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Science for living Us 18982 Demonstrate a Knowledge of Earth Science 2 credits Element 1: Describe the structure of the Earth. • Features of the Earth include the mantle, core, crust and plates. • THE STRUCTURE OF THE EARTH crust mantle Outer core Inner core 1 Think about? • What moves when there is an Earthquake? • What comes out of volcanoes? • What is the pumice that you find around Taupo Lake? • Which section is the hottest? • Which section contains liquid metal? • Which section contains solid metal? LAYERS OF THE EARTHwhat’s it made up of? • Crust – thin, solid rock. Broken into about 20 plates. • Mantle – molten rock (magma), heated from the core and moving in convection currents which moves the plates. • Outer core – mainly molten iron and nickel. • Inner core – solid iron due to immense pressure. NB: as you move deeper into earth pressure and heat increases. Movement of plates caused this Tectonic plates • Crust is divided into plates which move around on the moving magma below. • They can collide or pull away. • They cause volcanic activity. • They cause Earthquakes as the plates collide and rocks break. • Ring of Fire is the edges of the pacific plate – the collisions cause a lot of volcanic activity. THE MAJOR TECTONIC PLATES PLATE TECTONICS • Earth’s crust is made of around 11 large tectonic plates and several smaller ones. • Convection currents in the Mantle cause the plates to move slowly. • Plate tectonics (movement) cause Earthquakes and volcanic activity. • Plates consist of continental crust and oceanic crust. • NZ lies on the boundaries of the Pacific and Australian plates. San Andreas Fault – Tectonic Plates colliding – North American Plate and Pacific Plate. COLLISION OF THE AUSTRALIAN AND PACIFIC PLATES New Zealand's deep earthquakes from 1990-1994 become deeper from east to west THREE GROUPS OF ROCK MAKE UP THE EARTH’S CRUST Igneous – formed when magma cools and solidifies, in an around volcanoes. Sedimentary – formed from sediment (sand, pebbles, shells) at bottom of a body of water, eg, lake, river, sea, swamp. Metamorphic – formed when other rocks are heated and compressed deep within the Earth’s crust, often near magma. Sedimentary Rocks • • • • • Sediment wash down into the ocean. They may contain shells or fossils. Layered. Sediments are cemented together. They are pushed up out of the water by tectonic plate movement. • Eg, Sandstone, Limestone Sandstone • Sedimentary. • Formed on the beach from sediments of sand. • Soft, grainy. • Mudstone is also a sedimentary rock with fine particles. • Predominant in Marlborough as Greywacke. Limestone • Limestone is found in cliffs. • It has fossil shell remains in it because it was formed on the beach which has shellfish on it. • A hard sedimentary rock which is often the last to erode. Limestone of Cathedral Caves Sawcut gorge davidwallphoto.com Igneous Rocks • Rocks are pushed down into the mantle and become molten. • Molten rock cools in the crust to form solid, igneous rocks. • Or, the magma comes out of the Earth through a Volcano and cools and solidifies. • It will cool fast if it comes out (extrusive) and will have small or no crystals, eg, Basalt. • Slow cooling inside the crust (intrusive) will produce larger crystals, eg, granite. Basalt • Fast cooling Magma. • Small crystals. • Dark coloured. Granite Granite • Magma cools slowly, often in cracks in the crust. • Gives time for mineral crystals to form in the rocks. • Pretty. Metamorphic • Rocks are pushed down near the mantle or under mountains. • Intense heat from the mantle and/or pressure from above cause the rocks to change. • They become very hard and pretty. • Eg, Pounamu (jade), Marble. Pounamu • Metamorphic. • Formed by heat and pressure. Marble • • • • Metamorphic. Formed in the same way as jade. Formed from limestone. Often used to make benches and ornaments. Marble The rock cycle – how rocks change