Chapter 1 living with tectonic hazardPresentation Transcript
CHAPTER 1 LIVING WITHTECTONIC HAZARD
LESSON OUTCOMES 1. We will be able toStudents would compare the different be able to : types of natural hazards. 2. Describe the internal structure of the Earth (core, mantle, crust) and tectonic plates. 3. Explain the movement of plates.
NATURAL HAZARDDefinition: Naturally occurring event that threatens human lives and causes damage to property Tectonic Natural Hazard Climate Related Natural Hazard
NATURAL HAZARD Tectonic Caused by plate movements when continental crusts and ocean floorsNatural Hazard move Eg. Earthquakes, volcanic eruptions and tsunamis Climate Related Caused by severe and extreme weather and climate conditions Natural Hazard Eg. Drought, tropical cyclones and floods
Let’s test it out• Classify the following hazards into climate or tectonic hazard• Describe the impact of each hazard Distribute Handout 2
Gas Emissions at Volcan Copahue http://earthobservatory.nasa.gov/NaturalHazards/view.php?id=80095
Gas Emissions at Volcan CopahueThe Chilean National Service of Geology and Mining, reported that theeruption was likely caused by water vaporizing as it interacted with magmarising inside the volcano. Since then, intermittent steam and gas plumes,accompanied by continuing earthquakes was observed. The earthquakessuggest that magma is fracturing rock as it rises from beneath the volcano.Volcán Copahue is a composite volcano located in the Andes, on the border ofChile and Argentina. This natural-color satellite image shows a blue-tinted gasplume streaming toward the east. The nearest settlement is Caviahue, anArgentinian ski resort.
Tropical Cyclone DumileTropical Storm Dumile formed at the beginning of 2013 in theIndian Ocean, east of Madagascar. The storm moved southwardas it strengthened into a tropical cyclone.On January 3, 2013, the U.S. Navy’s Joint Typhoon WarningCenter (JTWC) reported that Dumile had maximum sustainedwinds of 120 kilometers per hour and gusts up to 150 kilometersper hour.Dumile’s clouds extended over the islands of Réunion andMauritius but stopped short of Madagascar’s capital city ofAntananarivo.
Wildfires in Tasmania
Wildfires in TasmaniaIn January 2013, intense bushfires blazed in Tasmania anisland south of Australia. NASA’s Terra satellite captured thisimage showing numbers of fires burning across the island onJanuary 7, 2013. Red outlines indicate hot spots wheresatellites detected unusually warm surface temperaturesassociated with fires.Extreme heat and strong winds fueled the fires. Temperaturesin Hobart, the capital of Tasmania, soared to a record high of41.8°Celsius (107.2°Fahrenheit) on January 4. The blazesdestroyed more than 100 homes, including many in the smallcommunity of Dunalley. More than 100 people were missingafter fire tore through the town.
Storm turns the Taklimakan Desert white http://earthobservatory.nasa.gov/NaturalHazards/view.php?id=80058
Storm turns the Taklimakan Desert whiteSnow-covered deserts are rare, but that’s exactly what NASA’s Aquasatellite observed as it passed over the Taklimakan Desert in westernChina on January 2, 2013. Snow has covered much of the desert sincea storm blew through the area on December 26.The Taklimakan is one of the world’s largest and hottest sandy deserts.Water flowing into the Tarim Basin has no outlet, so over the years,sediments have steadily accumulated.In parts of the desert, sand can pile up to 300 meters (roughly 1,000feet) high. The mountains that enclose the sea of sand—the Tien Shanin the north and the Kunlun Shan in the south were also covered withwhat appeared to be a significantly thicker layer of snow in January2013.
CHAPTER 1 LIVING WITHTECTONIC HAZARD Part 2
Which one of these is not a Natural Disaster?
