Water Erosion: How do processes involving water change Earth s surface?

Water Erosion: How do processes involving water change Earth s surface?

What is the MAJOR agent of erosion that has shaped Earth s land surface? Moving Water (Water Erosion)

Water moving over land s surface is called runoff. This may cause sheet erosion.

The amount of water runoff in an area depends on 5 main factors:

1. The amount of rain an area receives. 2. Vegetation - grasses, shrubs & trees reduce runoff 3. Type of soil - some absorb more water than others 4. Shape of the land steep slopes has more run-off, which causes more runoff 5. How people use the land parking lots & crop removal increase run-off

Runoff overtime: How does runoff over time affect the land and water? It can create: ~rills (tiny grooves in the soil) ~gullies (rills that enlarge to become deeper channels).

* Gullies join together to form a larger channel called a stream. Water continuously flows here and rarely dries up. Small streams may be called creeks or brooks. Small streams flow together to form a large stream called a river.

* Rill erosion at a construction site. Image by M. Mamo, Labels added by UNL Gully erosion in a pasture. Image by NRCS Stream

* Streams grow together by getting water from tributaries. A tributary is a stream or river that flows into a larger river. An example: The Missouri & Ohio rivers are tributaries of the Mississippi river. Tributaries collect their water from the drainage basin or watershed.

* http://images.google.com/imgres?imgurl=http://knol.google.com/k/-/-/3ajhc7zrwtav1/c1ssz4/figure-1%2520(2).bmp&imgrefurl=http://knol.google.com/k/new- orleans-the-geologic-difficulties-with-the-big-easy-part-1&usg= SPqqMAUDGF2VVgD-x0Wwvs- 5xk=&h=394&w=432&sz=31&hl=en&start=5&um=1&tbnid=ShJceJzlrtYlWM:&tbnh=115&tbnw=126&prev=/images%3Fq%3DMississippi%2Briver%2Band%2Bits%2 Btributaries%26hl%3Den%26um%3D1

Rivers cause erosion and create valleys, waterfalls, flood plains, meanders and oxbow lakes. Rivers form on steep mountain slopes.

How do they flow? Quickly & follow a narrow path How do they erode? Rapidly The result is that rivers form deep, V-shaped valleys.

* http://www.google.com/imgres?imgurl=http://cgz.e2bn.net/e2bn/leas/c99/schools/cgz/accounts/staff/r chambers/geobytes%2520gcse%2520blog%2520resources/images/rivers/vshapedvalley.jpg&imgrefurl=http://geobytesgcse.blogspot.com/2006/11/upper-course-of-river-v-shapedvalleys.html&usg= Hp8C8YOunbWzJy9E7kbQcOiURzA=&h=308&w=411&sz=47&hl=en&start=0&zoom=1 &tbnid=giwf1fppyfy8zm:&tbnh=116&tbnw=154&ei=kk2tfktemh68abi 2tBA&prev=/images%3Fq%3Dvshaped%2Bvalley%26um%3D1%26hl%3Den%26sa%3DN%26biw%3D1280%26bih%3D531%26tbs%3Disch: 10%2C35&um=1&itbs=1&iact=hc&vpx=247&vpy=77&dur=701&hovh=194&hovw=259&tx=161&ty=116&o ei=g0k2tbg1l4t58aa8noc7aw&esq=12&page=1&ndsp=22&ved=1t:429,r:1,s:0&biw=1280&bih=531 http://images.travelpod.com/users/theboy_picot/3.1149265860.580x-nice-v-shapedvalley.jpg

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Occur where? * Where a river meets an area of hard & slowly eroding rock Then flows over softer rock downstream. How does softer rock erode? What results from this erosion? The softer rock erodes away faster & a waterfall develops.

