WEATHERING AND EROSION

Weathering THE BREAKDOWN OF ROCKS AT OR NEAR THE SURFACE OF THE EARTH  PHYSICAL WEATHERING THE BREAKDOWN OF ROCK INTO SMALLER PIECES WITHOUT CHEMICAL CHANGE

ICE WEDGING (FROST ACTION) WATER HELD IN THE CRACKS OF ROCKS WEDGES THE ROCK APART WHEN IT FREEZES ROOT WEDGING (PLANT ACTION) TINY ROOTS GROW INTO CRACKS IN THE ROCK AND THEN AS THE ROOT GROWS THE ROCK SPLITS

EXFOLIATION WHEN LARGE MASSES OF ROCK, MAINLY IGNEOUS, ARE LIFTED UP TO THE SURFACE THE RELIEF OF OVERLYING PRESSURE CAUSES THE ROCK TO EXPAND. UPWARD EXPANSION LEADS TO CURVED BREAKS WHICH MAY PEEL OFF IN LAYERS

CHEMICAL WEATHERING OXIDATION THE BREAKDOWN OF ROCK THROUGH A CHANGE IN MINERAL OR CHEMICAL COMPOSITION OXIDATION THE CHEMICAL REACTION OF OXYGEN WITH OTHER SUBSTANCES. IRON IS MOST EASILY ATTACKED RESULTING IN RUST (IRON OXIDES)

CARBONIC ACID WHEN CARBON DIOXIDE DISSOLVES INTO WATER. IT DISSOLVES MANY COMMON MINERALS

MINERALS RESISTANCE TO WEATHERING DIFFERENT MINERALS AND ROCKS HAVE DIFFERENT PHYSICAL AND CHEMICAL PROPERTIES WHICH ALLOW THEM TO WEATHER AT DIFFERENT RATES QUARTZ ALMOST UNCHANGED BY CHEMICAL WEATHERING. IT IS HARD AND DOES NOT HAVE CLEAVAGE SO IT ALSO RESISTS MECHANICAL WEATHERING

SEDIMENTARY ROCKS FELDSPAR, MICA, CALCITE, AND GYPSUM AFFECTED BY BOTH TYPES OF WEATHERING AND WILL BREAK DOWN INTO CLAY WITH CALCITE AND GYPSUM DISSOLVING AND BEING CARRIED OFF IN SOLUTION. SEDIMENTARY ROCKS SHALE IS THE LEAST RESISTANT TO MECHANICAL WEATHERING

SANDSTONE IS THE MOST RESISTANT TO MECHANICAL WEATHERING THE TYPE OF CEMENT WHICH HOLDS THE SANDSTONE TOGETHER DETERMINES HOW RESISTANT THE ROCK IS CALCITE – LOW RESISTANCE SILICA - HIGH RESISTANCE ROCKS WHICH CONTAIN THE MINERAL CALCITE, SUCH AS LIMESTONE or MARBLE, ARE SOMEWHAT RESISTANT TO MECHANICAL WEATHERING BUT IS THE LEAST RESISTANT TO CHEMICAL WEATHERING

FACTORS AFFECTING RATE OF WEATHERING EXPOSURE THE CLOSER TO THE SURFACE OF THE EARTH, THE FASTER IT WILL WEATHER - RATE AND TYPE OF WEATHERING DEPENDS ON EXPOSURE OF ROCKS TO AIR, WATER AND THE ACTION OF LIVING THINGS

SURFACE AREA THE GREATER THE SURFACE AREA EXPOSED TO WEATHERING THE FASTER THE RATE OF WEATHERING **TWO SAMPLES OF THE SAME MATERIAL HAVING THE SAME MASS CAN HAVE DIFFERENT SURFACE AREAS. IF ONE SAMPLE IS A LARGE PIECE OF MARBLE WITH A MASS OF 50g, AND THE OTHER IS 50g OF MANY SMALL PIECES OF MARBLE. THE SMALLER SIZE PIECES WILL HAVE THE GREATER SURFACE AREA

CLIMATE EFFECT ON WEATHERING CHEMICAL WEATHERING IS USUALLY GREATER IN WARM, MOIST CLIMATES PHYSICAL WEATHERING IS USUALLY GREATER IN MOIST AREAS WITH TEMPERATURE VARIATIONS (COLD AND WARM)

SOILS SOIL IS MADE OF LOOSE, WEATHERED ROCK AND ORGANIC MATERIAL IN WHICH PLANTS WITH ROOTS CAN GROW. THE ROCK MATERIAL IS COMPOSED OF SAND, SILT, AND CLAY.

PARENT MATERIAL IS THE MATERIAL FROM WHICH A SOIL IS FORMED RESIDUAL SOIL – SOIL THAT HAS THE BEDROCK BENEATH THE SOIL AS A PARENT MATERIAL TRANSPORTED SOIL – SOILS FORMED FROM DEPOSITS LEFT BY WINDS, RIVERS, AND GLACIERS.

