. b. Down-cutting will increase and the river bank erosion will decrease. c. Both down-cutting and the river bank erosion will decrease. d. Both down-cutting and the river bank erosion will increase. 15. If no uplift of Earth's crust occurs in this area within the next 200 years, the average gradient of the riverbed between points A and D will: a. Decrease, only b. Increase, only c. Decrease, then increase d. Remain the same Rivers Worksheet 5
16. The following illustration is an aerial view of a stream flowing through an area of loose sediments. Arrows show the location of the strongest current. Which river profile best represents the cross-section between A-A'? The following illustration pertains to Questions 7-10. The diagrams show 3 different rivers, each with the same volume of water but each one in a different stage of river development. Rivers Worksheet 6
17. Which River shows the most advanced stage of river development? (The oldest river) a. River 1 b. River 2 c. River 3 18. The oxbow lake in the River 3 view was formed because of: a. The weathering of granite bedrock. b. The erosion and deposition of sediments in the surrounding floodplain. c. An increased volume of water in the river. d. Uplift of the crust in the area. 19. What is true concerning the velocity of river water in Views 2 and 3? a. Water velocity is fastest on outside meander curves. b. Water velocity is fastest on inside meander curves. c. Water velocity is equal on both the outside and inside meander curves. 20. Which of the following is a significant difference between the 3 river views as one observes first River 1, then River 2 and finally River 3? a. The river channels become increasingly narrower. b. Water volume increases. c. An ever-widening floodplain forms. d. The amount of vegetation in the area decreases. This assignment and questions 7-10 are L. Immoor Geoteach.Com, Geolor 2006 Illustrations and questions 1-6 are The University Of the State of New York; Board of Regents; Earth Science Regents Examinations June 1998, June 1999, June 2005 NYS Earth Science Regents Exams Rivers Worksheet 7