Erosion

process of natural forces move weathered rock and soil from one place to another

sediment

the material moved by erosion

consists of rock/soil remains plants and animals

Deposition

happens when WHERE the agents of erosion deposit (or lay down) sediment

it changes the shape of the land - like when Zander take all her toys and puts them all over the room, she acts like an agent of erosion and deposition

Weathering, erosion and deposition act together in a cycle that wears downand builds up Earth's surface

A mountain wears down in one place and new plateaus/landforms build up in other places just as those are being worn down...

Gravity

the force that moves rock and other materials DOWNHILL

Mass Movement

processthat moves sediment downhill that can be fast or slow

• landslides
• mudflows
• slump
• creep

Landslides

• most destructive 
• occur when rock and soil slide quickly down a STEEP slope

mudflows

• rapid downhill movement of WATER rock and soil
• 60% water can be seen in mixture

Slump

• a mass of rock and soil suddenly slips down a slope
• looks like someone pulled the bottom out from the under part of the slope (picture page 68)

creep :(

• very slow downhill movement of rock and soil...at a snails pace!
• caused by freezing and thawing of water in cracked layers of rock

Moving Water

major agent of the erosion that has shaped Earth's land surface

Runoff

water that moves over Earth's surface and flows in a thin layer over the land causing a type of erosion called SHEET EROSION

Don't runoff with the sheets!!

Amount of Runoff depends on 

5 Factors

more runoff =more erosion

1. amount of rain an area gets
2. vegetation (aborb water & hold soil)
3. type of soil (some aborb more water)
4. shape of land(steep slope,bad)
5. how folks use land (parking lot, farmer just cleared crops)

rills

runoff travels and forms these tiny grooves in the soil 

gully

a large groove, or channel, in the soil that carries runoff after a rainstorm

gullies only contain water after it rains

Stream

Gullies join to form this larger channel which water is continually flowing down a slope

Streams flow together and form larger bodies of flowing water called a River

Tributary

A stream or river that flows into a larger river. (the Missouri and Ohio rivers both flow into the Mississippi River,for example)

Erosion by Rivers

River Erosion creates:

• valleys
• waterfalls
• flood plains
• meanders
• oxbow lakes

V-Shaped Valley

Rivers form on steep mountains slopes and begin fast flowing straight narrow course

Erode steep slopes along river to make the deep V-shaped word we are defining.

Waterfalls

If River meet very Hard rock that erodes slowly it flows over this rock to softer rock and water tumbles over hard rock

Flood Plain

the flat, wide area of land along a river

meander

loop-like bend in the course of a river

oxbow lake

a meander that has been cut off from the river...sediments dam up the ends of the meander and the river takes a new course

Deposit by the River: Alluvial Fan and Delta

Alluvial Fan

a wide, sloping deposit of sediment formed where a stream leaves a mountain range -- the deposit is shaped like a fan

Delta

Sediment deposited where a river flows into an ocean or lake builds up this landform

Can a flood we good or beneficial?

soil on flood plains

You bet dude!  Deposit Sediment on Flood Plains is new soil that makes the river valley fertile, dense forests can grow and the soil is perfect  for growing crops

Groundwater Erosion

• water that soaks into the groundfilling the openings in the soil that trickles into cracks and spaces in layers of rock
• causes erosion though chemical weathering

Cave Formations

action of carbonic acid on limestone form stalactite and stalagmite  (remember the caves in Ireland?)

Stalactite 

a deposit that hangs like a icicle from the roof of a cave 

HOLD TIGHT TO THE TOP OF THE CAVE

Stalagmite

slow dripping buildings up cone-shaped deposits from the cave floor

LAG ON THE FLOOR

sinkhole

a layer of limestone so close to the surface that it collapses and results in a sinkhole

water power-- ENERGY

the ability to do work or cause change

Potential Energy

stored and waiting to be used later

Kinetic Energy

energy an object has due to its motion

So...Gravity pulls water down a slope, the water's potential energy changes to kinetic energy that can do work. flip for example

Merrimack River in MA falls through many rapids and waterfalls whose energy was harnessed into mechanical energy run machines that could spin thread and weave cloth!  how cool..

