Transcript Weathering, Soil, Erosion, Groundwater, & Surface Water

Chapters 10, 11, & 12
• Breaking down rocks by
physical means, like ice, wind,
water, gravity, and
plants/animals
• Ice wedging occurs when
water squeezes into cracks in
rocks, freezes, expands, and
cracks the rock open
• Plant roots also act like
ice…they wedge themselves
into cracks, splitting the rock
apart
• Abrasion occurs when rocks
and sediment grind against
each other, wearing away the
exposed surfaces. This can
happen with wind and water.
Lichens
Grave stone
attacked by
acid rain
• Breaking down rocks by
changing their chemical
composition
• Major agents are water, acids,
and air
• When carbon dioxide and
water combine, they form
carbonic acid, which is found
in precipitation (acid rain)
• Acids are also found in the
roots of decaying plants and
lichens (fungi and algae)
• The oxygen in the air also
chemically changes iron and
turns soil a reddish color
(oxidation)
•
•
•
Soil is a mixture of pieces of broken
down rocks and organic matter
The organic material in soil is
called humus
Soil forms in layers, called horizons.
Thickness and presence of horizons
depends on climate.
1. “O” horizon: decomposed
plant and animal matter or
humus
2. “A” horizon: also called topsoil,
very dark in color and lots of
humus
3. “B” horizon: also called subsoil,
is lighter than A and may have
parts of A contained in it
through leaching
4. “C” horizon: partly weathered
bedrock or parent material
Profile
showing
the
horizons
Actual soil
profile
Cave
Sinkhole
Natural
Bridge, VA
• Karst topography is a
landscape created by acidic
groundwater dissolving
sedimentary rock such as
limestone. Abundant in the
Valley & Ridge province.
• Caves: Natural cavities
beneath the surface of the
earth, created by groundwater
dissolving rock.
• Sinkholes: Rounded depressions
in the landscape. Sinkholes are
often collapsed caves and can
be quite deep, or they can be
shallow holes. Sinkholes collect
surface water running off the
surrounding land, and the
runoff goes directly into the
groundwater.
• Natural bridges: Arches that are
the remnants of collapsed
caves, usually fairly short.
• The cycling of water from the
ocean, to the atmosphere, into
and on the ground, and back
to the oceans again
• Evaporation: changing from the
liquid to gaseous state
• Condensation: changing from
the gaseous to liquid state
through cooling (clouds)
• Precipitation: when clouds are
fully saturated, they give back
extra water through rain and
snow
• Runoff: water that remains on
the surface in rivers and streams
• Infiltration: water that soaks into
the soil and added to the water
table
• Transpiration: water vapor given
back to the atmosphere
through photosynthesis in plants
• Permeability is a measure of the
ability of a rock or sediment to
transmit water or other liquids.
• Water does not pass through
impermeable materials.
• Porosity is the available pore
spaces in rocks that can store
water. Mixtures of sediments,
such as gravel and sand, are
the most porous and can hold
the most water.
• A good aquifer is both porous
AND permeable.
Zone of Aeration
Water Table
Zone of Saturation
• A substantial amount of
water is stored in
permeable soil and
rock underground.
• Earth’s fresh water
supply is finite.
• Water is continuously
being passed through
the water cycle.
• Human activities, such
as waste disposal, can
pollute groundwater
supplies.
• Estuaries, like the Chesapeake
Bay, are areas where fresh and
salt water mix, producing
variations in salinity and high
biological activity.
• Four major regional watershed
systems in Virginia lead to the
Chesapeake Bay: PotomacShenandoah, Rappahannock,
York, James
• Two major watersheds drain into
the North Carolina Sounds:
Chowan and Roanoke
• Two major watersheds lead to the
Gulf of Mexico via the Ohio River:
New and Tennessee
• James River drains most of the
surface water in Virginia