Our Changing EarthRevision Earth is made up of four distinct layers:1. The inner core is in the centre and is the hottest part of the Earth. It issolidand made up of iron and nickel with temperatures of up to 5 500°C. Withitsimmense heat energy, the inner core is like the engine room of the Earth.2. The outer core is the layer surrounding the inner core. It is a liquidlayer,also made up of iron and nickel. It is still extremely hot, withtemperaturessimilar to the inner core.3. The mantle is the widest section of the Earth. It has a thickness ofapproximately 2 900 km. The mantle is made up of semi-molten rockcalledmagma. In the upper parts of the mantle the rock is hard, but lower downthe rock is soft and beginning to melt.4. The crust is the outer layer of the earth. It is a thin layer between 0-60kmthick. The crust is the solid rock layer upon which we live. There are twodifferent types of crust: continental crust, which carries land, andoceaniccrust, which carries waterStructure of the Earthscrustmantleouter coreInnercore How do the Earth’s plates move?At DIVERGENT BOUNDARIES the plates move apart.Pressure that builds up inthe middle of the Earth can push two plates and causethem to spread apart.This usually happens under the ocean because the plateis thinner there, but can also happen on land. This formsmid-oceanic ridges (in the ocean) and riftvalleys (on land).At CONVERGENT BOUNDARIES the plates movetowards each other. Pressure cancause two plates to push together. Over a very long time,this pushing can create mountains.At TRANSFORMING BOUNDARIES the plates slidepast each other. Plates can move past each other inopposite directions, or they can move in the same directionat different speeds. The plates are pushed togetherstrongly so, as they move past each other, a lot ofpressure builds up. An earthquake happens when thispressure is released How earthquakes formWhen tectonic plates move against each other, they do not slide smoothly. Thetectonic plates become stuck, even though they are under pressure to move.The pressure builds up until suddenly, the tectonic plates give way and move,releasing the built-up energy. Some of the energy is released in the form of‘seismic waves’ (energy that travels in the form of waves through the Earth).These waves radiate in all directions, including towards the Earth’s surface,where they are felt as a shaking or displacement of the ground. We call theseevents earthquakes. Aftershocks are tremors that follow the largest shock. Theyare smaller than the main shock and can continue over a period of weeks,months, or even years. And can cause tsunami`s, a landslide or intense groundshaking.Most earthquakes occur on and adjacent to the boundaries of tectonic plates, butsometimes they are felt in the middle of tectonic plates. As tectonic platescontinue to move and tectonic plate boundaries change over millions of years,weakened boundary regions become part of the interior of the tectonic plates.These zones of weakness within the continents can cause earthquakes inresponse to the stresses at the edges of the tectonic plate or inside the Earth’scrust. "There are always one or a fewvolcanoes acting up somewherealong the Ring of Fire, and thereare frequent earthquakes. Why?The main tectonic plates which cover the surface of theEarth. Pay specific attention to the movement of the plates andgeological features formed due to this movement. A BCStudy these pictures carefully. What do you thinkhas happened here?(Think about the movement of tectonic plates) What causes a tsunami?...A tsunami is a large ocean wave that iscaused by sudden motion on the oceanfloor. This sudden motion could bean earthquake, a powerful volcaniceruption, or an underwater landslide.The impact of a large meteorite couldalso cause a tsunami. Tsunamis travelacross the open ocean at great speedsand build into large deadly waves in theshallow water of a shoreline. LEINÉEWarminga layer summa fa Ed's dadcopper although notashstastuinnercne.EEmadeof semimoltenmindbottomof theocean How the earths platymole At drergent boundplates more apart pressurethatbuilds up can p h2 plots case then tospread apart Usually happenin ocean became plate thinnerHereA transforming Sounderplate stile past eachotherin opposite directions arein