Student Study GuideCh. 10 Running Water
.... Topic 5 V-Shaped Valleys and Canyons Q: Why do young streams have v-shaped valleys? A: This is because youthful streams tend to flow at high speeds. This fast movement erodes the streambed. The walls are also widened by weathering and erosion. Q: What factors show how long it will take a river to form a canyon? A: 1. Kind of rock 2. Amount of water and sediment in the river 3. Climate Topic 6 Base Level: Widening the Valley Q: What is a river’s base level if it flows in the ocean? Into a lake or river? A: Ocean=sea level Lake/river=level of the lake or river Q: What are the changes in a stream as it gets near its base level? A: The slope of the streambed and speed of the stream decrease Topic 7 Lengthening the Valley Q: How are gullies formed? A: When a hillside loses its covering, a heavy rain may for a small stream valley. When the rain ends, the stream may disappear, but the valley or gully will remain. Q: What happens as a gully grows in length and depth? A: The stream may cut below the water table. This causes the stream to become permanent. A river system occurs if a tributary gully cuts below the water table. Topic 8 Divides and Drainage Basins Q: What is a divide and what is the major divide in the U.S.? A: Divide=the high land that separates on river valley or gully from the next. The Continental Divide. Q: What is a drainage basin and which is the largest in the U.S.? A: Drainage basin=area of land surface drained by a river system. Mississippi River System. Topic 9 Stream Piracy Q: What is stream piracy and how does it occur? A: The diversion of the upper part of one stream by the headward growth of another stream. Q: How often does stream piracy occur? A: Geologists think that stream piracy has been an important factor is the early growth of many great river systems. Topic 10 Water Gaps and Wind Gaps Q: How does a water gap form? A: When a river meets an unusually resistant rock formation, the formation will wear away more slowly and create a ridge in the river. Q: How is a wind gap thought to form? A: When the water of the gap was captured by a neighboring river. Topic 11 Potholes and Plunge Pools Q: How do potholes form? A: When a stream’s whirlpools pick up particles, they grind deep oval or circular holes. Q: What are very large potholes and where do they commonly occur? A: Plunge pools. They are commonly found near the base of waterfalls, such as in Niagara Falls. Topic 12 Waterfalls and Their Recession Q: What caused the formation of The Great Falls of the Potomac, the falls in Yosemite Valley and the two on the Yellowstone River? A: The Great Falls of the Potomac= Where water flows over hard igneous rock onto soft sedimentary rock. Yosemite Valley= Glaciers eroded one valley more deeply than others. Yellowstone River= Intrusions of igneous rock. Q: How does undermining affect waterfalls? A: The water falling into the plunge pool erodes the rock near the base, causing the rock to overhang. This overhanging rock will tend to break off and the waterfall will recede. Topic 13 Meanders and Oxbow Lakes Q: Why is the flood plain widened as time goes on? A: As the river cuts its bed lower and lower, the speed and slope decrease. The river is more easily deflected sideward, eroding the banks and valley walls. Q: How is a meander formed? A: When a river turns, the fastest water is on the outside of the bend. Erosion is rapid there. Sediment is deposited on the inside of the bend. As this pattern continues, it forms the wide curves known as meanders. Topic 14 Why Rivers Deposit Sediment Q: What factors cause a river’s s...