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Chap 3 Erosion and Deposition
Erosion, the Course of a River, Glacier, Wind
72
Science
8th Grade
12/15/2011

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Term

Erosion

Definition

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

Term

sediment

Definition

the material moved by erosion

 

consists of rock/soil remains plants and animals

Term

Deposition

Definition

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

Term

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

Definition

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

 

Term

Gravity

Definition

the force that moves rock and other materials DOWNHILL

Term

Mass Movement

Definition

processthat moves sediment downhill that can be fast or slow

  • landslides
  • mudflows
  • slump
  • creep
Term

Landslides

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

mudflows

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

Slump

Definition
  • 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)
Term

creep :(

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

Moving Water

Definition

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

Term

Runoff

Definition

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!!

Term

Amount of Runoff depends on 

5 Factors

more runoff =more erosion

Definition
  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)
Term

rills

Definition

runoff travels and forms these tiny grooves in the soil 

Term

gully

Definition

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

 

gullies only contain water after it rains

Term

Stream

Definition

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

Term

Tributary

Definition

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

Term

Erosion by Rivers

Definition

River Erosion creates:

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

V-Shaped Valley

Definition

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.

Term

Waterfalls

Definition

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

 

 

Term

Flood Plain

Definition

the flat, wide area of land along a river

Term

meander

Definition

loop-like bend in the course of a river

Term

oxbow lake

Definition

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

Term

Deposit by the River: Alluvial Fan and Delta

 

Alluvial Fan

Definition

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

Term

Delta

Definition

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

Term

Can a flood we good or beneficial?

soil on flood plains

Definition

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

Term

Groundwater Erosion

Definition
  • 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
Term

Cave Formations

Definition

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

Term

Stalactite 

Definition

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

HOLD TIGHT TO THE TOP OF THE CAVE

Term

Stalagmite

Definition

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

LAG ON THE FLOOR

Term

sinkhole

Definition

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

Term

water power-- ENERGY

Definition

the ability to do work or cause change

Term

Potential Energy

Definition

stored and waiting to be used later

Term

Kinetic Energy

Definition

energy an object has due to its motion

 

Term

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

Definition

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..

Term

Water Erosion

Definition

Sediment erosed from the bottom and sides of the river.

Term

Abrasion

Definition

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

Term

load

Definition

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

Term

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

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

Steeper Slope=Faster River

Faster River=better Erode Power

 

increase water = increase volume flow

 

streambead shape affects amount of friction between water and streambed

 

 

Definition

hi :)

Term

friction

Definition

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

Term

turbulence

Definition

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

Term

Glacier

Definition

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

continental and valley

Term

continental glacier

Definition

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

Term

ice ages

Definition

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

Term

valley glacier

Definition

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

Term

Glaciers and Depth of Snow/Ice

Definition

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

Term

The two processes by which glaciers erode the land

Definition

plucking and abrasion

Term

plucking

Definition

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

Term

erosion

Definition

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

Term

Glacial Deposition

Definition

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

Term

horn

Definition

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

Term

till

Definition

mixture of sediments that a glacier deposits directly on the surface

 

made up of all sorts of different particles of different sizes

Term

moraine ( sounds like migraine lol!)

Definition

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

Term

kettle ( not for tea! )

Definition

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

Term

Waves

Definition

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

Term

headland

Definition

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

Term

Landforms Created by Wave Erosion

Definition

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

Term

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

Definition

beaches

spits

barrier beaches

Term

beaches

Definition

 

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

Term

longshore drift

Definition

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

Term

spit

Definition

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!!!

Term

sandbars and barrier beaches

Definition

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.

Term

WIND!!! CAUSES SAND DUNES

Definition

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

Term

Wind causes erosion by....

Definition

deflation

loess

Term

Deflation (not as in the balloon!!)

Definition

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

Term

Loess Deposits

Definition

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!!

Term

cirque

Definition

a bowl-shaped lollow eroded by a glacier

Term

arete

Definition

a sharpe ridge separating two cirques

Term

u-shaped valley

Definition

a flowing glacier scoops out a u-shaped valley

Term

fliord

Definition

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

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