crucial factors: source rock from which sediment derived transport mechanism (wind, water, ice)
DESCRIPTION
SEDIMENTARY ROCKS- MINERAL OR ROCK FRAGMENTS OR MATERIAL OF ORGANIC ORIGIN ARE ERODED OR DISSOLVED AND THEN DEPOSITED IN LAYERS AT EARTH'S SURFACE. CRUCIAL FACTORS: SOURCE ROCK FROM WHICH SEDIMENT DERIVED TRANSPORT MECHANISM (WIND, WATER, ICE) - PowerPoint PPT PresentationTRANSCRIPT
CRUCIAL FACTORS:
SOURCE ROCK FROM WHICH SEDIMENT DERIVED
TRANSPORT MECHANISM (WIND, WATER, ICE)
SITE OF DEPOSITION (RIVER, LAKE, OCEAN, DESERT)
PLATE TECTONIC SETTING
SEDIMENTS 5% OF EARTH'S CRUST, BUT MOST COMMON SURFACE ROCKS, RECORD EARTH HISTORY, & VALUABLE FOR RESOURCES (oil, gas, coal, building material)
SEDIMENTARY ROCKS-MINERAL OR ROCK FRAGMENTS OR MATERIAL OF ORGANIC ORIGIN ARE ERODED OR DISSOLVED AND THEN DEPOSITED IN LAYERS AT EARTH'S SURFACE
SEDIMENTARY ROCK TYPES
CLASTIC SEDIMENTS: GRAINS PRODUCED BY MECHANICAL OR CHEMICAL WEATHERING AT EARTH'S SURFACE (EXAMPLE: SANDSTONE)
BIOCHEMICAL SEDIMENTS: MATERIAL OF ORGANIC (LIVING THINGS) ORIGIN SUCH AS SHELL OR CORAL FRAGMENTS (EXAMPLES: LIMESTONE, COAL)
CHEMICAL SEDIMENTS: INORGANIC CHEMICALS PRECIPITATED (CRYSTALIZED) FROM WATER (EXAMPLE: SALT DEPOSITS)
Size and shape of sedimentary grains reflects transportation history.
Davidson 4.20
Beach sand
Davidson 4.19
SEDIMENTARY ROCK TYPES
Large grains indicate transport and deposit by strong currents: mountain streams, beaches with large waves, or glacial melt streams
Deposited by gentle currents, so small particles settle out of the water: deep ocean, coasts with weak tides
Deposited by moderate currents that removed finer sediment: rivers, coasts with moderate waves, wind-produced dunes.
COMPACTION, LITHIFICATION, DIAGENESISUNCONSOLIDATED SEDIMENT TURNS INTO HARD
SEDIMENTARY ROCKS
Davidson 4.25Similar to snow turning to ice
Sedimentary Structures:
Cross-bedding: sediment carried by moving fluid (water, air)
Ripple Marks
Graded Bedding: grains become finer upward in layer
Mud Cracks: shallow water deposit
Davidson 4.24
MIDWEST HAS FEATURES FORMED BY SEDIMENT
TRANSPORTED BY GLACIERS
MANY FORMED 25,000 - 14,000 YRS AGO DURING LAST ICE AGE
VAST ICE SHEET OVER CANADA
GLACIERS FLOW AWAY FROM ICE SHEET'S CENTER
18,000 YRS AGO- SOUTHERMOST ADVANCE OF GLACIER THAT FLOWED THROUGH LAKE MICHIGAN BASIN AND INTO NE ILLINOIS
SINCE THEN, ICE MELTED BACK
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MAXIMUM EXTENT OF GLACIATION LAST 2 MILLION YEARS
Davidson 14.15
ECCENTRICITY, TILT, & PRECESSION CAUSE VARIATIONS IN SUNLIGHT (UP TO ABOUT 5% AT HIGHER LATITUDES), SO CLIMATE VARIES BETWEEN WARMER AND COLDER PERIODS.
