Transcript Dynamic Crust

(ALFRED WEGENER 1915)
I PANGEA- A LARGE
LANDMASS CONTAINING ALL
OF THE CONTINENTS.
WHICH EVENTUALLY BROKE
INTO TWO LANDMASSES
a) LAURASIA- N.
AMERICA,EUROPE, ASIA
b) GONDWANALANDAFRICA, S. AMERICA,
ANTARCTICA,
AUSTRALIA, INDIA
CONTINENTS SEEM TO FIT TOGETHER
FOSSILS OF INDIVIDUAL SPECIES CAN BE FOUND ON
MANY DIFFERENT CONTINENTS WHICH ARE NOT
CLOSE TOGETHER. (EX. LYSTROSAURUS WAS LOCATED
IN ANTARCTICA, S. AMERICA, AFRICA, INDIA)
DEPOSITS OF CERTAIN ROCK AND MINERAL TYPES
CORRELATE AMONG CONTINENTS
APPALACHIAN MTS. FOUND IN NORTHEAST OF U.S.
ARE SIMILAR IN AGE AND STRUCTURE AS MTS. IN
GREENLAND AND SCANDINAVIA
PRESSURE AND TEMPERATURE INCREASE AS YOU
MOVE TOWARD THE CENTER OF THE EARTH
CRUST- THE OUTER MOST LAYER OF THE EARTH
a) CONTINENTAL CRUST- COMPOSED MAINLY OF
GRANITE, LOW IN DENSITY
b) OCEANIC CRUST- COMPOSED MAINLY OF BASALT,
HIGH IN DENSITY
LITHOSPHERE- CRUST AND UPPERMOST SOLID PART
OF THE MANTLE
ASTHENOSPHERE- UNDERLIES THE LITHOSPHERE,
COMPOSED OF PARTIALLY MOLTEN ROCK
MOHO- THE BOUNDARY BETWEEN THE CRUST AND
THE MANTLE
MANTLE- THE LAYER OF MOLTEN ROCK EXTENDING
FROM THE CRUST DOWNWARD 2850 KM
OUTER CORE- BETWEEN MANTLE AND INNER CORE,
COMPOSED OF IRON AND NICKEL
INNER CORE- SOLID IRON AND NICKEL LOCATED AT
THE CENTER OF THE EARTH
Please turn to the Inferred Properties of
Earth’s Interior chart on page 10 in the ESRT
PLATE TECTONICS IS THE
STUDY OF THE FORMATION
AND MOVEMENT OF PLATES
PLATES ARE COMPOSED OF
LITHOSPHERE
(CONTINENTAL=THICK,
OCEANIC=THIN) 12 MAJOR
AND SEVERAL MINOR PLATES
** PLATES MOVE BECAUSE OF CONVECTION
CELLS IN THE ASTHENOSPHERE**
CONVECTIONCELL- A CIRCULATORY MOTION IN A
LIQUID OR GAS TRANSFERRING HEAT ENERGY THAT
RESULTS FROM DIFFERENCES IN DENSITY WITHIN THE
FLUID
*PLACE WHERE TWO PLATES ARE MOVING
APART FROM EACH OTHER.
a) MID-ATLANTIC RIDGE- SEA FLOOR
SPREADING AT THE MID OCEAN RIDGES
RECORDED BY THE REVERSAL OF THE
MAGNETIC POLES IN MINERAL GRAINS
PALEOMAGNETISM- THE STUDY OF
MAGNETISM IN ANCIENT ROCKS
POLAR WANDERING- AS METALLIC MINERAL GRAINS
ALIGN THEMSELVES WITH THEIR MAGNETIC POLES
ROCK RECORDS SHOW THAT THE GRAINS REVERSE
THE DIRECTION IN WHICH THEY POINT
*WHEN TWO PLATES MOVE TOWARDS EACH OTHER
COLLISION- WHEN TWO PLATES CARRYING
CONTINENTS COLLIDE THEY PUSH UP USUALLY
CAUSING MOUNTAINS. (EX. HIMALAYAS)
SUBDUCTION- WHEN BOTH PLATES DO NOT
CONTAIN CONTINENTS, ONE OF THE PLATES IS
FORCED TO SINK UNDER THE OTHER ONE.
