Water Erosion How do processes involving water change

Water Erosion: How do processes involving water change Earth’s surface? 1

What is the MAJOR agent of erosion that has shaped Earth’s land surface? 2

Moving water 3

Water moving over land’s surface is called runoff. 4

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

Factors that affect Runoff 1. The amount of rain an area receives. *More rain = more runoff 2. Vegetation - grasses, shrubs & trees reduce runoff. *More vegetation=less runoff 3. Type of soil - some soils absorb more water than others 4. Shape of the land – steep slopes have more run-off, which causes more erosion 5. How people use the land – parking lots & crop removal increase run-off. 6

Runoff overtime: How does runoff over time affect the land water? 7

Rills & Gullies As runoff travels across the soil, rills form. Rills are tiny grooves in the soil that grow larger forming gullies. A gully is a large groove or channel in the soil that carries runoff after a storm. It moves soil & rocks. Rills & Gullies only contain water after it rains. 8

Streams & Rivers 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. 9

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Rill, Rill erosion at a construction site. Image by M. Mamo, Labels added by UNL Gully, Stream Gully erosion in a pasture. Image by NRCS Stream 11

Tributaries 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. 12

Rivers: * cause erosion and create valleys, waterfalls, flood plains, meanders and oxbow lakes. *form on steep mountain slopes. 13

How do they flow? Quickly and follow a narrow path How do they erode? Rapidly The result is that rivers form deep, V-shaped valleys. 14

Valleys http: //www. google. com/imgres? imgurl=http: //cgz. e 2 bn. net/e 2 bn/leas/c 99/schools/cgz/accounts/staff/r chambers/Geo. Bytes%2520 GCSE%2520 Blog%2520 Resources/Images/Rivers/Vshapedvalley. jpg&imgrefurl=http: //geobytesgcse. blogspot. com/2006/11/upper-course-of-river-v-shapedvalleys. html&usg=__Hp 8 C 8 YOunb. Wz. Jy 9 E 7 kb. Qc. Oi. URz. A=&h=308&w=411&sz=47&hl=en&start=0&zoom=1 &tbnid=giw. F 1 Fpp. YFy 8 z. M: &tbnh=116&tbnw=154&ei=kk 2 Tf. Kt. EMH 68 Ab. I__2 t. BA&prev=/images%3 Fq%3 Dvshaped%2 Bvalley%26 um%3 D 1%26 hl%3 Den%26 sa%3 DN%26 biw%3 D 1280%26 bih%3 D 531%26 tbs%3 Disch: 10%2 C 35&um=1&itbs=1&iact=hc&vpx=247&vpy=77&dur=701&hovh=194&hovw=259&tx=161&ty=116&o ei=g 0 k 2 Tb. G 1 L 4 T 58 Aa 8 n. OC 7 Aw&esq=12&page=1&ndsp=22&ved=1 t: 429, r: 1, s: 0&biw=1280&bih=531 http: //images. travelpod. com/users/theboy_picot/3. 1149265860. 580 x-nice-v-shapedvalley. jpg 15

Features of rivers: What features are formed by erosion along a river? 16

Waterfalls Occur where? Where a river meets an area of hard & slowly eroding rock Then flows over softer rock downstream. How does softer rock erode? The softer rock erodes away faster. What results from this erosion? A waterfall develops. 17

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=__k. BYWa. Wcel. Jl. Cs. NAEDq 6 zr 8 e. LY=&h=599&w=800&sz=162&hl=en&start=5&um=1&tbnid=WO 5 G 4 j. C_r. IKDMM: &tbnh=107&tbnw=143&prev=/images%3 Fq%3 Dminnehaha%2 Bfalls, %2 B 18 mn%26 ndsp%3 D 18%26 hl%3 Den%26 sa%3 DG%26 um%3 D 1

Flood Plain 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. 19

Flood Plain 20

Meanders 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. 21

Mississippi River Meanders http: //images. google. com/imgres? imgurl=http: //www. ecology. info/img/Mississippi. River. jpg&imgrefurl=http: //www. ecology. info/article. aspx%3 Fcid%3 D 12%26 id%3 D 10&usg=__B 9 Cvp. JJ 70 Ydm 7 HE 2 Lj. Hs 3 GW 76 Ec=&h=450&w=600&sz=57& hl=en&start=8&tbnid=Q 3 zaqd. FNmc 7 QVM: &tbnh=101&tbnw=135&prev=/images%3 Fq%3 Dmeanders%26 gbv%3 D 2%26 hl%3 Den%26 sa%3 DG 22

Oxbow Lakes What is an oxbow lake? A meander that has been cut-off from the river. They may form when a river floods as high water finds a straighter path downstream. As flood waters fall, sediments dam up the ends of the meander and a lake forms. 23

Oxbow Lakes http: //muller. lbl. gov/travel_photos/Amazon. Web. Pages-Images/1. jpg 24

Alluvial Fan • Where a stream flows out of a steep, narrow mountain valley, the stream suddenly become wider and shallower. The water slows down. The sediments continue moving creating a fan shape. 25

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Delta • A river ends its journey when it flows into a still body of water, such as an ocean or a lake. Because the river water is no longer flowing downhill, the water slows down. At this point, the sediment in the water drops to the bottom. Sediment deposited where a river flows into an ocean or lake builds up a landform called a delta. • Deltas can be a variety of shapes. 27

Ground Water Erosion • Groundwater is the term geologists use for the underground water. Like running water on the surface, groundwater affects the shape of the land. • Groundwater can cause erosion through a process of chemical weathering. When water sinks into the ground, it combines with carbon dioxide to form a weak acid, called carbonic acid. 28

Carbonic Acid • Carbonic acid can break down limestone. • Groundwater containing carbonic acid flows into cracks in the limestone. The limestone changes chemically and is carried away in a solution of water. • This gradually hollows out pockets in the rock. Over time, these pockets develop into large holes underground, called caves or caverns. 29

Stalactites and Stalagmites • carbonic acid on limestone can also result in deposition. • Water containing carbonic acid and calcium from limestone drips from a caves roof. As the water evaporates, a deposit of calcite forms. • A deposit that hangs like an icicle from the roof of a cave is called a? • Stalactite. • Slow dripping builds up on the cave floor is called a? • Stalagmite. 30

Karst Topography • A landscape that is characterized by numerous caves, sinkholes, and underground streams. • Karst topography usually forms in regions of plentiful rainfall where bedrock consists of rock, such as limestone, that is easily dissolved. 31

Sink Hole 32