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

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

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)

Igneous rock textures

Vesicular

(Open spaces, bubbles)

Igneous rock textures

Glassy

Shiny 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 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

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 Faults

1.Strike slip fault– San

Andreas

2.Normal Fault

3.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 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

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

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)

Earthquakes

• Earthquakes are measured by two different scales.

– Richter Scale – measures magnitude or energy of earthquake• 1-10