Ch 5 (& Ch 6 Later) Weathering … Erosion / Deposition

Ch 5 Lesson 1 I)Weathering: breaking down!! *Mechanical processes *Chemical processes *Change objects on Earth’s surface *Over … TIME

Lesson 1 Cont. II) What do processes do to Rocks & Rock Surfaces? * BREAK *WEAR * Abrade (scrape away) *Chemically alter (makes rock easier to break down over time.)

Lesson 1 Cont. III) Results (1000’s and 1000’s of years) of the break down of rock SOIL. Sediment Size … SAND SILT CLAY (largest) (smallest)

Lesson 1 Cont. IV) Rate of weathering depends on …. 1) Surface area of rock surface. 2) Environment *Slow in cold, dry places **Faster in wet areas or areas w/ lots of freezing and thawing. 3) Type of Rock *If rock has minerals low on hardness scale – will weather quicker.

Lesson 1 Cont. V) Mechanical Weathering – Physical processes that break down ROCK. (Composition does not changed.) 4 types …. 1)Ice Wedging (most effective) *Water enters cracks (pores, any space) *Temp drops = freezing *Water expands when freezes = widens the cracks. *Process repeats = rocks breaking.

Lesson 1 Cont. 4 Types Cont. 2) Abrasion – grinding away by friction or impact. Ex) Stream carries loose fragments downstream – fragments hit each other & other rocks – eventually makes smaller & smaller pieces. Ex) Others: - Glaciers (as they move) - Wind (picks up small bits – hit against rock as moves) - Waves (picks up small bits – hit against rock as moves)

Lesson 1 Cont. 4 types … cont. 3) Plants *Grow into / thru cracks in rock *Roots absorb chemicals from rock *Makes rock weaker *Continues to grow until rock breaks 4) Animals – burrowing into soil *Causes holes that water enters. *Causes rocks to break as they dig, etc.

Lesson 1 Cont. VI) Chemical Weathering A) Changes the material that is part of the rock. *Composition, of smaller pieces, is altered – actually different from original rock. B) HOW: 3 ways ….

3 ways 1)WATER (most) – dissolve substances – move thru spaces – SLOWLY wears down. 2) Acids – enters rain thru pollutants, volcanoes, burning coal, etc. (Acid Rain – more damage than reg. rain.) 3) Oxidation – oxygen combines with other elements *Metallic minerals ….. RUST!!! *Not evenly – happens on the outside of the rock first.

Ch 5 Lesson 2: Soil Formation Rocks breaking down eventually make SOIL. I)Soil is a mixture of *weathered rock *rock fragments *decayed organic matter *water In pores (small spaces between pieces). *air

Lesson 2 Cont. II) Organic Matter *Def: once living things like … leaves, dead insects animal “potty” *Decomposes – end result is the dark colored organic matter in soil. (Humus) Good “stuff” for growing plants!

Lesson 2 Cont. III) What affects soil formation: (6) 1) Parent Material – original rock or sediment that starts forming the soil. 2) Climate affects speed. Ex) freezing / thawing /wet … 3) Topography – shape & steepness of land. - How water moves or soaks in. *Flat – water soaks in well – more dark material *Steep – water runs away – not as good.

Lesson 2 Cont. 4) Biota *Def: all organisms that live in a region. *More: speeds up soil formation process. 5) Time – soil formation is a SLOW & CONSTANT process. Soil 1000 yr. old is considered “young” soil.

Lesson 2 cont. 6) How deep the LAYERS (horizons) A Horizon: top *Part we see. *Part w/ plant growth *Darker = organic matter B Horizon: Middle *Water picks of clay particles from A and deposits them in B along w/ other material. C Horizon: Bottom *Weathered parent material (rocks / sediment)

Lesson 2 cont. Why do we care about soil formation? ? SUPPORTS life (comes from rocks ) Done w/ Ch 5 … whew! Start reviewing!