OCEAN-CONTINENT THE OCEAN FLOOR IS MORE
DENSE SO IT SUBDUES TO THE CONTINENTAL CAUSING
OFFSHORE TRENCHES, MOUNTAINS OR VOLCANOES
(EX. WESTERN COAST OF S. AMERICA
OCEAN-OCEAN ONE PLATE WILL SUBDUE
TO THE OTHER ONE USUALLY CAUSING A
DEEP TRENCH (EX. MARIANA’S TRENCH)
WHEN PLATES SLIDE PAST ONE ANOTHER USUALLY
CAUSING A BUILD UP OF PRESSURE WHICH IS
RELEASED IN THE FORM OF AN EARTHQUAKE
SAN ANDREAS FAULT- MANY EARTHQUAKES ARE
COMMON ALONG THE FAULT WHERE THE NORTH
AMERICAN PLATE IS SLIDING PAST THE PACIFIC
PLATE
MAGMA – MOLTEN ROCK
UNDERGROUND
FELSIC – MAGMAS WITH
RELATIVELY HIGH SILICA ARE
THICK, LIGHT COLORED, AND SLOW
MOVING
MAFIC – RELATIVELY LOW SILICA
CONTENT, THINNER, DARKER, AND
FLOW MORE EASILY
MAGMA CONTAINS DISSOLVED GASES THAT ARE
GIVEN OFF AS THE MAGMA ERUPTS. THE MOST
IMPORTANT OF THESE GASES ARE WATER VAPOR,
CARBON DIOXIDE, AND SULFUR.
MAGMAS CONTAINING LARGE AMOUNTS OF
DISSOLVED GASES TEND TO PRODUCE MORE
EXPLOSIVE ERUPTIONS.
LAVA – MOLTEN ROCK THAT HAS
REACHED THE SURFACE
FELSIC LAVA – THICK AND STIFF CALLED AA
LAVA. PRODUCE EXPLOSIVE ERUPTIONS.
MAFIC LAVA – THIN AND FLUID CALLED
PAHOEHOE LAVA. LAVA POURS OUT
SMOOTHLY (LESS EXPLOSIVE)
LAVA FRAGMENTS
TEPHRA – SOLID FRAGMENTS OF LAVA
PRODUCED FROM EXPLOSIVE ERUPTIONS.
SMALL
ASH
LAPILLI
LARGE
BOMBS
KINDS OF ERUPTIONS
RIFT ERUPTIONS – OCCUR AT LONG, NARROW
FRACTURES IN THE CRUST SUCH AS MID-OCEAN
SPREADING CENTERS
WHEN LAVA FLOWS OUT SMOOTHLY AND
FLUIDLY IT FORMS A VOLCANIC MOUNTAIN WITH
A BROAD BASE AND GENTLY SLOPING SIDES
CALLED A SHIELD CONE
SUBDUCTION BOUNDARY ERUPTIONS – ARE THE
RESULT OF THICK MAGMA THAT FORMS AT
SUBDUCTION BOUNDARIES.
THESE ERUPTIONS AR MORE EXPLOSIVE
DUE TO THE LARGE AMOUNT OF GASES IN
THE MAGMA.
FORMS A CINDER CONE WITH VERY STEEP SIDES
HOT SPOTS
HOT SPOTS ARE AREAS OF VOLCANIC
ACTIVITY IN THE MIDDLE OF
LITHOSPHERIC PLATES.
SIMILAR TO RIFT ERUPTIONS. SMOOTH
FLOWING LAVA AND SHIELD CONES.
** THE HOT SPOT STAYS IN THE SAME
LOCATION AS THE LITHOSPHERIC PLATE
ABOVE IT MOVES **
Who created the theory of “continental drift” ?
Give two forms of evidence to support this theory.
What is the difference between the lithosphere and the asthenosphere?