COLDER WINTERS, MORE ICE ACCUMULATES, CAN START ICE AGE
OTHER FACTORS MAY ACT INCLUDING MOUNTAIN UPLIFT (HIMALAYA)
MILANKOVITCH CYCLESEarth’s orbit changes Earth’s tilt changes
GLACIERS- THICK ICE, LASTS ALL YEAR; RECRYSTALLIZED SNOW MOVES DOWNSLOPE BY GRAVITY OR RADIALLY OUTWARD BY ITS OWN WEIGHT
Robeson Glacier, Canada
GLACIERS ERODE & DEPOSIT SEDIMENT - TILL
ADVANCING GLACIERS SLOWLY PUSH EARTH & ROCK FORWARD DEPOSIT THESE MATERIALS WHEN GLACIERS MELT (RETREAT)
TILL - DEBRIS DEPOSITS, POORLY SORTED FORM CHARACTERISTIC LANDFORMS
END MORAINESTILL DEPOSITS AT GLACIER
MARGIN
Sheridan Road, Winnetka
Glencoe Beach
Glacial Park, McHenry
Palos Park
Kettle Morraine State Forest, WI
DRUMLINS
ROUNDED & ELONGATED HILL OF GLACIAL TILL
BUILT UNDER ICE MARGINS SHAPED BY GLACIERS FLOW
BLUNT NOSE IN DIRECTION FROM WHICH ICE CAME & GENTLE SLOPE TAPERED IN OTHER DIRECTION
ESKERS
LONG SAND & GRAVEL RIDGES LEFT BY SEDIMENT IN MELTWATER TUNNELS UNDER GLACIER
VOLO BOG (McHENRY, IL)- A KETTLE LAKE
FORMED 15,000 YEARS AGO WITH GLACIER'S RETREAT
LEFTOVER LARGE BLOCKS OF ICE ON GROUND
MELTS AS CLIMATE WARMS
FORMS KETTLE-HOLE DEPRESSION
EVENTUALLY FILLS
RETREATING GLACIERS; MUCH STILL UNDER ICE
RECENTLY DEGLACIATED AREAS COVERED WITH BARE SHEETS OF TILL & SLOWLY REVEGETATED
LARGE LAKES WHERE MORRAINES DAM WATER COMING OFF MELTING GLACIERS
LAKES, MARSHES, AND BOGS COMMON
COOLER CLIMATE- DIFFERENT PLANTS AND ANIMALS THAN TODAY
ILLINOIS 16,000 YRS AGO
EVAPORITES - SALTS OF SODIUM, CALCIUM, MAGNESIUM, POTASSIUM DEPOSITED AS DESERT LAKES, SEAS DRY UP.
EXAMPLES-
DEAD SEA
BONNEVILLE SALT FLATS (GREAT SALT LAKE) REMAIN FROM HUGE LAKE DURING ICE AGES
MEDITERRANEAN (6 MYR AGO)
CHEMICAL SEDIMENTS: CRYSTALLIZED FROM WATER WHEN THEIR CONCENTRATION EXCEEDS THAT WHICH CAN BE DISSOLVED (SOLUBLE) IN WATER
GREAT SALT LAKE - UTAH LATEST OF LAKES THAT EXISTED OFF AND ON FOR PAST 15 MYRS.
NO OUTLET BECAUSE AT BOTTOM OF A BASIN. FRESH WATER ENTERING FROM RIVERS CAN ONLY EXIT BY EVAPORATION OR SEEPAGE INTO DEEP GROUNDWATER LAYERS.
CURRENT CLIMATE OF HIGH EVAPORATION AND LOW INPUT OF FRESH WATER GIVES SALINE LAKE.
SALT WATERS’ MAJOR ELEMENTS: SODIUM, MAGNESIUM, POTASSIUM, CHLORIDE, AND SULFATE.
MAJOR MINERAL INDUSTRY
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5-6 million years ago the Mediterranean became isolated from the Atlantic Ocean, causing the sea water to evaporate, and leaving immense dried-up basins, shown by a large accumulation of salt deposits sandwiched between deep-water marine sediments.
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CAN INVOLVE CHANGES IN MINERALOGY, TEXTURE, & CHEMICAL COMPOSITION
ALTHOUGH SHALLOW BURIAL CAN PRODUCE LITHIFICATION & DIAGENESIS OF SEDIMENT INTOSEDIMENTARY ROCK, ONLY PLATE TECTONIC PROCESSES CAN CAUSE PRESSURES AND TEMPERATURES HIGH ENOUGH TO PRODUCE METAMORPHIC ROCKS
METAMORPHIC ROCKS INDICATE TEMPERATURE & PRESSURE CONDITIONS UNDER WHICH THEY FORMED
METAMORPHIC ROCKS- FROM ALTERATION OF PRE-EXISTING ROCKS BY HEAT, PRESSURE, & CHEMICAL REACTIONS
Davidson 4.26
PRESSURE & TEMPERATURE INCREASE WITH DEPTH
METAMORPHIC ROCKS: MARBLE
HEAT AND PRESSURE METAMORPHOSE LIMESTONE INTO MARBLE
Metamorphic rocks formed by increasing pressure/temperature on a mudstone to
slate,
then schist,
then gneiss,
then remelted & recrystallized
Davidson 4.26
INTERNAL ENERGY (HEAT) FROM EARTH ACTS VIA PLATETECTONICS TO CAUSE VOLCANISM & MOUNTAIN BUILDING
EXTERNAL ENERGY FROM SUN CAUSES WEATHER, THUS WEATHERING, EROSION, TRANSPORTATION, & DEPOSITION OF SEDIMENTS
ROCKS BURIED, METAMORPHOSED, MELTED & UPLIFTED BY TECTONIC PROCESSES
THE ROCK CYCLE- INTERCONNECTIONS BETWEEN ROCK-FORMING PROCESSES
Davidson 4.30