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Mrs. Wright Hugh B. Bain Middle School Cranston, RI SLOW Processes that Shape the Earth PART 2. EROSION.

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Presentation on theme: "Mrs. Wright Hugh B. Bain Middle School Cranston, RI SLOW Processes that Shape the Earth PART 2. EROSION."— Presentation transcript:

1 Mrs. Wright Hugh B. Bain Middle School Cranston, RI SLOW Processes that Shape the Earth PART 2. EROSION

2 Earth - developed over long periods of time through continual change processes. STUDENTS: Evaluate slow processes of 1) weathering 2) erosion and 3) mountain building. The following slides are on erosion. Determine how the earth has changed and will continue to change over time.

3 EROSION Process by which natural forces or agents (wind, water, ice, or gravity) move weathered rock and soil from one place to another Sediment Deposition Material moved by erosion (pieces of rock, soil, plant, & animal) Occurs where agents of erosion deposit sediment & changes shape of land cover0116 ‑ sediment.jpg creek edge showing tiers of sediment deposition & gravel

4 Causes of Erosion 1. Gravity 2. Running Water 3. Glaciers 4. Waves 5. Wind

5 What is gravity ? Force that moves rock and other materials downhill causing mass movement 1. Gravity

6 Types of Mass Movement Caused by Gravity A. Landslides B. Mudflows C. Slump D. Creep

7 A.a FAST Process LandslidesLandslides Occurs when rock & soil slide quickly down a steep slope Most destructive landslide.jpg In my earlier post, we discussed the causes of landslides.

8 B. a FAST Process MudflowsMudflows ueol_02_img0070.jpgueol_02_img0070.jpg Rapid downhill movement of a mixture of water, rock, & soil

9 C. a FAST Process Slump Mass of rock & soil suddenly slips down a slope in one large mass (often when water soaks bottom of clay soil) slump1.jpgslump1.jpg Slump at Double Ditch - April, 1988 (Burleigh County, N.D.) more mass...

10 D. Creep Very slow downhill movement of rock & soil (often from freezing & thawing of water in cracked layers of rock beneath soil creep_kathryn1.jpgcreep_kathryn1.jpg

11 Major agent of erosion that shaped Earth’s land surface 2. Running Water splash_eriosion.jpgsplash_eriosion.jpg Raindrop Raindrops loosen soil & carry particles.

12 Runoff Water that runs over the Earth’s surface runoff.jpg Surface runoff

13 Forms of Runoff (smallest to largest): Rills → Gullies → Streams → Rivers → Lake

14 Running Water - Runoff Rill → rill.jpg

15 Gully → runoff ‑ jpg A channel with water only after it rains

16 Stream → 9907_05_15 ‑‑‑ Stream_web.jpg9907_05_15 ‑‑‑ Stream_web.jpg Stream

17 River → falls ‑ river ‑ towards ‑ sheep ‑ falls.jpgfalls ‑ river ‑ towards ‑ sheep ‑ falls.jpg rivers

18 Lake → Vg ‑ 025.jpgVg ‑ 025.jpg large lake

19 Rivers Through erosion, rivers can create a variety of features falls ‑ river ‑ towards ‑ sheep ‑ falls.jpg rivers

20 River Features A. Valleys B. Waterfalls C. Floodplains D. Meanders E. Oxbow lakes

21 A. Valley Elongated low area between hills formed by a stream _87b9bf351d.jpg Kullu Valley's Beas River formed...

22 B. Waterfall Occur where a river meets rock that erodes slowly & flows over softer rock downstream waterfallLG.jpg Largest waterfall in Lesotho, Africa

23 C. Floodplain Flat, wide area of land along river. Lower down on its course where land slopes gently, river spreads out forming a river valley Floodplains here floodplain.jpgfloodplain.jpg floodplain

24 D. Meander Loop-like bend in the river (S shape - Mississippi) meander_word_picture.jpgmeander_word_picture.jpg Meandering

25 E. Oxbow Lake Meander that has been cut off from the river Horseshoe shape Oxbow_lake,Yamal_Peninsula,Russia.JPG

26 Oxbow Lake During a flood, high water finds a straighter pass downstream As water falls, sediments dam up ends of meander Forming an Oxbow jpg Oxbow Lakes Kentucky, United States...

27 What are glaciers? Any large mass of ice that moves slowly over land 3. Glaciers

28 Types of Glaciers A. Continental Glaciers B. Valley Glaciers

29 A. Continental Glacier Covers much of a continent Flow in all directions as they move (like pancake batter in frying pan) In distant past – covered one third of Earth’s land Have advanced, then retreated (last time - 10,000 yrs ago), or melted back, several times ContinentalIce.jpgContinentalIce.jpg The Continental Ice Sheet is the most significant of all the glacial agents...

