alfred wegener ( alfred wegener (vayg-uh-nur) continental drift –the claim that all of the...
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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/ problems
What 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
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
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
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
Coarse
mineral 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)
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
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
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 cones
B. cinder cones
C. composite cones
D. fissure eruptionsSMART 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
• 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
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
• S-waves– Secondary Waves– Can only travel
through solids
– Moves rock particles side to side, at right angles
Surface Waves
Slowest 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
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
Earthquakes
StationP-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 StationEpicenter 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)