Unit1 Plate Tectonics

Unit 1 PLATE TECTONICS

Index

1 The Internal Structure of the Earth2 The Movement of Continents3 The theory of Plate Tectonics4 The ocean5 The Mechanisms behind Plate Tectonics

11 Earth internal layers

Types of classification

Compositional layers (depending on thecomposition)

bullCRUST

bullOceanic (10 km basalt denser)

bullContinental (70 km Si less dense)

bullMANTLE peridotite

bullCORE Fe + Ni

Physical layers (depending on the physical state)

bull LITHOSPHERE rigid

bull LOW VELOCITY ZONE (in the past ASTHENOSPHERE) ductile and partially molten

bull LOWER MANTLE or MESOSPHERE solid

bullCORE

bullOutermolten

bull Inner solid

Low velocity zone

Page 9 In pairs analyse the graph and explain your answer

Temperature increases with depth Pressure increases with depht The melting point increases

(the temperature is below the melting pointIt does not reach the melting point

As long as the temperature (green line) is below the melting point(red line) SOLID

12 Seismic discontinuities

Methods forstudying the

interior of theEarth

drilling meteoritesstudy of seismic

waves

Kola Peninsula Hole Control Centre

Types of seismic wavesP Primary waves

bullThe fastest

bull through SOLIDS and LIQUIDS

S Secondary waves

bullSlower

bullOnly through SOLIDS

R and L

bull On the surface

SEISMOGRAPH (sismoacutemetro o sismoacutegrafo) = device used for

detecting and recording seismic waves It draws a seismogram (sismograma)

seismograph seismogram

Seismic Network Operations in Toledo (Spain)

Imagine you are a scientific and obtain this graph How would you interpret thebehaviour of the seismic waves

Primary wave

= Secondary wave

The speed of waves changes very obviously in specific places

SEISMIC DISCONTINUITY = boundary between different internal layers where there isA change in the speed of the internal seismic waves

Mohorovicic discontinuity between the crust and the mantle CONTINENTS 30-40 Km depth OCEANS 10 km depth

Gutenberg discontinuity between the mantle and the core 2900 km depth

Why do S-waves dissapear here Because they cannot travel through LIQUIDS

Lehman discontinuity between outer and inner core

The speed of P-waves increases after Lehman discontinuitybecausehellip

The inner core is SOLID

Activities 1 2 and 3 page 11

Theory of continental drift (1912 Wegener)(teoriacutea de la deriva continental)

Alfred Wegener

200 million years ago all the continents were joinedtogether as one called PANGEA

Continents have separated sliding over a continouslayer

Theory of continental drift (1912 Wegener)

ldquo650millionYearsIn80secondsrdquo videohttpwwwyoutubecomwatchv=VrBPB1dHYawampfeature=related

Evidence of thetheory of

Continental Drift

Paleolithicevidence identicalfossils in continents

far apart

Biologicalevidence identical

or similar living beings in continents

far apart

Geological evidence continents fit togetheralong their coastlinesand have similar rocks

Paleoclimaticevidence glaciar

rests appear in places where now

the climate iswarmer

Paleolithic evidence

Rhea (South America)

Ostrich (Africa)

Emu(Australia)

Biological evidence

Geological evidence

Paleoclimatic evidence

Activities 7 and 8 page 11

31 Seismic and volcanic belts

Earthquakes and volcanoes are located in narrow bands called seismic belts Theycoincide with the plate boundaries

32 Lithospheric plates

Lithospheric or tectonic plates are fragments of the lithosphere

Types

Oceanic Nazca Plate

Continental Arabian Plate

Mixed African Plate

33 Types of plate boundaries

Divergent boundaries (constructive) New ocean lithosphere is created

Pillow lavas

httpwwwjuntadeandaluciaesaverroesmanualestectonica_animadatect_swf_files01[1]swf

Volcanoes + earthquakes

Convergent boundaries (destructive)