30 B. Valley Glacier Long & narrow glacier Forms when snow & ice build up high in a mountain valley Sides of mountain keep them from spreading out in all directions Usually move down valleys already cut by rivers Much smaller than continental glaciers Tidewater ‑ Glacier.jpgTidewater ‑ Glacier.jpg There are an estimated valley glaciers

31 Processes of Glacial Erosion A. Plucking B. Abrasion

32 A. Plucking Glacier picks up rocks as it flows over land; Rock fragments & boulders freeze to glacier bottom & are carried _75mhadaidh.jpg PLUCKING – a type of erosion.

33 B. Abrasion Many rocks remain on bottom & get dragged along Gouges & scratches bedrock striations.jpgstriations.jpg Abrasion sometimes results in striations (scratches on the bedrock)…

34 Landforms from Glacial Deposition A. Till B. Moraine C. Kettle

35 A. Till Mixture of sediments (sand, silt, clay, boulders) deposited directly on surface till2.gif Area adjacent to Sherman glacier is covered with a coarse glacial till.

36 B. Moraine Till deposited at edges of glacier form ridge (Long Island, NY) 03 river ‑ thumb ‑ 608x456.jpg Much of New York's Long Island was once the...

37 C. Kettle Depression formed when ice is left in glacial till When ice melts, kettle remains forming ponds or kettle lakes kettle1.gifkettle1.gif The largest kettle shown is ~ 150 feet in diameter. Bering Glacier flows...

38 Form from wind that blows across water’s surface Shape coast through erosion by breaking down rock & transporting sand & other sediment. 4. Waves

39 Landforms Created by Wave Erosion A. Headland B. Sea Arch C. Sea Cave D. Sea Stack E. Wave Cut Cliff

40 A. Headland Part of shore sticks out into ocean Made of hard rock that resists erosion longer headland_soldiers_rock.jpg Headland right of Soldier's Rock

41 B. Sea Arch sea ‑ arch ‑ volcan oes ‑ national.jpg Sea arch - Volcanoes National Park ‑ 045.jpg Ilena in her kayak going through a sea arch(cave) the_other_way sea ‑ arch.jpg Sea arch, Tutukaka, New Zealand. Poor Knights Islands

42 C. Sea Cave Folga Skerry.jpg Sea Caves → Sea+Cave.jpg Just one of many sea caves seen on the trip. ↓ Sand Island Sea Caves. jpg Madeline Island Sea Caves. Top Canoe destination in the world,... ↓

43 D. Sea Stack Climbers_on_the_450ft_Sea_Stack_Old _Man_Of_Hoy,_Orkney.jpg Climbers on the 450ft sea stack Old Man Of Hoy, Orkney IMG_3180.jpgIMG_3180.jpg Sea Stacks

44 E. Wave Cut Cliff calif_wavecutcliff.jpgcalif_wavecutcliff.jpg wave cut cliff

45 Deposits by Waves A. Beach B. Longshore Drift C. Sandbar D. Barrier Beach

46 A. Beach EastBeach2.JPG East Beach...

47 B. Long Shore Drift Waves repeatedly hit beach, beach sediment moves down beach with current spit – beach that projects out like a finger result of longshore process CapeFear.jpgCapeFear.jpg longshore drift. dungeness ‑ spit.jpg Dungeness Spit, Straight of Juan de Fuca

48 C. Sand Bar Long ridges of sand parallel to shore Australia_Lakeland_Island_Sand_Bar.jpg 735 × Lakeland Island Sand Bar

49 D. Barrier Beach Form when storm waves pile up large amounts of sand forming long, narrow island parallel to coast 14.jpg Gravel barrier beach, Coombs Cove, Hermitage Peninsula.

50 Wave Terms A. Impact B. Abrasion

51 A. Impact Large waves hit rocks with force & break apart rocks stock ‑ photo ‑ small ‑ wave ‑ impact ‑ stone ‑ jpg small wave impact stone

52 B. Abrasion Wave in shallow water picks up sediment that hits land where it wears away at rock coast.jpg AbrasionWave Pounding

53 5. Wind

54 Wind causes erosion by: A. Deflation B. Abrasion

55 A. Deflation Process where wind removes surface materials deflation_sm.jpg deflation

56 B. Abrasion May polish rocks but causes little erosion rock_wind_abrasion_p _NRCS.jpg Figure 20.4 Rock sculpted by wind, Utah. Courtesy NRCS

57 Deposition Forms: A. Sand Dunes B. Loess Deposits

58 A. Sand Dunes egypt ‑ sand ‑ dunes ‑ ‑ ga.jpg Photo: Sand dunes... photography.nationalgeo

59 B. Loess Deposits Very fine sediment made up of silt & clay so it travels far D015 ‑ 060.jpg Loess Deposits

60 Looking at the SLOW process of erosion just discussed, how has the earth changed over time? Is it still changing? How do you know? Give at least three examples.

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