A-HORIZON TOPSOIL B-HORIZON SUBSOIL C-HORIZON UNWEATHERED BEDROCK DARKEST COLOR DUE TO ORGANIC MATERIAL B-HORIZON SUBSOIL 1) CLAY IS WASHED TO THE SUBSOIL 2) MAY CONTAIN SOLUBLE MINERALS, SUCH AS CALCIUM AND MAGNESIUM CARBONATES 3) COLOR IS USUALLY RED-BROWN FROM IRON OXIDES THAT FORM ABOVE AND WASH DOWN C-HORIZON MADE OF SLIGHTLY WEATHERED PARENT MATERIAL (ROCK FRAGMENTS) UNWEATHERED BEDROCK

CLIMATE TROPICAL SOILS FORM IN AREAS WITH HIGH TEMPERATURES AND HEAVY RAINFALL. A THICK INFERTILE SOIL PROFILE ARE RESULTS OF HEAVY RAIN. GRASSLAND SOILS FORM IN AREAS WITH ENOUGH RAINFALL FOR HEAVY GRASS, BUT NOT TREES. ABOUT 1 METER THICK AND FERTILE

FOREST SOILS FORM IN HUMID REGIONS WITH COOL SEASONS. SOIL PROFILE IS LESS THEN 1 METER THICK WITH WELL DEVELOPED A, B, AND C HORIZONS DESERT SOILS FORM IN VERY DRY CLIMATES. SOIL PROFILE IS A FEW CENTIMETERS THICK AND BE VERY FERTILE WHEN THEY ARE WATERED ARCTIC SOILS FORM AT HIGH ELEVATIONS AND HIGH LATITUDES. POORLY DRAINED SURFACES AND THE BOTTOM LAYERS ARE CONSTANTLY FROZEN.

MASS MOVEMENTS MOVEMENTS OF LOOSE EARTH MATERIAL DOWN A SLOPE. A)      **GRAVITY IS AN AID IN WEATHERING AND EROSION. STEEP SLOPES WEATHER TO GENTLE SLOPES. CREEP - SLOW, IMPERCEPTIBLE DOWN SLOPE MOVEMENT OF THE SOIL. CAUSES OBJECTS THAT ARE FIXED IN THE SOIL TO LEAN DOWNHILL. WATER IN THE SOIL IS WHAT ADDS THE WEIGHT. MUDFLOW - THE RAPID MOVEMENT OF A WATER SATURATED MASS OF SOIL.

SLUMP - OCCURS WHEN A SECTION OF LAND MOVES DOWNHILL AS A WHOLE BECAUSE OF A PLANE OF WEAKNESS IN THE UNDERLYING SOIL. LANDSLIDE - SUDDEN MOVEMENT OF A MASS OF BEDROCK OR LOOSE ROCK DOWN THE SLOPE OF A HILL OR MOUNTAIN. (AVALANCHE - SNOW, ICE, ROCK AND SOIL) TALUS - IS A PILE OF ROCK FRAGMENTS AT THE BASE OF A CLIFF.

EROSION

Wind Erosion WIND TRANSPORTS MATERIALS BY CAUSING THEIR PARTICLES TO MOVE IN DIFFERENT WAYS. SUSPENSION – A METHOD OF TRANSPORT BY WHICH STRONG WINDS CAUSE SMALL PARTICLES TO STAY AIRBORNE FOR LONG DISTANCES. SALTATION – CAUSES A BOUNCING OF MOTION OF LARGER PARTICLES. SALTATION ACCOUNTS FOR MOST SAND TRANSPORT BY WIND.

VENTIFACTS ARE ROCKS SHAPED BY WINDBLOWN SEDIMENTS. WIND EROSION IS GREATEST IN ARID CLIMATES (LOW PRECIPITATION) WITH LITTLE VEGETATION. (DESERTS AND SEA SHORES) **ABRASION IS A PROCESS OF EROSION FOUND IN WIND, WATER, AND ICE. IT OCCURS WHEN PARTICLES SUCH AS SAND RUB UP AGAINST THE SURFACE OF ROCKS OR OTHER MATERIALS.                                       VENTIFACTS ARE ROCKS SHAPED BY WINDBLOWN SEDIMENTS.

WIND DEPOSITION OCCURS IN AREAS WHERE WIND VELOCITY DECREASES. DUNES ARE PILES OF WINDBLOWN SAND THAT HAVE A GENTLE SIDE AND A STEEP SIDE. THE GENTLER SLOPE OCCURS WHEN THE SIDE ON WHICH THE WIND IS BLOWING (WINDWARD SIDE). THE STEEPER SLOPE OCCURS ON THE SIDE PROTECTED FROM THE WIND (LEEWARD SIDE).

LOESS – THICK DEPOSITS OF FINE LIGHTWEIGHT PARTICLES (SILT, CLAY) THAT ARE CARRIED BY THE WIND IN GREAT QUANTITIES OF LONG DISTANCES. THEY ARE SOME OF THE MOST FERTILE SOILS.

