year 9 geography -rivers

• What are the three distinct paths of a river's course?

  Upper course, middle course, and lower course
• Why is the velocity of water faster in the upper course of a river?


  Because of the steep gradient
• What characterizes the middle course of a river?


  The valley floors are wider and the sides are more gently sloping
• What landforms are typical in the middle course of a river?

  Meanders
• What is the slope like in the lower course of a river?


  The slope is gentle and almost flat
• What features are typically found in the lower course of a river?


  Oxbow lakes and deltas
• How are meanders formed in a river?


  They are formed as the river flows through almost a flat plane and develops a winding course
• What causes the river to swing in great s-shaped curves?


  Irregularities of the ground force the river to swing
• What happens to the water flow at the outside bend of a river?


  The water flows faster due to centrifugal force
• What occurs at the inside bend of a river?


  The water is relatively slow and deposits sand and mud
• What is created at the site of erosion on the outside bend of a river?


  A steep river cliff
• What is the effect of the bottom current set up in a corkscrew motion?


  It deposits eroded material on the inner bank
• How does a meander become pronounced in the lower course of a river?


  The outside bend gets eroded rapidly, making the loop almost a complete circle
• What happens to the narrow necks of the meander loop over time?


  They erode further and intersect each other
• What occurs when the river cuts through the intersection of a meander?


  The meander loop is abandoned and forms an oxbow lake
• What happens to an oxbow lake over time?


  It may turn into a swamp and eventually dry up
• What is the website mentioned for more information about the study material?

  www.mptv.org/outdoorwisconsin
• What is the main topic of the tutorial?

  The formation of waterfalls and gorges along a river
• How does a waterfall begin to form?


  It starts with a river flowing over bands of rock with harder geology on top and softer geology below
• What geological feature contributes to the distinct profile of a waterfall?


  The presence of harder rock above softer rock creates a vertical drop
• What is hydraulic action in the context of waterfall formation?


  It is the force of water that erodes the softer geology as the water flows downwards
• How does vertical erosion contribute to the formation of a waterfall?


  Vertical erosion occurs more on the softer geology, leading to a distinct vertical profile
• What happens to the softer geology as the waterfall continues to erode it?


  The softer geology is undercut, creating a plunge pool at the base of the waterfall
• What is an overhang in the context of a waterfall?


  An overhang is the harder geology that sits above the softer geology
• What occurs when the overhang collapses?

  The waterfall profile changes, and the waterfall retreats back up the river valley
• What does the retreat of a waterfall create over time?


  It creates a gorge as the waterfall moves backwards
• What are the stages of waterfall retreat as shown in the time lapse diagram?


  1. Waterfall flows in position one
  2. Waterfall retreats to position two
  3. Waterfall retreats to position three
  4. Continuous erosion leads to gorge formation
• What is a plunge pool?


  A plunge pool is formed at the base of a waterfall due to erosion
• What geological evidence can be seen in the photograph of High Force waterfall?


  The hard windal geology above the softer geology below
• How does the retreating waterfall affect the river valley?


  It creates a steep-sided river valley
• What is the process of gorge formation from a waterfall?


  • Waterfall retreats due to erosion
  • Creates a steep-sided river valley
  • Takes thousands of years to form
  • Typically found high in the river valley near the source
• Where are gorges typically formed in relation to a river?


  They are formed high up in the river valley near the source of the river