Transcript How do weathering & erosion work together to change the

How do weathering & erosion work
together to change the shape of Earth’s
surface?
Erosion
• The movement of rock particles by wind,
water, ice, or gravity
Weathering
• The process that breaks down rock &
other substances on Earth’s surface
2 types of weathering:
• Mechanical
• Chemical
Mechanical Weathering
• Rock is physically broken into smaller
pieces
• By the process of:
– Freezing & thawing
– Release of pressure
– Growth of plants
– Actions of animals
– Abrasion
Mechanical weathering can wear away more
than whole rock…
New mechanical
weathering terms:
• Abrasion: grinding away of rock by rock
particles carried by water, ice, wind, or
gravity
• Ice wedging: wedges of ice in rocks widen
& deepen cracks
Chemical Weathering
• Breaks rocks down through chemical
changes
• By the process of:
– Water
– Oxygen
– CO2
– Living organisms
– Acid Rain
Water…
• The most important chemical agent
• Water weathers rock by dissolving it
How does water assist in
weathering & erosion?
• Runoff: all the remaining water that moves
over Earth’s surface
– It picks up soil particles as it moves across the
land
Rills
• Tiny grooves in the soil caused from runoff
Gullies
• Large grooves, or channel, in the soil the
carries runoff after a storm
• They flow only after it rains
Stream
• Channel in which water flows in constantly
Tributary
• A stream that flows into a larger stream
River
• A large stream
• Rivers erosion creates:
– valleys
– waterfalls
– flood plain
– meanders
– oxbow lakes
Valley
Waterfalls
Flood Plain
• Flat, wide area of land that runs along side
a river
Meander
• Looplike bend in the course of a river
Oxbow Lake
• A meander that has been cut off from the
river
River Deposits
• Water moves sediments & rocks with it
depositing them elsewhere
• River deposits create landforms like:
– Alluvial fans
– Deltas
– Soil on a flood plains
Alluvial Fan
• Wide, sloping deposit of sediment formed
where a stream leaves a mountain range
Delta
• Sediment deposited where a river flows
into an ocean
• Can be shaped like an arc, triangular,
bird’s foot
How do sediments enter rivers &
streams?
• Most washes or falls into the river as a
result of mass movement or runoff
• Other sediments erode from the bottom or
sides of the river
Abrasion
• Wearing away of rock by a grinding action
• Boulders become smaller and smaller as
they move down a streambed
How much sediment can a river
carry?
• A load!
• Load: the amount of sediment that a river
carries
Groundwater can create erosion
too!
• Groundwater: underground water
• Stalactite: a calcite deposit that hangs like
an icicle from the roof of a cave
• Stalagmite: cone shaped calcite deposit
growing up from the cave floor
What does the amount of runoff
depend on?
• 5 factors determine the amount of runoff
an area receives:
– Amount of rainfall
– Vegetation
– Type of soil
– Shape of land
– How people use land
How does ice change the shape of
the land?
• Glaciers: large mass of ice that moves
slowly over land
• 2 kinds:
– Valley
– continental
Valley Glacier
• Long, narrow glacier that forms when
snow & ice build up high in a mountain
valley
Continental Glaciers
• Glacier that covers much of a continent or
island
• Much larger than valley glaciers
• They cover @ 10% of Earth
How do glaciers form?
• They form in areas where more snow falls
than melts
• Snow builds up over time
• The pressure compacts the snow into ice
How do glaciers move?
• Gravity!
• Valley glaciers flow a few cm-a few meters
each day
• Continental glaciers flow in all directions
How do glaciers change the land?
• Glaciers erode the land through 2
processes called plucking & abrasion
Plucking
• When a glacier flows over land, it picks up
rocks in the process
• Rock fragments freeze to the bottom of the
glacier
Abrasion
• As the glacier drags the rocks across the
land it gouges & scratches the bedrock
What is glacial deposition?
• When the glacier melts, it deposits the
sediment it eroded from the land creating
various landforms
– Moraine
– Prairie pothole
– Kettle Lake
Moraine
• A ridge formed by the till deposited at the
edge of a glacier
Kettle
• A small depression that forms when a
chunk of ice is left in glacial till
Wave Erosion
Wind Erosion
How does gravity assist in
weathering & erosion?
• Gravity: a force that moves rocks & other
materials downhill
• Gravity causes mass movement
• Mass Movement: any type of process that
moves sediment downhill
– Ex: landslides, slump, mudflows, creep
Landslides
• Most destructive kind
• Occurs when rock & soil slide quickly
down a steep slope
• Caused by earthquakes, roadwork
Slump
• A mass of rock& soil that suddenly slips
down a slope
Mudflows
• Rapid, downhill movement of a mixture of
water, rock, & soil
• Amount of water can be as much as 60%
• Can occur during heavy rains or
earthquakes
Creep
• Very slow downhill movement of rock &
soil
• It’s barely noticeable
• It can tilt telephone poles, fenceposts, or
gravestones in weird ways
At what rate does rock weather?