A) Two OCEANIC PLATES collide

Volcanoes + earthquakes

One of the plates slides down the other (subduction) forming an oceanic trench and an arch of volcanicislands

Example Japan

Mariana Islandsand Mariana Trench

The Pacific Plate subducts forming the Mariana Islands and Philippines

Japan

B) One CONTINENTAL and one OCEANIC PLATE collide

Volcanoes + earthquakes

The oceanic plate which is denser subducts underthe continental plate forming an oceanic trench and a mountain range

Example Andes

B) TWO CONTINENTAL PLATES collide

Earthquakes

None of the plates subducts A mountain range is formed

Ex Himalayas Pirenees

Transform boundaries (passive)

Two plates slide horizontally against each other These fractures

are called transform faults (fallas transformantes)

Earthquakes

Example San Andreas Fault in California

Pacific PlateNorthamerican Plate

httpswwwyoutubecomwatchv=OjMhUGsF_Nw

BENIOFF ZONE = area of seismic activity in a subducting plate

Type of boundary

Type of movement

Ocean floor Landformproduced

Activityproduced

Complete

Type of boundary

Type of movement

Ocean floor Landformproduced

Activityproduced

Divergent Separation Creates Oceanic ridges Earthquakesand volcanoes

Convergent Collision Destroys Trenches island archs volcanicmountains

Earthquakesand volcanoes(except continental collision)

Transform Lateral None transformfaults

ONLY earthquakes

Activity 5 page 22

The lithosphere is divided into blocks called plates

Most of the internal geological activityhappens at their boundaries

Ocean floor is

generated along the ridges new oceansare created

destroyed by subduction in the trenchesmountain ranges are lifted up

Activities 13 16 page 17

41 The ocean floor

Landforms

Mid-ocean ridge volcanic mountainrange under water

Trenches narrow deep channels They appear as a consequence of

subduction

Rift = central channel

Faults = perpendicularfractures which crossthe ridge

Composition of the ocean floor

Volcanic rocks (basalt) covered in marine sediment No older than 180 million years

(submerged)

age age

basalt

42 Sea floor spreading

Magma rises up from the mantle at the oceanic ridges

This magma pushesout the older lava

deposits

We can findsymmetrical bands

of ocean floor(different ages)

parallel to the axis of the ridge

The ocean floorspreads and

extends

oceanic lithosphereis formed at the

ridges

oceanic lithosphereis destroyed at the

trenches

51 Wilson cycle

A Rift Valley Stage

Magma rises up through fractures making the lithospherethinner and lower

(Drawing 1 and 2 book)

B Red Sea Stage

Deep lakes are formed at the bottom of the valleywhich spreads and spreads

(Drawing 3 book)

C Atlantic Ocean Stage

New oceanic lithosphere is beingproduced aund the Atlantic Oceanis expanding

(Drawing 4 book)

D Pacific Ocean Stage

The oceanic lithosphere becomes olderand denser Subduction zones appear

where the lithosphere is destroyedThe Pacific Ocean is getting smaller

(Drawing 5 and 6 book)

E Indian Continent Stage

The ocean closes as the continents converge Marine sediments are trapped and continentalmasses join together A mountain range is formed

(Drawing 7 and 8 book)

Activities 20 21 23 and 24 page 21

52 How plates move

Convection currents inside the mantle`push the plates

Hot currents not only rise up throughthe ridge but also through hot spots(puntos calientes)

Gravity pulls down on both sides of the lithosphere

The sinking plate pulls down (slab pull)

Slab pull force occurs when a denser oceanic plate is forced beneatha less dense continental plate or oceanic plate in a process called subduction

httpswwwyoutubecomwatchv=8LBjaoQe3EEWilson Cycle video

Hot spots

Read page 20 53

Development of basic competences 1 2 3 and 4

seismic discontinuity continental drift seismic belt hypocentre seismograph

Review Continental Drift Video