Gas Emissions at Volcan Copahue Tropical Cyclone Dumile Wildfires in Tasmania Storm turns the Taklimakan Desert white
Not a Natural Hazard Storm turns the Taklimakan Desert white
Recap: Natural Hazards• Definition – Naturally occurring event that threatens human lives and causes damage to property – Tectonic Natural Hazard • Caused by plate movements when continental crusts and ocean floors move • Eg. Earthquakes, volcanic eruptions and tsunamis – Climate Related Natural Hazard • Caused by severe and extreme weather and climate conditions • Eg. Drought, tropical cyclones and floods
Natural Hazards occur everywhere. Some areas may be more prone to Natural Hazards. Impact of Natural Hazards depend onthe where these Natural Hazards occur.
TODAY’S LESSON OUTCOMESStudents would 1. Describe the internal be able to : structure of the Earth (core, mantle, crust) and tectonic plates. 2. Explain the movement of plates.
Compare your drawing – Have you seen this picture before? – Did you use any of the terms used in your textbook?• Draw a diagram showing the internal structure of the earth. Annotate the diagram using the terms listed below. 28
Take note of the command words used!• Draw – Make a sketch of a geographical form – Include labels to the diagram – Question may be written as ‘Using a diagram’ or ‘Illustrate with a sketch’• Annotate – Add notes of explanation – Label with short comments a diagram, map or photograph to describe or explain – If asked ‘Using only an annotated diagram…’ only the diagram and attached notes will be marked – Insert/Label – Place specific names or details to an illustrative technique
Structure of the EarthThe Earth is made upof 3 main layers: Mantle – Core Outer core – Mantle Inner core – Crust Crust
Internal Structure of the Earth: Core• Inner core- Solid – Pressure exerted on it by surrounding layers – 1,200 km thick• Outer Core- Liquid – 2,100 km thick
Internal Structure of the Earth: Mantle• Solid rock that flows under high temperature and pressure• Layer of solid rock and the asthenosphere – In the Asthenosphere, high temperatures and pressure bring the rocks close enough to their melting point for them to be easily deformed Solid rock that flows?
The Crust• This is where we live!• The Earth’s crust is made of: Continental Crust Oceanic Crust - thick (10-70km) - thin (~7 km) - buoyant (less dense - dense (sinks under than oceanic crust) continental crust) - mostly old - young
Internal Structure of the Earth: Crust• Hard shell made up of thick slabs or rocks that are constantly moving – Plates• Oceanic Crust: crust beneath oceans• Continental Crust: crust beneath continents• Crust + Uppermost mantle = Lithosphere – Lithosphere melts, hot molten rock known as magma is formed
Internal Structure of the Earth: Plates• Crust is broken into tectonic platesType of Crust Location Thickness Type and age of rockOceanic crust Beneath deep Between Consists mainly of basalt, a heavy oceans 5 and and dense rock formed from 8km magma which has coolded quickly Rock of less than 200 million years agoContinental Beneath the earth’s Between Consists of lighter rock, includingcrust continental land 30 and granite masses and under 60km A wide range of rock ages, from shallow seas close very recent to nearly 4 billlion years to continents old
Class Discussion: Convectionarmanalluwie.blogspot.com Currents/ Slab Pull 37
Wegener, Continental Drift and Pangaea
Evidence for Continental Drift• Jigsaw Puzzle fit of continents Alfred Wegener
More evidenceMatching fossils on continents now locatedthousands of miles apart.Example = Mesosaurus, a freshwater reptile
More evidence • Matching geologic structures including: – Mountain chains – Ore deposits – Same rocks of same age
More evidence• Climate change evidence – Glacial deposits at current equator – Fossilized palm trees in Greenland• Map shows why according to the placements of current continents within Pangaea
Earth is made up of the core, mantle and crust. Oceanic crust is denser than a continental crust.Plate movement is caused by convection currents and slab- pull force
TODAY’S LESSON OUTCOMESStudents would 1. Describe the global be able to : distribution of tectonic plates 2. Types of plate boundaries.