• Depends on type of rock & climate
Type of rock
• Permeable: material is full of tiny,
connected air space that allow water to
seep through it
Climate
• Average weather conditions in an area
• Chemical & Mechanical weathering occurs
faster in wet climates
• Chemical reactions occur faster in higher
temperatures
What is soil?
• Soil is loose, weathered material on
Earth’s surface
How does soil form?
• It forms when rock that is broken down by
weathering mixes with other materials on
the surface
• Soil is constantly formed where bedrock
(layer of rock beneath the dirt) is exposed
What’s in the soil?
• Soil is a mixture of rock particles, minerals,
dead stuff, air, & water
• Type of rock depends on bedrock &
weathering
• Humus: dark substance that forms as
plant & animal remains decay
How does the soil feel?
• Sand is gritty while clay is smooth
• Texture depends on size of individual soil
particles
• Texture is important for plant growth
• Largest to smallest:
– Gravel
– Sand
– Silt
– Clay
Loam
• Soil made of equal parts of clay, sand, &
silt
• Holds both water & air
• Best for growing most types of plants
What is a soil horizon?
• Layer of soil that differs in color & texture
from the layers above or below it
• Soil is divided into 4 horizons:
– Horizon A-Topsoil: dark brown, crumbly layer
– Horizon B-Subsoil: clay, little humus, particles
– Horizon C-Parent Material: partly weathered
rock
– Horizon D-Bedrock: large pieces of rock`
What lives in the soil?
• Organisms make space in the soil for air &
water
– Ex: mice, ants, snails, beetles, worms, lots of
plants
What do these organisms do to the
soil?
• Plants shed leaves which is called litter
• Litter & dead plants become part of the
soil
• The organisms living there turn the dead
organic stuff into humus
• This process is called decomposition
– Decomposers: organisms that break down the
remains of dead organisms
– Ex: fungi, bacteria, worms
Is the soil in Montana the same as
in Georgia?
• NO!
• Soil is classified into groups according the
climate, plants, composition
• 7 groups: tundra, n. forest, prairie,
mountain, s. forest, desert, tropical
How do people use soil?
• Agriculture, development, mining,
recreation
Is soil important to me & you?
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YES!
Everything needs soil
It’s a renewable resource
However it can take a long time for new
soil to form
How is our soil being damaged?
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Overused
Polluted
Eroded away
Desertification: the advance of desertlike conditions in an area due
– Caused by climate change, overgrazing, cutting down trees
What was the Dust Bowl?
• 1930’s
• Most of the Great Plains had been turned
into farm or ranch land
• This caused the topsoil to dry out and dust
to form
• Lots of people moved away abandoning
their farms
What does it mean to conserve
soil?
• Soil conservation: the management of soil
to prevent its destruction
What are some ways to conserve
soil?
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Crop rotation
Contour plowing
Conservation plowing
Windbreaks
Terracing
Is it possible to restore destroyed
land?
• Yes!
• Land reclamation: restoring an area of
land to a more natural, productive state
Where does our trash go?
• In the soil!
Municipal Solid Waste
• Waste materials produced in homes,
businesses, and other places in a
community
• 3 ways of handling solid waste:
– Bury it
– Burn it
– Recycle it
Staten Island Landfill
New York City
Burying Trash
Landfill: holds solid waste
• PROS
– Can be used for parks
• CONS
– Pollute groundwater
– Pollute soil
– They eventually fill to
capacity
Burning Trash
Incineration: burning of solid waste
• PROS
-Doesn’t take up as much
space as a landfill
-Doesn’t pollute
groundwater
-Heat produced can be
changed into electricity
• CONS
– Pollute the air
– Some waste still
remains
– More expensive than
landfills
Recycling Trash
Recycling: process of reclaiming of reusing raw materials
• PROS
– Conserves
nonrenewable
resources
– Inexpensive
– Saves trees
– Can be used to make
other products
• CONS
– You can’t recycle
everything
What can you do to help?
• Reduce, Reuse, & Recycle
– Reduce: create less waste in the 1st place
– Reuse: reuse items in your house
– Recycle: take your recycling to a local center
where they can break it down & make new
things from it
The Decomposition Times we used were:
•Glass Bottles/Jars 1,000,000 years
•Aluminum Cans 80-100 years
•Plastic Bags 10-20 years
•Plastic Coated Paper 5 years
•Orange and Banana Peels 2-5 weeks
•Newspaper 2-4 weeks