How do weathering erosion work together to change

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 – CO 2 – 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 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 1 st 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 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