Types of Plate Boundaries 52
Different types of plate boundaries• Divergent: where plates move away from each other• Convergent: where plates move towards each other• Transform: where plates move past each other 53
Note areas with earthquakes & volcanic activities
Divergent Plates• Areas where two plates move away from each other• Magma moves upward to the surface where it cools to form new oceanic crust along these boundaries – Oceanic-oceanic – Continental-continental 55
Oceanic-oceanic At various points along the ridge, magma builds The newly formed (youngest) rocks are closest to up above the ocean to form volcanic islands. the middle of the ridge/plate boundaries. Magma rises at the zone of divergence/spreading New sea floor is formed when the magma coolsMagma rises fromformmantle to fill the gap floor called mid- zone to the a ridge of new ocean and solidifies. This process is called sea-floor oceanic ridge. between the plates as they diverge. spreading. 56
Oceanic-oceanic Learn how to draw this!
Diverging: Continental- Continental African Plate African Plate (Nubian) (Somalian) East African Block Rift Valley BlockMountain Mountain
Rift valleys and Block mountains• A fault – Fracture in the rocks along which the rocks are displaced – Due to tensional forces• Rift Valley – Is a valley with steep sides that is formed when the sections of the crust extend along fault lines• Block Mountain – A block of land with steep sides 62
Afar Triangle,Triple Divergent Triangle
Converging: Oceanic- Oceanic Oceanic Trench Magma rises through crust and forms volcanoesDenser Plate Subducts Crust of subducted plate melts and forms magma
Converging: Continental- Continental EURASIAN PLATE Himalayas Tibetan Plateau Layers of rock compressedINDIAN together, causingPLATE massive folding Resist subduction
Converging:Continental- Continental Fold Mountain Range
Actions at Plate Boundaries At a transform fault boundary, plates grind past each other without destroying the lithosphere. Transform faults • Most join two segments of a mid-ocean ridge. • At the time of formation, they roughly parallel the direction of plate movement. • They aid the movement of oceanic crustal material.
Transform Fault Boundary
Recap Review• Question 1 – It is not a natural hazard as it is 6000km away – And a naturally occurring event is only a hazard when lives are affected and when properties are destroyed.• Question 2 – Convection currents are movements of heat within the mantle – Material in the mantle is heated by the core, causing the mantle material to expand, rise and spread out beneath the plates – This causes plates to be dragged along and to move away from each other – Then the hot mantle material cools slightly and sinks, pulling the plate along
Recap Review• Question 3 – Oceanic crust is found beneath deep oceans – Continental crust is found beneath earth’s continental masses and under shallow seas close to continents – Oceanic crust has a thickness of between 5 and 8km which is thinner than the continental crust which has a thickness of between 30 and 60km – Oceanic crust is heavier and denser than the continental crust. – Oceanic crust consists mainly of basalt while a continental crust consists mainly of granite
Important Note!• Plates are NOT continents• Plates include both continental and oceanic crust.
Recap and AdditionalInformation
Plate tectonics• Sea floor spreading provides the driving mechanism for movement• However, it is not the continents that are moving, but the “plates” of lithosphere “floating” in effect on the asthenosphere• The lithosphere is made up of about 20 plates which move relative to each other in several ways
“Plates” of lithosphere are moved around by the underlying hot mantleconvection cells
Plate TectonicsAn overview of the tectonic system.
Boundaries Divergent boundaries (also called spreading centers) are the place where two plates move apart. Convergent boundaries form where two plates move together. Transform fault boundaries are margins where two plates grind past each other without the production or destruction of the lithosphere.
Boundaries• Convergent – where plates come together.