* Waterfalls at the Plitvicka Jezera National Park in Croatia Minnehaha Falls, Minneapolis Minnesota http://images.google.com/imgres?imgurl=http://realestate-inminnesota.com/images/minneapolis.jpg&imgrefurl=http://realestate-inminnesota.com/&usg= kby- WaWcelJlCsNAEDq6zr8eLY=&h=599&w=800&sz=162&hl=en&start=5&um=1&tbnid=WO5G4jC_rIKDMM:&tbnh=107&tbnw=143&prev=/images%3Fq%3Dminnehaha%2Bfalls,%2B mn%26ndsp%3d18%26hl%3den%26sa%3dg%26um%3d1

What is a flood plain? A wide valley in which a river flows What happens to the land during a flood? The water in the river over flows its banks into this wide river valley area. *

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* What are meanders? Loop-like bends in the course of a river. Where & how do they occur? They occur as the outer bank of a river is eroded & deposits are dropped on the inner bank of the bend in a river.

Example: The southern stretch of the Mississippi River meanders on a wide, gently sloping flood plain area.

* http://images.google.com/imgres?imgurl=http://www.ecology.info/img/mississippi- River.jpg&imgrefurl=http://www.ecology.info/article.aspx%3Fcid%3D12%26id%3D10&usg= B9CvpJJ70Ydm7HE2LjHs3GW76Ec=&h=450&w=600&sz=57& hl=en&start=8&tbnid=q3zaqdfnmc7qvm:&tbnh=101&tbnw=135&prev=/images%3fq%3dmeanders%26gbv%3d2%26hl%3den%26sa%3dg

Deposits by rivers are made as the water slows down and the fine particles settle in the river bed. Larger stones quit rolling and sliding.

Deposits by Rivers: What features result from deposition along a river?

An Alluvial Fan is a wide, sloping deposit of sediment formed where a stream leaves a steep, narrow mountain valley range. This deposit is shaped like a fan. *

* http://images.google.com/imgres?imgurl=http://www.windows.ucar.edu/earth/geology/images/alluvial_fan_lg.jpeg&imgrefurl=http://www.geol.umd.edu/~jmerck/geo l100/lectures/29.html&usg= VqWMw_HzDv3NLfoFn6sm1k93LcI=&h=341&w=512&sz=65&hl=en&start=2&um=1&tbnid=U5ue3WUHzgtnSM:&tbnh=87&tbnw=131&pre v=/images%3fq%3dalluvial%2bfan%26hl%3den%26sa%3dn%26um%3d1

Deltas form when sediments are deposited where a river flows into an ocean or a lake. This landform is built up as the sediments drop. *

http://www.dmcii.com/disasters/new_orleans/mississippi_delta.jpg *

Groundwater Erosion: What results from water seeping into the ground & mixing with CO 2?

Not all rain water evaporates or becomes runoff. How does water get underground? Water soaks into the ground, filling openings in the soil and trickling into cracks & spaces in layers of rock.

Groundwater causes which type of erosion? Chemical weathering What acid forms when carbon dioxide & water combine? Carbonic Acid This weak acid can break down limestone that will gradually hollow out pockets in the rock. Over time, the pockets develop into large holes called caves or caverns.

Cave Formations: What are the features found in a cave? How do they form?

What are stalactites? Calcite deposits that hang from the cave s roof like icicles What are stalagmites? Cone-shaped calcite deposits that build up from the cave floor

* http://www.georgiaencyclopedia.org/nge/article.jsp?id=h-2130 http://www.georgiaencyclopedia.org/nge/article.jsp?id=h-2130

Karst Topography: What happens when land rich in limestone is weathered by groundwater?

A type of landscape that is created in a region where a layer of limestone near the surface forms deep valleys, caverns and sinkhole *

* http://www.virginiacaves.org/lok/ccvup56.jpg

Karst Topography http://4.bp.blogspot.com/_jrp7tjwtx4a/s8z8b2hemvi/aaaaaaaaavk/h0mjosaroq0/s320/karst_cave.jpg