LOUIS AGASSIZ IS KNOWN FOR THE IDEA THAT GLACIERS ONCE COVERED MANY PARTS OF THE WORLD. FORMATION OF A GLACIER GLACIERS ARE ACCUMULATIONS OF ICE LARGE ENOUGH TO SURVIVE SUMMER MELT – FORMS FROM SNOW UNDER PRESSURE WHICH TURNS TO ICE                                                          SNOW LINE – THE LOWEST LEVEL THAT PERMANENT SNOWS REACH IN SUMMER HIGHEST NEAR THE EQUATOR

FIRN IS GRANULAR ICE MATERIAL FORMED IN SNOW FIELDS FROM FRESHLY FALLEN SNOW BECOMING COMPRESSED AND RECRYSTALLIZING THE LOWER LAYERS BECOME ICE AND BEGIN FLOWING DOWNWARD OR OUTWARD BECAUSE OF OVERLYING PRESSURE.

Alpine Glaciers (valley glaciers) Occur in mountain regions above the snow line Flow downhill and carve out U-shaped valleys

Continental Glaciers (ice sheets) A glacier that spreads over a wide geographic area. FORM IN POLAR AREAS WHERE THE SNOW LINE IS CLOSE TO SEA LEVEL AND WIDE AREAS ARE ABOVE THE SNOW LINE (responsible for much of the landscape in NY) 20,000 YEARS AGO, NEW YORK STATE WAS COVERED BY A HUGE ICE SHEET THAT ORIGINATED IN CANADA

Glacier Movement THE OVERLYING WEIGHT OF SNOW AND ICE CAUSES GRAINS OF ICE TO PARTIALLY MELT AND REFREEZE. AS THIS HAPPENS ICE GRAINS SLIP PAST EACH OTHER AND MOVE DOWNHILL GLACIERS MOVE MORE RAPIDLY AT THE SURFACE THAN AT THE BASE AND FASTER AT THE CENTER THAN AT THE SIDES. FRICTION WITH THE VALLEY WALLS SLOW THE FLOW * FLOW AT A RATE OF A FEW CM TO SEVERAL METERS PER DAY

CREVASSES ARE CRACKS ACROSS THE WIDTH OF THE GLACIER THAT FORM WHEN GLACIERS MOVE OVER STEEP SLOPES

ICE FRONT IS THE END OF A GLACIER THE ICE FRONT IS STATIONARY AS LONG AS THE RATE OF MOVEMENT AND MELTING ARE EQUAL A GLACIER RECEDES WHEN IT MELTS FASTER THAN NORMAL A GLACIER ADVANCES WHEN THE RATE OF MOVEMENT IS GREATER THEN THE RATE AT WHICH IT MELTS.

CALVING IS WHEN BLOCKS OF ICE BREAK OFF INTO THE SEA

PIECES OF ROCK ARE PICKED UP AS GLACIERS MOVE AND THEN ARE DRAGGED ALONG THE BEDROCK AND/OR VALLEY WALL FINE SAND ACTS AS SANDPAPER AND POLISH THE BEDROCK LARGER SEDIMENTS LEAVE LONG PARALLEL SCRATCHES CALLED STRIATIONS ** STRIATIONS SHOW THE DIRECTION OF MOVEMENT**

THE FINGER LAKES OF NY WERE FORMED AS ADVANCING ICE DEEPLY SCOURED OUT VALLEYS

GLACIAL TROUGH ARE FORMED WHEN A GLACIER CARVE OUT A VALLEY FORMING A U-SHAPED VALLEY VALLEY GLACIERS LEAVE SHARP MOUNTAIN TOPS WHILE CONTINENTAL GLACIERS LEAVE ROUNDED TOPS

HERE ARE A FEW DEPOSITIONAL FEATURES OF GLACIERS.. MORAINE IS A GLACIAL DEPOSIT OF UNSORTED ROCK MATERIAL GROUND MORAINE – CARRIED ALONG THE BOTTOM LATERAL MORAINE – LONG LINES OF ROCK PIECES ALONG THE VALLEY SIDES MEDIAL MORAINE – WHEN TWO GLACIERS COME TOGETHER AND THERE LATERAL MORAINES JOIN TOGETHER

ARETES MEDIAL MORAINES LATERAL MORAINES CIRQUE

TERMINAL MORAINES – PILES OF UNSORTED SOIL AND ROCK LEFT AT THE FRONT OF GLACIER WHERE IT STOPPED MOVING. THIS MARKS THE FARTHEST ADVANCE OF THE GLACIER.

DRUMLINS – ACCUMULATIONS OF ROCK AND SOIL THAT BUILD UP IN FRONT IF THE ICE AS THE ICE MOVED UP AND OVER THESE PILES ROUND END FACES THE DIRECTION IN WHICH THE GLACIER ADVANCED

KETTLES – WHEN BURIED ICE LEFT BY A GLACIER MELTS AND LEAVES A DEPRESSION KETTLE LAKE – WHEN THESE DEPRESSIONS FILL WITH WATER LIKE A POND