Deltas

• What is a condition required for delta formation?

  Standing body of water with negligible currents
• What type of river is necessary for delta formation?

  Heavily laden river
• What type of water is involved in delta formation?

  Saline water
• What geological factor is important for delta formation?

  Local geology
• What environmental change can affect delta formation?

  Sea level changes
• What biological factor can influence delta formation?

  Plant growth
• What human factor can impact delta formation?

  Human impact
• Why is active erosion important for delta formation?

  It supplies large amounts of sediments
• Why is a strong current detrimental to delta formation?

  It may wash away sediments
• How does sediment resistance affect deposition in deltas?

  Less resistant sediment increases deposition
• What are the three types of sediment beds in a delta?

  • Bottomset beds
  • Foreset beds
  • Topset beds
• What is the composition of the bottomset bed?

  Primarily clay and fine-grained sediments
• What process occurs when clay meets salt water?

  Flocculation takes place
• What happens to clay particles during flocculation?

  They clump together and sink
• How far can fine sediments from the bottomset bed be transported?

  A fair distance from the river’s mouth
• Where is the foreset bed located in a delta?

  On top of the bottomset bed
• What type of sediments compose the foreset bed?

  Coarser sediments
• Why are sediments in the foreset bed not transported far?

  Due to a fall in river’s velocity
• How are sediments in the foreset bed transported?

  By traction and saltation
• How does the foreset bed dip?

  Towards deep water in river's flow direction
• What is the characteristic of the topset bed?

  It is horizontally bedded
• How are topset beds built up?

  By the work of numerous distributaries
• What is the shape of an arcuate delta?

  • Shaped like a triangle
  • Forms when river meets sea with alternating currents
  • Example: River Nile
• What is the shape of a cuspate delta?

  • Vaguely shaped like a V
  • Curved sides
  • Forms when river flows into sea with head-on waves
  • Example: River Ebro, Spain
• What is the shape of a birds foot delta?

  • Shaped like a bird's foot
  • Extends far into body of water
  • Forms when river's current is stronger than sea waves
  • Example: River Mississippi
• How do the shapes of arcuate, cuspate, and birds foot deltas differ?

  Arcuate is triangular, cuspate is V-shaped