Describe how a convection cell works.
EARTHQUAKES
AN EARTHQUAKE IS A SHAKING OF EARTH’S CRUST
CAUSED BY THE RELEASE OF ENERGY.
REASONS WHY THEY OCCUR:
ERUPTION OF A VOLCANO
THE COLLAPSE OF A CAVERN
THE IMPACT OF A METEOR
SUDDEN MOVEMENT ALONG A PLATE BOUNDARY
CAUSED BY THE RELEASE OF STRESS
DEPTH OF EARTHQUAKES
FOCUS – THE POINT ON A FAULT PLANE AT
WHICH THE FIRST MOVEMENT OCCURS
EPICENTER – THE POINT ON EARTH’S SURFACE
DIRECTLY ABOVE THE FOCUS
THREE BASIC KINDS OF WAVES
P-WAVES (PRIMARY) – BACK AND FORTH
WAVE MOTION; CAN TRAVEL THROUGH ANY
MATERIAL; FASTEST
S-WAVES (SECONDARY) – SIDE TO SIDE
WAVE MOTION; CAN TRAVEL THROUGH
SOLIDS BUT NOT THROUGH LIQUIDS OR
GASES
L-WAVES (SURFACE) – FORM WHEN P AND S
WAVES REACH THE SURFACE WHICH MOVE
SLOWLY LIKE RIPPLES ON A POND; SLOWEST
LOCATING AN EARTHQUAKE
SEISMOGRAPH – THE INSTRUMENT THAT DETECTS
AND RECORDS EARTHQUAKE WAVES
SEISMOGRAM – THE SHEET WHICH DISPLAYS THE
ZIG-ZAG TRACE OF EARTHQUAKE WAVES
**P-WAVES ALWAYS ARRIVE BEFORE S-WAVES**
P AND S WAVE ARRIVAL TIME DIFFERENCE CAN THEN
BE USED TO DETERMINE THE DISTANCE FROM THE
RECORDING STATION TO THE EPICENTER
THE SHADOW ZONE IS A WIDE BELT
AROUND EARTH ON THE SIDE
OPPOSITE THE FOCUS OF THE
EARTHQUAKE. SEISMIC STATIONS
RECEIVE NEITHER P NOR S WAVES.
THE CAUSE OF THE SHADOW ZONE IS THE
EARTH’S OUTER CORE. S-WAVES CAN NOT
TRAVEL THROUGH THE LIQUID OUTER
CORE. WHILE P WAVES ARE REFRACTED
(BENT) IN A SMOOTH ARC BACK TO THE
SURFACE.
Locating an Epicenter
Triangulation
We then use the epicenter distance’s from at least 3
recording stations to locate the epicenter
You need to next measure the distance to scale and
drawing a circle from each station. Once 3 circles
are drawn they will intersect at one common point.
This location is the epicenter
OTHER CRUSTAL CHANGES
ORIGINAL HORIZONTALITY- CONCEPT THAT
SEDIMENTARY ROCKS FORM IN HORIZONTAL
LAYERS PARALLEL TO THE EARTH’S SURFACE.
DEFORMED ROCKS- ANY ROCK LAYERS WHICH
NO LONGER SHOW HORIZONTALITY
UPLIFT- LAND WHICH HAS BEEN RAISED UP TO ITS
PRESENT POSITION (EVIDENCE- MARINE FOSSILS IN
MOUNTAINS)
SUBSIDENCE – LAND WHICH HAS BEEN
LOWERED FROM ITS PAST POSITION
OTHER CRUSTAL CHANGES
FOLDS- ROCK LAYERS WHICH ARE BENT OR
CURVED CAUSED FROM GREAT PRESSURE ON THE
ROCK
FAULTS- ROCK LAYERS OFFSET OR DISPLACED
ALONG A CRACK
HANGING WALL- IS ON THE TOP OF THE CRACK
FOOT WALL- IS ON THE BOTTOM OF THE CRACK
PLEASE TURN TO PAGE 11 IN YOUR
ESRT