Age of Oceanic Crust Courtesy of www.ngdc.noaa.gov
Mid Atlantic Ridge Mid Atlantic Ridge
Divergent Boundaries• Spreading ridges – As plates move apart new material is erupted to fill the gap
Iceland: An example of continental rifting• Iceland has a divergent plate boundary running through its middle• North American Plate and Eurasia Plate diverging
East Africa Rift Valley
East Africa Rift Valley
Subduction • Oceanic lithosphere subducts underneath the continental lithosphere • Oceanic lithosphere heats and dehydrates as it subsides • The melt rises forming volcanism • E.g. The Andes
Continent-Oceanic Crust Collision• Called SUBDUCTION
Deep Ocean Trench
Andes Mountains in South America
Andes Mountains formedalong the coast of South America • Nazca Plate dives under the South American Plate • Subduction
Volcanoes in Japan Japan
Japan formed as an island chain as the Pacific Plate dives beneath the Eurasian Plate Mt Fuji
Aleutian Islands Chain off Alaska
Aleutian Islands formed as an island chain as PacificPlate dives beneath North American Plate
Continent-Continent Collision• Forms mountains, e.g. European Alps, Himalayas
Alps in EuropeCollision of Africa and Eurasia
Interesting plate collision • This picture shows a place in Newfoundland where a massive collision actually forced mantle rock on top of the crust, during the collision that formed Pangaea and the Appalachian mountains. This looks down the old plate boundary.
Mantle rocks are toxic • These rocks have very different compositions than crustal rocks. • They contain heavy metals, which do not support life forms on the earth’s surface, so few organisms live there. • However, in some places their heavy metal concentrations produce rich metal deposits and are mined
Divergent Boundaries • Found at spreading centers – either mid ocean ridges or mid continental rift zones
Transform fault boundary• This shows the San Andreas Fault.• It is a transform fault boundary, where the plates move sideways past each other, rather than away from each other (at divergent boundaries), or towards each other (at convergent boundaries)
Transform Fault Boundary
Review of different boundaries• Divergent – mid ocean ridge like Iceland or continental rift zone like the African Rift Valley• Convergent – Ocean/ocean like Japanese Islands – Continent/ocean like Andes and Cascades – Continent/continent like the Himalayas• Transform fault like the San Andreas fault• Hot spots are not at plate boundaries, but give us information about plate motion• Activity
What causes plate tectonics? • Convection in the mantle, as the plastic asthenosphere flows, carrying the plates with it. • This is probably aided by slab pull at subduction zones and ridge push at mid ocean ridges and rising plumes in the mantle • This diagram shows several different model hypotheses
Formation of mountains• Two forces are constantly at work on the earth. – Weathering and erosion tear structures down while – Plate tectonics builds them up
So we have mountains!But they will not last forever?
Mountains form in different ways -Volcanic mountains-• Volcanoes form by subduction and melting of plates• Volcanic mountains form over hot spots• Volcanic mountains form at rift zones
Other mountain types• Folded mountains - form from converging continents like the Himalayas• Fault block mountains - form where blocks of rock drop at faults mostly near plate boundaries, but not always• Uplifted mountains – form where large sections of the crust are pushed up, perhaps by magma, or other forces
Isostasy• Just as a boat sinks or rises with changes in weight, so does the crust sink or rise with changes in weight. Plate tectonics builds mountains and the extra weight causes the crust to sink. As erosion occurs the weight of the mountains decreases and the crust rises again. This process is called isostasy or isostatic change
StressDue mostly to plate movements,the earth’s crust is under a lot ofstress. There are 3 types, shownat the rightA occurs where plates pull apart,divergent boundaries, and iscalled tensionB occurs where plates converge,and is called compressionC occurs where plates move pasteach other, at transform faultboundaries and is called shearing
Strain • This stress leads to strain on theanticline syncline crust which bends it. – • If it is warm, underground, it can bend. This called ductile deformation. Features are calledA fold above and a fault below folds. Upturned folds are anticlines while downturned folds are synclines. • Or, the rock may break, if it is brittle. This causes faults –breaks of the earth.
Different faults• Faults move in different ways, depending on the 1 type of stress on them. Here are 3 types that form. 2 – 1 is a normal fault – 2 is a strike slip fault – 3 is a reverse fault 3
Matching• These form at different plate boundaries. Can you figure out which 1 forms where? Match them 2 A. Convergent 3 B. Divergent 1 C. Transform Fault 2 3
Can you match the stress and strain? 1 2 3 A is 1st, B is 3rd, C is 2nd