Alfred Wegener ( VAYG-uh- nur )
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Transcript of Alfred Wegener ( VAYG-uh- nur )
Alfred Wegener(VAYG-uh-nur)
• Continental drift– the claim that all of the
continents were once together, forming one large continent called Pangaea. (All land)
Alfred Wegener German scientist (weather man) came up with the idea
Continental drift-Fact or fiction?
Support/ Evidence• Continents seem to fit
together• Fossil record seems to
match• Rock structures match
– Rock ages match• Changes in climates
– Glacier debris
Opposition/ problemsWhat Continental drift couldn’t answer!• How can the continents
move?– No mechanism to make
them move– Ocean crust is to hard for
the continents to move through
Continental DriftPossible mechanism?
Modern EvidencePlate Tectonic theory
Mid-Ocean ridges & Sea floor spreading
• Mid-Ocean ridge – Large under water mountain range, with
a deep valley down the center – Ocean floor was moving,
• Why not continents?• Sea floor spreading
– new oceanic crust is formed through volcanic activity and then gradually moves away from the ridge
Modern EvidencePlate Tectonic theory
Paleomagnetism• Study of Earth’s magnetic field through
rocks and minerals
• Shown by different magnetic properties preserved in the rock record• Magnetic poles reverse • NS, SN
Cause/ Mechanism • Convection
– Hot magma rises cool magma sinks– Causes movement within the mantle
Plate tectonics theory • There are 52 tectonic
plates.– 14 major plates– 38 minor plates
So what is going on at all these plates?
The theory that the earth’s lithosphere is
divided into plates that move on the Asthenosphere.
ASK THIS How many plates
are there Mr. Hernandez?
The Crust (Lithosphere)
• Oceanic: more dense and younger – 510 km thick
• Continental: Older less dense material made from recycling of Oceanic crust– 1580km thick
How do we know?• Seismic waves caused by earth quakes
– Waves travel at different speeds through different mediums. (a medium is the material a wave travels through)
– Primary (P) waves: Travels fast through liquid, solid, gas
– Secondary (S) waves: Solids only and slower
Lithosphere vs Asthenosphere
Types of plate boundaries
1. Divergent– Pulling apart– Ex.
• Mid-Atlantic ridge• Great rift Valley Africa
Types of plate boundaries
3. Transform Boundary – One plate slides past
another• Ex. San Andreas fault
– Causes earthquakes in California
Types of plate boundaries
2. Convergent (push)– Two plates crashing
into each other• Three types of plate
collisions– Ocean-Continent– Ocean-Ocean– Continent--Continent
When will California fall off of the United States?
NEVER !!!
Types of plate boundaries
• Ocean to Continental – Ocean plate is more
dense subducts under continental plate.• Ex.• Alaska island arc
Types of plate boundaries– Ocean-Ocean
• Two oceanic plates collide
• Ex.– Marianas trench
• 1,600 miles long,43 miles wide, 36,200ft deep
– Island arcs (volcanoes)
Types of plate boundaries
2. Continent-Continent – Two continental
plates crashing into each other
– Himalayan mountains. Formed by this grow an inch a year
I. Igneous rocks are rocks that from molten material (magma/lava).
A. Extrusive igneous rocks are formed when moltenrock (lava) cools above ground. Usually they are formedafter the material has been erupted by a volcano.
1. This molten materialcools quickly.
2. No crystals are visibleto the eye.
B. Intrusive igneous rocks are formed when molten rock cools below ground.
1. These rocks cool very slowly.
2. There is lots of time for visible crystals to grow
Igneous rock textures
Coarsemineral grains easily visible (grains several
mm in size or larger)
Granite
Igneous rock textures
Fine mineral grains smaller than 1mm (need hand lens or microscope to see minerals)
Igneous rock textures
Vesicular (Open spaces, bubbles)
Igneous rock textures
GlassyShiny no visible crystals (looks like glass)
Felsic VS Mafic
Mineral Composition Over all color of the rock
Felsic: light in color– pink, grey, white…
Mafic: Dark in color– black, brown, red…
Felsic: rich in light minerals feldspar and quartz
Mafic: Rich in dark minerals Magnesium and Iron (Ferric)
Intrusive rock features a) Batholith:
Largest intrusions of rock “deep rock”
b) Laccolith:Intrusion of rock that is parallel to the rock layers “lake of rock”
c) Dikes:Vertical cross cutting layer of rock
d) Sills:Parallel sheet of rock
Volcanoes
TYPES OF VOLCANOES
1.SHIELD VOLCANOES• Mostly made up of
lava flows• Highly Mafic• Ex. Hawaiian
islands
Haw
aii
Shield Volcanoes
Shape:Very large but gentle slopes
Composition:Low silica Low gases
Eruptive Style: ?
