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PLATE TECTONICS QUICK REVIEW: EARTH’S STRUCTURE CRUST MANTLE CORE QUICK REVIEW: EARTH’S STRUCTURE CRUST: Top layer, rocky MANTLE: middle, Hot, rock & metal CORE: innermost, Very hot, very dense Iron & Nickel Partly liquid NEW INFO: EARTH’S STRUCTURE TECTONIC PLATES – sections of the crust and upper mantle that are stuck together TECTONIC PLATES – “float” on top of the rest of the mantle and are slowly moving (a few centimeters per year) 7 major plates on the Earth- the African, North American, South American, Eurasian, Australian, Antarctic, and Pacific plates + several smaller plates THE EARTH’S TECTONIC PLATES The place where the two plates meet is called a plate boundary There are 3 TYPES of Plate Boundaries. THE EARTH’S TECTONIC PLATES: 3 Types of Boundaries: Divergent Convergent Transform Convergent boundaries Occur when plates crash into each other Example: Indian Plate is crashing into Eurasian Plate Subduction occurs at Convergent Boundaries • When one plate slides underneath another • Crust (solid) melts back into magma (liquid) Ring of Fire - Japan • Sits where Philippine plate and Pacific plate are subducting under Eurasian plate • Feel earth tremors every few weeks • Lots of earthquakes, volcanoes and tsunamis (tidal waves) • 2011 Tsunami in Japan caused by underwater earthquake Ring of Fire Divergent boundaries Occur when plates move apart as new rock is pushed up from mantle Sea-floor Spreading Mid-Atlantic Ridge is an example of a divergent boundary • Under Atlantic ocean • South American Plate is pulling away from African Plate • Magma (liquid) comes up from mantle and cools to form new crust (solid rock) • Volcanic mountains form deep underwater • Extra heat at great depths provides home to many strange animals So, old crust subducts and melts into magma at Convergent Boundaries And, new crust is formed from cooling magma at Divergent Boundaries Transform Boundaries Places where plates slide past each other are called transform boundaries Transform Boundaries • San Andreas Fault in California – 5 Major Earthquakes in past 20 years! Loma Prieta Earthquake 1989 WHAT HAPPENS AT BOUNDARIES? MOUNTAINS – at convergent boundaries – one of the plates is pushed upwards and forms Mountain ranges! EARTHQUAKES – Plates are giant slabs of rock pushing on each other. They do not glide by smoothly! Sometimes they build up huge amount of energy and then slip violently – an Earthquake! VOLCANOS – at convergent boundaries – one plate subducts and the pressure melts it! The newly formed liquid rock (magma) can be pushed to the surface – a Volcano!. At Divergent boundaries, magma is always flowing out – a slow stead oozing volcano! TSUNAMI– when earthquakes occur under water – they can trigger huge tidal waves - Tsunamis WHAT HAPPENS AT BOUNDARIES? So, even thought he plates are only moving a few centimeters per year – that much Earth moving at all has a lot of energy and can release it in Very dramatic ways Tidal wave caused by underwater earthquake • types of boundaries WHAT HAPPENS AT BOUNDARIES? HEY WAIT! IF ALL THE PLATES ARE MOVING DOES THAT MEAN THE CONTINENTS ARE MOVING TO? DO NOT TRY TO COPY PICTURES ON NEXT SLIDES – BUT DO TAKE SOME GENERAL NOTES THE EARTH’S PLATES TODAY THE EARTH’S PLATES 30 MILLION YEARS AGO THE EARTH’S PLATES 65 MILLION YEARS AGO THE EARTH’S PLATES 140 MILLION YEARS AGO THE EARTH’S PLATES 200 MILLION YEARS AGO This “super-continent” was called Pangaea THE EARTH’S PLATES 100 MILLION YEARS IN FUTURE? ACTIVITY • Plate tectonics puzzle