How do weathering & erosion work together to change the shape of Earth’s surface?

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?

• 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?

• 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?

• 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 LandfillNew York City

Burying Trash

• PROS– Can be used for parks

• CONS– Pollute groundwater– Pollute soil– They eventually fill to

capacity

Landfill: holds solid waste

Burning Trash

• 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

Incineration: burning of solid waste

Recycling TrashRecycling: 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