Types of Volcanoes
2. Cinder cone Volcano– Mostly made of cinders and other fragments
• Ex. Paricutin in Mexico
Paricutin volcano in Angahuan, Mexico was born on March 4th 1943. How do we know this? Dionisio Pulido, was plowing his field when he noticed steam coming up from the footprints of the oxen, pulling his plow. Soon, the earth shook and cracks began to form in his field. Dionisio panicked and tried to fill the steaming holes, while his wife called all the villagers to help. As you might have guessed, the volcano was born in spite of their efforts. Luckily, no one was killed. However, the village was eventually covered by lava, sparing only the front and back walls of the cathedral.
Cinder Cone Volcanoes
Shape:Very small but steep slopes
Composition:Medium silica High gases
Eruptive Style: ?
Types of Volcanoes3. Composite Volcanoes
(stratovolcano)– Alternating layers
of ash and Lava flows
• Steep sides– Ex. Mt. St Helens
• Cascade mountain range
• Mt. Rainier • Mt. Pinatubo• Mt. Fuji
May 17,1980
MAY 18, 1980
TODAY
Clicker questionMost Hawaiian island volcanoes are gently sloping and experience quieter eruptions of lava that produce basalt. Based on this description, most Hawaiian volcanoes are:
A. shield conesB. cinder conesC. composite conesD. fissure eruptions
SMART Response QuestionTo set the properties right click and selectSMART Response Question Object->Properties...
Composite Volcanoes
Shape:Very large and steep slopes
Composition:high silica high gases
Eruptive Style: ?
Volcanoes• Fissure eruption
– Shape:– Flat; crack in the
ground or on the ocean floor
– Composition:– Low silica – Low gases
– Eruptive Style: ?
Hot spot Volcanoes
-volcanic regions They may be on, near to, or far from tectonic plate boundaries.
Ex.Hawaii
Which Direction is the PACIFIC plate moving towards?
Hazards
• Earthquake- Sudden release of energy in the Earth’s crust, occurring at a Fault
• Faults are breaks in the Earth’s crust– Multiple Faults are called Fault Zones
• Three types of Faults1.Strike slip fault
– San Andreas
2.Normal Fault3.Reverse Fault
• Earthquakes are a result of elastic rebound.– fault is locked;
stress builds; rocks “bend”
– When stress is too high, rocks break
– Rocks rebound back to original shapes
• We call this THE ELASTIC REBOUND THEORY
Earthquakes• The point at which the
movement occurs or the center of an Earthquake is called its Focus.
• The point directly above the Focus at the Surface is known as an Earthquakes EPICENTER
• Energy that is being released from the movement of the tectonic plates, is released IN THE FORM OF vibrations, in other words WAVES.
• WAVES are measured by an instrument called a seismograph– Measure vibrations of Seismic waves
• Earthquakes have 3 types of waves–Body Waves--S waves–Surface waves
Body Waves– P-waves: Primary
Waves• Fastest waves,
travels through both solids and liquids
• First to reach the seismograph
• Moves rock back and forth in same direction as the wave travels- compression
Body Waves• P-waves
Body Waves• S-waves
– Secondary Waves– Can only travel
through solids
– Moves rock particles side to side, at right angles
Body Waves• S-waves
Surface WavesSlowest moving waves
– Cause the most damage– 2 types of surface waves
• Love waves• Rayleigh waves
Surface Waves• Love waves
– Move side to side– And perpendicular to
the wave motion
Surface Waves• Rayleigh waves
– Elliptical waves– Similar to water waves
Locating an epicenter
• Difference between arrival times of P and S waves – This tells you the distance to the epicenter– Need 3 different stations to find the epicenter– This is called triangulation
Time-travel graph
Earthquakes
Station P-Wave Arrival(hrs:min:sec)
S-Wave Arrival(hrs:min:sec)
S-P Lag Time (min:sec)
Distance (km)
Flagstaff 04:14:15 04:18:45
Tucson 04:22:30 04:30:00
Reno 04:18:45 04:21:15
Earthquake Magnitude
Seismic Station Epicenter Distance (km)
Maximum amplitude of S-wave (mm)
St. Louis, MO 280 50
Springfield, IL 600 2
Memphis, TN 60 500
Earthquake scales
–Richter Scale – measures
magnitude or energy of earthquake
–1-10
Earthquakes are measured by two different scales.
Earthquake scales
• Mercalli Scale –– measures intensity of earthquake– Intensity = Damage caused–Measured with Roman Numerals– I – XII (1-12)
Earthquakes• Earthquakes are
measured by two different scales.
– Richter Scale – measures magnitude or energy of earthquake• 1-10