Water Erosion and Deposition
Chapter 8
SURFACE WATER
Section 8.1
Runoff
What can water do when it rains on the earth?
Surface Water
Water does one of the following after it rains:
Evaporates
Soaks into earth and becomes ground water
Becomes runoff
Surface Water
What are the factors affecting runoff?
Surface Water
Factors Affecting Runoff:
Amount of rain
Time
Slope of the land
Amount of vegetation
The Effects of Gravity
What are some effects of gravity?
The Effects of Gravity
Effects of Gravity:
Water runs down hill
Water gains speed as it runs down hill
Fast moving water erodes more quickly than slow moving water
Water Erosion
What is rill and Gully Erosion?
Water Erosion
Rill Erosion small streams from during heavy rain leaving small channels
Gully Erosion when rill channel becomes broader and deeper
Water Erosion
Describe Sheet Erosion.
Water Erosion
Sheet Erosion
Water not in a channel
Occurs in flat areas
Moves down gentle slope
Water Erosion
Describe Stream Erosion.
Water Erosion
Stream Erosion
Water continues to flow along a depression
Water picks up sediment from the bottom and sides of the stream
Lighter sediments are carried along in the water
Larger sediments roll on the bottom
Sediments scrape sides and bottom, wearing it away
Gradually gets wider and deeper
River System Development
Describe a River System.
River System Development
River System small streams form larger streams
Rills
Gullies
Smaller streams
Branches
Creeks
Rivers
River System Development
What is a Drainage Basin?
River System Development
Drainage Basin
Land area from which a stream gets its water
Stages of Stream Development
Give the three stages of stream development.
River System Development
Three stages of stream development:
Young
Mature
Old
River System Development
Describe a young stream.
River System Development
Young Stream
Swift
Steep valley
Steep sides
White water rapids
Water falls
Bottom is eroded more than sides
River System Development
Describe a mature stream.
River System Development
Mature Streams
Less swiftly
Rocks that caused rapids and waterfalls are eroded away
Erodes more from sides
Curves develop because speed of water varies across the width of the stream
River System Development
Mature Stream (Cont.)
Shallow water slows down
Deep water flows faster
More erosion on sides of stream where water is deeper
Curves(meanders) form
River System Development
What is a floodplain?
River System Development
Flood Plain broad, flat valley floor carved by a meandering stream
River System Development
Describe an Old Stream.
River System Development
Old Stream
Slow
Broad, flat floodplain
River System Development
River system contains streams of all stages
Young stage at the outer edge of the system
Old stage on the interior and mouth of the system
Deposition by Surface Water
Give some examples of deposition by surface water.
Deposition by Surface Water
Surface Water Deposition
Alluvial Fan triangle of sediment usually at the base of a steep mountain
Delta deposit at the mouth of a river when it empties into the ocean
Groundwater
Section 8.2
Groundwater System Development
What is groundwater?
Groundwater System Development
Groundwater water that soaks into the ground collects in pores
Groundwater System Development
What is permeability?
Groundwater System Development
Permeability soil or rock that water can pass through easily
Impermeable not permeable
Groundwater System Development
What increases permeability?
Groundwater System Development
Pores increase permeability.
More pores
Larger pores
Groundwater System Development
What causes Groundwater Movement?
Groundwater System Development
Groundwater keeps going lower until it reaches an impermeable layer.
Once the impermeable layer is reached groundwater can only move horizontally and not down.
Groundwater System Development
What is an aquifer?
Groundwater System Development
Aquifer layer of permeable rock that transmits water freely
Groundwater System Development
What is the zone of saturation?
Groundwater System Development
Zone of saturation area where all of the pores in the rock are filled with water
Groundwater System Development
What is the water table?
Groundwater System Development
Water table upper surface of the zone of saturation
Wells, Springs, and Geysers
What are two types of wells?
Wells, Springs, and Geysers
Two types of wells:
Mechanical wells need a pump to bring the water to the surface
Artesian well top of the well is below the highest point of an aquifer, no pump is needed
Wells, Springs, and Geysers
Describe a spring.
Wells, Springs, and Geysers
Spring water table is exposed to surface
Hot spring groundwater is heated by hot molten material under the Earths surface
Wells, Springs, and Geysers
What is a geyser?
Wells, Springs, and Geysers
Geyser hot spring that erupts periodically, shooting water and steam into the air
Groundwater Erosion and Deposition
How are caves formed?
Groundwater Erosion and Deposition
Caves
formed when cracks in limestone are enlarged
Ground water dissolves the limestone
The groundwater is acidic because carbon dioxide dissolved in the rainwater from the air.
Groundwater Erosion and Deposition
What are two cave formations?
Groundwater Erosion and Deposition
Cave formations:
Stalactites from ceilings of caves
Stalagmites from floor of caves
Groundwater Erosion and Deposition
How are sinkholes formed?
Groundwater Erosion and Deposition
Sinkhole:
Underground rock near surface is dissolved.
Ceiling of cave collapses
Ocean Shoreline
Section 8.4
The Shore
Describe two types of shorelines.
The Shore
Two types of shore lines:
Sandy beach, gentle slope
Rocky beach, steep slope
The Shore
Forces that affect the shoreline:
The Shore
Forces that affect the shoreline:
Waves
Tides
Currents
The Shore
What is a longshore current and what causes it
The Shore
Longshore current
Waves collide with the shoreline at an angle, causing water to run parallel to the shoreline.
Rocky Shorelines
What cause a rocky shoreline?
Rocky Shorelines
Rocky Shorelines occur when the sediments are carried away from the shore.
Steep shoreline
Sandy Beaches
What causes Sandy Beaches?
Sandy Beaches
Sandy Beaches occur when sediments are deposited on the beach.
Gentle sloped shoreline
Sandy Beaches
Sand Erosion and Deposition
Sand is carried down beach and deposited by longshore currents.
Sandy Beaches
Describe a Barrier Island.
Sandy Beaches
Barrier Island sand deposits that parallel the shore but are separate from the mainland.
Underwater sand ridges formed by breaking waves
Storms add sediment
Ridge raised to sea level
Wind blows exposed sand into dunes
