1. Lower Course Landforms- Deltas Flashcards
What is an Arcuate Delta?
A tide-dominated delta that tends to be fan-shaped with many divided channels called distributaries.
Describe a Bird Foot Delta.
A delta where fast-flowing water extends outward into a lake or sea, relative to slower marine currents.
What characterizes a Cuspate Delta?
A wave-dominated delta with straight or evenly distributed sediments creating a flattened triangle shape and few distributaries.
Define Distributaries.
Separate channels that form across the delta.
What is Flocculation?
The process explaining how minute clays flock together and gain weight due to a static charge created when mixing with salt water.
What are Bars in the context of deltas?
Areas of deposition.
Define Lagoons.
Closed or open bodies of water within the delta, containing brackish water.
What is Brackish water?
Water created by the mix of freshwater and seawater.
What are Topsets, Foresets, and Bottom sets?
Sections of the delta characterized by location height and sediment size.
What conditions are needed for delta formation?
- A large amount of transported load in the river due to high erosion rates
- Limited opportunity to deposit load along the course
- Slow river velocity at the mouth leading to deposition
- Relatively weak tidal and marine currents
- Shallow coastal water, e.g. continental shelf
What are the three main types of delta?
- Cuspate Delta
- Arcuate Delta
- Bird Foot Delta
What are the physical characteristics of deltas?
- Divided channels called distributaries
- Extensive alluvium mudflats or bars
- Creeks and lagoons
How does river flow affect delta characteristics?
River flow levels and marine energy change over the year, affecting rates of deposition and erosion of sand bars.
What are topset beds in a delta?
The uppermost layer made up of larger, coarser sediments typically consisting of sand bars, lagoons, and creeks.
What forms the lower foreset beds in a delta?
Smaller sediments that are transported further out and deposited.
What are bottomset beds composed of?
The smallest and lightest sediments, typically fine clays.
True or False: High river energy is required to transport fine sediments.
False.
What is the significance of flocculation in delta formation?
It allows fine clays to stick together, gain weight, and be deposited rather than transported away.