Ch 6 already Erosion / Deposition Remember … Earth’s Surface – CONSTANTLY SHAPING & RESHAPING – COMBINATION OF: Constructive Processes – like lava from volcanoes. Destructive Processes – like hurricanes, weathering …

Lesson 1 I)Reshaping Processes Weathering Erosion Deposition *Breaking down! *PICKING UP & moving*PUTTING Down *Agents: *Factors affect rate or “settling” -water -weather *ENERGY slows or -wind -climate stops & pieces -ice -topography get dropped. -type of rock *Rounding -well rounded = more erosion -poorly rounded = less erosion *Sorting – sorts by size

Lesson 1 cont. II) Interpreting Landforms A) Characteristics of Landforms (what to look for) 3 things!! 1) Structure 2) Elevation 3) Rock exposure B) Those (1-3) tell us whether Constructive or Destructive made the landform

Lesson 1 cont. III) Landforms created by Erosion (destructive) *Look for tall, jagged structures w/ cuts in rock layers. *Examples: P ) See: exposed layers of rock 2) See: unusual shapes 3) See: U shaped valleys (from glaciers) 4) See unique shapes like sea cliffs, caves, sea arches.

Pictures

Lesson 1 cont. IV) Land shapes caused by Deposition. *Characteristics – flat & low lying. Examples: 1)By WIND: gradually for deserts of sand. 2)Where Mt. streams meet Valleys = ALLUVIAL FAN (apron of deposited sediment) 3)By WATER: happens all the way along any moving water. 4)By Glaciers: leave ESKERS and MORRAINES -Which are LONG narrow deposits of sediment.

Lesson 2 Water & Wind I)Water Erosion Pause for a video on the power of water …

Lesson 2 Cont. A)Streams – how much erosion depends on ENERGY of stream. *Tell a YOUNG stream by … straighter, faster moving *Tell an OLDER stream by … CURVEY MEANDER – Large C shaped curves in stream.

3 stages of stream development 1 st stage: YOUNG – Rapid water movement – Moves downhill – Carves out V shaped valleys 2 nd stage: MATURE – Reached gentle slopes – Slows – Erodes the sides more than its bottom = starts making curves. 3 rd stage: OLD – Slows even more – More erosion on the outside of bends (curves) = water moves faster – More deposition on the inside of bends = water moves slower

Lesson 2 cont. B) Coasts – waves crash onto shore OR currents running parallel will move weathered material. C) Ground water – underground water creates CAVES. D) HUMANS – we can increase erosion by building, plowing etc. WHY?

Lesson 2 Cont. II) Wind Wind Erosion – causes ABRASION Wind Deposition – Dune: pile of windblown sand - Loess: crumble-y deposit of silt & clay

Lesson 3 Mass Wasting & Glaciers I)Mass Wasting – downhill movement of LARGE mass of rock or soil because of GRAVITY. **REMEMBER – gravity always wins!**

Lesson 3 Cont. II) 3 Types of Mass Wasting 1) Landslides – RAPID movement 2 kinds … a) Rock Fall or Rock Slide Chunks of rock or sections of rock fall down a steep area b) Mudslide *area of thick layers of loose sediment *heavy rains *thick & pasty * once it loses energy – it deposits all it is carrying.

Video / pictures video of rockslide Tenn Afganistan mud slide Why do we care about these things? KNOW WHERE AND WHAT YOU ARE BUILDING ON OR BY!!!! Gravity ALWAYS will WIN.

2) Slump – DEF: material moves down along a curved surface – Looks like: curved scar – HOW happens: Base can’t support rock & sediment. Water moves to base & weakens area. Strong layer on top of a weak layer. It slips.

Example of Slump

3) CREEP Def: sediments slowly shift down hill. Common in areas w/ freezing & thawing. EX) Leaning trees or leaning fence posts.

CREEP

Lesson 3 cont. IV) Deposition by Mass Wasting 1)Talus – pile of angular rocks and sediment after rock fall. 2)Glaciers *Large mass of ice *Moves SLOWLY across land *Picks up rock / sediment as it moves & deposits them. *Deposits are called: TILL Moraine Outwash (You can copy definition out of book.)

Lesson 3 Cont. 2) Glaciers cont. – 2 TYPES a) Alpine *most common *in mountains *moves downhill b) Ice Sheets *covers HUGE areas of land (more common during the “Ice Age”) *moves outward.

Lesson 3 Cont. 2) Glaciers cont *WEATHER AND ERODE AS THEY MOVE *SCRATCHES IN ROCKS = STRIATIONS *LAND SHAPES CAUSED BY Glacier erosion 1) Horn 2) Arete 3) Cirque 4) U shaped valley 5) Hanging valley (you look up definitions)

Glacier Feature Pictures ne_glacial_glossary/glossary.html ne_glacial_glossary/glossary.html