agents of erosion are...
Post on 03-Aug-2020
1 Views
Preview:
TRANSCRIPT
Geologic Processes & Freshwater Resources • Earth’s agents of erosion are constantly
changing Earth’s surface.
Agents: – Wind – Water – Ice – Gravity
Geologic Processes & Freshwater Resources • These changes can happen slowly- Creep.
Example of slump
Geologic Processes & Freshwater Resources
Avalanche Slump
Creep Flow Rockslide
Gravity and water content determine the type of sudden movement (often called mass movement or mas wasting) that occurs.
Geologic Processes & Freshwater Resources Porosity – The amount of pore space between particles of sediment.
Permeability – The ability of water to flow/permeate/percolate through the soil or rock.
CHAPTER HOME CHAPTER
SECTION OUTLINE
VOCABULARY 12.4 Hydrologic Cycle 12 Weathering, Soil, and Erosion
soil fertility
soil depletion
salinization
soil_savvy video
Distribution of Earth’s Water
Zone of aeration
Capillary fringe
Zone of saturation
Impermeable layer
Zone of aeration
Zone of saturation
Water table
Geologic Processes & Freshwater Resources
Geologic Processes & Freshwater Resources
Geologic Processes & Freshwater Resources
Geologic Processes & Freshwater Resources • Groundwater containing carbonic acid dissolves
limestone, forming caverns and features of karst topography.
Limestone Cave Formation
1. Rainwater containing carbonic acid seeps into the ground.
2. Limestone dissolves, forming underground caves.
3. Below the water table, the cave is filled with water.
• Ground water is found beneath the soil mantle in rock fractures and sediment formations. Large units that yield water to wells are called aquifers. The annual recharge to the groundwater system from precipitation ranges from 8 inches in western Virginia to 10 inches in the Coastal Plain. About 2 million Virginians, or 34%, depend entirely on wells for drinking water.
Geologic Processes & Freshwater Resources
Threats to Groundwater • Sediments - from soil erosion • Urban and suburban stormwater flows - from storm
events • Phosphates and nitrates - from agricultural sources • Improperly treated sewage - from overflows during storm
events, or from failing septic systems • Industrial wastes such as acids, oils, and grease - from
factories and other industrial facilities • Acids and leachates - from abandoned mines and dumps • Encroaching salt water - from the ocean into groundwater
supplies • Herbicides and pesticides - from water and sediments
running off the land
Geologic Processes & Freshwater Resources
Geologic Processes & Freshwater Resources
River Systems
Geologic Processes & Freshwater Resources
• Rivers move at different velocities based the the angle of the land and volume of water.
• Rivers cut paths through the rock called channels.
Geologic Processes & Freshwater Resources
Surface Water
• Over time the river starts to wander from side to side.
• This is called a meandering river
Geologic Processes & Freshwater Resources
Surface Water
• A very mature river may meander so much, loops connect, cutting off pre-existing sections of the river forming oxbow lakes.
Geologic Processes & Freshwater Resources
Stages of River Development ! Youthful Stream ! Mature Stream ! Old Age Stream
Geologic Processes & Freshwater Resources
Geologic Processes & Freshwater Resources • Youthful rivers form steep-sided canyons and
V-shaped valleys. The lowest level to which a river can erode its bed is called its base level
Meanders
Geologic Processes & Freshwater Resources
Meander
Geologic Processes & Freshwater Resources
Geologic Processes & Freshwater Resources
floodplain
Valley wall
Oxbow lake
Meander
Meander • The Pearl
River meanders nearly a full loop in Mississippi. USA.
Geologic Processes & Freshwater Resources
Meandering River
Geologic Processes & Freshwater Resources
• The tumbling waters cut away the shale and sandstone layers until the undermined top layer collapses, thus maintaining the vertical face of the Falls.
Geologic Processes & Freshwater Resources
Niagara Falls from above
Geologic Processes & Freshwater Resources
Flood Plain • Flood-plain zoning, which places
restrictions on the use of land on flood plains, can reduce the cost of flood damage. Local governments may pass laws that prevent uncontrolled building or development on flood plains to limit flood risks and to protect nearby property. Landowners in areas that adopt local ordinances or laws to limit development on flood plains can purchase flood insurance to help cover the cost of damage from floods.
Geologic Processes & Freshwater Resources
Deposition of Sediment
Geologic Processes & Freshwater Resources
Rivers Deposit Sediments
Geologic Processes & Freshwater Resources
Rivers Cary Sediment • Flowing water transports gravel,
rocks, and boulders downstream by rolling or sliding them along the bottom of the streambed.
• Small grains of sand and gravel can bounce along the bottom in a series of jumps.
• Smaller sand, silt, and clay particles are transported in suspension. The particles move downstream suspended in the turbulent water, giving the water a muddy appearance.
• Dissolved rock materials (not visible) move downstream in solution.
Geologic Processes & Freshwater Resources
Deposition - Deltas • Deltas are accumulations
of sediments that form where rivers empty into bodies of quieter water. When flowing water enters a lake or ocean basin, its speed slows. The slower water drops its sediments to the bottom of the basin and they accumulate to form a delta.
Geologic Processes & Freshwater Resources
Deposition – Alluvial Fans • An alluvial fan forms
on land where a river emerges from a mountainous area and flows out onto a more gently sloping plain
• They typically form when there is a sharp change in slope.
Geologic Processes & Freshwater Resources
The Watersheds of VA
Glencoe- Watershed
What is the largest watershed in VA?
Chesapeake Bay Watershed
Maryland
Delaware
New York
District of Columbia
Virginia
West Virginia
Pennsylvania
Water from these 6 states is drained into the Bay: Virginia Maryland West Virginia Delaware New York Pennsylvania
The water from over 50 rivers empties into the Bay. Can you name the 5 major rivers that flow into the bay?
Susquehanna River
Potomac River
Rappahannock River
York River
James River
top related