Water Erosion

Sediment erosed from the bottom and sides of the river.

Abrasion

the wearing away of rock by grinding action, where particles bump into streambed again and again and wear it away

load

the amount of sediment that a river carries

gravity and force of the moving water casue it to move downstream...large pieces fall to bottem and roll and slide and small pieces bounce along

What affects the speed of River and how much sediment it can erode?

1. The rivers SLOPE
2. river's VOLUME OF FLOW
3. SHAPE of river's STREAMBED

Steeper Slope=Faster River

Faster River=better Erode Power

increase water = increase volume flow

streambead shape affects amount of friction between water and streambed

hi :)

friction

force that opposes the motion of one surface as it moves across another surface and it affects the river's speed

turbulence

roughness of shallow water in big boulders increases friction and reduces the river's speed. Instead of moving downstream, the water goes 'crazy' and moves every which way in this type of movement

Glacier

any large mass of ice that moves slowly over land.  there are two kinds:

continental and valley

continental glacier

covers much of a continent or large island that today cover 10% of Earth's land (Antarctica & Greenland)

ice ages

2.5 million years ago continental glaciers covered 1/3 of the Earth's land and finally retreated 10,000 years ago

valley glacier

a long narrow glacier that forms when snow and ice build up high in a mountain valley

Glaciers and Depth of Snow/Ice

Glaciers can form only in an area when more snow falls and melts.  Once the depth of the snow and ice reaches more than 30 to 40 meters, gravity begins to pull the glacier downhill

The two processes by which glaciers erode the land

plucking and abrasion

plucking

as a glacier flows over the land it picks up rocks in this process

erosion

glaciers can carve a mountain peak into a sharp horn and grind out a V-shaped valley to form a U-Shaped Valley at the very bottom

Glacial Deposition

when a glacier melts, it deposits the sediment it eroded from the land, creating various landforms

horn

when gkacuers carve awat the sides of a mountain, the result is a horn or sharpened peak

till

mixture of sediments that a glacier deposits directly on the surface

made up of all sorts of different particles of different sizes

moraine ( sounds like migraine lol!)

the till deposited at the edges of a glacier forms this ridge

kettle ( not for tea! )

retreating glaciers form this small depression that is made when a chunk of ice is left in glacial till -- the ice melts and this is what remains

Waves

energy in waves come from wind that blows across the water's surface

they are a major force of erosion along coasts

shape the coast through erosion by breaking down rock and transporting sand and other sediment

headland

a part of the shore that sticks out into the ocean because they are made of harder rock and resist erosion

Landforms Created by Wave Erosion

wave-cut cliff

sea stack

headland

sea cave (as wave action hollows out the cliff)

sea arch (when sea caves on either side of headland join)

see page 98 for pictures

Wave shape a coast when they deposit sediment forming coastal features : 

beaches

spits

barrier beaches

beaches

area of a wave-washed sediment along a cost....sediment is mostly sand

longshore drift

as waves repeatedly hit beach sediment moved down (drifts)   the beach with the current

spit

result of a longe shore drift is the formation of a beach thatprojects like a finger out into the water -- just like the duxbury beach we drive on!!!

sandbars and barrier beaches

incoming waves carrying sand build sandbars. barrier beaches form when STORM WAVES like up HUGE amounts of sand above sea level forming a narrow isalnd parallel to the coast...kind of like a little island just off shore.

WIND!!! CAUSES SAND DUNES

 a deposit of wind-blown sand like deserts or 200 meter dunes near beaches -- think of the dunes on Westport beach!

Wind causes erosion by....

deflation

loess

Deflation (not as in the balloon!!)

the process by which wind removes sures materials (very much like bottom of river - wind blows up fine particles, bounces small particals and rolls larger ones) creates blow outs and desert pavements

Loess Deposits

Sediment finer  than sand (clay or silt) deposited in layers far from its source--- this sediment is  pronounced (LES) but spelled really CRAZY  in the term  section!!

cirque

a bowl-shaped lollow eroded by a glacier

arete

a sharpe ridge separating two cirques

u-shaped valley

a flowing glacier scoops out a u-shaped valley

fliord

forms when the level of the sea rises, filling a valley once cut by the glacier